Objective: The objective of the study was to investigate a reverse correlation between blood lactate levels and rSO2, and distinguish between hypoxic and non-hypoxic hyperlactatemia seen in the early postoperative period.

The objective of the prospective study was to investigate a reverse correlation between blood lactate levels and rSO2, and distinguish between hypoxic and non-hypoxic hyperlactatemia seen in the early postoperative period.

Sixty American Society of Anesthesiologists (ASA) II-III patients were included in this study. Perioperative data, including age, weight, body surface area, gender, body temperature, preoperative co-morbidities, intraoperative and postoperative hemodynamic parameters, arterial blood gas analysis (ABG), cardiopulmonary bypass and aortic cross-clamp duration, flow rate, urine output, and blood product and inotropic agent usage, were recorded. Postoperative plasma lactate levels were measured simultaneously with cerebral tissue oxygen saturation (rSO2) in both cerebral hemispheres at 10 different time points.

Inclusion Criteria:

• ASA) II-III patients, aged 43-80 years, undergoing on-pump coronary artery bypass grafting

Exclusion Criteria:

• Active congestive cardiac failure, intraoperative death, urgent cardiac surgery or reoperation, hemodynamic instability or need of inotropic support before the operation, the elevation of any parameters preoperatively suggestive of systemic hypoperfusion, coagulopathy, renal failure, hepatic dysfunction, local or systemic infection, and inflammation.

Patients who will undergo elective bypass surgery and extracorporeal circulation