Risk Factors and Consequences of Late-Onset Hyperlactatemia After Cardiac Surgery With Cardiopulmonary Bypass: A Single-Center Retrospective Study.

OBJECTIVE: Mechanisms and consequences of late-onset hyperlactatemia after cardiac surgery remain unclear. The aim of this study was to identify risk factors and outcomes of late hyperlactatemia, defined as a lactate value ≥3 mmol/L developing in the intensive care unit (ICU) after not being elevated on admission after cardiac surgery with cardiopulmonary bypass. DESIGN: A retrospective analysis of prospectively collected data. SETTING: A single-center University Hospital. PARTICIPANTS: Patients who underwent elective cardiac surgery with cardiopulmonary bypass in 2019 and who had normal lactatemia at ICU admission. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were divided in 2 groups according to their lactatemia on postoperative day 1 (14.0 ± 3.0 hours after ICU admission): normal lactatemia (control group) and late hyperlactatemia (HL group). Risk factors for late hyperlactatemia were identified using a multivariate analysis, and postoperative outcomes were compared using a composite criterion of severe outcomes. Of the 432 included patients, 37 (8.5%) presented with late hyperlactatemia. Risk factors independently associated with hyperlactatemia were afternoon surgery (odds ratio [OR] 4.24, 95% CI 2.00-9.35), a bleeding >300 mL within the 6 hours after surgery (H6) (OR 3.77, 95% CI 1.71-8.30), and H6 fluid loading >250 mL (OR 2.64, 95% CI 1.22-5.55). Patients with hyperlactatemia presented more frequently with major postoperative complications, including acute kidney injury, and received more frequent red-cell transfusion. CONCLUSION: The strongest risk factors associated with late-onset hyperlactatemia in the authors' population were afternoon surgery and H6 bleeding >300 mL. Poor postoperative outcomes were more frequent in patients with late hyperlactatemia, even in the absence of early hyperlactatemia or severe obvious condition.