One hundred fifty-three critical care patients with documented cimetidine and antacid use were prospectively studied with serial gastric pH determinations and semiquantitative gastric fluid cultures. This study documents the abnormal gastric colonization of patients with therapeutically altered gastric acidity by hospital acquired gram negative rods (GNR). Three hundred twenty-four gastric fluid cultures from 153 patients revealed 152 (47%) positive cultures for GNR, 78 (24%) sterile specimens, and 94 (29%) positive for mixed oropharyngeal flora. One hundred forty (59%) of the 236 cultures at a pH of 4 or greater were positive for GNR. In contrast, only 12 (14%) of the 88 cultures at a pH of less than 4 were positive for GNR (p<.001). Forty-six (52%) of 88 cultures at a pH of less than 4 were sterile as compared to only 32 (14%) of 236 sterile cultures at a pH of 4 or greater (p<.001). At low pH, cultures are predominately sterile and at a pH of 4 or greater the flora dramatically changes to hospital acquired GNR. This artificially maintained reservoir of gram negative rods in the critically ill patient is a potential reservoir of organisms causing nosocomial bacteremia or pneumonia in this high risk population.

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causing low output and death. In the remaining 21 patients the cause of death was unrelated to mechanical valve failure. All of the patients in whom this phenomenon of triangulation of the aortic root was noted had undergone aortic valve replacement using the Starr-Edwards model No 2320, in which the three cage struts are cloth covered. This model was discontinued in 1976 and the current models use three stellite struts without the cloth covering. While the older models probably had greater potential to cause outflow obstruction with incorporation of the cloth covered struts into the aortic wall, the tendency to cause triangular deformity with this style of valve prosthesis remains. Although the risk of acute failure and the operative mortality associated with artificial heart valves are small, the medium and long term morbidity is not negligible. Current mechanical prostheses may well prove superior to those used previously but they are not trouble free. Conservative valve reconstruction needs to be encouraged.