Serum Lactate Is not Correlated with Mixed or Central Venous Oxygen Saturation for Detecting Tissue Hypo Perfusion During Coronary Artery Bypass Graft Surgery: A Prospective Observational Study.

Objectives: Effective assessment of tissue perfusion is highly important during Coronary Artery Bypass Graft (CABG). Mixed venous O2 saturation (Svo2) is one of the best and routinely used markers of tissue perfusion. However, this method is costly and leads to considerable complications. Thus, the present study aimed to determine whether the Svo2 can be substituted with central venous saturation (Scvo2) and if there is any correlation between lactate level and Svo2.

Methods: This prospective observational study was conducted on 62 patients scheduled for CABG. After induction and maintenance of anesthesia, blood samples drawn from central venous, pulmonary artery, and radial artery were used to measure Scvo2, Svo2 and serum lactate level respectively before and after Cardio Pulmonary Bypass (CPB). Pearson's correlation test was used to determine the correlation between Svo2 and Scvo2 as well as between Svo2 and serum lactate level. Besides, P < 0.05 was considered as statistically significant.

Results: Overall, 62 Patients, 33 males (53.2%) and 29 females (46.8%) were enrolled into the present study. The most common coexisting illness was hypertension detected in 33 patients (53.2%) followed by hypercholesterolemia in 28 ones (44.4%). In this study, Svo2 was positively correlated with Scvo2 (r = 0.63, P < 0.001). However, no correlation was found between Svo2 and lactate (r = 0.124, P = 0.348).

Conclusions: In summary, Scvo2 is considered as the best substitute of Svo2 for detecting tissue hypo perfusion during CPB. Although the lactate level had been considered as an appropriate marker of tissue perfusion and ischemia, it was not correlated to Svo2 during CABG.