Failure of gastric pH control by antacids or cimetidine in the critically ill: a valid sign of sepsis.

To compare the ability of antacids and cimetidine to control gastric pH and potential hemorrhage, 77 critically ill patients were randomized into two groups initially receiving either antacids (37 patients) or cimetidine (40 patients). Gastric pH was monitored hourly and the dosage of medication adjusted as required to maintain gastric pH above 4. Forty-nine patients maintained a pH above 4 while receiving a standard dose of antacids (29 patients) or cimetidine (20 patients). Only 8 of these 49 patients proved to be septic, compared to 20 of the 28 patients who required additional medication to maintain pH above 4 (P less than 0.001). There were five episodes of gastrointestinal hemorrhage occurring in septic patients who had a gastric pH consistently below 4 despite treatment. Excluding septic patients, 8 of 23 failed to maintain a gastric pH of 4 on cimetidine compared to 0 of 26 receiving antacids (P less than 0.005). The data suggest that (1) persistent failure of antacids and/or cimetidine to maintain gastric pH above 4 is yet another indicator of often unappreciated infection, (2) maintaining gastric pH above 4 largely prevents gastrointestinal hemorrhage, and (3) cimetidine is not as consistently effective as antacids in maintaining gastric pH above 4.