An 18-month-old undergoing cleft lip repair suddenly develops sinus bradycardia with a heart rate of 58/min and SpO2 of 84% during airway manipulation. The MOST likely cause and immediate action are:

• A Vagal reflex; give atropine before correcting oxygenation
• B Hypoxia; ventilate with 100% oxygen immediately ✓
• C Sevoflurane overdose; reduce inspired concentration first
• D Hyperkalaemia; check serum potassium

Explanation

In paediatric anaesthesia, hypoxia is the commonest cause of intraoperative bradycardia, and the immature myocardium responds to hypoxaemia with bradycardia rather than the tachycardia seen in adults. The immediate action is ventilation with 100% oxygen. Atropine 0.02 mg/kg is given only if bradycardia persists after oxygenation is restored, since treating the vagal component first would delay correction of the true driver. Hyperkalaemia is rare here and sevoflurane overdose typically causes hypotension before marked bradycardia.

Reference: Smith's Anesthesia for Infants and Children, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.