Anaes · Intravenous induction agents
Intravenous induction agents
Also known as IV induction · Propofol · Thiopental · Ketamine · Etomidate · Midazolam
The intravenous induction agents produce a rapid, smooth loss of consciousness whose recovery is governed by redistribution from the brain to the muscle and fat. The framework rests on four exam-critical ideas: the agents act principally at the GABA-A receptor (propofol, thiopental, etomidate and the benzodiazepines), with ketamine the exception at the NMDA receptor; their speed of onset and offset is the property of a lipid-soluble drug distributing into a large volume and then redistributing; propofol is the default, but its hypotension, its propofol-infusion syndrome, and its emulsion base each carry a caveat; and the choice of agent is governed above all by the patient's haemodynamic and disease state — the shocked patient needs ketamine or etomidate, not propofol; the asthmatic needs ketamine; and etomidate carries the adrenal-suppression controversy. Built on the etomidate-adrenal meta-analysis (Albert 2011), the propofol-infusion-syndrome papers (Kam & Cardone 2007, Bray 1999), the ketamine-in-traumatic-brain-injury trials (BIKe, KETA-BID), the esketamine review (Hu 2026), and the pharmacogenomics review (Kassab 2026).
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8 MCQs with explanations
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Meet the patient
A hypovolaemic trauma patient in shock needs rapid-sequence induction. The registrar reaches for propofol out of habit. The consultant stops them — propofol's vasodilation will drop what little pressure remains. The right agent here is ketamine (sympathetic stimulation) or etomidate (haemodynamic neutrality).[1]
The single rule that governs induction-agent choice is the patient's haemodynamic and disease state, not the agent the anaesthetist happens to like. Match the agent's profile to the patient, and everything else follows.[1][7]
You have read the opening of this topic. The complete unit — every section and its primary-source references — is part of the Anaesthesia fellowship atlas.
References7Show ledgerHide ledger
- [1]Albert SG, Ariyan S, Rather A. The effect of etomidate on adrenal function in critical illness: a systematic review Intensive Care Med, 2011.PMID 21373823
- [2]Kam PC, Cardone D. Propofol infusion syndrome Anaesthesia, 2007.PMID 17567345
- [3]Bray RJ. Propofol-infusion syndrome in children Lancet, 1999.PMID 10376650
- [4]De Sloovere V, Mebis L, Wouters P, et al. Brain Injury and Ketamine study (BIKe): a prospective, randomized controlled double blind clinical trial to study the effects of ketamine on therapy intensity level and intracranial pressure in severe traumatic brain injury patients Trials, 2025.PMID 40437634
- [5]Andreasen TH, Olsen MH, Gluud C, Lindschou J, et al. S-ketamine versus placebo for cortical spreading depolarisation in severe acute brain injury (KETA-BID): protocol for a pilot, randomised, blinded clinical trial BMJ Open, 2025.PMID 40721263
- [6]Hu HL, Huang QZ, Xie PX. A comprehensive review of the clinical progress of esketamine: From anesthesia to antidepressant therapy Medicine (Baltimore), 2026.PMID 42065202
- [7]Kassab N, Abourjeili J, Eid MJ, Raphael CK. Pharmacogenomics of commonly used intravenous anesthetics Pharmacogenet Genomics, 2026.PMID 41437621