Utility of Central Venous Oxygen Saturation Gradient in Predicting Mortality in Dialysis with Catheter Access

BACKGROUND Central venous oxygen saturation (ScvO2), a biomarker that is well-correlated with arterial oxygen saturation, can predict mortality. Few studies have focused on blood volume, ScvO2, and mortality in patients on maintenance dialysis. This retrospective study used hospital record data of 144 dialysis patients with central venous catheter access (CVC) and aimed to evaluate the ScvO2 gradient, blood volume, and patient mortality. We examined the associations among absolute blood volume (ABV), mean ScvO2, intradialytic slope of ScvO2, and mortality in patients on dialysis. MATERIAL AND METHODS Adult patients receiving dialysis via CVC from 2022 to 2024 were enrolled. ScvO2, ABV, and protocol-based ultrafiltration were monitored using Crit-Line IV (Fresenius Medical Care, Bad Homburg, Germany). Participants were assessed and followed until death or administrative censor. Multiple fractional polynomial (MFP) regression was used to determine best-fitting polynomial function between predictors and mortality. We also constructed proportional hazard model to compare trends of ScvO2 for mortality. RESULTS In a total of 144 eligible patients, the incidence of mortality was 14.5 per 1000 patient-months. The correlation between mean ScvO2 and mortality was weak (r=-0.05), whereas the association between ABV change and mean ScvO2 were a reverse U curve. The intradialytic slope of ScvO2 was independently associated with mortality (adjusted odds ratio [95% CI]=0.421 [0.226-0.783], P<0.05). Those with descending slope of ScvO2 had higher risk of mortality than those with an ascending slope (HR [95% CI]=3.98 [1.22-13.03], P<0.05). CONCLUSIONS A negative trend of intradialytic ScvO2 was associated with mortality.