Oxygen Extraction and Mortality in Patients Undergoing Chronic Haemodialysis Treatment: A Multicentre Study

Patients on haemodialysis (HD) suffer a high mortality rate linked to developing subclinical hypoxic parenchymal stress during HD sessions. The oxygen extraction ratio (OER), an estimate of the oxygen claimed by peripheral tissues, might represent a new prognostic factor in HD patients. This study evaluated whether the intradialytic change in OER (Delta OER) identified patients with higher mortality risks. We enrolled chronic HD patients with permanent central venous catheters with available central venous oxygen saturation (ScvO2) measurements; the arterial oxygen saturation was measured with peripheral oximeters (SpO2). We measured OER before and after HD at enrolment; deaths were recorded during two-years of follow-up. In 101 patients (age: 72.9 +/- 13.6 years, HD vintage: 9.6 +/- 16.6 years), 44 deaths were recorded during 11.6 +/- 7.5 months of follow-up. Patients were divided into two groups according to a 40% Delta OER threshold (Delta OER < 40%, n = 56; Delta OER >= 40%, n = 45). The Delta OER >= 40% group showed a higher incidence of death (60% vs. 30%; p = 0.005). The survival curve (log-rank-test: p = 0.0001) and multivariate analysis (p = 0.0002) confirmed a Delta OER >= 40% as a mortality risk factor. This study showed the intradialytic Delta OER >= 40% was a mortality risk factor able to highlight critical hypoxic damage. Using a Delta OER >= 40% could be clinically applicable to characterise the most fragile patients.

Automated summary

Patients on haemodialysis have a high mortality rate due to subclinical hypoxic parenchymal stress during HD sessions. This study investigated whether changes in the oxygen extraction ratio (OER) during HD could predict mortality risk. The results showed that patients with a Delta OER >= 40% had a higher incidence of death, suggesting that Delta OER >= 40% is a significant mortality risk factor in HD patients.