Anaesthetics Study Guide

UNSW School of MedicineUNSW School of Medicine

Liverpool Clinical SchoolLiverpool Clinical School

Year VI Critical Care RotationYear VI Critical Care Rotation

Blair Munford, BMedSc, MB,ChB, FFARACS, FANZCABlair Munford, BMedSc, MB,ChB, FFARACS, FANZCA

Senior Specialist Anaesthetist, Liverpool HospitalSenior Specialist Anaesthetist, Liverpool Hospital

Aims of Anaesthetic Attachment To understand the scope of the practice of anaesthesia.To understand the scope of the practice of anaesthesia. To understand the role of the anaesthetist as part of the surgical or To understand the role of the anaesthetist as part of the surgical or

procedural team.procedural team. To gain exposure to airway management and other procedural skillsTo gain exposure to airway management and other procedural skills To understand the importance of the perioperative process including To understand the importance of the perioperative process including

pre-anaesthetic assessment, investigations, and optimisation.pre-anaesthetic assessment, investigations, and optimisation. To understand post anaesthetic care including pain management, and To understand post anaesthetic care including pain management, and

the indications for specialised postanaesthetic monitoring & support.the indications for specialised postanaesthetic monitoring & support. To reviseTo revise/enhance/enhance key concepts & simple competencies in emergency key concepts & simple competencies in emergency

assessment and resuscitation, including CPR/BLS/ALS.assessment and resuscitation, including CPR/BLS/ALS. For those interested, to acquire insight into anaesthetics as a medical For those interested, to acquire insight into anaesthetics as a medical

career option.career option.

Introductory Case Study

““Don’t play with that!” …Don’t play with that!” …

A simple paediatric case - NOTA simple paediatric case - NOT

My first ever weekend on duty as an anaesthetics registrar . . .

Case transferred from country hospital for theatre:Case transferred from country hospital for theatre: 3 year old girl, previously well3 year old girl, previously well Mixed total/partial toe amputation Mixed total/partial toe amputation

(From playing with grandfather’s axe!)(From playing with grandfather’s axe!) 18 hours ago, fasted since18 hours ago, fasted since IV in situ, IV fluids running.IV in situ, IV fluids running. Has had antibiotics/narcotic analgesics.Has had antibiotics/narcotic analgesics.

No problem, even for a junior registrar, right?No problem, even for a junior registrar, right?

What happened next . . .

To OT as scheduled.To OT as scheduled. Rapid sequence induction, uneventful anaesthesia.Rapid sequence induction, uneventful anaesthesia. Extubated near awake at end (in hindsight, too Extubated near awake at end (in hindsight, too

soon)soon) Vomited undigested food, developed Vomited undigested food, developed

laryngospasm, desaturated.laryngospasm, desaturated. Re-paralysed, intubated, pharynx sucked out, Re-paralysed, intubated, pharynx sucked out,

suction down ET tube – no evidence aspirationsuction down ET tube – no evidence aspiration Awoken & re-extubated uneventfully.Awoken & re-extubated uneventfully.

The lessons from this:

Specific: Beware occult delayed gastric emptying Specific: Beware occult delayed gastric emptying – predictable in hindsight.– predictable in hindsight.

General:General:1.1. There is minor surgery but there is no minor There is minor surgery but there is no minor

anaesthesia!anaesthesia!2.2. Anaesthetic practice is more than just being able Anaesthetic practice is more than just being able

to give an anaesthetic – just like being a 747 to give an anaesthetic – just like being a 747 captain is more than just holding the controls!captain is more than just holding the controls!

Part I:Scope & Development of Scope & Development of

Anaesthetic PracticeAnaesthetic Practice

Imagine a world without anaesthesia . . .

What medicine was like prior to the invention of anaesthesia:

Surgical operations performed rarely & only as a last Surgical operations performed rarely & only as a last resort. Death was the expected and usual outcome, resort. Death was the expected and usual outcome, from shock, haemorrhage, or infection.from shock, haemorrhage, or infection.

When surgery unavoidable, patient was held down by When surgery unavoidable, patient was held down by assistants & surgeons operated as fast as possible. The assistants & surgeons operated as fast as possible. The first incision was often deliberately brutal in the hope first incision was often deliberately brutal in the hope that the patient would faint, allowing less haste.that the patient would faint, allowing less haste.

No analgesia in labour & interventional/operative No analgesia in labour & interventional/operative obstetrics essentially unknown – except post mortem obstetrics essentially unknown – except post mortem (original meaning of Caesarean Section)(original meaning of Caesarean Section)

Without anaesthesia . . .

Surgical advances would have been Surgical advances would have been minimal.minimal.

Childbirth would remain a major risk for Childbirth would remain a major risk for baby and/or mother.baby and/or mother.

Concepts of intensive care & resuscitation Concepts of intensive care & resuscitation would not have developed.would not have developed.

Pain - acute and chronic - would have Pain - acute and chronic - would have remained an inevitable part of life.remained an inevitable part of life.

Without doubt the development of anaesthesia Without doubt the development of anaesthesia has been one of the top ten medical advances has been one of the top ten medical advances of all time.of all time.

Some have even ranked it as the most Some have even ranked it as the most important medical invention ever.important medical invention ever.

Others rank it amongst greatest discoveries of Others rank it amongst greatest discoveries of any typeany type in human history. in human history.

But what is anaesthesia?

A state that encompasses (1)A state that encompasses (1)analgesiaanalgesia plus (2) plus (2) arreflexiaarreflexia (muscle relaxation or lack of (muscle relaxation or lack of movement) and (in the case of general movement) and (in the case of general anaesthesia) (3) anaesthesia) (3) hypnosishypnosis; enabling painful ; enabling painful or distressing procedures to be performed or distressing procedures to be performed humanely.humanely.

This is the “Triad of Anaesthesia”This is the “Triad of Anaesthesia”

The other triad of anaesthesia

THE MISSION IS (in order of importance):THE MISSION IS (in order of importance):1.1. Preserve lifePreserve life

2.2. Relieve sufferingRelieve suffering

3.3. Provide optimum conditions for procedureProvide optimum conditions for procedure

(Any fool can do the third by ignoring the first. Doing the (Any fool can do the third by ignoring the first. Doing the second by ignoring the first is called euthanasia. The second by ignoring the first is called euthanasia. The

art is in being able to provide all three.)art is in being able to provide all three.)

Anaesthesia can be: CerebralCerebral

Sedation/analgesiaSedation/analgesia GeneralGeneral

Inhalational/spontaneous ventilatingInhalational/spontaneous ventilatingBalanced/controlled ventilationBalanced/controlled ventilation

Neuro-interruptiveNeuro-interruptive LocalLocal RegionalRegional NeuraxialNeuraxial

(Or some combination of two or more of these)

Classification of Anaesthetics

General Regional

Anaesthesia

Controlledventilation

Spontaneousventilation

Intubated

LMA

Mask

Intubated

Manual

Mechanical

Surface/topical

infiltration

Nerve/plexus block

Spinal blocks

SubarachnoidEpidural:

cervical, thoracic, lumbar, caudal

Single shot, intermittent, continuous

Dissociative

Auditory

Electrical

Hypnosis

Acupuncture

Local anaesthetic, narcotic/adjuvant, combination

AlternativeAlternative

But wait . . . there’s more:

Scope of Anaesthetic Practice Anaesthesia for surgeryAnaesthesia for surgery Sedation/anaesthesia for other proceduresSedation/anaesthesia for other procedures Obstetric analgesia/anaesthesia servicesObstetric analgesia/anaesthesia services Pre-anaesthetic assessment & perioperative medicinePre-anaesthetic assessment & perioperative medicine Acute & Chronic Pain ServicesAcute & Chronic Pain Services Vascular access services: Central venous lines, et al.Vascular access services: Central venous lines, et al. Resuscitation: Trauma team/MET/PrehospitalResuscitation: Trauma team/MET/Prehospital Teaching: Procedural skills/resuscitation/analgesiaTeaching: Procedural skills/resuscitation/analgesia Intensive Care practice/cover/supportIntensive Care practice/cover/support Operating theatre management/coordinationOperating theatre management/coordination Critical care transportCritical care transport

(It’s a broad church!)(It’s a broad church!)

Part II: Perioperative Medicine

“The way of the future”

What is perioperative medicine?

““Integrated multidisciplinary Integrated multidisciplinary management of the surgical or management of the surgical or procedural patient’s hospital procedural patient’s hospital admission & stay.”admission & stay.”

Perioperative system includes:

Identification of patient requiring procedureIdentification of patient requiring procedure Referral to perioperative serviceReferral to perioperative service Screening for level of workup requiredScreening for level of workup required Pre-anaesthetic assessment/plan Pre-anaesthetic assessment/plan Referral & investigations as required.Referral & investigations as required. Admission at appropriate pre-op intervalAdmission at appropriate pre-op interval Post-operative drug/fluid/other therapyPost-operative drug/fluid/other therapy Appropriate post op level of care & stayAppropriate post op level of care & stay Discharge at earliest appropriate pointDischarge at earliest appropriate point

But why?

Minimize unnecessary pre-op bed days.Minimize unnecessary pre-op bed days. Minimize preoperative cancellationsMinimize preoperative cancellations Enable more predictable bed occupancyEnable more predictable bed occupancy Minimize pseudo-urgent blood tests & other Minimize pseudo-urgent blood tests & other

investigationsinvestigations Improve post operative care & shorten post Improve post operative care & shorten post

operative stayoperative stay

The Pre-anaesthetic Consultation What? Targeted history & examination, & What? Targeted history & examination, &

formulation of anaesthetic/perioperative plan. formulation of anaesthetic/perioperative plan. Who? Ideally by the anaesthetist for the procedure Who? Ideally by the anaesthetist for the procedure

(not always possible). (not always possible). Whom? All patients should have some form of this.Whom? All patients should have some form of this. When? At the earliest appropriate opportunity When? At the earliest appropriate opportunity

(Obviously this varies on a case by case basis)(Obviously this varies on a case by case basis) Why? To enable optimimum pre-anaesthetic Why? To enable optimimum pre-anaesthetic

preparation, risk minimisation, informed consent, preparation, risk minimisation, informed consent, and allaying of anxiety.and allaying of anxiety.

Pre-operative preparation may include premedication

Use if required, not “one size fits all”Use if required, not “one size fits all”

Aims:Aims:1.1. Ameliorate anxietyAmeliorate anxiety

Usually with a benzodiazepine such as temazepamUsually with a benzodiazepine such as temazepam

2.2. Relieve painRelieve pain – predominantly in the acute setting – – predominantly in the acute setting –

usually with narcotics.usually with narcotics. 3.3. Prevent reflux/aspiration - Prevent reflux/aspiration - in at risk patientin at risk patient

Usually (a) H2 blocker or PPI 6-8 hrs preop if Usually (a) H2 blocker or PPI 6-8 hrs preop if possible, then (b) non particulate antacid possible, then (b) non particulate antacid immediately preop.immediately preop.

4.4. Treat other medical conditionsTreat other medical conditionse.g. asthma prophylaxis.e.g. asthma prophylaxis.

Most regular medications are continued, Most regular medications are continued, including on the day of surgeryincluding on the day of surgery

Exceptions include:Exceptions include:

(a)(a) Oral hypoglycaemicsOral hypoglycaemics

(b)(b) Antithrombotic agents (mostly)Antithrombotic agents (mostly)

ASA Physical Status ASA 1ASA 1 – Healthy patient – Healthy patient ASA 2ASA 2 – Mild or controlled systemic disease – Mild or controlled systemic disease ASA 3ASA 3 – Significant systemic disease – Significant systemic disease ASA 4ASA 4 – Severe systemic disease – current – Severe systemic disease – current

or constant threat to lifeor constant threat to life ASA 5ASA 5 – Moribund patient unlikely to – Moribund patient unlikely to

survive with or without proceduresurvive with or without procedure ASA 6ASA 6 – Brain dead patient (organ donor) – Brain dead patient (organ donor)

+/- E = Emergency procedure+/- E = Emergency procedure

Relevance of this?

Risk stratificationRisk stratification

Workload/resource utilisation planningWorkload/resource utilisation planning

Remuneration aspectsRemuneration aspects

Perioperative (Preanaesthetic) Clinic

Surgical clinic

Nurse Clinic

Checked up, satisfied as fit & suitable

Decides to proceed with planned time, date & procedure

Not certain;sends only case notes to

anaesthetist to review it

Satisfied with it; decides to send it back to her

for mx

Not quite satisfied; takes over review & mx

Decides to further investigate. May cancel, postpone, refer case or

decide to do it

Surgeon refers case

The Doctor takes a quick history, leading The Doctor takes a quick history, leading questions are allowed as major diagnoses questions are allowed as major diagnoses should already be knownshould already be known

Asks for hypertension, diabetes, Asks for hypertension, diabetes, asthma,epilepsy, previous anaesthetics, asthma,epilepsy, previous anaesthetics, allergies, complications, medications allergies, complications, medications being usedbeing used

A quick examination is done, Ix like Xray, A quick examination is done, Ix like Xray, ECG, UES & Blood ix are doneECG, UES & Blood ix are done

ASA categorised, anaesthesia decidedASA categorised, anaesthesia decided Explained to patient about anaesthetics, Explained to patient about anaesthetics,

risks, PCA & possible complicationsrisks, PCA & possible complications

Preanaesthetic Clinic

Based on:Based on: HistoryHistory

Examination, Investigation . . .Examination, Investigation . . .

