Paper I — 2024 June (Supplementary) (2019 Scheme) — Q1
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Paper I
2024 June (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
Classify general anaesthetics. Write the mechanism of action, uses and adverse effects
of Halothane. Enumerate four drugs used as pre-anaesthetic medication with its
rationale for use. Discuss the management of Morphine poisoning. (4+3+6+2)
Q115 marksEssays
Answer
Classification of general anaesthetics
Type
Examples
Inhalational — volatile liquids
Halothane, Isoflurane, Sevoflurane, Desflurane
Inhalational — gas
Nitrous oxide
IV — barbiturate
Thiopentone
IV — non-barbiturate
Propofol, Etomidate, Ketamine
Halothane — mechanism, uses, adverse effectsMechanism: potentiates GABA-A receptor-mediated chloride channel opening and inhibits excitatory synaptic transmission, producing dose-dependent CNS depression; exact molecular mechanism of volatile agents is not fully settled but correlates with lipid solubility (Meyer-Overton rule). Uses: maintenance of general anaesthesia (now largely superseded by newer agents). Adverse effects: halothane hepatitis (rare but severe immune-mediated hepatic necrosis from a reactive trifluoroacetyl metabolite, more common with repeated exposure), marked myocardial sensitization to catecholamines (arrhythmia risk with concurrent adrenaline use), malignant hyperthermia (rare, in genetically susceptible individuals), respiratory depression, hypotension.
Four pre-anaesthetic medications, with rationale
Midazolam — anxiolysis and amnesia.
Glycopyrrolate — reduces salivary/bronchial secretions and blocks vagal reflexes.
