Perioperative central venous oxygen saturation and its correlation with mortality during cardiac surgery: an observational prospective study

BACKGROUND: Cardiac surgery can produce persistent deficit in the ratio of Oxygen Delivery (DO(2)) to Oxygen Consumption (VO(2)). Central venous oxygen Saturation (ScvO(2)) is an accessible and indirect measure of DO(2)/VO(2) ratio. OBJECTIVE: To monitor perioperative ScvO(2) and assess its correlation with mortality during cardiac surgery. METHODS: This prospective observational study evaluated 273 patients undergoing cardiac surgery. Blood gas samples were collected to measure ScvO(2) at three time points: T0 (after anesthetic induction), T1 (end of surgery), and T2 (24 hours after surgery). The patients were divided into two groups (survivors and nonsurvivors). The following outcomes were analyzed: intrahospital mortality, length of Intensive Care Unit (ICU) and hospital stay (LOS), and variation in ScvO(2). RESULTS: Of the 273 patients, 251 (92%) survived and 22 (8%) did not. There was a significant perioperative reduction of ScvO(2) in both survivors (T0 = 78% ± 8.1%, T1 = 75.4% ± 7.5%, and T2 = 68.5% ± 9%; p < 0.001) and nonsurvivors (T0 = 74.4% ± 8.7%, T1 = 75.4% ± 7.7%, and T2 = 66.7% ± 13.1%; p < 0.001). At T0, the percentage of patients with ScvO(2)< 70% was greater in the nonsurvivor group (31.8% vs. 13.1%; p = 0.046) and the multiple logistic regression showed that ScvO(2) is an independent risk factor associated with death, OR = 2.94 (95% CI 1.10−7.89) (p = 0.032). The length of ICU and LOS were 3.6 ± 3.1 and 7.4 ± 6.0 days respectively and was not significantly associated with ScvO(2). CONCLUSIONS: Early intraoperative ScvO(2) < 70% indicated a higher risk of death. A perioperative reduction of ScvO(2) was observed in patients undergoing cardiac surgery, with high intraoperative and lower postoperative levels.