Awake intubation

Indications :- Airway anomalies- Any suspicion on difficulty intubating- Facial trauma- Significant hemodynamic instability

Advantages :- Airway patency

Disadvantages : - Trauma- Increased blood pressure and intracranial

IntroductionIntroduction During routine anaesthesia the incidence of difficult tracheal

intubation has been estimated at 3-18%.

Class I: the vocal cords are visible Class II: the vocals cords are only partly visible Class III only the epiglottis is seen Class IV the epiglottis cannot be seen.

Cormack RS, Lehane J. "Difficult intubation in obstetrics." Anaesthesia 1984;39:1105-11

Predicting Difficult Intubation (1)Predicting Difficult Intubation (1)

"sniffing the morning air" position History and examination Specific Screening Tests to Predict Difficult Intubation. View obtained during Mallampati test: 1. Faucial pillars, soft palate and uvula visualised 2. Faucial pillars and soft palate visualised, but uvula masked by the base of the tongue 3. Only soft palate visualised

4. Soft palate not seen.

Samsoon GLT, Young JRB. "Difficult tracheal intubation: a retrospective study." Anaesthesia 1987;42:487-90

Predicting Difficult Intubation (2)Predicting Difficult Intubation (2)

Thyromental distance Grade 3 or 4 Mallampati who also had a thyromental distance

of less than 7cm were likely to present difficulty with intubation

Frerk CM. "Predicting difficult intubation." Anaesthesia 1991;46:1005-8

Sternomental distance A sternomental distance of 12.5cm or less predicted difficult

intubation Savva D. "Prediction of difficult tracheal intubation." British Journal of

Anaesthesia 1994;73:149-53

Predicting Difficult Intubation (3)Predicting Difficult Intubation (3)

Protrusion of the mandible If the patient cannot get the upper and lower incisors into

alignment intubation is likely to be difficult. Calder I, Calder J, Crockard HA. "Difficult direct laryngoscopy in patients

witH cervical spine disease." Anaesthesia 1995;50:756-63

X-ray studies Various studies have been used to try to predict difficult

intubation by assessing the anatomy of the mandible on X-ray. These have shown that the depth of the mandible may be important, but they are not commonly used as a screening test.

Preoperative assessmentPreoperative assessment

A combination of the above tests is better than using only one. The modified Mallampati, thyromental distance, ability to protrude the mandible and craniocervical movement are probably the most reliable.

Preparation for Intubation (1)Preparation for Intubation (1)

Anaesthetists should be ready to deal with difficulties in intubation at any time. The correct equipment must be immediately available. This will include:

laryngoscopes with a selection of blades a variety of endotracheal tubes introducers for endotracheal tubes (stylets or better, flexible

bougies) oral and nasal airways

Preparation for Intubation (2)Preparation for Intubation (2)

a cricothyroid puncture kit (a 14 gauge cannula and jet insufflation with high pressure oxygen is the simplest and cheapest kit

reliable suction equipment a trained assistant laryngeal mask airways, sizes 3 & 4

After intubationAfter intubation

The anaesthetist should ensure that the patient is in the optimal position for intubation and must be able to oxygenate the patient at all times.

After intubation correct placement of the tube should be confirmed by:

a stethoscope listening over both lung fields in the axillae observing the tube pass through the cords successful inflation of the chest on manual ventilation

Special techniques for intubationSpecial techniques for intubation

Awake intubation under local anaesthesiaOral intubationNasal intubation is the best method of awake intubation using a

fibreoptic bronchoscope or other intubating fibrescope via the nose.

Retrograde intubation (1)Retrograde intubation (1)

is a technique first described in Nigeria Waters DJ "Guided blind endotracheal intubation for patients with deformities of the upper

airway." Anaesthesia 1963;18:158-62

Retrograde intubation has recently been used successfully for traumatised airways when conventional techniques had failed

Barriot P, Riou B. "Retrograde technique for tracheal intubation in trauma patients."Critical Care Medicine. 1988;16:712-3

the membrane between the cricoid and first tracheal ring can also been used.

Shanther TR. "Retrograde intubation using the subcricoid region." British Journal of Anaesthesia. 1992;68:109-12

Retrograde intubation (2)Retrograde intubation (2)

The Laryngeal Mask AirwayThe Laryngeal Mask Airway

is a common device in anaesthesia and can often provide a good airway in patients in whom intubation is difficult. Following insertion the anaesthetist may use it to maintain the airway during anaesthesia, or may use it as a route to allow tracheal intubation.

The McCoy laryngoscopeThe McCoy laryngoscope

is designed with a movable tip which allows the epiglottis to be lifted and intubation often made easier

McCoy EP, Mirakhur RK. "The levering laryngoscope." Anaesthesia 1993;48:516-9

A light wandlight wand is a long flexible device which has a bright light at the end and can be directed into the trachea with an endotracheal tube mounted over it

Robelen GT, Shulman MS. "Use of the lighted stylet for difficult intubations

in adult patients (abstract)." Anesthesiology 1989;71:A439 The Combi-tubeCombi-tube is a tube which may be inserted

blindly and used to ventilate the patient in an emergency Frass M, Frenzer R. Zahler J, Lilas W, Leithner C. "Ventilation via the

esophageal tracheal combitube in a case of difficult intubation." Journal of Cardiothoracic Anaesthesia 1987;1:565-8

Planning Anaesthesia Planning Anaesthesia During general anaesthesia patients must never be given muscle

relaxants unless the anaesthetist can be certain of being able to ventilate them.

