Cimetidine in the prevention of the pulmonary acid aspiration (Mendelson's) syndrome.

Cimetidine 200 mg was given i.v. 1 h before induction of anaesthesia to 20 patients about to undergo emergency surgery. There was an increase in pH of gastric aspirate in all patients (P less than 0.001) and in 80% pH was greater than 2.5 units at the time of induction of anaesthesia. The pH of gastric aspirate continued to increase after induction of anaesthesia and was greater than 4 units in all patients at the time of tracheal extubation and in the early recovery period.