Comparison of mixed venous oxygen saturation after in vitro calibration of pulmonary artery catheter with that of pulmonary arterial blood in patients undergoing living donor liver transplantation

Introduction: Mixed venous saturation (SvO₂) reflects the balance between oxygen delivery and consumption throughout the body. A multifunction pulmonary artery catheter (PAC) can monitor continuous SvO ₂ after in vitro calibration (CSvO₂), obviating the need for in vivo calibration with pulmonary arterial blood. In critically ill patients CSvO₂ has shown a good correlation with measured SvO ₂ of pulmonary arterial blood using co-oximetry (MSvO₂). The aim of this study was to compare CSvO₂ and MSvO₂ in liver transplantation (OLT) recipients. Methods: We enrolled 44 OLT recipients for comparison with 24 coronary artery bypass graft (CABG) controls free of end-stage liver disease. After anesthetic induction, the PAC was inserted after in vitro calibration and CSvO₂ and MSvO₂ simultaneously measured. In OLT recipients, additional measurements of CSvO₂ and MSvO₂ were performed at anhepatic and postreperfusion phases. Pearson's correlation analysis was used to evaluate the correlation between the 2 measurements. A Bland-Altman analysis was used to determine precision of and bias between the 2 measurements. With ±3% regarded to be interchangeable. Results: Cardiac output and intrapulmonary shunt in CABG patients were lower than among OLT recipients. OLT recipients, showed a significant correlation between CSvO₂ and MSvO₂, but the coefficients were different during the three phases of OLT (r = 0.597, 0.753, and 0.756). In addition, bias values between the two measurements were 6.0%, 6.4%, and 2.9% for the preanhepatic, anhepatic, and postreperfusion phases, respectively, with 29.5%, 31.8%, and 50% of them being interchangeable. In contrast CABG patients showed bias in -0.17% with 75% of measurements interchangeable. Conclusion: While in vitro calibration of the PAC can be used in CABG patients, MSvO ₂ is higher than CSvO2 in OLT recipients. Therefore, in vivo calibration with pulmonary arterial blood is necessary for accurate monitoring of SvO₂ in OLT recipients.