4200 INTERACTIONS BETWEEN INTRADIALYTIC CENTRAL VENOUS OXYGEN SATURATION, RELATIVE BLOOD VOLUME, AND ALL-CAUSE MORTALITY IN HEMODIALYSIS PATIENTS

Abstract Background and Aims In maintenance hemodialysis patients, low central venous oxygen saturation (ScvO2) and small decline in relative blood volume (RBV) have been associated with adverse outcomes [1,2]. Here we explore the interactions between ScvO2 and RBV change in relation to all-cause mortality. Method We conducted a retrospective study in maintenance hemodialysis patients with central venous catheters as vascular access. During a 6-month baseline period, Crit-Line (Fresenius Medical Care, Waltham, MA) was used to measure continuously intradialytic ScvO2 and hematocrit-based RBV. We defined four groups per median change of RBV and median ScvO2. Patients with ScvO2 above median and RBV change below median were defined as reference. The follow up period was 3-years. We constructed a Cox proportional hazards model with adjustment for age, diabetes, and dialysis vintage to assess the association between ScvO2 and RBV and all-cause mortality during follow-up. Results Baseline comprised 5,231 dialysis sessions in 216 patients. The median RBV change was –5.5% and median ScvO2 was 58.8%. During follow-up, 44 patients (20.4%) died. Kaplan-Meier analysis is shown in Figure 1. In the adjusted model, all-cause mortality was highest in patients with ScvO2 below median and RBV change above median (HR 6.32; 95% confidence interval [CI] 1.37 to 29.06), followed by patients with ScvO2 below median and RBV change below median (HR 5.04; 95% CI 1.14 to 22.35) and ScvO2 above median and RBV change above median (HR 4.52; 95% CI 0.95 to 21.36). Figure 1: Kaplan-Meier analysis of survival probabilities in the four subgroups of patients based on the level of central venous oxygen saturation (ScvO2) and relative blood volume (RBV) above and below the median of 58.8% and −5.5%, respectively. Conclusion Concurrent combined monitoring of intradialytic ScvO2 and RBV change may provide additional insights into a patient's circulatory status. Patients with low ScvO2 and small changes in RBV may represent a specifically vulnerable group of patients at particularly high risk for adverse outcomes, possibly related to poor cardiac reserve and fluid overload.