Anaes SAQs · Volatile & inhalational agents

Desflurane: pharmacology, the heated vaporiser and the environmental debate

Final — desflurane (fluorinated methyl ethyl ether; BP 23.5 degrees C — BOILS at room temperature, needs the heated pressurised Tec 6 vaporiser at 39 degrees C and 2 atm; non-flammable; EXTREMELY PUNGENT — coughing, breath-holding, laryngospasm, never for mask induction; blood-gas 0.42 — the LOWEST of any volatile, fastest onset and offset; oil-gas 19, low lipid solubility; MAC about 6.0 percent — the HIGHEST of all volatiles; about 0.02 percent metabolised, virtually unmetabolised, exhaled unchanged; rapid emergence ideal for day-case, neuroanaesthesia, obesity; sympathetic activation above 1 MAC and on rapid up-titration — tachycardia/hypertension; CO formation worst of volatiles with desiccated absorbent; MH trigger. Environmental — the WORST greenhouse gas of all anaesthetics: GWP 2540, atmospheric lifetime 14 years, vs sevoflurane (GWP 130, 1 year) and isoflurane (GWP 510, 3 years); some institutions have banned or restricted it; low-flow techniques and avoidance in routine cases; the rapid-recovery-benefit-versus-environmental-cost debate.