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Drugs for General Anaesthesia

TCD 4thmed Pharmacology & Therapeutics

Dr Tom Schnittger FFARCSI30.10.08

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Anaesthesia uses drugs to create

an altered physiological state:

Unconciousness

Analgesia

Amnesia

Muscular relaxation

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General Anaesthesia:

Variable statereversible

Polypharmacy

Fast acting, short acting, pure drugs

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Every General Anaesthetic is

unique:

Tailored to the state of the patient

Tailored to the nature of the operation

Tailored to the style of the anaesthetist

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General Anaesthesia:

Every patient responds to a drug as an

individual, not as a mean

Safe anaesthesia requires constant vigilance

and monitoring

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Phases of a General Anaesthetic

Induction

Maintenance

Reversal

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Phases of a General Anaesthetic

Pre-operative phase

Induction

Maintenance

Reversal

Post-operative phase

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General Anaesthesia 1908

Premedication: morphine/gin

Induction: ether/air

Maintenance: ether/air

Reversal: turn off ether

Recovery: nothing/morphine

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General Anaesthesia 2008

Pre-operative evaluation/optimisation

Induction

Maintenance

Reversal

Recovery, I.C.U. and Pain management

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Pre-operative phase:

Pre-operative clinical evaluation & preparation

Reassurance/Advice: smoking, wt. loss, OCP, fasting

Anxiolytics: benzodiazepines Analgesics: opiates/NSAIDS

Bronchodilators: b2agonists, anti-cholinergics

Cardiac drugs: GTN, anti-arrythmics, anti-bp

Diabetic drugs: glucose-insulin-potassium

Endocrine drugs: glucocorticoids

Anti-embolism: heparin/TEDS

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Induction phase:

Intravenous fluid: crystalloid/colloid

Induction agent: propofol/thipentone/ketamine/sevoflurane

Analgesic: fentanyl/morphineMuscle relaxant: suxamethonium/atracurium/rocuronium

Local anaesthetic: lignocaine/levobupivicaine

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Maintenance phase: Oxygen/Air or Oxygen/Nitrous Oxide

Vapour: Sevoflurane/Isoflurane Halothane/Ether Muscle relaxants

Analgesics:

morphine/fentanyl bolus or remifentanyl infusion

diclofenac/paracetamol Anti-emetics:

ondansetron, dexamethazone, cylizine, prochlorperazine

IV fluids: blood, platelets, plasma, factors

Other drugs: antibiotics, diuretics

Cardiac drugs:

Inotropes: adrenaline, noradrenaline

Chronotropes: atropine, isoprenaline, b-blockers

Hypotensives: GTN, labetalol, nitroprusside

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Reversal phase:

Muscle relaxant: neostigmine &

glycopyrollate/atropine

Opiate: naloxone

Benzodiazepine: flumazenil

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Post-operative phase:

Oxygen

Analgesics

Anti-emetics

Inotropes

IV fluids

Intensive Care:

Cardiac support, Ventilation, Dialysis, TPN

Pain management:

Analgesic optimisation, PCA, Epidural analgesia,continuous nerve block

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Anaesthesia scenarios - Case 1

87 year old woman

Abdominal pain, distension & vomiting for 3 days

Past medical history: MI 5 yrs previously,angina & hypertension

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Case 1issues:

Elderly

Dehydration

Electrolyte abnormalities

Aspiration risk

IHD and hypertension Relative emergency

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Case 1 - management

Rehydration, restoration of electrolyte balance

Analgesia, oxygen

Anti-anginal, anti-hypertensive

Monitor blood pressure invasively Rapid Sequence Induction

Analgesia, anti-emesis

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Anaesthesia scenarios - Case 2

11 year old girl

severe asthma

foreign body in her ear

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Case 2 - issues

Childanxiety

Asthmaairway management

Semi-elective procedure

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Case 2 - management

Treatment of asthma

Adequate pre-medication/anxiolysis

Gas induction

No instrumentation of airway

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Case 3

Obese 34 yr old

Insulin dependent diabetic

Acute abdomen - ? appendicitis

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Case 3 - issues

Acute abdomen: relative emergency,dehydration, electrolytes,

risk of vomiting

Diabetes: hyper/hypoglycaemia

Obesity: IV access, airway, woundhealing, ?IHD

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Case 3 - Management

Rehydration

Normalisation of electrolytes & blood sugar

Invasive blood pressure monitoring/sampling

Rapid sequence induction

Intubation aids

Antibiotics, surgical technique

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Case 4

Previously healthy 46 yr old post-op

GA for ankle fracture repair

30 minutes later on ward:

unconcious, cyanosed, laboured respirations

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Case 4 - issues

EMERGENCY

Differential diagnosis

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Case 4 - management

Call for help, ABC

Airway

Breathing

Circulation

Oxygen, IV access

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Case 4management

Diagnose:

Respiratory event

Cardiac event Too much opiate

Inadequate reversal of muscle relaxant

Treat accordingly