Positive Correlation Between Regional Cerebral Oxygen Saturation and Mixed Venous Oxygen Saturation During Off-Pump Coronary Artery Bypass Surgery

BACKGROUND: The balance of oxygen delivery and consumption is essential in patients who are critically ill. Mixed venous oxygen saturation (S v̄O 2 ) is a standard method to evaluate oxygen delivery and consumption during anesthesia. However, S v̄O 2 is monitored through a pulmonary artery catheter, which is invasive. Regional cerebral oxygenation (rScO 2 ) reflects oxygen saturation in a small region of the frontal lobes and is monitored noninvasively through near-infrared spectroscopy. In the present study, the correlation between rScO 2 and S v̄O 2 was calculated during off-pump coronary artery bypass grafting surgery to determine whether a positive correlation exists between rScO 2 and S v̄O 2 . METHODS: A total of 56 subjects were consecutively enrolled in the study. Then rScO 2 and S v̄O 2 were simultaneously monitored. The parameters were recorded at 5 time points: T 1 , 10 min after intubation (1.0 F IO 2 for 10 min); T 2 , 20 min after intubation (0.60 F IO 2 for 10 min); T 3 , at the end of the revascularization of the left anterior descending artery (0.60 F IO 2 ); T 4 , after protamine infusion (0.60 F IO 2 ); and T 5 , 10 min after protamine infusion (1.0 F IO 2 for 10 min). The correlation between rScO 2 and S v̄O 2 and the variation trend between rScO 2 and S v̄O 2 when F IO 2 increased from 0.60 to 1.0 were analyzed. RESULTS: There was a significant positive correlation between rScO 2 and S v̄O 2 at these 5 time points (r 2 = 0.77, 0.81, 0.70, 0.83, and 0.92, respectively). There also was a significant positive correlation between Δ rScO 2 and Δ S v̄O 2 ( n = 112, r 2 = 0.72, P < .001). Linear regression analysis revealed that S v̄O 2 had a positive correlation with rScO 2 and cardiac output (r 2 = 0.68, P = .013). CONCLUSIONS: There was a positive correlation between rScO 2 and S v̄O 2 during off-pump coronary artery bypass grafting surgery, and there also was a positive correlation in the variation trend between rScO 2 and S v̄O 2 .