Intra-dialytic blood oxygen saturation (SO2): association with dialysis hypotension (the SOGLIA Study)

Background Intradialytic hypotension (IDH) has a dramatic impact on the main outcomes of dialysis patients. Early warning of hemodynamic worsening during dialysis would enable preventive measures to be taken. Blood oxygen saturation (SO2) is used for hemodynamic monitoring in the critical care setting and may provide useful information about IDH onset. Aim To evaluate whether short- and medium-term variations in the SO2 signal (ST-SO2var, MT-SO2var,) during dialysis are a predictor of IDH. Methods In this 3-month observational cohort study, 51 hypotension-prone chronic hemodialysis (HD) patients, with vascular access by arteriovenous fistula (AVF) or central venous catheter (CVC), were enrolled. Continuous non-invasive blood SO2 was monitored (fc = 0.2 Hz) by an optical sensor on the arterial line of the extracorporeal circulation; blood pressure (every 30 min), symptoms and their time of appearance were noted. Predictive power of IDH was expressed by the area under curve (AUC) sensitivity and specificity based on intradialytic variations in SO2. Results A total of 1290 HD sessions were analyzed. Overall, off-line ST-SO2var analysis proved able to correctly predict IDH in 67 % of the sessions where IDH occurred. The best predictive performance was found in the presence of highly arterialized AVF (SO2 > 95 %) (75 % sensitivity; AUC 0.825; p < 0.05). On the contrary, in sessions with CVC, IDH prediction proved more efficient by MT-SO2var (AUC 0.575; p = 0.01). Conclusions Intradialytic SO2 variability could be a valid parameter to detect in advance the hemodynamic worsening that precedes IDH. Appropriate timely intervention could help prevent IDH onset.