Decision:Decision:

Preanaesthetic Clinic

To do the planned

procedure

To postpone the procedure till fully

investigated optimised

To cancel the procedure

CASE STUDY IICASE STUDY II

Perioperative managementPerioperative management

Diabetic patient for vascular surgery

History 65 year old man, BMI 3565 year old man, BMI 35 Type II DM, 15 yrs, on OHGs, poor controlType II DM, 15 yrs, on OHGs, poor control Smoker 60+ pack yearsSmoker 60+ pack years HypertensionHypertension HypercholesterolaemiaHypercholesterolaemia Ischaemic heart diseaseIschaemic heart disease Diabetic nephropathy, (eGFR ~ 30mls/min)Diabetic nephropathy, (eGFR ~ 30mls/min)

For (R) femoro-popliteal bypassFor (R) femoro-popliteal bypass

What are the issues and risks here?What are the issues and risks here?

1.What are the issues and risks here?1.What are the issues and risks here?

2. How can we optimise him preoperatively?2. How can we optimise him preoperatively?

1. What are the issues and risks here?1. What are the issues and risks here?

2. How can we optimise him preoperatively?2. How can we optimise him preoperatively?

3. What are our anaesthetic options & 3. What are our anaesthetic options & problems?problems?

1. What are the issues and risks here?1. What are the issues and risks here?

2. How can we optimise him preoperatively?2. How can we optimise him preoperatively?

3. What are our anaesthetic options & problems?3. What are our anaesthetic options & problems?

4. How do we manage him postoperatively?4. How do we manage him postoperatively?

Part III: Safety & Monitoring

in Anaesthesia

Safety in anaesthesia is paramount

““When it goes right, no-one remembers. . . When it goes right, no-one remembers. . . When it goes wrong, no-one forgets”When it goes wrong, no-one forgets”

. . . So the aim is to make anaesthesia as . . . So the aim is to make anaesthesia as forgettable as possible!forgettable as possible!

Safety Initiatives in Anaesthesia

Anaesthetists have been the leaders in safety initiatives in Anaesthetists have been the leaders in safety initiatives in medicine – e.g. :medicine – e.g. :

Privileged reporting & investigation of deaths under or Privileged reporting & investigation of deaths under or associated with anaesthesia in most states.associated with anaesthesia in most states.

Systematic reporting of incidents and near missesSystematic reporting of incidents and near misses Collegial policies on minimum standards for facilities, Collegial policies on minimum standards for facilities,

equipment, monitoring, staffing, & training.equipment, monitoring, staffing, & training. Publication of algorithms – e.g: difficult airway Publication of algorithms – e.g: difficult airway

management; malignant hyperthermiamanagement; malignant hyperthermia Simulation & contingency training e.g. difficult airway Simulation & contingency training e.g. difficult airway

workshops, emergency management of anaesthetic workshops, emergency management of anaesthetic crises (EMAC) course.crises (EMAC) course.

Principles of Safety Recognise risk – pre anaesthetic consultationRecognise risk – pre anaesthetic consultation Avoid risk if possible – e.g. can procedure be done Avoid risk if possible – e.g. can procedure be done

under LA?under LA? Mitigate risk – optimise patient condition, select Mitigate risk – optimise patient condition, select

safest technique/agents/resources – e.g “cardiac” safest technique/agents/resources – e.g “cardiac” anaesthetic & postop ventilation.anaesthetic & postop ventilation.

Plan & be prepared for emergencies – e.g. Plan & be prepared for emergencies – e.g. predrawn emergency drugs, backup airway plan.predrawn emergency drugs, backup airway plan.

Observe/monitor for deviations & crises.Observe/monitor for deviations & crises. Respond in a timely& appropriate fashion.Respond in a timely& appropriate fashion. Call for help/backup if required. Call for help/backup if required.

“The price of safety is eternal vigilance”

““Clinical observation is the cornerstone of Clinical observation is the cornerstone of patient monitoring”patient monitoring”

- ANZCA Policy statements (several)ANZCA Policy statements (several)

OR . . . OR . . . ““The best patient monitor is still the one The best patient monitor is still the one

between your ears – so make sure it’s between your ears – so make sure it’s switched on”switched on” – my take on the above.– my take on the above.

Monitoring in anaesthesiaBasic (all/most patients)Basic (all/most patients) Pulse oximetryPulse oximetry ECGECG Noninvasive (cuff) BPNoninvasive (cuff) BP CapnographyCapnography Oxygen concentrationOxygen concentration Agent monitoringAgent monitoring Airway pressuresAirway pressures TemperatureTemperature

Others as indicatedOthers as indicated Invasive arterial BPInvasive arterial BP Precordial stethescopePrecordial stethescope Ventilator alarm(s)Ventilator alarm(s) Nerve stimulatorNerve stimulator BIS/entropyBIS/entropy SpirometrySpirometry CVPCVP ““Swann Ganz” (PAP)Swann Ganz” (PAP) Transoesophageal echoTransoesophageal echo

Pulse oximetry First monitor I put on most patients & first I First monitor I put on most patients & first I

usually look at.usually look at. If this is OK, then patient has a pulse, a survivable If this is OK, then patient has a pulse, a survivable

blood pressure (at least 60/) and is oxygenating blood pressure (at least 60/) and is oxygenating their blood.their blood.

But if it’s not right, it’s not very specific – i.e. it But if it’s not right, it’s not very specific – i.e. it may be as simple as a dislodged probe, or as may be as simple as a dislodged probe, or as serious as a cardiac arrest.serious as a cardiac arrest.

Doesn’t Doesn’t guaranteeguarantee tissue oxygenation – may be tissue oxygenation – may be relatively normal in extreme anaemia, carboxy- relatively normal in extreme anaemia, carboxy- haemoglobinaemia, cyanide posoning, etc.haemoglobinaemia, cyanide posoning, etc.

Electrocardiogram Good monitor for:Good monitor for:

Arrhythmias/ectopicsArrhythmias/ectopics Some electrolyte abnormalities (K+ & Ca++)Some electrolyte abnormalities (K+ & Ca++) Ischaemic/strain changesIschaemic/strain changes

((Provided leads are placed correctly!)Provided leads are placed correctly!) Does Does notnot monitor: monitor:

Volume statusVolume status Cardiac outputCardiac output Blood pressureBlood pressure

Remember: it is entirely possible to die Remember: it is entirely possible to die

with a relatively normal ECG!with a relatively normal ECG!

Noninvasive arterial blood pressure (NIBP) monitoring

Usually automatedUsually automated Convenient but not reliable:Convenient but not reliable: Dependant on correct cuff size & positionDependant on correct cuff size & position Not continuousNot continuous Usually under-estimates true hyper-& over-Usually under-estimates true hyper-& over-

estimates true hypotensive values.estimates true hypotensive values. Interferes with IV infusions & pulse oximetryInterferes with IV infusions & pulse oximetry Should not be placed on limb with AV fistula or Should not be placed on limb with AV fistula or

lymphoedema.lymphoedema.

Capnography““Gold standard” for verification of ETT placement. Gold standard” for verification of ETT placement.

Can also give information on:Can also give information on: Dead space/V-Q mismatchingDead space/V-Q mismatching Adequacy of ventilationAdequacy of ventilation Spontaneous respiratory effort during controlled Spontaneous respiratory effort during controlled

vent’n.vent’n. Rebreathing: circuit problems or inadequate gas flow.Rebreathing: circuit problems or inadequate gas flow. Venous return, RV function & pulmonary blood flow Venous return, RV function & pulmonary blood flow

e.g. thrombotic, gas or fat embolisme.g. thrombotic, gas or fat embolism

Oxygen monitoring Monitors machine rather than patient.Monitors machine rather than patient. The only The only specificspecific monitor of oxygen supply monitor of oxygen supply

(Other safety features assume/depend on the gas (Other safety features assume/depend on the gas from O2 outlets & cylinders actually from O2 outlets & cylinders actually beingbeing oxygen)oxygen)

N.B. Before adoption/mandating of oxygen N.B. Before adoption/mandating of oxygen monitoring, all reported (& thankfully very monitoring, all reported (& thankfully very

rare) “wrong gas” anaesthetic incidents rare) “wrong gas” anaesthetic incidents (misconnected pipelines or incorrectly filled (misconnected pipelines or incorrectly filled cylinders) resulted in the death of the first cylinders) resulted in the death of the first

patient exposed in every case.patient exposed in every case.

Anaesthetic agent monitoring

Identifies (hopefully confirms!) anaesthetic agent Identifies (hopefully confirms!) anaesthetic agent being usedbeing used

Measures inspiratory & expiratory concentrationsMeasures inspiratory & expiratory concentrations Expiratory (alveolar) concentration enables Expiratory (alveolar) concentration enables

calculation of MAC fraction or multiple – i.e. calculation of MAC fraction or multiple – i.e. estimation of anaesthetic depth.estimation of anaesthetic depth.

Now mandatory when inhalational anaesthetic agents Now mandatory when inhalational anaesthetic agents are used.are used.

Temperature monitoring Anaesthesia promotes hypothermia by:Anaesthesia promotes hypothermia by:

Decreased metabolic rate -> decreased heat productionDecreased metabolic rate -> decreased heat production Redistribution of blood flow -> increased heat lossRedistribution of blood flow -> increased heat loss

Patients may need temperature supportPatients may need temperature support Passive (prevent heat loss)Passive (prevent heat loss) Active warming: forced air/ heated IV fluidsActive warming: forced air/ heated IV fluids

What you support you must monitorWhat you support you must monitor Ideally monitor core temperature:Ideally monitor core temperature:

Nasopharyngeal/oesophageal/bladder/PV Nasopharyngeal/oesophageal/bladder/PV Better thanBetter than

Skin/axillary/oral/rectalSkin/axillary/oral/rectal

Airway manometryAirway manometry

Usually analogue Usually analogue gauge on circle circuitgauge on circle circuit

Monitors inflation Monitors inflation pressurepressure

With IPPV can help With IPPV can help identify:identify:

Airway obstructionAirway obstruction

BronchospasmBronchospasm

Circuit leaks/faultsCircuit leaks/faults

Ventilator monitorVentilator monitor

Mandatory when Mandatory when mechanical IPPV mechanical IPPV employed.employed.

Usually integrated into Usually integrated into ventilator w/automatic ventilator w/automatic activation.activation.

High (overpressure) & High (overpressure) & low (disconnect) low (disconnect) functionsfunctions

Precordial stethescopePrecordial stethescope

““Traditional” monitorTraditional” monitor Still used in some Still used in some

paediatric casespaediatric cases Can monitors:Can monitors:

Heart & respiratory rateHeart & respiratory rate

Breath sounds presence Breath sounds presence & quality.& quality.

Only as good as the person Only as good as the person listening to it!listening to it!

Direct arterial pressure Direct arterial pressure monitoringmonitoring

Invasive procedure, but:Invasive procedure, but: Gold standard for real Gold standard for real

time haemodynamic time haemodynamic assessmentassessment

Accurate, reliable.Accurate, reliable. Immediate warning of Immediate warning of

hypo/hypertension of hypo/hypertension of any aetiology.any aetiology.

Nerve stimulatorNerve stimulator

Used with muscle relaxants Used with muscle relaxants (neuromuscular blockers):(neuromuscular blockers):

Electrical stimulus to nerve Electrical stimulus to nerve then observation of innervated then observation of innervated muscle.muscle.

Commonest site: Ulnar nerveCommonest site: Ulnar nerve Nondepolarising block Nondepolarising block

characterised by “fade” – characterised by “fade” – weakening of contraction with weakening of contraction with (4) successive impulses “train (4) successive impulses “train of four.”of four.”

Assesses: - Density of blockAssesses: - Density of block- Return of functionReturn of function

- Point of safe reversalPoint of safe reversal

Depth of Anaesthesia Depth of Anaesthesia monitoringmonitoring

Uses simplified EEG recording & algorithm to produce number related to level of conciousness (lower no=deeper anaesthesia)

Two methods: bispectral edge (“BIS”) and entropy.

Role/value still controversial Probably indicated for:

TIVA (as no MAC to monitor)

Patient with a history of awareness

Where lightest possible plane of anesthesia essential

Other monitors Central venous line.Central venous line.

- Mostly used for drug - Mostly used for drug infusions but can also infusions but can also measure CVP as a (not very measure CVP as a (not very accurate) guide to volume accurate) guide to volume status.status.

Pulmonary artery (Swann Pulmonary artery (Swann Ganz) catheterGanz) catheter

- Can estimate LV filling Can estimate LV filling pressure (preload) – a better pressure (preload) – a better guide to functional volume guide to functional volume status than CVPstatus than CVP

- Also can measure cardiac Also can measure cardiac output by thermodilutionoutput by thermodilution..

Trans-Oesphageal Echo-Trans-Oesphageal Echo-cardiography (TOE)cardiography (TOE)Has become the gold standard Has become the gold standard

cardiac function monitor. cardiac function monitor. Able to estimate:Able to estimate:

- Ejection fraction/stroke Ejection fraction/stroke volume/cardiac outputvolume/cardiac output

- LV & RV Preload/pressuresLV & RV Preload/pressures- Diastolic dysfunction (early Diastolic dysfunction (early

index of ischaemia)index of ischaemia) SpirometrySpirometry

Measurement of pressure Measurement of pressure volume loops & hence work volume loops & hence work of breathing in controlled, of breathing in controlled, spont. & ass’t’d ventilationspont. & ass’t’d ventilation

CASE STUDY IIICASE STUDY III

Gynaecological laparoscopyGynaecological laparoscopy

Patient with polycystic ovaries for laparoscopic cystotomies as day case procedure

History 25 year old woman25 year old woman Height 165cm, weight 80kgHeight 165cm, weight 80kg BMI 29.5BMI 29.5 Typical PCOS history/findings.Typical PCOS history/findings. Allergies nilAllergies nil Rx: Metformin 0.5G b.d.Rx: Metformin 0.5G b.d. Previous GA – E/O wisdom teeth – OKPrevious GA – E/O wisdom teeth – OK O/Ex: Overweight, otherwise O/Ex: Overweight, otherwise

unremarkable.unremarkable.

