ObjectiveTo compare the frequency of acute stress ulceration and secondary pneumonia caused by aerobic Gram-negative bacilli in ICU patients treated with either sucralfate or ranitidine.DesignProspective, randomized study.SettingICU, university hospital.PatientsSixty adult patients who were mechanically ventilated and at risk of developing stress ulceration.InterventionThe patients were randomized to receive either sucralfate (1 g every 6 hrs) via the nasogastric tube or iv ranitidine (50 mg every 6 hrs). If the gastric pH wasMeasurements and Main ResultsOn admission, the frequency rate of erosion/ulceration (assessed with the endoscope) was 13.5%. After 4 days, this rate had increased to 18% in sucralfate-treated patients and 36% in ranitidine-treated patients (NS). Mean gastric pH was more alkaline in the ranitidine-treated patients (5.50) compared with the sucralfate-treated patients (4.26) (p< .01). This pH permitted a higher occurrence rate of gastric colonization by aerobic Gram-negative bacilli in ranitidine-treated patients (64.3%) compared with sucralfate-treated patients (23.8%) (p< .01). Retrograde bacterial colonization from the stomach to oropharynx and trachea occurred more frequently in ranitidine-treated patients compared with sucralfate-treated patients. Ultimately, the occurrence rate of pneumonia was greater in the ranitidine-treated (35.7%) than in the sucralfate-treated patients (10.3%) (p< .05).ConclusionBased on our findings, we recommend the adoption of sucralfate for routine prophylaxis against stress ulceration. (Crit Care Med 1991; 19:1491)