Hemoglobin trigger and approach to red blood cell transfusions during veno-venous extracorporeal membrane oxygenation: the international TRAIN-ECMO survey

Introduction: Optimal red blood cell transfusion practice during veno-venous extracorporeal membrane oxygenation (VV ECMO) is still under debate. This survey aimed to assess the Hb trigger (also comparing with other critically ill patients) and major physiologic determinants considered for transfusions during veno-venous extracorporeal membrane oxygenation. Methods: Voluntary Web-based survey, endorsed by the European Society of Intensive Care Medicine, conducted among VV ECMO pratictioners worldwide. Results: A total of 447 respondents worldwide answered the questionnaire: 277 (61.9%) from Europe, 99 (22.1%) from North America, 36 (8.2%) from Asia and Oceania, and 35 (7.8%) from Central and South America. Among the respondents, 59.2% managed less than 12 venous extracorporeal membrane oxygenation runs/year, 19.4% between 12 and 24 runs/year, and 21.4% more than 24 runs/year. Of the respondents, 54.4% do not use a predefined Hb trigger in veno-venous extracorporeal membrane oxygenation, and, while the rate of adoption of a defined trigger varied worldwide, the effective value of Hb did not differ significantly among macro-regions. In patients on veno-venous extracorporeal membrane oxygenation, the Hb trigger to initiate red blood cell transfusion, was higher than in other critically ill patients: 9.1 ± 1.8 g/dL versus 8.3 ± 1.7 g/dL, p < 0.01. The Hb trigger was lower in centers with more than 24 venous extracorporeal membrane oxygenation runs/year (8.4 mg/dL (95% CI: 7.7-8.9)); (8.9 mg/dL (95% CI: 8.2-9.7)) in centers with between 12 and 24 venous extracorporeal membrane oxygenation runs/year; and (9.6 mg/dL (95% CI: 9.1-10.0)) in centers with fewer than 12 venous extracorporeal membrane oxygenation runs/year (p < 0.01). Several and variable adjunctive parameters are considered in cases of uncertainty for transfusion: the principal are hemodynamic status, SvO2, lactates, and fluid balance. Conclusion: Although the use of a predefined Hb trigger is still under-adopted among centers with low or median extracorporeal membrane oxygenation case volume, the majority of respondents use a higher Hb trigger for veno-venous extracorporeal membrane oxygenation patients compared with other critically ill patients. Higher volume centers tolerate lower Hb levels.