The relationship between hemoglobin concentration and mortality in patients receiving venovenous extracorporeal...

Restrictive red blood cell (RBC) transfusion strategies are increasingly used during venovenous extracorporeal membrane oxygenation (VV ECMO), but the prognostic implications of sustained exposure to low hemoglobin concentrations remain uncertain. We investigated the associations of longitudinal hemoglobin exposure with 60-day mortality and successful ECMO weaning in patients receiving VV ECMO.

We retrospectively analyzed adults receiving VV ECMO for at least 48 hours at a single center between January 2015 and May 2024. Patients who were pregnant or had received ECMO for >3 days at an outside hospital before transfer were excluded. Time-weighted average hemoglobin (TWA-Hb) was calculated from serial venous complete blood count measurements by weighting each hemoglobin value according to the time interval represented by that measurement. Patients were categorized as <70, 70-<80, 80-<90, and ≥90 g/L. The proportion of ECMO support time with hemoglobin <70 g/L was calculated as an exploratory measure of cumulative severe-anemia exposure. The primary outcome was 60-day mortality.

Among 182 patients, the median age was 59 years, 74.2% were male, and 97.3% received RBC transfusions (median 20 units). Seventy-five patients (41.21%) died within 60 days. Compared with the ≥90 g/L group, TWA-Hb <70 g/L was associated with a higher hazard of 60-day mortality [adjusted hazard ratio (HR) 3.47, 95% confidence interval (CI): 1.00-12.03, P=0.049]. In adjusted logistic regression, the odds ratios (ORs) for successful ECMO weaning within 60 days were 0.13 (95% CI: 0.04-0.38, P<0.001) for the <70 g/L group and 0.26 (95% CI: 0.09-0.72, P=0.01) for the 70-<80 g/L group, compared with the ≥90 g/L group.

TWA-Hb <70 g/L during VV ECMO was associated with higher 60-day mortality and a lower likelihood of successful ECMO weaning. Sustained exposure to severe anemia below 70 g/L warrants particular clinical attention and should be minimized when feasible. These findings support further prospective evaluation of hemoglobin-management strategies aimed at reducing prolonged severe-anemia exposure during VV ECMO.