Relationship between intraoperative serum lactate and hemoglobin levels on postoperative renal function in patients undergoing elective cardiac surgery.

Abstract

We examined the relationship between serum lactate and hemoglobin levels on renal function and postoperative outcome in low-risk elective coronary artery bypass graft (CABG) patients. Intraoperative hemoglobin and lactate levels were measured in elective isolated CABG patients. Patients with renal dysfunction (baseline creatinine>2 mg/dL) were excluded. Multivariate logistic regression was used to determine associations between lactate, hemoglobin, and acute kidney injury (AKI). A total of 375 patients met study requirements, and 56/375 (15%) developed AKI. Of the patients who developed AKI, 43/278 (15.5%) were males, 13/97 (13.4%) females, and 11/44 (25%) African-Americans. Bivariate analysis between AKI and non-AKI subgroups found significant differences in age, race, baseline estimated glomerular filtration rate, preoperative hemoglobin, peak serum lactate, initial hemoglobin, and nadir hemoglobin. A high peak Lactate level (odds ratio [OR] 1.44[1.15-1.82]), low hemoglobin (OR 0.69[0.49-0.96]), and African American race (OR 2.26[0.96-5.05]) were independently associated with acute kidney injury. A significant relationship between decreasing intraoperative hemoglobin and increasing intraoperative serum lactate levels was observed exclusively in patients who developed postoperative AKI. Serum creatinine levels peaked, on average, 48 h postoperatively in the AKI subset of patients. In this series, 15% of patients who underwent elective cardiopulmonary bypass developed transient acute renal dysfunction. High lactate levels and low hemoglobin levels during cardiopulmonary bypass were associated with an increased risk of kidney injury.