Intraoperative regional myocardial acidosis predicts the need for inotropic support in cardiac surgery

Objective To determine the impact of regional myocardial acidosis encountered during cardiac surgery on the need for inotropic and intra-aortic balloon (IAB) support. Methods Intramyocardial tissue pH37C was measured in 247 patients undergoing cardiopulmonary bypass (CPB). Inotropic support (INO) was defined as requiring one or more of norepinephrine/epinephrine/amrinone/dobutamine/>2.5 μg/kg/min dopamine, for at least 45 minutes intraoperatively, and intraoperative or postoperative IAB use. PH (corrected to 37°C, pH37C) during surgery was compared in patients who needed INO versus those who did not. Multivariate logistic regression models identified the determinants of INO. Results Fifty patients (20.2%) required INO intraoperatively. pH37C was significantly lower throughout reperfusion in patients needing INO. Preoperative ejection fraction and pH37C during reperfusion were identified as independent predictors of INO. Conclusions This is the first study to show that intraoperative regional myocardial acidosis, a preventable condition, independently determines the need for intraoperative INO. Increased INO is associated with greater postoperative mortality and morbidity.