Prognostic value of peak lactate during cardiopulmonary bypass in adult cardiac surgeries: A retrospective cohort study

Objective: Tissue hypoperfusion during cardiopulmonary bypass (CPB) affects cardiac surgical outcomes. Lactate, an end product of anaerobic glycolysis from oxygen deficit, is a marker of tissue hypoxia. In this study, we aimed to identify the prognostic value of blood lactate level during CPB in predicting outcomes in adults undergoing cardiac surgeries. Materials and Methods: We retrospectively reviewed the medical records of patients who underwent cardiac surgeries with CPB from January 2015 to December 2015. Data about the characteristics of patients, preoperative status, type of surgery, and intraoperative lactate levels were collected. The outcomes were in-hospital mortality and complications. The receiver operating characteristics (ROC) curves were used to assess the ability of peak lactate level during CPB in predicting in-hospital mortality. Results: A total of 97 patients, including 61 who underwent emergent or urgent surgery, were enrolled. The types of surgery included coronary artery bypass grafting (CABG, n = 52), valve surgery (n = 27), combined surgery (CABG and valve surgery, n = 4), great vessel surgery (including aortic dissection, n = 9), and others (n = 5). The median CPB time was 139 min (interquartile range = 120-175). The median initial lactate and peak lactate levels during CPB were 0.9 and 4.2 mmol/L, respectively. In-hospital mortality was 14.4%, which was significantly associated with age and peak lactate level in the multivariate logistic regression model. When the peak lactate level during CPB reached 7.25 mmol/L, in-hospital mortality could be predicted with an area under the ROC curve of 0.75 (95% confidence interval: 0.59-0.90; P = 0.003), with a sensitivity of 57% and specificity of 93%.Conclusion: Hyperlactatemia during CPB was associated with increased in-hospital mortality. Thus, early detection of such conditions and aggressive postoperative care are important.