The association among gastric mucosal pH, endotoxemia, and low systemic vascular resistance after cardiopulmonary bypass

Abstract

Previously, it was found that a number of patients suffer a "low systemic vascular resistance syndrome" after cardiopulmonary bypass, and this was hypothesized to be secondary to endotoxemia, resulting from intestinal ischemia during bypass. Prospective cohort. University teaching hospital. Thirty-two patients undergoing cardiac surgery. A number of variables relating to adequacy of tissue perfusion were measured at seven time periods perioperatively: cardiac output, systemic vascular resistance, oxygen delivery and consumption, oxygen extraction ratio, gastric mucosal pH, serum lactate, and endotoxin levels. Investigators could not find any association between systemic vascular resistance and mucosal pH or endotoxin levels after bypass. There were significant changes in oxygen flux and extraction ratio (p < 0.001) as well as serum lactate (p < 0.001). There was no significant change in endotoxin levels or mucosal pH. The systemic vascular resistance at 6 hours postbypass could be predicted from the vascular resistance reading at 1 hour postbypass by a regression equation. A significant correlation between systemic vascular resistance and mixed venous oxygen was found at 4 and 6 hours postbypass (p < 0.01) as well as with oxygen extraction (p < 0.01). There was a negative correlation between mucosal pH and serum lactate, particularly at 6 hours postbypass (p < 0.01). There was no correlation between mucosal pH and endotoxin levels, oxygen flux, or cardiac output. The investigators therefore could not find any evidence that intestinal ischemia during bypass, as measured by gastric mucosal pH, predisposes to endotoxemia, or low systemic vascular resistance after cardiac surgery.