Control of gastric pH with ranitidine in critically ill patients. Comparison of two intravenous regimens.

The effects of continuous versus bolus administration of ranitidine on gastric pH were compared in critically ill patients admitted to our intensive care unit. Patients were randomized to receive 0.2 mg/kg/hr ranitidine in continuous infusion or 50 mg in bolus every 4 hr. The pH was monitored throughout a 24-hr period, 2 hr in basal conditions and 22 hr during treatment, with a gastric probe. Basal gastric pH was 2.1 +/- 0.2 in the infused and 2.4 +/- 0.2 in the bolus group (P greater than 0.05). The hydrogen ion concentrations were 25.1 +/- 8 and 20.0 +/- 7 mmol/liter, respectively (P greater than 0.05). After ranitidine administration, mean pH was 6.3 +/- 0.6 in patients treated by infusion and 4.5 +/- 0.5 (P less than 0.001) in those who received the drug in bolus; hydrogen ion concentration was 2.5 +/- 2 and 6.9 +/- 6, respectively, (P less than 0.001). Percent of inhibition of acid secretion was 90% in the infused and 68% in the bolus group. Infusion raised pH to values constantly above 4, whereas bolus administration resulted in wide fluctuations. These data indicate that continuous infusion of ranitidine is superior to bolus administration in controlling gastric acidity in critically ill patients.