Procedural sedation medicines — formative SAQs

SAQ 1 (10 marks)

A 5-year-old, 18 kg, presents with a displaced distal forearm fracture requiring reduction. She has a clear chest and no airway abnormality. The team plans procedural sedation with ketamine. [1]

1. Describe the pharmacology of ketamine that makes it suitable for this procedure, and state the intravenous and intramuscular doses for a child of this weight. (4) [1]
2. Outline the pre-sedation setup and monitoring you would put in place before giving the drug, including the role of capnography. (3) [5]
3. The procedure is urgent and the child ate an hour ago. Explain how the fasting evidence informs your decision to proceed. (3) [4]

Model answer

Ketamine is a non-competitive NMDA receptor antagonist that produces dissociative sedation with genuine analgesia; it stimulates the sympathetic nervous system so blood pressure and heart rate are preserved, and it maintains airway reflexes and muscle tone, which is why it is tolerated for painful procedures outside the operating theatre. For an 18 kg child the intravenous dose is roughly 1 to 2 milligrams per kilogram, about 18 to 36 milligrams, titrated to effect, and the intramuscular dose is 4 to 5 milligrams per kilogram, about 72 to 90 milligrams, used when intravenous access is not feasible. Its predictable adverse effects are hypersalivation, nausea and vomiting, nystagmus, and emergence phenomena, and its serious events, laryngospasm and transient apnoea, are rare and cluster in the very young and the heavily dosed. [1] [2]

Before the drug, I confirm an independent sedationist whose sole task is the airway, distinct from the proceduralist, and run the SOAP-ME checklist: working suction, oxygen and a mask, appropriately sized airway adjuncts and a supraglottic device, drawn-up sedatives with naloxone and flumazenil, and monitors. Monitoring is continuous pulse oximetry, ECG, and intermittent blood pressure with alarm limits set, plus continuous capnography. Capnography matters because it detects the shallow or slowing breaths of hypoventilation within seconds, whereas pulse oximetry lags badly once supplemental oxygen is given, so it can read normal while the child becomes hypercapnic. [5]

The fasting evidence informs but does not delay the decision. Bhatt's multicentre cohort in JAMA Pediatrics found that the duration of preprocedural fasting was not associated with the risk of desaturation, vomiting, or aspiration during emergency department sedation, and earlier and later studies reached the same conclusion. For an urgent painful fracture reduction I would therefore proceed without a fasting delay, document the decision, and manage the small aspiration risk with suction readiness, lateral recovery positioning, and an alert team rather than with postponement. [4]

SAQ 2 (10 marks)

A 3-year-old becomes stridulous and develops paradoxical chest movement during ketamine sedation for facial laceration repair. [2]

1. Give your immediate stepwise management of this event. (4) [2]
2. Name the risk factors that predict laryngospasm in paediatric procedural sedation and how you would screen for them before sedating. (3) [2]
3. Contrast nitrous oxide and dexmedetomidine as alternatives or adjuncts, including one key contraindication and one key adverse effect of each. (3) [3]

Model answer

I would stop the procedure and the sedative at the first sign of stridor or paradoxical movement and call for help. I apply a firm jaw thrust, a continuous positive airway pressure seal, and one hundred per cent oxygen, and suction any secretions; many episodes resolve with these steps. If spasm persists I deepen with a propofol bolus or give a small dose of a rapid-acting neuromuscular blocker by skilled hands, and I have the difficult-airway pathway and a supraglottic device ready, because a child who cannot be ventilated is seconds from harm; if ventilation fails I move to a supraglottic device or rapid sequence intubation. [2]

The predictors of laryngospasm in paediatric procedural sedation are young age, an active upper respiratory infection, procedures around the airway and head and neck, and underlying airway or neurological abnormality. I screen before sedating by asking about recent coryza, cough, snoring, and obstructive symptoms, by examining for stridor or stertor, mouth opening, and neck stiffness, and by weighing age and procedure site against the plan; a young child with an upper respiratory infection having a facial procedure is exactly the combination that should make me reconsider depth, agent, or setting. [2]

Nitrous oxide is an inhaled agent giving minimal to moderate sedation with analgesia and a rapid onset and recovery, suited to brief, moderately painful procedures; its key contraindication is any state where gas expansion is dangerous, such as pneumothorax or bowel obstruction, and it is also contraindicated in vitamin B12 or folate deficiency because it inhibits methionine synthase. Dexmedetomidine is a selective alpha-2 agonist producing rousable, natural-sleep sedation that spares respiratory drive and is useful in the neurodevelopmentally complex child or for imaging; its characteristic adverse effects are bradycardia and hypotension, and combining it with ketamine blunts ketamine emergence phenomena. [3] [5]