Anaes SAQs · Volatile & inhalational agents

Isoflurane: pharmacology, metabolism and adverse effects

Final — isoflurane (fluorinated methyl ether; BP 48.5 degrees C; non-flammable; PUNGENT — not for inhalational induction; blood-gas 1.4, oil-gas 91; MAC about 1.15 percent adults; about 0.2 percent metabolised, the least metabolised volatile, no compound A, negligible fluoride). Onset and offset slower than sevoflurane (0.65) and desflurane (0.42) due to higher solubility. Vasodilator — reduces SVR and MAP, more vasodilation than sevoflurane, cardiac output preserved; coronary steal historically feared but clinically insignificant in well-managed coronary disease. Preconditioning via RISK pathway and mitochondrial K-ATP channels — preclinical cardio- and neuroprotection, clinical significance debated, balanced against neurotoxicity in the developing brain. Adverse effects: pungency (cough/laryngospasm if used for induction), MH trigger, neurotoxicity in neonates, postoperative cognitive dysfunction in the elderly (debated), greenhouse gas.