Association of Central Venous Oxygen Saturation Variability and Mortality in Hemodialysis Patients

Abstract

Background: Central venous oxygen saturation (ScvO 2 ) is correlated with cardiac output. In most patients, ScvO 2 declines during hemodialysis (HD) due to factors such as reduced preload, myocardial stunning, and intermittent arrhythmias. Previous research has shown that low ScvO 2 is associated with higher mortality in chronic HD patients. In this research, we tested the hypothesis that ScvO 2 variability is associated with all-cause mortality. Methods: We conducted a retrospective study in 232 chronic HD patients with central venous catheter as vascular access. ScvO 2 was recorded 1× per minute during dialysis using the Crit-Line monitor. A 6-month baseline comprising at least 10 dialysis treatments with ScvO 2 recordings preceded a follow-up period of up to 3 years. The coefficient of variation (CV) of ScvO 2 (100 times the ratio of the standard deviation and mean of ScvO 2 ) served as a measure of ScvO 2 stability during baseline. Patients were stratified by median population CV of ScvO 2 during baseline, and survival during follow-up was compared between the 2 groups by Kaplan Meier and multivariate Cox analysis. The association between CV of ScvO 2 and all-cause mortality during follow-up was further assessed by Cox analysis with a spline term for CV of ScvO 2 . Results: The mean CV ± standard deviation of ScvO 2 in our population was 6.1 ± 2.7% and the median was 5.3%. Univariate Kaplan-Meier analysis (p = 0.043) and multivariate Cox analysis (hazard ratio [HR] 1.16; p = 0.0005) indicated that a CV of ScvO 2 > 5.3% was significantly associated with increased mortality. In Cox analysis with spline term, a CV of ScvO 2 > 11% was associated with a significantly increased HR for all-cause mortality. Conclusion: High ScvO 2 variability during dialysis is associated with increased all-cause mortality.