Common lies told by surgeons - Common lies told by surgeons - number 2: “Just a quick number 2: “Just a quick

laparoscopy”!laparoscopy”!

What are the issues and risks here?What are the issues and risks here?

Anaesthetic issues

Medical conditionMedical condition Prolonged surgeryProlonged surgery Laparoscopy/pneumoperitoneumLaparoscopy/pneumoperitoneum TrendellenbergTrendellenberg AnalgesiaAnalgesia PONVPONV

“Quiet victory”

Largely uneventful anaesthesia/surgeryLargely uneventful anaesthesia/surgery Problems maintaining normocarbia without excessive Problems maintaining normocarbia without excessive

airway pressures when head down airway pressures when head down Mild permissive hypercapnoea, corrected at endMild permissive hypercapnoea, corrected at end Polymodal antiemetic therapy – no PONVPolymodal antiemetic therapy – no PONV Comfortable on combined analgesiaComfortable on combined analgesia Home as day case.Home as day case. A typical “straightforward” case that was expected to go A typical “straightforward” case that was expected to go

well - & did - so is not memorable to anyone but the well - & did - so is not memorable to anyone but the anaesthetist who worked hard to make it that way. anaesthetist who worked hard to make it that way.

““There are a million stories in the naked There are a million stories in the naked city, this is one of them.”city, this is one of them.”

- The Naked City, US crime drama series

The practice, safety & reputation of anaesthesia is The practice, safety & reputation of anaesthesia is built on thousands of such cases – far more so built on thousands of such cases – far more so than the glamorous emergency cases & heroic than the glamorous emergency cases & heroic

saves. saves.

Part IV: Anaesthetic Equipment& Airway Management

Introduction to/overview of the Anaesthetic Machine

Consists of three main parts:Consists of three main parts:1.1. ““A cocktail bar”A cocktail bar”

This is the This is the backbarbackbar – which – which blendsblends piped &/or bottle piped &/or bottle gassesgasses: O2, : O2, N2O & air, and the N2O & air, and the vapourvapour of (usually one only) of (usually one only) volatile volatile anaesthetic agentanaesthetic agent (liquid) to produce the desired blend. (liquid) to produce the desired blend.

2.2. ““A delivery service”A delivery service”This is the This is the breathing circuitbreathing circuit – which delivers the fresh gas mixture – which delivers the fresh gas mixture to the patient and removes carbon dioxide. (There are three main to the patient and removes carbon dioxide. (There are three main classes of circuits – discussed later)classes of circuits – discussed later)

n “A bunch of hangers on”These are all the ancillaries attached to the anaesthetic machine but not part of its core function: typically suction system, patient monitors, drawers/trays for airway equipment, and a mechanical ventilator for hands-free controlled ventilation.

A Note of Caution:

Modern anaesthetic machines are complex devices that Modern anaesthetic machines are complex devices that require special knowledge to operate.require special knowledge to operate.

In particular, knowledge of the pharmacology of inhaled In particular, knowledge of the pharmacology of inhaled anaesthetic agents is essential.anaesthetic agents is essential.

Undetected mishaps can be rapidly fatal.Undetected mishaps can be rapidly fatal. A thorough check prior to use, appropriate for the A thorough check prior to use, appropriate for the

particular machine, by an experienced person, is vital.particular machine, by an experienced person, is vital. Some parts of the circuit e.g. filters & hoses, need to be Some parts of the circuit e.g. filters & hoses, need to be

changed after every or certain cases, or a different type of changed after every or certain cases, or a different type of circuit may be selected & attached. An abbreviated re-circuit may be selected & attached. An abbreviated re-check must be carried out after any such change.check must be carried out after any such change.

Anaesthetic CircuitsAnaesthetic CircuitsThree principal types:Three principal types:

1.1. Drawover or “semi-open” systems: where non-rebreathing valves are Drawover or “semi-open” systems: where non-rebreathing valves are used to ensure unidirectional flow of gas. Principally now used in used to ensure unidirectional flow of gas. Principally now used in resuscitation & field anaesthetic systems, because of the ability to use resuscitation & field anaesthetic systems, because of the ability to use ambient air instead of (some or even all) pressurised gas supply.ambient air instead of (some or even all) pressurised gas supply.

2.2. Simple or “semi-closed” systems with pressurised fresh gas inflow, Simple or “semi-closed” systems with pressurised fresh gas inflow, reservoir tube & bag in one of several different configurations. reservoir tube & bag in one of several different configurations. (Sometimes called Maplesen systems, after the man who classified & (Sometimes called Maplesen systems, after the man who classified & evaluated the different configurations). The patient breathes ‘to & fro’ evaluated the different configurations). The patient breathes ‘to & fro’ through the reservoir tube & bag & the system relies on an adequate through the reservoir tube & bag & the system relies on an adequate fresh gas flow to minimise rebreathing. Commonest example: the fresh gas flow to minimise rebreathing. Commonest example: the “Jackson-Rees T-piece (Maplesen “F”)” paediatric circuit“Jackson-Rees T-piece (Maplesen “F”)” paediatric circuit..

3.3. Circle, or closed circuit systems which use one way valves to direct Circle, or closed circuit systems which use one way valves to direct expired gas through a carbon dioxide absorber. This gas can then be expired gas through a carbon dioxide absorber. This gas can then be supplemented with only enough fresh gas mix to replenish the oxygen supplemented with only enough fresh gas mix to replenish the oxygen and anaesthetic agents taken up, and then rebreathed. This is the and anaesthetic agents taken up, and then rebreathed. This is the commonest type of anaesthetic circuit in modern practice.commonest type of anaesthetic circuit in modern practice.

Remember:

The commonest anaesthetic circuit most The commonest anaesthetic circuit most medical & nursing staff will ever use is the medical & nursing staff will ever use is the non-rebreathing resuscitation bag (“Laerdal non-rebreathing resuscitation bag (“Laerdal

bag” or similar) . . . bag” or similar) . . .

. . . to give the commonest anaesthetic and . . . to give the commonest anaesthetic and resuscitation drug of all: resuscitation drug of all: OxygenOxygen

Another rule of three:The triad of resuscitationThe triad of resuscitation

A – AIRWAYA – AIRWAYB – BREATHINGB – BREATHING

C – CIRCULATIONC – CIRCULATION

Or . . . Alternatively:Or . . . Alternatively:

(The triad of resuscitation – my own version)(The triad of resuscitation – my own version)

1.1. Air goes in & outAir goes in & out2.2. Blood goes round & roundBlood goes round & round3.3. Variations on the first two are a Variations on the first two are a BAD THINGBAD THING

Note that Note that airway always comes firstairway always comes first

Airway isn’t everything . . . Airway isn’t everything . . . . . . but without it everything else is nothing.. . . but without it everything else is nothing.

This is why anaesthetists are good people to This is why anaesthetists are good people to have around at a resuscitation – and why a have around at a resuscitation – and why a grounding in anaesthesia is good training grounding in anaesthesia is good training

for emergencies.for emergencies.

Airway Control – Why?Airway Control – Why?

Prevent Prevent obstructionobstructionAnatomical/foreign bodyAnatomical/foreign body

Protect against Protect against aspirationaspirationVomit/blood/secretionsVomit/blood/secretions

Permit controlled Permit controlled ventilationventilationWith paralysis/deep anaesthesiaWith paralysis/deep anaesthesia

Where ventilatory support requiredWhere ventilatory support required Enable Enable special manoeuvresspecial manoeuvres

e.g IPPV & PEEP for thoracotomy, laryngeal surgery e.g IPPV & PEEP for thoracotomy, laryngeal surgery with microlaryngeal tube, single lung deflation with with microlaryngeal tube, single lung deflation with double lumen ET tube.double lumen ET tube.

Classification of airwaysClassification of airways

SUPRAGLOTTIC TRANSGLOTTIC SUBGLOTTIC

Oropharyngeal airway

Orotracheal tube Cricothyrotomy

Nasopharyngeal airway

Nasotracheal tube Transtracheal jet catheter

Laryngeal Mask Airways (various)

Intubating LMA (w/ETT placed thru it)

Tracheostomy

Combitube/PTL * (85% of placements oesophageal)

(Combitube/PTL) - if one of the 15% placed tracheally

The winner, and still champion:

Endotracheal intubation Endotracheal intubation (usually oral), remains the (usually oral), remains the gold standard for airway gold standard for airway management, . . . but . . . management, . . . but . . .

It is also the most difficult to It is also the most difficult to master and carries the master and carries the highest risk. highest risk.

Remember: An unrecognised Remember: An unrecognised oesophageal intubation has a oesophageal intubation has a

100% mortality100% mortality

Emergency Airway ManagementEmergency Airway Management(in anaesthesia (in anaesthesia && resuscitation) resuscitation)

Rapid sequence Rapid sequence intubation intubation

[or unmodified (“cold”) [or unmodified (“cold”) intubation if apnoeic & intubation if apnoeic &

arreflexic]arreflexic]

Other techniques:Other techniques:

Fibreoptic intubationFibreoptic intubation

Supraglottic airwaySupraglottic airway

Surgical airwaySurgical airway

>90%>90% <10%<10%

Rapid Sequence Intubation:How to do it properly

PreoxygenationPreoxygenation: 3mins or 5 VC breaths.: 3mins or 5 VC breaths. IV induction agent – titrated to effectIV induction agent – titrated to effect Cricoid pressureCricoid pressure – 30N. – 30N. SuxamethoniumSuxamethonium 1.5mg/kg (IBW). 1.5mg/kg (IBW).

or Modified RSI: 0.9mg/kg rocuroniumor Modified RSI: 0.9mg/kg rocuronium NoNo bag mask ventilation (unless hypoxic) bag mask ventilation (unless hypoxic) Intubation & Intubation & confirmation of placementconfirmation of placement (then & (then & onlyonly then) Cricoid pressure released. then) Cricoid pressure released.

Remember (1) : Remember (1) : everyevery intubation attempt is a intubation attempt is a potential failed intubation.potential failed intubation.

You should always have a backup plan You should always have a backup plan

- i.e. a failed intubation drill.- i.e. a failed intubation drill. Backup begins even before you start - Backup begins even before you start - with with

preoxygenation for every IV inductionpreoxygenation for every IV induction

Remember (2): People don’t die of failure to Remember (2): People don’t die of failure to intubate, but of intubate, but of failure to oxygenatefailure to oxygenate

Supraglottic rescue Supraglottic rescue airway e.g. LMA airway e.g. LMA

SUCCESSFUL?SUCCESSFUL?

Subglottic (surgical) Subglottic (surgical) airwayairway

1.1. Bag mask ventilationBag mask ventilation

2.2. Repeat attempt &/or Repeat attempt &/or alternate technique to alternate technique to intubateintubate

SUCCESSFUL?SUCCESSFUL?

FIRSTLY FIRSTLY MAINTAIN MAINTAIN OXYGENATION!OXYGENATION!

FAILED INTUBATION DRILLFAILED INTUBATION DRILL

CAN YOU MASK VENTILATE? [With Geudels &/or

nasopharyngeal airway if necessary]

NO

NO

YESYES

NO

Non endotracheal airways

There’s more to anaesthetic airways than just ET tubes!There’s more to anaesthetic airways than just ET tubes!

Laryngeal masks (of various types) are the most widely Laryngeal masks (of various types) are the most widely used airways in modern anaesthetic practice:used airways in modern anaesthetic practice:

ClassicClassic (original) & its various copies – reuseable or (original) & its various copies – reuseable or single use.single use.

ReinforcedReinforced – kink resistant & more flexible upper lumen – kink resistant & more flexible upper lumen to permit alternative positioning after insertion for to permit alternative positioning after insertion for oral/facial procedures.oral/facial procedures.

ProsealProseal - second lumen to communicate with oesophagus - second lumen to communicate with oesophagus & allow drainage of gastric contents or placement of & allow drainage of gastric contents or placement of gastric tube.gastric tube.

IntubatingIntubating – modified shape, more rigid, & lacking – modified shape, more rigid, & lacking apeture bars – to enable passage of a special ET tube apeture bars – to enable passage of a special ET tube through itthrough it..

Non endotracheal airways II

Advantages of laryngeal masks:Advantages of laryngeal masks:

Hands free (compared to face Hands free (compared to face mask/oral airway)mask/oral airway)

Easier to insert & become Easier to insert & become proficient at compared to ETTproficient at compared to ETT

Tolerated at lighter plane of Tolerated at lighter plane of anaesthesia than ETT.anaesthesia than ETT.

Good protection against “top” Good protection against “top” aspiration - of saliva/mucus.aspiration - of saliva/mucus.

Pressure support & in some Pressure support & in some cases IPPV can be given.cases IPPV can be given.

Disadvantages of laryngeal masksDisadvantages of laryngeal masks

Less secure airway - more prone to Less secure airway - more prone to dislodgement than ETTdislodgement than ETT

No protection against No protection against laryngospasmlaryngospasm

Poor protection against “bottom” Poor protection against “bottom” aspiration – of gastric contents aspiration – of gastric contents (Except “Proseal”)(Except “Proseal”)

Not guaranteed to permit Not guaranteed to permit satisfactory IPPV – especially satisfactory IPPV – especially where high pressures required.where high pressures required.

