Protection against pulmonary acid aspiration with ranitidine. A new histamine H2-receptor antagonist

Abstract

Ninety patients presenting for elective surgery were randomly divided into three groups A, B and C and studied on a double-blind basis to assess the effects of ranitidine, a new histamine H2 -receptor antagonist and placebo on gastric secretion. Group A received 150 mg ranitidine orally at 2200 hours on the evening before surgery and a further 150 mg 1-2 hours before operation. Group B received 150 mg ranitidine with premedication only, while Group C received a placebo at 2200 hours and again with premedication on the day of surgery. Gastric fluid was aspirated immediately after induction of anaesthesia and the volume and pH of the aspirate measured. Gastric volumes were significantly greater in the placebo group when compared to Group B, but not to Group A. The proportion of patients with pH greater than 2.5 at induction of anaesthesia was 100, 82.3 and 67.9% in Groups A, B and C, respectively. The percentage of patients who had measured gastric volume less than 25 ml or pH greater than 2.5 were Group A--90%, Group B--75.9% and Group C--57%. Thus ranitidine 150 mg orally on the evening before surgery and on the morning prior to anaesthetic induction lowered the mean volume and raised the average pH of gastric content to safe levels in all cases.