Monitoring Value of Central Venous Oxygen Saturation, the Substitute for Mixed Venous Oxygen Saturation, in Postoperative Care of Congenital Heart Disease with Pulmonary Arterial Hypertension:a Multicenter Prospective Study

  Objective   This study aimed to investigate the agreement of central venous oxygen saturation (ScvO₂) with mixed venous oxygen saturation (SvO₂) in postoperative care of congenital heart disease (CHD)with pulmonary arterial hypertension (PAH).

  Methods   Forty-three patients undergoing CHD-PAH repairing surgery were prospectively selected from Henan Provincial People's Hospital, Fuwai Hospital, the Eighth Affiliated Hospital of Sun Yat-sen University, and the First People's Hospital of Guanyuang from March 2016 to March 2017. Data of ScvO₂ and SvO₂ were synchronously collected after cardiopulmonary bypass (CPB), and 6, 12, 24, and 48 hours after admission to the intensive care unit. In addition, hemodynamic parameters, hemoglobin, and arterial lactate were recorded. Data were analyzed by Bland-Altman test and linear regression analysis.

  Results   The overall R² of ScvO₂ to SvO₂ for the pooled measurements was 0.369. R² of post-CPB, 6, 12, 24, 48 hours after admission to the intensive care unit were 0.515, 0.375, 0.605, 0.712, and 0.252, respectively. Bland-Altman test for ScvO₂ and SvO₂ showed that the mean bias was -1.3% and limits of agreement (LOA) were -17.0% to 14.4%. In general, the influences of oxygen extraction rate (O₂ER) (R²=0.030, P < 0.05), pulmonary artery systolic pressure (SPAP) (R²=0.030, P < 0.05), and heart rate (HR) (R²=0.032, P < 0.05) on △ScvO₂-SvO₂ were relatively small; when ScvO₂ was < 70%, the influences of O₂ER (R²=0.203, P < 0.01), SPAP (R²=0.110, P < 0.01), and HR (R²=0.150, P < 0.01) were much greater, and ScvO₂ would underestimate SvO₂; ScvO₂ might overestimate SvO₂ when ≥ 70%. Bland-Altman test indicated during mechanical ventilation the mean bias of ScvO₂ and SvO₂ (△ScvO₂-SvO₂) was -1.3% and LOA were -16.1% to 13.5%, the only factor influencing △ScvO₂-SvO₂ was O₂ER (R²=0.122, P < 0.01); without mechanical ventilation, the mean bias was -1.3% and LOA were -19.5% to 16.8%, and the influence on △ScvO₂-SvO₂ were O₂ER (R²=0.320, P < 0.01) and arterial oxygen saturation (R²=0.320, P < 0.01).

  Conclusions   ScvO₂ cannot replace SvO₂ in postoperative care for patients with CHD-PAH. ScvO₂ and SvO₂ should be monitored respectively to exclude the hypo-perfusion state when ScvO₂ ≥ 70%.