Remember, the traditional facemask/chin lift +/- Geudel’s airway is still an acceptable – possibly even underutilised – technique for short simple cases.

Part V: Anaesthetic Drugs: Pharmacology, Use &

Related Issues

Classification of drugs used for anaesthesia

““The Big Five “The Big Five “ Inhalation anaesthetic agentsInhalation anaesthetic agents – gasses/vapours – gasses/vapours IV anaesthetic agentsIV anaesthetic agents alias “Hypnotics” or “induction alias “Hypnotics” or “induction

agents”agents” Narcotic (& other) analgesicsNarcotic (& other) analgesics Muscle relaxantsMuscle relaxants – neuromuscular blocking agents – neuromuscular blocking agents Local anaesthetic agentsLocal anaesthetic agents

Other agents are often given as part of anaesthesia – e.g. Other agents are often given as part of anaesthesia – e.g. antiemetics & autonomic agents, but are not antiemetics & autonomic agents, but are not

conventionally regarded as anaesthetic agents conventionally regarded as anaesthetic agents per seper se..

Pharmacology 1:Inhalational Anaesthetic AgentsInhalational Anaesthetic Agents

Inhaled – therefore delivered via apparatusInhaled – therefore delivered via apparatus Gasses or volatile liquidsGasses or volatile liquids Moderate to high lipid solubility – “solvents”Moderate to high lipid solubility – “solvents” Effects related to physical properties Effects related to physical properties

(rather than to a generic chemical structure)(rather than to a generic chemical structure) Effects on multiple organ systemsEffects on multiple organ systems Actual mode of action not yet fully elucidated, but Actual mode of action not yet fully elucidated, but

thought to be by dissolving into cell membranes & thought to be by dissolving into cell membranes & causing secondary changes in configuration of ion causing secondary changes in configuration of ion channels. channels.

Nitrous oxideNitrous oxide ( (N20N20)– a gas. )– a gas. Insufficiently potentInsufficiently potent to produce full anaesthesia on its own, but is rapid to produce full anaesthesia on its own, but is rapid acting, pleasant to inhale & is the acting, pleasant to inhale & is the only currently only currently used agent that is also analgesicused agent that is also analgesic..

SevofluraneSevoflurane DesfluraneDesflurane all liquids that are flourinated ethers all liquids that are flourinated ethers IsofluraneIsoflurane

Earlier volatile agents such asEarlier volatile agents such as etherether, , chloroformchloroform && halothanehalothane have been superceded due to issues such have been superceded due to issues such as flammability, slow recovery, & toxicity.as flammability, slow recovery, & toxicity.

Currently Used Inhalational Anaesthetics (shown in their international colour codes):

Practical Pharmacology of Practical Pharmacology of Inhalational AgentsInhalational Agents

Used for induction sometimes (predominantly in children) & Used for induction sometimes (predominantly in children) & maintenance of anaesthesia in the majority of cases - either maintenance of anaesthesia in the majority of cases - either alone, or in combination with narcotics & muscle relaxants.alone, or in combination with narcotics & muscle relaxants.

Modern flourinated agents are good hypnotics, & provide a Modern flourinated agents are good hypnotics, & provide a degree of muscle relaxation at high doses, but not analgesia.degree of muscle relaxation at high doses, but not analgesia.

In contrast, nitrous oxide is analgesic, but doesn’t decrease In contrast, nitrous oxide is analgesic, but doesn’t decrease muscle tone, and is a poor hypnotic except at very high (i.e. muscle tone, and is a poor hypnotic except at very high (i.e. hypoxic) concentrations.hypoxic) concentrations.

The combination of a volatile agent, e.g. sevoflurane, with a The combination of a volatile agent, e.g. sevoflurane, with a 50:50 nitrous oxide/oxygen mix is a useful combination that 50:50 nitrous oxide/oxygen mix is a useful combination that combines the attributes of both agents.combines the attributes of both agents.

Practical Pharmacology of Practical Pharmacology of Inhalational Agents (2)Inhalational Agents (2)

SevofluraneSevoflurane has superceded has superceded isofluraneisoflurane as probably the most as probably the most widely used agent, & has also superceded widely used agent, & has also superceded halothanehalothane as the as the agent of choice for inhalational induction in children.agent of choice for inhalational induction in children.

All currently used agents have relatively low solubility in All currently used agents have relatively low solubility in blood & tissue – meaning that their partial pressures rise & blood & tissue – meaning that their partial pressures rise & fall quickly, producing more rapid induction & emergence.fall quickly, producing more rapid induction & emergence.

The classical stages of anaesthesia are still seen with The classical stages of anaesthesia are still seen with modern agents – including the delerium phase – modern agents – including the delerium phase – characterised by restlessness & risk of laryngospasm. This characterised by restlessness & risk of laryngospasm. This stage is usually seen on emergence, or with inhalational stage is usually seen on emergence, or with inhalational inductions in children.inductions in children.

Practical Pharmacology of Practical Pharmacology of Inhalational Agents (3)Inhalational Agents (3)

Nitrous oxide, as a gas is delivered by a flowmeter (as are O2 Nitrous oxide, as a gas is delivered by a flowmeter (as are O2 & air – the 3 flowmeters on a typical modern anaesthetic & air – the 3 flowmeters on a typical modern anaesthetic machine). A linkage between the N20 & oxygen flowmeters machine). A linkage between the N20 & oxygen flowmeters stops the delivery of any mixture <25%O2. Most anaesthetic stops the delivery of any mixture <25%O2. Most anaesthetic machines also only allow delivery of either N20/O2 or air/O2, machines also only allow delivery of either N20/O2 or air/O2, not all 3 & none allow air/N2O (a hypoxic mixture).not all 3 & none allow air/N2O (a hypoxic mixture).

Volatile agents are delivered by vapourisers – devices which Volatile agents are delivered by vapourisers – devices which add a precise percentage of vapour to the gas mixture. Modern add a precise percentage of vapour to the gas mixture. Modern vapourisers are agent specific and colour coded/labelled vapourisers are agent specific and colour coded/labelled accordingly. They have numerous mechanisms to ensure accordingly. They have numerous mechanisms to ensure accurate delivery, plus safety measures such as “keyed” filling accurate delivery, plus safety measures such as “keyed” filling systems that match only the correct bottle; and machines that systems that match only the correct bottle; and machines that can have more than one vapouriser fitted must have interlocks can have more than one vapouriser fitted must have interlocks that prevent more than one being turned on. that prevent more than one being turned on.

Pharmacology 2: IV anaesthetic “induction” agentsIV anaesthetic “induction” agents

Used for:Used for:

Induction of anaesthesiaInduction of anaesthesia

Sole agent for brief proceduresSole agent for brief procedures

By infusion for longer procedures - in place of By infusion for longer procedures - in place of inhaled agents – i.e. total intravenous anaaesthesia inhaled agents – i.e. total intravenous anaaesthesia “TIVA”“TIVA”

Classification of intravenous agentsClassification of intravenous agents

Barbiturates – ThiopentoneBarbiturates – Thiopentone Benzodiazepines – MidazolamBenzodiazepines – Midazolam Dissociative agents – KetamineDissociative agents – Ketamine Others- PropofolOthers- Propofol

+ Alpha-2 agonists – Dexmetomidine . . . + Alpha-2 agonists – Dexmetomidine . . . maybe “the next big thing”maybe “the next big thing”

General features of IV agents

Lipid solubleLipid soluble High volume of distribution (Vd)High volume of distribution (Vd) Initial distribution to VRGInitial distribution to VRG Offset of (initial) effect predominantly Offset of (initial) effect predominantly

by redistributionby redistribution More complex when used as infusionsMore complex when used as infusions

(Computerised multicompartment (Computerised multicompartment pharmacokinetic modelling required)pharmacokinetic modelling required)

Propofol

Most widely used agent nowMost widely used agent now Rapid(ish) onset & offsetRapid(ish) onset & offset Shorter elimination halftimeShorter elimination halftime Less CVS & respiratory depressionLess CVS & respiratory depression Doesn’t predispose to laryngospasmDoesn’t predispose to laryngospasm ED50 for induction: ED50 for induction: ~ 2 mg/kg~ 2 mg/kg Suitable kinetics for infusionSuitable kinetics for infusion

Other IV agentsTHIOPENTONETHIOPENTONE

First widely used agentFirst widely used agent Rapid onset & initial offset Rapid onset & initial offset

by redistribution by redistribution Long elimination halftimeLong elimination halftime CVS & resp depressantCVS & resp depressant LaryngospasmogenicLaryngospasmogenic ED50: ED50: ~ 5mg/kg~ 5mg/kg Still used for RSIStill used for RSI““The correct dose of thiopentone is The correct dose of thiopentone is

enoughenough” (and no more!!)” (and no more!!)

MIDAZOLAMMIDAZOLAM Low CVS & resp depressantLow CVS & resp depressant Anxiolytic, good initial Anxiolytic, good initial

adjuvant agent, not often used adjuvant agent, not often used as sole agentas sole agent

KETAMINEKETAMINE ““Dissociative” agentDissociative” agent Phencyclidine derivativePhencyclidine derivative Cardiorespiratory Cardiorespiratory stimulantstimulant (in (in

vivo)vivo) Maintains airway reflexesMaintains airway reflexes Analgesic in subanaesthetic Analgesic in subanaesthetic

dosesdoses““The disaster anaesthetic”The disaster anaesthetic”

Total intravenous anaesthesiaTotal intravenous anaesthesia“TIVA”“TIVA”

Not practical until introduction of propofol , with Not practical until introduction of propofol , with its short elimination half life, meaning minimal its short elimination half life, meaning minimal accumulation with infusion.accumulation with infusion.

Usually target controlled infusion using Usually target controlled infusion using computerised algorithm in syringe pump software. computerised algorithm in syringe pump software. Operator enters patient weight, age, & desired Operator enters patient weight, age, & desired blood level.blood level.

Often used in combo with remifentanil & Often used in combo with remifentanil & cisatracurium infusions for long cases (these also cisatracurium infusions for long cases (these also have good kinetics for use by infusion). have good kinetics for use by infusion).

TIVA –good & bad

AdvantagesAdvantages Good for cases of long Good for cases of long

or uncertain durationor uncertain duration Less effects on CBF & Less effects on CBF &

ICP than volatile ICP than volatile agentsagents

Less likely to cause Less likely to cause PONV then either PONV then either volatiles or N2O.volatiles or N2O.

DisadvantagesDisadvantages Long setup timeLong setup time More expensiveMore expensive Multiple syringe Multiple syringe

pumps requiredpumps required No direct measure of No direct measure of

blood or effect site blood or effect site concentration concentration

Pharmacology 3: Narcotic Analgesics Narcotic Analgesics

& Acute Pain Management& Acute Pain Management

A Definition of Pain:A Definition of Pain:

““An unpleasant localised sensory experience An unpleasant localised sensory experience perceived as actual or potential tissue damage.”perceived as actual or potential tissue damage.”

May be acute or chronicMay be acute or chronic

Classification of AnalgesicsClassification of Analgesics

Conduction blockadeConduction blockade OpiodsOpiods ParacetamolParacetamol NSAIDs & COX2sNSAIDs & COX2s Miscellaneous agentsMiscellaneous agents Complementary/Non pharmacologicalComplementary/Non pharmacological

An An opiodopiod is a drug that exhibits agonist activity at is a drug that exhibits agonist activity at opiate (endorphin/enkephalin) receptorsopiate (endorphin/enkephalin) receptors. A . A classification of opiods includes:classification of opiods includes:

Opiates Opiates (naturally occuring constituents of opium) (naturally occuring constituents of opium) & their derivatives:& their derivatives:

e.g. morphine, codeine, diamorphine (heroin)e.g. morphine, codeine, diamorphine (heroin) Synthetic opiodsSynthetic opiods

e.g. pethidine, fentanyl cogeners, oxycodonee.g. pethidine, fentanyl cogeners, oxycodone Partial agonistsPartial agonists

e.g. pentazocine e.g. pentazocine “Fortral”, “Fortral”, buprenorphinebuprenorphineN.B. This classification does not include the narcotic

antagonists e.g. naloxone “Narcan” & naltrexone; however these are closely related, being n-allyl substituted derivatives (hence their names)of opiods

Properties of opiodsProperties of opiods

AnalgesiaAnalgesiaSpinal ( Spinal ( μ/κ) μ/κ) & supraspinal (& supraspinal (μ)μ)

Respiratory depressionRespiratory depression Sedation/euphoria (addiction potential)Sedation/euphoria (addiction potential) EmesisEmesis Depression of GI motilityDepression of GI motility PruritisPruritis Urinary retentionUrinary retention

No difference in respiratory depression between No difference in respiratory depression between equi-analgesic doses of any narcotic agonistsequi-analgesic doses of any narcotic agonists

}} Neuraxial route Neuraxial route predominantlypredominantly

So the differences between opiods are So the differences between opiods are less in their analgesic efficacy than in:less in their analgesic efficacy than in:

OnsetOnset DurationDuration Potency/dosePotency/dose Histamine releaseHistamine release Autonomic effectsAutonomic effects Chest wall rigidityChest wall rigidity Effective routes of administrationEffective routes of administration

Routes of administration of opiods:Routes of administration of opiods: Intravenous: Intravenous: (a) (a) Boluses Boluses – titrated to effect – e.g recovery pain protocol – titrated to effect – e.g recovery pain protocol

(b)(b) Infusions Infusions – require close monitoring due to potential for overdose – require close monitoring due to potential for overdose as narcotic requirements fall away.as narcotic requirements fall away.

