Surgery & Perioperative/General anaesthetic

General anaesthetics

also: propofol · thiopental · sevoflurane · induction agent · volatile

Overview

Agents producing reversible unconsciousness. The anaesthetic triad = hypnosis + analgesia + muscle relaxation. Malignant hyperthermia is the key emergency.

Mechanism

Most potentiate GABA-A receptor inhibitory transmission (propofol, thiopental, volatiles) → CNS depression. Ketamine differs — NMDA-receptor antagonist (dissociative; maintains airway/BP). IV agents for rapid induction; volatile agents (sevoflurane) for maintenance.

Indications

Induction and maintenance of general anaesthesia

The agents

PropofolIV induction

rapid on/off

Most common; causes hypotension, apnoea; pain on injection; antiemetic.

ThiopentalIV barbiturate

very fast

RSI; care in porphyria/airway.

KetamineNMDA antagonist

Maintains BP/airway → trauma, paediatrics; emergence delirium.

Sevoflurane / isofluranevolatile maintenance

inhaled

Trigger for malignant hyperthermia.

Adverse effects

Malignant hyperthermiaserious

Volatiles + suxamethonium trigger; ↑↑temp, rigidity, ↑CO₂ — treat with dantrolene.

Hypotension & respiratory depressioncommon

Post-operative nausea & vomitingcommon

Ketamine: emergence phenomena, ↑secretionscommon

Cautions & contraindications

Personal/family history of malignant hyperthermiaall

Avoid volatiles + suxamethonium.

Propofol caution in egg/soya allergy, haemodynamic instabilityall

Interactions

Additive CNS/respiratory depression with opioids/benzodiazepines

Monitoring & kinetics

Continuous anaesthetic monitoring; temperature/EtCO₂ (MH)

IV induction → volatile maintenance, typically.

Source: BNF — General anaesthesia