Methods: The study included a total of 147 adult patients (104 males, 43 females; mean age 59±11 years; range 36 to 87 years) who underwent elective coronary artery bypass grafting with extracorporeal circulation between November 2011 and December 2012. Arterial blood gas, mixed venous gas, and hemodynamic variables were recorded at postoperative 30, 60, 120 and 240 min, and 24 hours. The patients were classified based on the use of inotropic agents: group 1 included 53 patients who received inotropic support and group 2 included 94 patients who did not. Both groups were assessed with respect to the correlation between the arterial lactate level and mixed venous oxygen saturation, and for other hemodynamic variables.

Results: Early postoperative mortality did not occur. In group 1, a significant correlation was found between the arterial lactate level and mixed venous oxygen saturation at 240 min postoperatively. In both groups and at any time points, the levels of arterial blood gas lactate and blood glucose consistently showed a significant correlation.

Conclusion: Although blood lactate levels provide invaluable information on the adequacy of tissue perfusion, changes in lactate levels do not correlate with mixed venous oxygen saturation, addressing the need for evaluating hemodynamic changes together with lactate levels.