(c) (c) PCA PCA – now widely used. Intrinsically safer than infusions, plus – now widely used. Intrinsically safer than infusions, plus positive psychological effect of patient knowing they are in control. positive psychological effect of patient knowing they are in control.

Neuraxial - Neuraxial - Epidural or intrathecal (spinal) – usually in combination Epidural or intrathecal (spinal) – usually in combination with regional anaesthesia, but may also be stand alone technique for with regional anaesthesia, but may also be stand alone technique for postoperative analgesia. Risk of late onset respiratory depression if agent postoperative analgesia. Risk of late onset respiratory depression if agent migrates into intracranial CSF in significant amount (highest with migrates into intracranial CSF in significant amount (highest with morphine, but this is also the longest acting)morphine, but this is also the longest acting)

IM/SC – decreasing importance with availability of PCA & better oral IM/SC – decreasing importance with availability of PCA & better oral agents, & multimodal therapy.agents, & multimodal therapy.

Oral – variable bioavailability: e.g. oxycodone high, morphine ~ 15% Oral – variable bioavailability: e.g. oxycodone high, morphine ~ 15% due to first pass metabolism.due to first pass metabolism.

Sublingual(buprenorphine) /Intranasal(fentanyl) – lipid soluble agents Sublingual(buprenorphine) /Intranasal(fentanyl) – lipid soluble agents fairly rapidly absorbed & this route avoids first pass effect (& injection)fairly rapidly absorbed & this route avoids first pass effect (& injection)

Transcutaneous – e.g. fentanyl patches for chronic painTranscutaneous – e.g. fentanyl patches for chronic pain

Problems with opiodsProblems with opiods

Respiratory depression/cough suppressionRespiratory depression/cough suppression ToleranceTolerance Abuse/addiction potentialAbuse/addiction potential Accountability/access/supply difficultiesAccountability/access/supply difficulties

- consequent to abuse potential.- consequent to abuse potential. Nausea & vomitingNausea & vomiting ConstipationConstipation

Multimodal analgesia optionsMultimodal analgesia options

Regional/local blockade (if possible)Regional/local blockade (if possible) ParacetamolParacetamol NSAID or COX2NSAID or COX2 Basal opiod (e.g. oxycontin); or tramadol Basal opiod (e.g. oxycontin); or tramadol

(or both)(or both) prn or PCA opiodprn or PCA opiod OtherOther

Clonidine or ketamineClonidine or ketamine

Pharmacology 4:Neuromuscular blockers

Purely paralysing agents – no analgesic or hypnotic Purely paralysing agents – no analgesic or hypnotic activity.activity.

Two types based on modes of action:Two types based on modes of action:Depolarising (Suxamethonium)Depolarising (Suxamethonium)

VersusVersusNondepolarising Nondepolarising

((NDNMBsNDNMBs, several available), several available)

Why use paralysing drugs at all?

Permit procedures at a lighter plane of Permit procedures at a lighter plane of anaesthesia – hence less CVS depressionanaesthesia – hence less CVS depression Intubation & ventilationIntubation & ventilation SurgerySurgery

Permit IPPV without interference Permit IPPV without interference Lower airway pressures by increasing chest Lower airway pressures by increasing chest

wall compliance.wall compliance. Lower O2 consumption in critical periodsLower O2 consumption in critical periods

Properties of NMBDs

Highly polar moleculesHighly polar molecules Low VLow VDD ( ( ~~ ECF volume) ECF volume) Do not cross BBB/placentaDo not cross BBB/placenta Renally excreted (with exceptions)Renally excreted (with exceptions) Range of actions at other ACh receptorsRange of actions at other ACh receptors Histamine releasers (most)Histamine releasers (most) Decrease VDecrease VO2O2 /ATP & heat production /ATP & heat production

“Sux” versus the NDNMBDs

SuxamethoniumSuxamethonium Rapid onset (30s)Rapid onset (30s) FasciculationsFasciculations Transient rise in ICP, IOP, Transient rise in ICP, IOP,

IAP/IGP, K+.IAP/IGP, K+. Rapid offset (usually) Rapid offset (usually)

by hydrolysis in plasmaby hydrolysis in plasma Unpredictable effects in Unpredictable effects in

repeat dosingrepeat dosing

NondepolarisersNondepolarisers Slower onset (3-7m)Slower onset (3-7m) No fasciculationsNo fasciculations Little to no effect on Little to no effect on

ICP, etc.ICP, etc. Varying durations Varying durations

with different drugswith different drugs OK for prolonged use OK for prolonged use

by boluses or infusionby boluses or infusion

Nondepolarising relaxantsFirst generationFirst generation

Curare/tubocurarineCurare/tubocurarine AlcuroniumAlcuronium MetocurineMetocurine GallamineGallamine PancuroniumPancuronium

““Modern” agentsModern” agents VecuroniumVecuronium AtracuriumAtracurium ciscisAtracuriumAtracurium RocuroniumRocuronium MivacuriumMivacurium

Brown = curare derivativesBrown = curare derivatives

Blue = aminosteroids (the “Blue = aminosteroids (the “oniumsoniums”)”)

Green = benzisoquinolines (the “Green = benzisoquinolines (the “uriumsuriums”)”)

Side effects of suxamethonium

MyalgiaMyalgia MH triggerMH trigger Masseter spasmMasseter spasm Phase II blockPhase II block Raises ICPRaises ICP Raises IOPRaises IOP BradycardiaBradycardia

(Usually in infants (Usually in infants or with 2or with 2ndnd dose) dose)

Raises serum K+Raises serum K+ Exaggerated action & Exaggerated action &

K+ rise in denervation, K+ rise in denervation, burns, muscle injury burns, muscle injury

Prolonged action with Prolonged action with pseudochlinesterase pseudochlinesterase variants/deficiency.variants/deficiency.

Histamine releaseHistamine release Anaphylaxis (1:5000)Anaphylaxis (1:5000)

Problems with nondepolarisers

Slow onset – not usually a major problem Slow onset – not usually a major problem Slow offset (situation/agent dependant)Slow offset (situation/agent dependant) AwarenessAwareness Hypothermia –reduced heat productionHypothermia –reduced heat production Autonomic side effectsAutonomic side effects InteractionsInteractions Failure to reverse/recurarisationFailure to reverse/recurarisation

Paralysis obviously mandates controlled ventilation

Modern anaesthetic machines are all equipped Modern anaesthetic machines are all equipped with ventilators.with ventilators.

Usual mode is volume controlled (delivers a set Usual mode is volume controlled (delivers a set size of breath, a set number of times a minute) size of breath, a set number of times a minute) with or without PEEP.with or without PEEP.

Most can also give, or be adapted to give, pressure Most can also give, or be adapted to give, pressure controlled ventilation, which is the mode of choice controlled ventilation, which is the mode of choice for paediatric patients (who usually have uncuffed for paediatric patients (who usually have uncuffed tubes, and hence a small leak).tubes, and hence a small leak).

The Physiology of Controlled Ventilation

““Spontaneous ventilation sucks; Controlled ventilation blows”Spontaneous ventilation sucks; Controlled ventilation blows”

Maintains constant minute volume & enables titration to Maintains constant minute volume & enables titration to desired pCO2 desired pCO2 – vital in neurosurgery & acidotic patients.– vital in neurosurgery & acidotic patients.

Uptake of volatile agents therefore usually higher than in Uptake of volatile agents therefore usually higher than in spontaneously breathing patient -> more CVS depression.spontaneously breathing patient -> more CVS depression.

Recruits alveoli & prevents collapse: minimises shunt.Recruits alveoli & prevents collapse: minimises shunt. Raises mean intrathoracic pressure – & hence RAP, so Raises mean intrathoracic pressure – & hence RAP, so

reduces venous return & cardiac output reduces venous return & cardiac output – especially in head up – especially in head up position & with pneumoperitoneum – e.g. laparoscopic cholecystectomy.position & with pneumoperitoneum – e.g. laparoscopic cholecystectomy.

Risk of barotrauma – esp. w/high tidal volume or pressures.Risk of barotrauma – esp. w/high tidal volume or pressures.

Pharmacology 5:Local anaesthetic agents

Local anaesthetics are membrane stabilisers that block Local anaesthetics are membrane stabilisers that block depolarisation in nervesdepolarisation in nerves

Non specific blockers of:Non specific blockers of: All sensory fibres (not just pain) All sensory fibres (not just pain) Motor fibresMotor fibres Autonomic fibres (mainly sympathetics in most blocks)Autonomic fibres (mainly sympathetics in most blocks)

Hence can produce analgesia & arreflexia in the distribution of Hence can produce analgesia & arreflexia in the distribution of the nerves blocked.the nerves blocked.

Lower concentrations of LA agents effect predominantly Lower concentrations of LA agents effect predominantly smaller axons: pain (Asmaller axons: pain (Aδ & C fibres), temperature, & autonomic δ & C fibres), temperature, & autonomic (unmyelinated sympthetic post-ganglionic(unmyelinated sympthetic post-ganglionic fibres) fibres)

““Your friendly local anaesthetic molecule”Your friendly local anaesthetic molecule”Think of a person standing in the water Think of a person standing in the water

– keeping their head high & dry– keeping their head high & dry

Head: benzene ring Head: benzene ring ((lipophiliclipophilic))

Body: (intermediate chain) Body: (intermediate chain) with either with either esterester or or amideamide link.link.

Tail: (feet) – Tail: (feet) – hydrophilichydrophilic due due to tertiary nitrogen capable to tertiary nitrogen capable of accepting proton & of accepting proton & rendering molecule water rendering molecule water soluble. (This is the form it soluble. (This is the form it is in in the ampoule)is in in the ampoule)

NNH+

A-A-

NN NN

ECFECF

NNH+

ICFICF

““The voyage of the molecule Lignocaine”The voyage of the molecule Lignocaine”

Cl-Cl-NN

H+

Lignocaine Lignocaine hydrochloride injectedhydrochloride injected

HCO3-

H2O + CO2

Tissue Tissue bufferingbuffering

Freebase lignocaine diffuses across cell membrane

H+

Lower Lower intra-intra-cellular pH cellular pH leads to re-leads to re-ionizationionization

Sodium channel

Understand this, and you will know:Understand this, and you will know:

Why local anaesthetics sting on injectionWhy local anaesthetics sting on injection(because of the low pH needed to maintain ionised state)(because of the low pH needed to maintain ionised state)

Why their onset of action is not immediateWhy their onset of action is not immediate(because of the buffering/diffusion/reionisation steps)(because of the buffering/diffusion/reionisation steps)

Why local anesthesia is poorly effective in inflamed/ infected Why local anesthesia is poorly effective in inflamed/ infected tissuetissue (because of the lack of buffering capability in acidotic tissue)(because of the lack of buffering capability in acidotic tissue)

Why LAs exhibit tachyphylaxisWhy LAs exhibit tachyphylaxis (exhaustion of buffering capability)(exhaustion of buffering capability)

(& why cocaine users end up needing nose reconstructions – (& why cocaine users end up needing nose reconstructions – from repeated insult to the nasal septum from an acid from repeated insult to the nasal septum from an acid

substance that is also a vasoconstrictor - which inhibits substance that is also a vasoconstrictor - which inhibits circulatory dilution of the acid load)circulatory dilution of the acid load)

Local Anaesthetic AgentsLocal Anaesthetic Agents

AGENTAGENT

Lignocaine Lignocaine (“(“XylocaineXylocaine”)”)

Bupivicaine Bupivicaine (“(“MarcainMarcain”)”)

Ropivicaine (“Ropivicaine (“NaropinNaropin”)”)

Levobupivicaine (“Chirocaine”)Levobupivicaine (“Chirocaine”)

Prilocaine (Citanest”)Prilocaine (Citanest”)

Max dose:Max dose:

Plain (+Adr)Plain (+Adr)

4 (7) mg/kg4 (7) mg/kg

2 mg/kg2 mg/kg

3-4mg/kg3-4mg/kg

4 mg/kg4 mg/kg

7(9) mg/kg7(9) mg/kg

Local Anaesthetic ProblemsLocal Anaesthetic Problems

Failed block - multiple causesFailed block - multiple causes High block (spinals/epidurals)High block (spinals/epidurals) CNS toxicity CNS toxicity

at high dose or with inadvertent IV injectionat high dose or with inadvertent IV injection Selective cardiotoxicity Selective cardiotoxicity (bupivicaine)(bupivicaine)

Needle/injection traumaNeedle/injection trauma Nerve damageNerve damage Other – e.g pneumothoraxOther – e.g pneumothorax

Adjuvant agents used with LAs

Adrenaline – Adrenaline – prolongs blockade, allows increased dose prolongs blockade, allows increased dose (lignocaine/prilocaine)(lignocaine/prilocaine)

Bicarbonate – Bicarbonate – Decreases acidity - speeds onset of blockDecreases acidity - speeds onset of block

Hyaluronidase –Hyaluronidase –Aids diffusion Aids diffusion ((Eye & brachial plexus Eye & brachial plexus blocks) blocks)

Glucose Glucose (spinals) – to produce hyperbaric solutions(spinals) – to produce hyperbaric solutions

Narcotics Narcotics (neuraxial) – synergistic analgesia(neuraxial) – synergistic analgesia

Other analgesics Other analgesics – – e.g clonidine in neuraxial blocks.e.g clonidine in neuraxial blocks.

