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 pH(37C) 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 mug/kg/min dopamine, for at least 45 minutes intraoperatively, and intraoperative or postoperative IAB use. PH (corrected to 37 degrees C, pH(37C)) 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. pH(37C) was significantly lower throughout reperfusion in patients needing INO. Preoperative ejection fraction and pH(37C) 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.