Emergency cimetidine prophylaxis against acid aspiration.

Preoperative cimetidine (300 mg IV) was given to assess timing and efficacy of prophylactic cimetidine to increase gastric pH in emergency surgical patients. Two-thirds had an initial gastric pH less than or equal to 2.5, with a mean pH of 2.13 +/- 0.60 as a group. Cimetidine administration resulted in a significant increase in mean pH at intubation (3.25 +/- 0.90), with a mean preoperative premedication interval of 59 +/- 20 minutes. However, 20% failed to achieve a gastric pH greater than 2.5 prior to intubation. The mean gastric pH at extubation (5.09 +/- 1.55) was also significantly increased compared to precimetidine and preintubation levels. Prophylactic cimetidine might protect many, but not all, emergency patients from acid-induced aspiration pulmonary injury at intubation or extubation.