Modes of Local Anaesthesia

(a) Peripheral(a) Peripheral SurfaceSurface

Topical (incl EMLA)Topical (incl EMLA) NebulisedNebulised Intrapleural/peritonealIntrapleural/peritoneal

InfitrationInfitration Intravenous regionalIntravenous regional Nerve/plexus blocksNerve/plexus blocks

Multiple typesMultiple types

(b) Neuraxial(b) Neuraxial Epi(extra)duralEpi(extra)dural

Single shot vs catheterSingle shot vs catheter Bolus vs infusionBolus vs infusion LA only vs combinationsLA only vs combinations Includes caudal blocksIncludes caudal blocks

Spinal/subarachnoidSpinal/subarachnoid Usually single shotUsually single shot LA only or LA/narcoticLA only or LA/narcotic

Combination (CSE)Combination (CSE)

Some common nerve/plexus blocks

Eye blocks:Eye blocks:

Peribulbar, retrobulbar, Peribulbar, retrobulbar, Sub-TenonsSub-Tenons

Superficial cervical plexus Superficial cervical plexus block block

Brachial plexus blocks:Brachial plexus blocks:

Axillary, supraclavicular, Axillary, supraclavicular, interscaleneinterscalene

Paravertebral blocksParavertebral blocks

Intercostal blocksIntercostal blocks Ilio-inguinal blockIlio-inguinal block Dorsal penile nerve Dorsal penile nerve

blockblock Pudendal nerve blockPudendal nerve block Femoral (+/- LCNT) Femoral (+/- LCNT)

blockblock Ankle blocksAnkle blocks

Spinal AnaesthesiaSpinal Anaesthesia

Relatively quick, defined end-point for placementRelatively quick, defined end-point for placement Small volume of LASmall volume of LA Usually single shot – “fire & forget”Usually single shot – “fire & forget” Block level depends on spread – varies with:Block level depends on spread – varies with:

VolumeVolume Speed of injectionSpeed of injection BaricityBaricity

Minimal respiratory effects – unless high blockMinimal respiratory effects – unless high block Autonomic effects: - Vasodilatation @ T12 & upAutonomic effects: - Vasodilatation @ T12 & up

- Bradycardia @ T4 & up- Bradycardia @ T4 & up

Epidural AnaesthesiaEpidural Anaesthesia

Alone, or with GA, or as CSE.Alone, or with GA, or as CSE. Cervical (rare), thoracic, lumbar, caudalCervical (rare), thoracic, lumbar, caudal Usually catheter placement (except caudal)Usually catheter placement (except caudal) High volumes LA +/- adjuvants.High volumes LA +/- adjuvants. ““Band” phenomenon.Band” phenomenon. Autonomic effects similar to spinal, but Autonomic effects similar to spinal, but

slower onsetslower onset

Considerations in regional blockade

Consent/communicationConsent/communication IV accessIV access Adjuvant sedation/analgesiaAdjuvant sedation/analgesia Time involvedTime involved Failed block/backup planFailed block/backup plan Management of side effects/reactionsManagement of side effects/reactions

Part VI: Sub-Specialty Anaesthesia

INCLUDES:INCLUDES:

1.1. Paediatrics Paediatrics

2.2. ObstetricsObstetrics

3.3. CardiothoracicCardiothoracic

4.4. ENTENT//Head & neckHead & neck

5.5. NeurosurgeryNeurosurgery

Subspecialty Anaesthetics A: Paediatric

““They’re not just small adults”They’re not just small adults”

. . . But . . .. . . But . . .

““Nor are they all just big neonates, eitherNor are they all just big neonates, either””

Case Study IV

Paediatric Hypospadias RepairPaediatric Hypospadias Repair

History

4 year old boy (obviously!)4 year old boy (obviously!) Grade III hypospadias & chordeeGrade III hypospadias & chordee For EUA/repairFor EUA/repair Background: Mild asthma & ADHDBackground: Mild asthma & ADHD

Issues

Preop assessment & stabilisationPreop assessment & stabilisation PremedicationPremedication Induction & IV insertionInduction & IV insertion Prolonged surgeryProlonged surgery Postoperative analgesiaPostoperative analgesia Postoperative IV & IUDCPostoperative IV & IUDC

Adult-Paediatric Differences

PsychosocialPsychosocial CNSCNS RespiratoryRespiratory

AirwayAirway OtherOther

CardiovascularCardiovascular Renal/fluidsRenal/fluids

GastrointestinalGastrointestinal Hepatic/metabolicHepatic/metabolic EndocrineEndocrine HaematologicalHaematological ImmunologicalImmunological MusculoskeletalMusculoskeletal IntegumentIntegument

The Psychosocial Dimension

There are (almost) always two patients – child and parent(s). There are (almost) always two patients – child and parent(s). If you don’t keep the parents happy, or at least reassured, the If you don’t keep the parents happy, or at least reassured, the child won’t be either – no matter how good the anaesthetic.child won’t be either – no matter how good the anaesthetic.

Children don’t understand that you are there to help – only Children don’t understand that you are there to help – only that you are a stranger.that you are a stranger.

Children hate needles. Parents hate their children having Children hate needles. Parents hate their children having needles. Even without this, cannulation can be difficult. needles. Even without this, cannulation can be difficult. Anything that ameliorates this is good: such as premedication, Anything that ameliorates this is good: such as premedication, EMLA to cannula sites & inhalational inductions.EMLA to cannula sites & inhalational inductions.

Parental presence at induction can be a good idea – as long as Parental presence at induction can be a good idea – as long as the parent is going to cope. If in doubt, a generous premed & the parent is going to cope. If in doubt, a generous premed & a goodbye outside may be a better option. a goodbye outside may be a better option.

Anatomical Differences 1

Body proportionsBody proportions Head largerHead larger Limbs smallerLimbs smaller

Increased surface Increased surface area to volume ratioarea to volume ratio

CNS differencesCNS differences

Brain & spinal cord Brain & spinal cord relatively largerrelatively larger

Anatomical Differences 2: Airway

Head largerHead larger Nares (relatively) largerNares (relatively) larger Larynx higherLarynx higher

C3 in neonate -> C6 in C3 in neonate -> C6 in adultadult

Epiglottis longer (& Epiglottis longer (& softer)softer)

Cricoid ring narrowest Cricoid ring narrowest part of airwaypart of airway

Paediatric Respiratory Physiology

Chest wall mechanicsChest wall mechanics & tracheobronchial tree & tracheobronchial tree “floppier”.“floppier”.

Tidal volumeTidal volume//dead spacedead space same as adults in mls/kg same as adults in mls/kg Respiratory rate & minute volumeRespiratory rate & minute volume higher higher FRC similar to adult in mls/kg, but vO2 higher, so FRC similar to adult in mls/kg, but vO2 higher, so

desaturate more quickly when apnoeic.desaturate more quickly when apnoeic. Control of respirationControl of respiration immature till ~ 15/12 post immature till ~ 15/12 post

conceptual age – up till then vulnerable to conceptual age – up till then vulnerable to apnoeas – especially post GA &/or narcotics.apnoeas – especially post GA &/or narcotics.

Paediatric CVS Physiology Refresher

Fetal circulationFetal circulation//Postnatal transitionPostnatal transition-predelivery: systemic & pulmonary circulations in parallel,

with oxygenation via placenta & high pressure/low flow on (R) side.

-Transition at birth to systemic & pulmonary circulations in series with fall in PVR & closure of shunts.

HaemodynamicsHaemodynamicsNeonates & infants have fixed stroke volumes: CO dependant Neonates & infants have fixed stroke volumes: CO dependant

on HR – i.e. bradycardia = hypotension & shock.on HR – i.e. bradycardia = hypotension & shock. Autonomic controlAutonomic control

Different in neonates & children – response to hypoxia is Different in neonates & children – response to hypoxia is bradycardia (“Diving reflex”) rather than tachycardia.bradycardia (“Diving reflex”) rather than tachycardia.

Blood & body fluids

Blood volume 80-90 mls/kgBlood volume 80-90 mls/kg (adult (adult ~ 70)~ 70) Birth Hb 180-200 g/LBirth Hb 180-200 g/L (adult 120-160) (adult 120-160)

Falls to ~ 110 @ 6/12 then rises. Falls to ~ 110 @ 6/12 then rises. Fetal haemoglobin (HbF)Fetal haemoglobin (HbF)

Different chainsDifferent chains Lower p50 (Hb-O2 curve shifted left)Lower p50 (Hb-O2 curve shifted left) 75% of Hb at birth 75% of Hb at birth minimal @ 6/12. minimal @ 6/12.

Body water 75-80% in neonateBody water 75-80% in neonate (adult 65%) (adult 65%) ECF compartment larger than ICFECF compartment larger than ICF

((crosscrossover @ over @ ~ 4/12)~ 4/12)

Paediatric Thermodynamics Infants at higher risk of hypothermiaInfants at higher risk of hypothermia Higher surface area to volume ratioHigher surface area to volume ratio Remember the four modes of heat loss:Remember the four modes of heat loss:

1.1. ConductionConduction2.2. ConvectionConvection3.3. RadiationRadiation4.4. EvaporationEvaporation

All four occur more when the surface area to All four occur more when the surface area to volume ratio is highervolume ratio is higher

Heat production & regulation

Controlled in hypothalamusControlled in hypothalamus Balances heat loss & heat productionBalances heat loss & heat production Heat productionHeat production

ShiveringShivering – poorly developed in neonate/infant – poorly developed in neonate/infant Metabolic thermogenesis (brown fat)Metabolic thermogenesis (brown fat)

Thermoneutral environment;Thermoneutral environment; Point of minimum O2 consumtionPoint of minimum O2 consumtion e.g. for unclothed term baby is e.g. for unclothed term baby is ~ 33°C~ 33°C

Subspecialty Anaesthetics B: Obstetrics

Remember, once again you have two Remember, once again you have two patients – but this time they are patients – but this time they are

physically connectedphysically connected

Case Study V

Caesarian SectionCaesarian Section

History

38 yr old lady, P0G138 yr old lady, P0G1 Booked LSCSBooked LSCS IVF pregnancyIVF pregnancy Moderate PIH/pre-ecclampsiaModerate PIH/pre-ecclampsia History of back painHistory of back pain Wants to be awake for deliveryWants to be awake for delivery Needle phobicNeedle phobic

Issues

Preop consultationPreop consultation InvestigationsInvestigations PremedicationPremedication Choice of anaesthetic techniqueChoice of anaesthetic technique Choice of IV fluidsChoice of IV fluids Backup anaesthetic planBackup anaesthetic plan Postoperative monitoringPostoperative monitoring Analgesia planAnalgesia plan

Principles Pregnancy is a normal, but vulnerable Pregnancy is a normal, but vulnerable

condition.condition. The prregnant patient The prregnant patient isis different different Delivery is hazardousDelivery is hazardous Operative intervention may be requiredOperative intervention may be required Labour & delivery can be agonisingly Labour & delivery can be agonisingly

painfulpainful Anaesthesia inevitably has (at least some) Anaesthesia inevitably has (at least some)

foetal effects/implications.foetal effects/implications.

Differences in Pregnancy

PsychosocialPsychosocial CNSCNS RespiratoryRespiratory

AirwayAirway OtherOther

CardiovascularCardiovascular Renal/fluidsRenal/fluids

GastrointestinalGastrointestinal Hepatic/metabolicHepatic/metabolic EndocrineEndocrine HaematologicalHaematological ImmunologicalImmunological MusculoskeletalMusculoskeletal IntegumentIntegument

Drugs & the Placenta

General rule: If it crosses the blood brain General rule: If it crosses the blood brain barrier, it crosses the placenta!barrier, it crosses the placenta!

Placental transfer:Placental transfer:

Narcotics/Sedatives/GA agents - Narcotics/Sedatives/GA agents - HIGHHIGH

Muscle relaxants -Essentially nilMuscle relaxants -Essentially nil

Local anaesthetics – Significant (in Local anaesthetics – Significant (in freebase form) . . . but peak maternal freebase form) . . . but peak maternal plasma levels usually post deliveryplasma levels usually post delivery

Scenarios

Analgesia for labourAnalgesia for labour Anaesthesia for operative deliveryAnaesthesia for operative delivery

EmergencyEmergency SemiurgentSemiurgent PlannedPlanned

Anaesthesia for post partum complicationsAnaesthesia for post partum complications Neonatal resuscitationNeonatal resuscitation

Analgesic options InhalationalInhalational – N2O as Entonox (50:50 N20/O2) or via – N2O as Entonox (50:50 N20/O2) or via

blender (up to 70% N2O – Caution!)blender (up to 70% N2O – Caution!) NarcoticsNarcotics

IM/SC prn – pethidine favoured by IM/SC prn – pethidine favoured by midwivesmidwives

Infusions – not often used Infusions – not often used PCA – remifentanil drug of choice.PCA – remifentanil drug of choice.

Epidural Epidural – usually initial bolus then either:– usually initial bolus then either:

(a) Infusion(a) Infusion [&/or][&/or] (b) bolus top-ups(b) bolus top-ups [or][or] (c) PCEA(c) PCEA Other regional/local blocks – Other regional/local blocks – e.g. pudendal block for e.g. pudendal block for

second stage.second stage.

Anaesthetic Options for CaesareanRegionalRegional

Spinal vs EpiduralSpinal vs Epidural Spinal quicker – unless Spinal quicker – unless

epidural already in situ & epidural already in situ & only needing top-up.only needing top-up.

Most mothers want to be Most mothers want to be awake.awake.

Beware the failed or Beware the failed or patchy block.patchy block.

