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]