Randomized Prospective Evaluation of Cimetidine and Antacid Control of Gastric pH in the Critically III

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Abstract
Critically ill patients (144) admitted to an intensive care setting were randomly assigned to cimetidine or antacid treatment groups. Gastric pH was monitored hourly. Patients (123, 85%) demonstrated a fall in pH to < 4 and were considered to require prophylaxis. Prophylaxis was considered adequate if the measured pH could be maintained at .gtoreq. 4. Patients (58) received antacids alone; the average requirement was 41 cm2/h. Patients (65) received cimetidine; 17 of them (26%) failed to raise their pH, and were then placed on hourly administration of antacid with successful elevations of pH to .gtoreq. 4 in all cases, on an average supplementary dose of 53 cm2/h. Risk factors, including sepsis, hypotension, head injury, respiratory failure, degree of trauma and age, were not statistically different in the 2 treated groups. Using these same criteria, responders to cimetidine could not be differentiated from nonresponders. All patients were protected from significant stress bleeding while on this study. Significant complications of either treatment were minimal. Antacids offered consistent protection against gastric acidity, and were 100% effective. A routine schedule of 300 mg every 6 h of cimetidine was effective in only 47% of patients, and the maximum dose of cimetidine was effective in only 74% of patients. Hourly measurement of intragastric pH is required for monitoring the resonse to prophylaxis of stress bleeding in severely ill patients.