GeneralGeneral Technique of choice for Technique of choice for

emergency LSCS emergency LSCS FastestFastest Better in hypovolaemiaBetter in hypovolaemia

Riskier for mother on raw Riskier for mother on raw figures, but:figures, but: GA population includes GA population includes

failed regionals & most failed regionals & most emergency cases.emergency cases.

So are we comparing So are we comparing apples to oranges?apples to oranges?

No difference (surprisingly) in foetal outcomes between GA & RANo difference (surprisingly) in foetal outcomes between GA & RA

Subspecialty Anaesthetics C/D:Cardiothoracic & ENT

What do these surgical disciplines What do these surgical disciplines have in common?have in common?

Remember the basic rules:

1.1. Air goes in & outAir goes in & out2.2. Blood goes round & roundBlood goes round & round3.3. Variations on this are a BAD Variations on this are a BAD

THINGTHING

. . . BUT (you knew there had to be a “but” . . . BUT (you knew there had to be a “but” somewhere, didn’t you) . . .somewhere, didn’t you) . . .

ENT, Thoracic, & Cardiac anaesthesia all ENT, Thoracic, & Cardiac anaesthesia all require some flexibility of these rules!require some flexibility of these rules!

Anaesthetic Factors in ENT/Oral Surgery: the A to E

A.A. Airway Airway - shared with surgeon . . . And they’re not - shared with surgeon . . . And they’re not good sharers sometimes!good sharers sometimes!

B.B. Bleeding Bleeding – even a little in the airway is a BAD – even a little in the airway is a BAD THINGTHING

C.C. Children Children – make up a large proportion of patients– make up a large proportion of patients

D.D. Disruptions Disruptions – see Airway!– see Airway!

E.E. Extubation strategies – Extubation strategies – deep versus awake: deep deep versus awake: deep prevents coughing but leaves patient without airway prevents coughing but leaves patient without airway protection; light ensures airway protection but patient protection; light ensures airway protection but patient coughing may exacerbate likelihood of bleeding. coughing may exacerbate likelihood of bleeding.

(No easy answer to this – has to be case by case basis)(No easy answer to this – has to be case by case basis)

Airway Management Options in ENT/Oral Surgery

None (!)None (!) Venturi ventilationVenturi ventilation Nasal tubesNasal tubes RAE tubesRAE tubes MLT tubesMLT tubes Laryngeal masks (yes!)Laryngeal masks (yes!) Subglottic airway i.e tracheostomySubglottic airway i.e tracheostomy

Anaesthetic Factors in Thoracic Surgery Open thorax Open thorax – mandates IPPV – mandates IPPV +/-+/- PEEP PEEP Pre existing lung diseasePre existing lung disease Lung isolation requirementsLung isolation requirements Intraoperative hypoxia Intraoperative hypoxia (lung isolation by (lung isolation by

definition creates a major shunt)definition creates a major shunt) Postoperative issuesPostoperative issues

Respiratory supportRespiratory support AnalgesiaAnalgesia

Lung separation techniques:

Endobronchial intubationEndobronchial intubation

(but this time not inadvertent!)(but this time not inadvertent!) Double lumen ET tubesDouble lumen ET tubes Bronchial blockersBronchial blockers Other (generally bodgie) methodsOther (generally bodgie) methods

Anaesthetic Factors in Cardiac Surgery

Cardiopulmonary bypassCardiopulmonary bypass Cardiopulmonary bypass!Cardiopulmonary bypass! Cardiopulmonary bypass!!Cardiopulmonary bypass!!

((ScaryScary, scary, , scary, scaryscary stuff) stuff)

Cardiopulmonary bypass (“CPB”) for dummies

Pump plus oxygenatorPump plus oxygenator(“Heart lung machine”)(“Heart lung machine”)

CardioplegiaCardioplegia(High K+ solution to cause (High K+ solution to cause

cardiac standstill)cardiac standstill) HypothermiaHypothermia

(Enables prolonged ischaemic (Enables prolonged ischaemic times)times)

Problems with CPB

Non-pulsatile flow – Non-pulsatile flow – can cause paradoxical can cause paradoxical circulatory responsescirculatory responses

Hypothermia/pH issuesHypothermia/pH issues – – What is the right pH in What is the right pH in hypothermia to maintain acid base status? hypothermia to maintain acid base status?

Red cell trauma – Red cell trauma – from pump rollers impellers, & from pump rollers impellers, & (especially “bubble” type) oxygenators(especially “bubble” type) oxygenators

Cardiac restarting/Weaning from bypassCardiac restarting/Weaning from bypass Post CPB syndrome – Post CPB syndrome – confusion & cognitive confusion & cognitive

impairment, sometimes long-term or permanent.impairment, sometimes long-term or permanent.

Other Anaesthetic Factors in Cardiac Surgery

Pre-existing cardiac disease – Pre-existing cardiac disease – well, obviously!well, obviously! Co-morbidities - Co-morbidities - high incidence CVD, PVD, high incidence CVD, PVD,

diabetes, renal impairment, etc.diabetes, renal impairment, etc. Concurrent medications – Concurrent medications – likely to be multiplelikely to be multiple Monitoring – Monitoring – In patient on CPB: there In patient on CPB: there isis no no

ECG, pulse (oximetry), conventional BP, or expired ECG, pulse (oximetry), conventional BP, or expired CO2 there to monitor. CO2 there to monitor. CanCan monitor MAP monitor MAP generated by bypass, ABGs, & BIS/entorpygenerated by bypass, ABGs, & BIS/entorpy

Subspecialty Anaesthetics E:Neurosurgical

It’s not rocket science . . .It’s not rocket science . . .

. . . but it . . . but it isis brain surgery brain surgery

Special considerations in neurosurgical anaesthesia:

AirwayAirway – secure, as access to it intraoperatively – secure, as access to it intraoperatively may be impossible.may be impossible.

BreathingBreathing - may need to manipulate CO2 to - may need to manipulate CO2 to control intracranial pressure/volume.control intracranial pressure/volume.

CirculationCirculation - maintain appropriate BP for desired - maintain appropriate BP for desired cerebral perfusion pressurecerebral perfusion pressure

Disability & ExposureDisability & Exposure - special positioning may - special positioning may be required – e.g. sitting or prone, all of which be required – e.g. sitting or prone, all of which carry particular risks. carry particular risks.

Anaesthesia Anaesthesia forfor emergenciesemergencies

Emergencies Emergencies fromfrom (or (or during) anaesthesiaduring) anaesthesia

Part VII: Emergencies,

Complications & Problems.

Anaesthetic Emergencies

A: Emergency Anaesthesia

ObstetricsObstetrics TraumaTrauma Gen. SurgicalGen. Surgical VascularVascular Neuro-surgical/-radiologicalNeuro-surgical/-radiological Cardio-thoracicCardio-thoracic Threatened airwayThreatened airway

Considerations in Emergency Anaesthesia

First: How much of an emergency is it, First: How much of an emergency is it, really? Then:really? Then:

Airway assessment Airway assessment Cardio-respiratory statusCardio-respiratory status Full stomach/fasting statusFull stomach/fasting status Pre-existing medical conditionsPre-existing medical conditions Medications/allergiesMedications/allergiesAssessment may itself be difficult because Assessment may itself be difficult because

of haste, patient compromise, etc.of haste, patient compromise, etc.

Anaesthetic management

AssessmentAssessment Management plan/schedulingManagement plan/scheduling Stabilisation & preparation Stabilisation & preparation (as much as the (as much as the

urgency of the presenting problem permits)urgency of the presenting problem permits) Pain managementPain management Then (& only then) commencement of Then (& only then) commencement of

anaesthesiaanaesthesia

Emergency Anaesthesia: Maintenance

Includes ongoing resuscitation & Includes ongoing resuscitation & RxRx

Monitoring: More not lessMonitoring: More not less

Postanaesthetic management plan?Postanaesthetic management plan?

“LITTLE SHOP OF HORRORS”

Selected excerpts fromSelected excerpts from

my trauma casebookmy trauma casebook

Trauma scenes are an everyday sight:Trauma scenes are an everyday sight:

When racing a train to a level crossing, When racing a train to a level crossing, coming first equal is not a good idea!coming first equal is not a good idea!

Airway Management I

““Seasonal Goodwill”Seasonal Goodwill” 28 year old male28 year old male 3 days prior to Christmas3 days prior to Christmas Hit in face . . . Hit in face . . . with a frozen turkey (?!!)with a frozen turkey (?!!) Le Fort III and mandibular #sLe Fort III and mandibular #s

Anaesthetic Management

Topical airway anaesthesia Topical airway anaesthesia with nebulised lignocaine – (then)with nebulised lignocaine – (then)

Attempted Fibreoptic assisted awake oral Attempted Fibreoptic assisted awake oral intubation – failed due blood in airway & restless intubation – failed due blood in airway & restless patientpatient

Plan B: RSIPlan B: RSI with head up position till inductionwith head up position till induction then Trendelenberg till airway securedthen Trendelenberg till airway secured

Lesson: In a crisis - do what Lesson: In a crisis - do what youyou do best and do best and youyou are are comfortable with.comfortable with.

Airway Management II

““Young & Silly”Young & Silly” 19 yr old female19 yr old female Unrestrained backseat passenger in MVAUnrestrained backseat passenger in MVA Hx of EtOH +++Hx of EtOH +++ GCS 9, HR 120, BP 90/60, distended abdoGCS 9, HR 120, BP 90/60, distended abdo . . . . . . Priorities?. . . . . . Priorities?

Anaesthetic management

Hi-flo O2 by mask, 2x large bore IV access.Hi-flo O2 by mask, 2x large bore IV access. Fluid bolus, then rapid sequence intubation.Fluid bolus, then rapid sequence intubation.

Midazolam/ketamine/suxamethoniumMidazolam/ketamine/suxamethonium In line Cx spine stabilisationIn line Cx spine stabilisation

To OT for laparotomy/splenectomy.To OT for laparotomy/splenectomy. Fentanyl/N20/relaxantFentanyl/N20/relaxant Circulatory support: Fluids/blood to MAP of 90Circulatory support: Fluids/blood to MAP of 90

Then CT scan – NAD.Then CT scan – NAD.Lesson: “Head injury + hypotension + hypoxia = Death”.Lesson: “Head injury + hypotension + hypoxia = Death”.

i.e. Secure the airway but oxygenate the brain too!i.e. Secure the airway but oxygenate the brain too!

Airway Management III

““There are old motorcyclists and there are There are old motorcyclists and there are bold motorcyclists . . . but are there any bold motorcyclists . . . but are there any

old and bold motorcyclists?”old and bold motorcyclists?” 56 yr old male motorcyclist56 yr old male motorcyclist Morbid obesity (approx 155kgs)Morbid obesity (approx 155kgs) Fractured ribs/pulmonary contusionsFractured ribs/pulmonary contusions Borderline hypoxia Borderline hypoxia

(SaO2 90-91% on high flow O2 via NRBM)(SaO2 90-91% on high flow O2 via NRBM) Suspected Cx/Tx spine #sSuspected Cx/Tx spine #s

Do you think that this just might be a difficult intubation?

Anaesthetic management

Topicalisation of airwayTopicalisation of airway Awake fibreoptic nasal intubationAwake fibreoptic nasal intubation

Surgical insistence on supine posture due Surgical insistence on supine posture due potential spinal #s.potential spinal #s.

Extremely technically difficult & patient hypoxic Extremely technically difficult & patient hypoxic throughout procedure.throughout procedure.

Improved after intubation & IPPV/PEEP.Improved after intubation & IPPV/PEEP.

Lesson: Although satisfactory result, could very well Lesson: Although satisfactory result, could very well have been a failed intubation due to failure to insist have been a failed intubation due to failure to insist

on optimal conditions for airway management.on optimal conditions for airway management.

Airway Management IV

““And Judas went and hanged himself”And Judas went and hanged himself” 18 yr old male; Hx of depressive illness18 yr old male; Hx of depressive illness Found hangingFound hanging Cardiac output always presentCardiac output always present GCS 3, pupils fixed & dilated, GCS 3, pupils fixed & dilated, Spontaneous respirations, trismusSpontaneous respirations, trismus Neck swollen, but no palpable subcutaneous Neck swollen, but no palpable subcutaneous

emphysema.emphysema.

Anaesthetic Management

Inhalational anaesthesia O2/sevofluraneInhalational anaesthesia O2/sevoflurane Laryngeal mask placedLaryngeal mask placed Bronchoscopy via LMA:Bronchoscopy via LMA:

No evidence of laryngeal/tracheal fracture.No evidence of laryngeal/tracheal fracture. Then relaxant, LMA replaced with ETT.Then relaxant, LMA replaced with ETT.

Lesson: Beware the potential airway disruption Lesson: Beware the potential airway disruption - the one time a correctly placed endotracheal - the one time a correctly placed endotracheal

tube can result in fatal loss of the airway.tube can result in fatal loss of the airway.

Respiratory Management I““Guns don’t kill people” (. . . it’s the bullets Guns don’t kill people” (. . . it’s the bullets

fired out of them that do that, sometimes).fired out of them that do that, sometimes). 16 yr old male, accidental GSW to chest.16 yr old male, accidental GSW to chest.

(7.62mm NATO [.308”] calibre – high velocity rifle)(7.62mm NATO [.308”] calibre – high velocity rifle)

Entry & exit wounds (R) chest.Entry & exit wounds (R) chest. (R) haemopneumothorax.(R) haemopneumothorax. Haemodynamically unstable.Haemodynamically unstable.

