Frequency, risk factors, and outcome of hyperlactatemia after cardiac surgery

Study objective: To determine the respective frequencies, risk factors, and outcomes of no hyperlactatemia (NHL), immediate hyperlactatemia (IHL), or late hyperlactatemia (LHL) > 3 mmol/L after cardiac surgery. Design: Prospective and observational study. Setting: Cardiac surgery ICU in a 130-bed private community nonteaching hospital. Patients: Consecutive patients (n = 325) undergoing cardiopulmonary bypass (CPB) for cardiac surgery. Intervention: None. Measurements: Arterial blood gas levels and lactate concentrations were measured at ICU admission, 4 h after surgery, between 6 h and 16 h after surgery, and on day 1. Main results: Sixty-seven patients (20.6%) had an IHL on ICU admission, and 56 patients (17.2%) acquired LHL during their ICU stay. ICU mortality was 1.5% for NHL, 3.6% for LHL, and 14.9% for IHL groups (p < 0.0001). The three groups differed significantly for elective surgery, type of operation, CPB duration, intraoperative mean arterial pressure, and intraoperative and postoperative use of vasopressor. Independent risk factors for IHL were nonelective surgery, CPB duration, and intraoperative use of vasopressor. Logistic regression identified hyperglycemia and epinephrine therapy for LHL as postoperative risk factors. Receiver operating characteristic curves showed that IHL more accurately predicted ICU mortality than LHL. Conclusions: Hyperlactatemia is common after cardiac surgery. A lactate threshold of 3 mmol/L at ICU admission is able to identify a population at risk of morbidity and mortality after cardiac surgery.