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

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.

To evaluate whether short- and medium-term variations in the SO₂ signal (ST-SO_2var, MT-SO_2var,) during dialysis are a predictor of IDH.

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.

A total of 1290 HD sessions were analyzed. Overall, off-line ST-SO_2var 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-SO_2var (AUC 0.575; p = 0.01).

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.