Lactate release during reperfusion predicts low cardiac output syndrome after coronary bypass surgery

Background. Cardioplegic arrest induces anaerobic myocardial metabolism wit h a net production of lactate from glycolysis. However, persistent lactate release during reperfusion suggests a delayed recovery oi normal aerobic me tabolism and may lead to depressed myocardial function necessitating inotro pic or intraaortic balloon pump support (low output syndrome [LOS]). We exa mined the relation between perioperative myocardial metabolism and postoper ative clinical outcomes in patients undergoing isolated coronary artery byp ass surgery (CABG). Methods. We reviewed 623 patients who were enrolled in clinical studies eva luating perioperative myocardial metabolism between 1983 and 1996. Arterial and coronary sinus blood samples were obtained intraoperatively to assess myocardial metabolism. Clinical data regarding patient demographics and pos toperative outcomes were prospectively collected and entered into our insti tutional database. Results. Low output syndrome developed in 36 patients (5.8%). Myocardial la ctate release was higher in these patients compared with those who did not develop postoperative LOS, Advanced age and poor preoperative left ventricu lar function were independent predictors of lactate release during reperfus ion. Persistent lactate release after 5 minutes of reperfusion was the only independent predictor of postoperative LOS in this low-risk population. Conclusions. Persistent lactate release during reperfusion occurs in a sign ificant proportion of low-risk patients undergoing isolated CABG and is an independent predictor of postoperative low cardiac output syndrome. Persist ent lactate release during reperfusion suggests a delayed recovery of aerob ic myocardial metabolism and may be related to intraoperative misadventure or inadequate myocardial protection. Myocardial lactate release may be usef ul as an alternative end-point in clinical trials evaluating perioperative myocardial protection. (C) 2001 by The Society of Thoracic Surgeons.