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

Background And Aim: 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.

Methods: 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).

Results: 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.

Conclusion: 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.