Early Mortality in Cardiac Surgery - Is Lactate Significant?

Introduction: Serum lactate is a consequence of tissue hypoperfusion and has been used routinely for patient management following cardiac surgery. This study aims to determine the association of lactate with early mortality and postoperative morbidity.

Methods: This is a prospective cohort study carried out in the Department of Cardiovascular and Thoracic Surgery, King George's Medical University (India), from January 2020 to December 2022. A total of 270 patients were included in this study. Serum lactate levels were measured preoperatively, intraoperatively on-pump, coming off-pump, and at six, 12, 24, and 48 hours postoperatively.

Results: Early mortality was noted in 17 cases (6.3%). While both lactate and lactate clearance correlated with duration of mechanical ventilation, vasopressor duration, and intensive care unit and hospital stay, correlation with early mortality was noted only with lactate at 24 hours. Logistic regression analysis demonstrated that lactate levels at preoperative period (adjusted odds ratio [OR] 4.76 [1.67-13.59], P=0.004) and at 24 hours after bypass (OR 1.21 [1.00-1.47], P=0.046) and vasopressor duration (OR 1.11 [1.04-1.19], P=0.002) are independent predictors of mortality. Receiver operating characteristic curve analysis showed that arterial lactate on-pump, off-pump, and at six, 12, and 24 hours after surgery had significant area under the curve for predicting mortality.

Conclusion: Arterial lactate and lactate clearance show good correlation with duration of mechanical ventilation, vasopressor support, and intensive care unit and hospital stay and can serve as a good indicator to guide therapeutic decisions in postoperative period. However, it fails to be a sensitive predictor of mortality.