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Kidney Week

Abstract: TH-PO222

Oxygen Extraction Ratio (OER) and Intradialytic Hypotension

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Rotondi, Silverio, Sapienza University of Rome, Roma, Italy
  • Tartaglione, Lida, Sapienza University of Rome, Roma, Italy
  • Mazzaferro, Sandro, Sapienza University of Rome, Roma, Italy

Intradialytic hypotension (IDH) worsens treatment tolerance, and outcome of hemodialysis (HD) patients. Attention has been given to the role of HD-induced hypoxia, evaluated by measuring arterial oxygen saturation (SaO2) and central venous saturation (ScvO2), in IDH prone patients. Oxygen Extraction Ratio (OER), the ratio between SaO2 and ScvO2, better than the two parameters alone theoretically describes intra-HD hypoxia. OER basal values and its changes occurring during HD (deltaOER) have been associated with mortality in Hd patients. A delta OER>40% seems to identify patients experiencing sub-clinical hypoxia and parenchymal stress.
Aim of our study was to evaluate if delta OER could help identify patients at higher risk of IDH.


We enrolled clinically stable patients on HD since 3 months, with Central Venous Catheter. we sampled arterial SO2 (oxymeter) and ScvO2 (blood gas analysis) to calculate OER basally and at the end of HD, for three consecutive HD sessions. Average individual measurements were obtained to divide patients into two groups with delta OER > or <40 %. we recorded IDH in each subject, during a 24-months follow-up period.


We divided patients into two group according to delta OER (threshold 40%). The group were not different for age, HD vintage, systolic (SBP) and diastolic blood pressure (DBP) and pulse rate. The group with delta OER >40% had a number of IDH significantly higher than delta OER<40% group (30±20vs.10±20;p= .011), which was associated with lower pre-HD OER (30±4vs.36±8;p<.025) and similar post HD OER values.


Our study indicates that in HD patients, delta OER associate with IDH, with a threshold value set at >40% the basal value. We suggest that we could use OER to identify patients at higher risk of IDH, deserving more intensive intradialytic monitoring. Regrettably, it is applicable only in patients with CVC.