The Difficult Airway

Careful preoperative assessment is essential including the evaluation of:

• upper teeth prominence

• presence of micrognathia

• mouth opening (should be > 2 cm.)

Intubation in some congenital syndromes associated with difficulty such as Pierre Robin becomes easier as the child ages, whilst intubation in other syndromes such as Treacher Collins becomes progressively more difficult as time passes. Examination of any previous anaesthetic records relating to intubation is mandatory.

• All sedative premedication must be avoided in the presence of upper airway obstruction.

• Inhalational induction with either sevoflurane or halothane is often safest

  • use of CPAP in the early stages of anaesthesia is beneficial. CPAP should be maintained and IV access should then be established whilst anaesthesia is deepened.

  • once a sufficient plane of anaesthesia has been achieved an oropharyngeal airway can be inserted. This may be extremely useful in gaining control of the airway but should not be attempted whilst the child is still "light" as laryngospasm may be precipitated.

• Wide range of ETT plus gum elastic bougies and introducers should be available, as well as a choice of straight and curved bladed laryngoscopes. The various strategies for dealing with difficult intubations are similar to those used in adults.

• Occasionally lymphoid hyperplasia of the tonsils may result in obstructive sleep apnoea.

• Affected children often:

  • snore at night

  • show daytime somnolence

  • have behavioural problems.

• Post tonsillectomy complications, including apnoea, are higher in such children.

• The child should have pre-operative sleep studies to detect periods of apnoea of hypopnoea.

• All sedative premedication agents are contraindicated in these children.

• As post-operative complications are higher in this group of patients, they should be closely monitored, including pulse-oximetry, after operation.

• Hypovolaemia due to blood loss is often underestimated

• Circulating volume should be restored and any severe anaemia corrected to restore normal cardiovascular indices preoperatively. Bleeding is rarely so rapid that complete restoration of blood volume can not be achieved.

• Further blood for transfusion should be readily available in case of need and a coagulation screen performed as occasionally the child may have an undiagnosed bleeding diathesis.

• The anaesthetic chart from the original tonsillectomy should be examined and a note made of the size of ETT used and of any anaesthetic difficulties encountered. It may only be possible to use an ETT half a size smaller than the original due to generalised oedema.

• There may be little blood visible, but much may have been swallowed. Blood is a gastric irritant and may precipitate vomiting upon induction of anaesthesia, at the very least regurgitation of gastric contents should be anticipated.

• Both an inhalational induction and a rapid sequence induction are acceptable, bearing in mind that the bleeding point will be supra glottic and thus the child can still aspirate if cricoid pressure is used.

• If an inhalational induction is planned then it should be performed in the left lateral, head down position to decrease the risk of aspiration.

• Suction must be readily available at all times.

• Stomach should be emptied of blood via a gastric tube prior to extubation and the child extubated fully awake once all the protective laryngeal reflexes have returned.

Acute Upper Airway Problems

Signs of airway obstruction include the presence:

• stridor

  • inspiratory stridor suggests an extrathoracic lesion e.g. laryngomalacia

  • expiratory stridor suggests an intrathoracic lesion e.g. tracheomalacia.

  • biphasic stridor is suggestive of a "fixed" lesion such as subglottic stenosis.

  • co-existing hoarseness suggests laryngeal pathology.

• recession of the tracheal, intercostal, supraclavicular and subcostal areas

• tachypnoea

• tachycardia

• flaring of the alae nasi

• grunting

• generalised restlessness, cyanosis and an impaired ability to feed.

Laryngotracheobronchitis (Croup)

• Usually of viral origin, mainly Parainfluenza type 1

Clinical features

• Longer history than epiglottitis

• Typically presents in the 2^nd year of life.

• Prodromal URTI is common

• Inspiratory and expiratory stridor with the classical "barking" cough.

Treatment

• Steroids

• Humidified oxygen

• +/- nebulised adrenaline (1ml/kg 1:1000 adrenaline, max 5ml, stop if heart rate exceeds 200bpm or dysrhythmias are seen).

• Occasionally intubation is required

  • management of anaesthesia is as for epiglottitis, although IV access will usually have been obtained pre-operatively.

  • extubate once there is an audible leak around the ETT, usually after 4-5 days

• antibiotics are only indicated in the presence of secondary bacterial infection.

• Most common indication for bronchoscopy in children aged 1-3 years.

• Peanuts are the most commonly inhaled objects in the UK; they are particularly dangerous as oil in the nut produces mucosal irritation, oedema and often a severe pneumonitis distal to the obstruction.

• Typically there is a history of choking followed by coughing, stridor, and occasionally dyspnoea or cyanotic attacks. 

• Presentation is usually immediately after aspiration but in up to 30% it may be delayed for more than 1 week.

• On examination there may be unilateral decreased air entry or wheezing.

• CXR: foreign body may be visible and distal pneumonia or emphysema (due to ball-valve effect) may be present. Both inspiratory and expiratory films should be taken.

Anaesthesia

• atropine pre-med, 20m g/kg intramuscularly should be given. IM is needed as this will ensure that the airway mucosa is sufficiently dry for topical lignocaine to work (it won't anaesthetise wet mucosa).

• induce with sevoflurane/halothane in oxygen and aim for deep anaesthesia.

• topical lignocaine (max 4mg/kg) to anaesthetise the airway, including the vallecula as this is were the surgical gag will be placed, to prevent coughing/laryngospasm upon surgical instrumentation.

• maintain spontaneous ventilation with the Ayre's T-piece connected to the side arm of the ventilating Storz bronchoscope, although assisted ventilation may be necessary. Procedure may be prolonged.

• biggest danger comes when the foreign body is withdrawn into trachea. May fall out of the forceps, lodging just below cords and totally obstructing airway. It is safest to push it back down the airway sufficiently far to allow adequate ventilation and then make a second attempt at removal. Monitor air entry to both lungs as the surgeon may dislodge the foreign body from one side to the other.

• good communication between the surgeon and anaesthetist is vital!

Post-operative care

• Dexamethasone (0.25 mg/kg IV and then 3 doses of 0.1 mg/kg IV 6 hourly - Great Ormond Street regime) is advisable if there has been repeated instrumentation of the airway with the bronchoscope.

• Humidification of air with or without oxygen and regular physiotherapy post-operatively is essential.

• Antibiotics should be administered if infection is present.