Rapid sequence intubation in children — formative SAQs

SAQ 1 (10)

A 4-year-old, 16 kg child presents with severe viral pneumonia and is now tiring, with oxygen saturations of 86 per cent on high-flow oxygen, reduced air entry, and increasing drowsiness. You decide to perform rapid sequence intubation. [1] [6]

1. State the endotracheal tube size you would prepare (uncuffed and cuffed) using the age-based formulae, and list three pieces of equipment that must be at the bedside before induction. (4) [1]
2. Outline the sequence of drug administration (induction agent, neuromuscular blocker, premedication) with doses for this child, and justify your choice of induction agent. (4) [3]
3. Describe how you would confirm correct tube placement and state the immediate action if the child desaturates during laryngoscopy. (2) [6]

Model answer

Tube size and equipment. The uncuffed tube internal diameter in mm equals (age/4) + 4 = (4/4) + 4 = 5.0 mm; the cuffed tube equals (age/4) + 3.5 = 4.5 mm. Have a half-size above and below ready. Equipment that must be ready: working suction with a Yankauer tip, high-flow oxygen connected to a bag-mask, a checked laryngoscope with a Macintosh 2 blade and a spare, an exhaled carbon dioxide detector, a bougie or stylet, and a supraglottic airway sized to the child. [1]

Drug sequence and induction choice. Preoxygenate with 100 per cent oxygen for three minutes. Give the induction agent and neuromuscular blocker in rapid succession without waiting to observe the induction effect. For this child, who has respiratory but not circulatory failure, a reasonable choice is ketamine 1 to 2 mg/kg IV (about 16 to 32 mg) for its bronchodilator and haemodynamically stable profile, or propofol 2 to 4 mg/kg IV if cardiovascularly stable. Paralyse with suxamethonium 1 to 2 mg/kg IV or rocuronium 1 mg/kg IV. Give atropine 20 micrograms/kg IV (minimum 100 micrograms) as premedication, appropriate for a young child receiving suxamethonium. The choice of ketamine is justified by the need to preserve blood pressure and bronchodilate. [3]

Confirmation and desaturation. Confirm placement with exhaled carbon dioxide (capnography or a colour-change detector), supported by bilateral chest rise and air entry and a rise in saturation. If the child desaturates during laryngoscopy, stop, return to bag-mask ventilation with 100 per cent oxygen, reposition, and reattempt — never persist with a blind or prolonged attempt. [6]

SAQ 2 (10)

A 9-month-old infant in septic shock needs intubation. The infant is cold, mottled, with weak pulses and a capillary refill of 5 seconds. [3] [5]

1. Explain why the choice of induction agent is critical in this infant, and state the agent and dose you would choose and why. (4) [3]
2. Outline the role and dose of atropine as a premedication in this infant, and explain the physiological basis for its use. (3) [5]
3. Describe two measures you would take to prevent cardiovascular collapse at the moment of induction. (3) [3]

Model answer

Induction agent choice. In septic shock the circulation is catecholamine-depleted, so a full dose of propofol or thiopentone can precipitate severe hypotension and cardiovascular collapse. Ketamine is the safest default because it preserves sympathetic tone; the dose is 1 to 2 mg/kg IV, and even ketamine can drop the pressure in a deeply depleted child, so a reduced dose is reasonable. Etomidate 0.3 mg/kg IV is an alternative that is haemodynamically stable, with the caveat of adrenal suppression. [3]

Atropine. Give atropine 20 micrograms/kg IV (minimum 100 micrograms) as premedication. This infant is under one year and is the group at highest risk of vagal bradycardia from laryngoscopy and suxamethonium. The physiological basis is that airway stimulation and suxamethonium provoke a vagal response, and the hypoxaemic, young infant is primed for a brisk fall in heart rate that can progress to arrest. [5]

Preventing cardiovascular collapse. First, have a fluid bolus drawn up and ready to give at induction, and have a vasoactive infusion (such as adrenaline) available to start immediately if the pressure drops. Second, choose a haemodynamically stable agent (ketamine or etomidate) at an appropriate, possibly reduced, dose, and avoid propofol and thiopentone as full induction doses. [3]