When the anaesthetist faces unexpected difficulty in intubation the priority is to ensure adequate mask ventilation and oxygenation of the patient.

Multiple attempts at endotracheal intubation may result in bleeding and oedema of the upper airway making the task even more difficult. Often it is better to accept failure after a few attempts and move on to a pre-planned failed intubation sequence

King TA, Adams AP. "Failed tracheal intubation." British Journal of Anaesthesia1990;65:400-414

Failed intubationFailed intubation

If intubation proves impossible the anaesthetist should consider whether to allow the patient to wake up and carry on surgery with regional anaesthesia, or whether to abandon the surgery altogether. In situations where surgery is of an urgent nature it may be prudent to carry on the general anaesthetic under face mask anaesthesia if the airway is easy to maintain.

If the airway is impossible to maintain and the patient is becoming hypoxic, an emergency cricothyroidotomy is required. If time allows an emergency tracheostomy can be considered.

ASA Algorithm Part 1ASA Algorithm Part 1

ASA Algorithm Part 2ASA Algorithm Part 2

Awake Intubation PathwayAwake Intubation Pathway

Non-surgical techniques for awake intubation include laryngoscopy, fiberoptic bronchoscopy and retrograde intubation. Surgical access may be secured by awake tracheostomy.

Awake intubation requires patient cooperation and should be performed with local anesthesia. See Local Anesthesia for more information.

If awake intubation efforts fail, the patient is unlikely to have compromised ventilation. Consider canceling the case, other intubation options or surgical access to the airway.

Intubation After Induction PathwayIntubation After Induction Pathway

After induction of anesthesia, if the initial intubation attempts are unsuccessful, consider returning to spontaneous ventilation, awakening the patient and calling for help.

If mask ventilation is adequate, go to the Non-Emergency Pathway. If mask ventilation is inadequate go to the Emergency Pathway.

If mask ventilation becomes inadequate at any time while following the Non-Emergency Pathway, go to the Emergency Pathway

Non-Emergency PathwayNon-Emergency Pathway

Follow the Non-Emergency Pathway when the patient is anesthetized, intubation is unsuccessful and mask ventilation is adequate. If mask ventilation becomes inadequate go directly to the Emergency Pathway.

Consider alternative approaches including fiberoptic intubation, intubation stylet, blind intubation, light wand and retrograde intubation.

If failure after multiple attempts, consider awakening the patient, surgical airway or surgery under mask anesthesia.

Emergency PathwayEmergency Pathway

Follow the Emergency Pathway when the patient is anesthetized, intubation is unsuccessful and mask ventilation is inadequate.

Time is critical. Call for help. Do one more intubation attempt or emergency non-surgical airway ventilation or emergency surgical airway.

Do not continue to attempt a previous unsuccessful technique. Emergency non-surgical airway ventilation techniques include:

transtracheal jet ventilation, intratracheal jet stylet, laryngeal mask, oral and nasopharyngeal airways, two person mask ventilation, and rigid ventilating bronchoscope.

Emergency non-surgical airway ventilation techniques are temporizing measures. Establish a definitive airway as soon as possible.

Succinylcholine

Side Effects & Clinical Considerations Succinylcholine is a relatively safe drug—assuming that its

many potential complications are understood and avoided. Because of the risk of hyperkalemia, rhabdomyolysis, and cardiac arrest in children with undiagnosed myopathies,

succinylcholine is considered contraindicated in the routine management of children and adolescent patients. In the absence of a difficult airway or full stomach, many clinicians have also abandoned the routine use of succinylcholine for adults.

Cardiovascular Succinylcholine not only stimulates nicotinic

cholinergic receptors at the neuromuscular junction, it stimulates all ACh receptors. Succinylcholine's cardiovascular actions are therefore very complex.

Stimulation of nicotinic receptors in parasympathetic and sympathetic ganglia and muscarinic receptors in the sinoatrial node of the heart can increase or decrease blood pressure and heart rate.

Low doses of succinylcholine can produce negative chronotropic and inotropic effects, but higher doses usually increase heart rate and contractility and elevate circulating catecholamine levels

Children are particularly susceptible to profound bradycardia following administration of succinylcholine. Bradycardia typically occurs in adults only if a second bolus of succinylcholine is administered approximately 3–8 min after the first dose.

A succinylcholine metabolite, succinylmonocholine, appears to sensitize muscarinic cholinergic receptors in the sinoatrial node to the second dose of succinylcholine, resulting in bradycardia.

Intravenous atropine (0.02 mg/kg in children, 0.4 mg in adults) is normally given prophylactically to children prior to the first dose and always before a second dose of succinylcholine

FasciculationsHyperkalemiaMuscle painsIntragastric Pressure Elevation Intraocular Pressure Elevation Masseter Muscle Rigidity Malignant Hyperthermia Intracranial Pressure

Conditions Causing Susceptibility to Succinylcholine-Induced Hyperkalemia

Burn injury Massive trauma Severe intraabdominal infection Spinal cord injury Encephalitis Stroke Guillain-Barré syndrome Severe Parkinson's disease Tetanus Prolonged total body immobilization Ruptured cerebral aneurysm Polyneuropathy Closed head injury Hemorrhagic shock with metabolic acidosis Myopathies (eg, Duchenne's dystrophy)