Ranitidine--bolus or infusion prophylaxis for stress ulcer.

Stress ulcer is a dangerous complication for the critically ill patient. Prophylaxis with antacids can undoubtedly reduce this risk, if gastric pH is maintained above 3.5. Histamine receptor antagonists may achieve this more conveniently. We have studied the effects of ranitidine, given either as 50-mg boluses every 6 h or as one of two infusion regimes (125 or 250 micrograms/kg.h), in controlling pH in critically ill patients on a ventilator. The percentage of samples with a pH less than 4 fell in all groups during therapy; while there was no significant difference between groups, pH control was achieved more rapidly in the bolus group. Infusion therapy with ranitidine is an attractive concept but a loading dose must be used. The presence of occult blood in the gastric juice did not correlate with pH and was not affected by ranitidine therapy.