Cimetidine in anesthesia: does it minimize the complications of acid aspiration?

The use of cimetidine, an H2-receptor antagonist, to minimize the complications of acid aspiration pneumonia is reviewed. Since Mendelson's early description of acid aspiration in 66 obstetrical patients, attempts have been made to decrease gastric acidity by administering perioperative antacids and/or antihistamine drugs such as atropine and glycopyrrolate. In this review of the literature, strict attention is given to study design and subject selection, methods of collecting gastric samples and reporting both pH and volume measurements, and medications taken on admission, given preoperatively, and as anesthetics. Clinical trials evaluating cimetidine alone and compared with other prophylactic regimens were reviewed, detailing the timing, route, and frequency of drug administration. Cimetidine appears to be effective in minimizing complications of acid aspiration since gastric acidity (pH less than 2.5) is a contributing factor in both the morbidity and mortality of this disease state. In general terms, cimetidine 300 mg po 1.5-2.0 h prior to intubation or 45-60 minutes iv before surgery will decrease gastric acidity below the critical level. This effect may be maintained for up to three hours. Perioperative cimetidine administration, to minimize the complications of acid aspiration, appears to be safe in terms of drug-drug interactions and effects on labor, the fetus, and the newborn child.