Decrease in blood pressure dose-dependent, due to myocardial depression and blunting of baroreceptor-mediated tachycardic response to hypotension. Sinus bradycardia, wandering pacemaker, and junctional rhythm not uncommon. Respiration depressed. Hypoxic pulmonary vasoconstriction depressed, which may lead to increased pulmonary shunt. Hypoxemia-induced increase in ventilation abolished at low halothane concentration. Can produce elevated carbon monoxide levels in presence of dry carbon dioxide absorbent within circle breathing system of anesthetic machine. May cause decrease in hepatic, renal and splenic blood flow. Induces hepatic microsomal enzyme function. Incidence of halothane-induced hepatitis is 1:10000 to 1:30000 anesthetics (less in children); most often occurs following repeat administration (etiology is probably immune-mediated; mortality is 50%). Dilates cerebral vasculature and may, in certain conditions, increase intracranial pressure. May trigger malignant hyperthermia; avoid use in susceptibility to malignant hyperthermia. Use of other inhaled anesthetics associated with rare cases of perioperative hyperkalemia (concomitant use of succinylcholine associated with many reported cases, but not all). Risk of hyperkalemia increased in pediatric patients with underlying neuromuscular disease (e.g. Duchenne muscular dystrophy). Other abnormalities may include elevation in CPK and myoglobinuria. Monitor closely for arrhythmias. Hyperkalemia should be identified and treated.