Anaesthetic Management

High flow O2/large-bore IV x2/chest drain.High flow O2/large-bore IV x2/chest drain. Rapid sequence inductionRapid sequence induction

Narcotic, low dose thiopentone/suxamethonium.Narcotic, low dose thiopentone/suxamethonium. (L) double lumen tube placed(L) double lumen tube placed

Checked clinically, confirmed w/bronchoscope.Checked clinically, confirmed w/bronchoscope. Other options: Univent tube; bronchial blocker.Other options: Univent tube; bronchial blocker.

Lesson: Must have a plan for rapid placement and Lesson: Must have a plan for rapid placement and checking of lung separation device; and strategies checking of lung separation device; and strategies

for oxygenation with one lung ventilation: e.g. for oxygenation with one lung ventilation: e.g. upper lung CPAP, or intermittent inflations.upper lung CPAP, or intermittent inflations.

Upper lung CPAP device on a double lumen ET tube

Respiratory Management II

““Just another holiday weekend”Just another holiday weekend” 9 yr old girl, MVA with associated fatality9 yr old girl, MVA with associated fatality GCS 7, initial haemodynamics & SaO2 OKGCS 7, initial haemodynamics & SaO2 OK Rapid sequence induction – sBP fell to 50mmHgRapid sequence induction – sBP fell to 50mmHg Abdo distension notedAbdo distension noted Fluid challenge 20mls/kg crystalloidFluid challenge 20mls/kg crystalloid

– – improved BP but SaO2 fell to 90%improved BP but SaO2 fell to 90% Where to from here?Where to from here?

Anaesthetic Management

PEEP 5 then 10cm – improved SaO2 but BP fell PEEP 5 then 10cm – improved SaO2 but BP fell again.again.

Further volume expansion with colloid & bloodFurther volume expansion with colloid & blood 3030°° head up tilt once BP adequate, to: head up tilt once BP adequate, to:

Reduce ICP rise from PEEPReduce ICP rise from PEEP Improve ventilation/perfusion matchingImprove ventilation/perfusion matching

To OT for laparotomy:To OT for laparotomy: Oversewing liver lacerations & mesenteric tear.Oversewing liver lacerations & mesenteric tear.

Lesson: Beware the occult lung injury: contusion, Lesson: Beware the occult lung injury: contusion, haemo- or pneumothorax . . . they all get worse.haemo- or pneumothorax . . . they all get worse.

Circulatory management

““Off with his head!”Off with his head!” 23 yr old male, partial beheading with machete23 yr old male, partial beheading with machete Severed (R) neck muscles, carotid & subclavian Severed (R) neck muscles, carotid & subclavian

arteries, probable phrenic/vagal/accessory nervesarteries, probable phrenic/vagal/accessory nerves HR 140, peripherally shut down, BP 65 systolicHR 140, peripherally shut down, BP 65 systolic Conscious, semi-orientated, distressed.Conscious, semi-orientated, distressed. Decreased R chest movement, SaO2 90%Decreased R chest movement, SaO2 90% Brought straight into theatre (2 mins warning).Brought straight into theatre (2 mins warning).

Anaesthetic Management

Continued direct haemostatic pressure on wound. Continued direct haemostatic pressure on wound. IV access & arterial line (L) arm.IV access & arterial line (L) arm. Rapid sequence induction:Rapid sequence induction:

(ketamine/suxamethonium)(ketamine/suxamethonium) Anaesthetic maintenance with ketamine/fentanylAnaesthetic maintenance with ketamine/fentanyl Volume support with crystalloid/blood: Volume support with crystalloid/blood:

to systolic BP of 65mmHg only.to systolic BP of 65mmHg only. Until surgical haemostasis obtainedUntil surgical haemostasis obtained

Lesson: Resuscitation to normotension may not be Lesson: Resuscitation to normotension may not be indicated – or possibleindicated – or possible

Circulatory management: Principles

Early arterial line & IABP Early arterial line & IABP where indicatedwhere indicated

Warm all fluidsWarm all fluids Early use of bloodEarly use of blood Monitor what you do:Monitor what you do:

Arterial gassesArterial gasses HaematocritHaematocrit Platelets/coagulation Platelets/coagulation

(+clinical consultation)(+clinical consultation)

Good (large) IV access vitalGood (large) IV access vitalPeripheral: exchange/cutdownPeripheral: exchange/cutdownCentral: femoral/jugularCentral: femoral/jugular

Consider controlled Consider controlled hypotension until haemostasishypotension until haemostasis

Exceptions to this:Exceptions to this: NeurotraumaNeurotrauma Elderly/hypertensiveElderly/hypertensive PregnancyPregnancy

““Appropriate BP theorem”Appropriate BP theorem”

Other problems: Hypothermia

34 year old man34 year old man ““Accidental” rectal insertion of vibratorAccidental” rectal insertion of vibrator Perforated sigmoid colonPerforated sigmoid colon Faecal soiling & peritonitis/sepsis/MOFFaecal soiling & peritonitis/sepsis/MOF Prolonged laparotomyProlonged laparotomy Significant hypothermiaSignificant hypothermia

Hypothermia in Trauma

Common problemCommon problem Increases morbidity & Increases morbidity &

mortalitymortality Decreases coagulation Decreases coagulation

& injury response& injury response May be therapeutic in May be therapeutic in

isolatedisolated neurotrauma neurotrauma

Be aware of risksBe aware of risks Practice passive heat Practice passive heat

conservationconservation Active warming:Active warming:

SurfaceSurface IV fluidsIV fluids Gas humidificationGas humidification

Other problems: Coexisting disease

““In the line of duty”In the line of duty” 29 yr old man, bartender29 yr old man, bartender Gunshot wound to stomach during armed holdupGunshot wound to stomach during armed holdup Obese, smoker, moderate to heavy EtOH.Obese, smoker, moderate to heavy EtOH. Conscious, distressed ++++Conscious, distressed ++++ HR 160, BP 180/120HR 160, BP 180/120

Anaesthetic Management Analgesia titrated against pain, hypertension & Analgesia titrated against pain, hypertension &

tachycardia.tachycardia. To OT for urgent laparotomy.To OT for urgent laparotomy. Intraoperative arrhythmias & arterial desaturation.Intraoperative arrhythmias & arterial desaturation.

No evidence ballistic damage to/near diaphragmNo evidence ballistic damage to/near diaphragm

Post op diagnosed with extensive anterior AMI.Post op diagnosed with extensive anterior AMI. Surgical recovery but ongoing poor LV function.Surgical recovery but ongoing poor LV function.

Would earlier analgesia have prevented this?Would earlier analgesia have prevented this?

Lesson: (a) Beware of occult disease even in the Lesson: (a) Beware of occult disease even in the young. (b) Pain young. (b) Pain doesdoes matter. matter.

Recreational drugs““High on cocaine – in both senses”High on cocaine – in both senses”

38 yr old woman38 yr old woman IVDU, formerly heroin, now IV cocaineIVDU, formerly heroin, now IV cocaine On naltrexoneOn naltrexone Sex industry worker, Hep B/C +ve Sex industry worker, Hep B/C +ve 3 story fall while under influence of cocaine3 story fall while under influence of cocaine 100% subluxation/# T12-L1 100% subluxation/# T12-L1 Complete neurological deficit at T10Complete neurological deficit at T10 Severe neuropathic painSevere neuropathic pain Difficult IV accessDifficult IV access

The geriatric trauma patient

““Somebody’s grandma”Somebody’s grandma” 86 yr old woman, Fractured NOF86 yr old woman, Fractured NOF Hypertensive on Rx Hypertensive on Rx (enalapril/diltiazem)(enalapril/diltiazem)

Fall secondary to ?TIA?Fall secondary to ?TIA? Ex smoker, mild to moderate CALEx smoker, mild to moderate CAL Exercise tolerance limited by arthritisExercise tolerance limited by arthritis For Austin Moore hemiarthroplastyFor Austin Moore hemiarthroplasty

Anaesthetic Management Potential problems:Potential problems:

Respiratory complications with GARespiratory complications with GA Hypertension/tachycardia with airway manipulationHypertension/tachycardia with airway manipulation Hypotension +/- cerebral ischaemia with regionalHypotension +/- cerebral ischaemia with regional

Attempted spinal Attempted spinal Technically difficult due calcification of spacesTechnically difficult due calcification of spaces Abandoned after several failures to locate spaceAbandoned after several failures to locate space

Converted to GA: - uneventful.Converted to GA: - uneventful. CVA 2/52 post op – died 1/52 later.CVA 2/52 post op – died 1/52 later.

Lessons: - Sometimes there is no “right” anaestheticLessons: - Sometimes there is no “right” anaesthetic - Just some may be less wrong than others- Just some may be less wrong than others

The Pregnant Patient

““Your next two patients are . . . “Your next two patients are . . . “ 38 year old female38 year old female P2G1 - 31/40 pregnantP2G1 - 31/40 pregnant MVA with #’d femurMVA with #’d femur For femoral nailing.For femoral nailing.

B: Anaesthetic Emergencies & Complications

““BIG ONES”BIG ONES” ArrestArrest AnaphylaxisAnaphylaxis Failure to intubateFailure to intubate Ventilator disconnectVentilator disconnect Laryngospasm/NPPOLaryngospasm/NPPO AspirationAspiration Nerve damageNerve damage

““Little ones”Little ones” Agitation/deleriumAgitation/delerium Sore throatSore throat PONVPONV PainPain Urinary retentionUrinary retention AtalectasisAtalectasis Cognitive dysfunctionCognitive dysfunction

Post Operative Nausea & Vomiting (PONV)“The Big Little Problem”The Big Little Problem”

Still affects up to 30% of patients.Still affects up to 30% of patients. Major subjective concern – studies suggest most patients Major subjective concern – studies suggest most patients

prefer pain to N&V.prefer pain to N&V. Most common cause of prolonged recovery stay, & delayed Most common cause of prolonged recovery stay, & delayed

discharge in daystay patientsdischarge in daystay patients MultifactorialMultifactorial::

Patient factors: Patient factors: ♀ ♀ > ♂> ♂; Non smoker > smoker.; Non smoker > smoker. Surgical: High incidence in eye, ENT, & Surgical: High incidence in eye, ENT, &

gynaecological laparoscopic surgery.gynaecological laparoscopic surgery. Anaesthetic: Narcotics, volatile & N2O all Anaesthetic: Narcotics, volatile & N2O all

potentially emetic. (Propofol usually not)potentially emetic. (Propofol usually not)

Treatment approach to PONVPrevention is better than cure

GeneralGeneral Identify at risk patientIdentify at risk patient

Anaesthetic historyAnaesthetic history Identify & ameliorate Identify & ameliorate

precipitant if possibleprecipitant if possiblee.g. narcoticse.g. narcotics

General supportive Rx:General supportive Rx:IV hydration, IV hydration, narcotic sparing, narcotic sparing,

multimodal analgesiamultimodal analgesia

Consider TIVAConsider TIVA

Antiemetic agents:Antiemetic agents: HT3 blockers - HT3 blockers - e.g. e.g.

ondansetron. Pre-emptive or ondansetron. Pre-emptive or reactively.reactively.

DexamethasoneDexamethasone – mode of – mode of action unknown. Most effective action unknown. Most effective premptively.premptively.

Dopamine antagonistsDopamine antagonists- e.g. droperidol. Good for - e.g. droperidol. Good for

narcotic related N&Vnarcotic related N&V Others: Others: - Anticholinergics- Anticholinergics

- Antihistamines/phenothiazines- Antihistamines/phenothiazines

- Prokinetics – metoclopramide- Prokinetics – metoclopramide

Anaesthetic Risk In Perspective

Risk of anaesthetic death (due to the Risk of anaesthetic death (due to the administration of the anaesthetic) < 1:50,000administration of the anaesthetic) < 1:50,000

No paediatricNo paediatric anaesthetic deaths in Australia in anaesthetic deaths in Australia in the last reported quinquennium.the last reported quinquennium.

Typical healthy elective surgical patient probably at Typical healthy elective surgical patient probably at more risk of death or serious injury from car trip more risk of death or serious injury from car trip

to/from hospitalto/from hospital

The figures are good but may lead to:

Overconfidence amongst anaesthetistsOverconfidence amongst anaesthetists Complacency by surgeons & under-appreciation Complacency by surgeons & under-appreciation

of risk of coexisting disease factors (which of risk of coexisting disease factors (which dodo kill kill patients). patients).

Anaesthesia & sedation services becoming a target Anaesthesia & sedation services becoming a target for cost cutting measures by politicians/managers for cost cutting measures by politicians/managers with consequent erosion of safety margins.with consequent erosion of safety margins.

The Eternal Triangle(In all health services, not just anaesthetics)

QUALITYQUALITY

ECONOMYECONOMYQUANTITYQUANTITY

(And if one of these is economy, are (And if one of these is economy, are you sure it’s not a false economy?!)you sure it’s not a false economy?!)

Pick Pick any any two!two!

The Bottom Line

Safe anaesthesia may not prevent the patient Safe anaesthesia may not prevent the patient dying of the disease.dying of the disease.

It will however help prevent them dying of It will however help prevent them dying of the treatment.the treatment.

Think as a potential surgeon: Isn’t this what Think as a potential surgeon: Isn’t this what you would want for your patient?you would want for your patient?

Think as a health consumer: Isn’t this what Think as a health consumer: Isn’t this what you would want for yourself or your family?you would want for yourself or your family?

The End

If you have any questions about the If you have any questions about the course material, or about course material, or about

anaesthesia as a potential career anaesthesia as a potential career choice, feel free to contact me:choice, feel free to contact me:

docblair@optusnet.com.audocblair@optusnet.com.au