Veno‑venous extracorporeal membrane oxygenation (VV‑ECMO) is associated with a high transfusion burden. While trials have concluded that red blood cell (RBC) storage does not impact patient morbidity and mortality in the critically ill or cardiac surgical cohorts, evidence is sparse for ECMO cohorts. A sheep model was to investigate this question. On an underlying injury of smoke inhalation, we compared fresh (< 5 days) or stored (35–42 days) RBC transfusion with no transfusion. Clinically relevant outcomes included pulmonary artery pressure as well as biochemical or histopathological markers of lung, liver, and renal injury.

Methods

Twenty‑four female Merino/Samm Border Leicester Cross sheep were anaesthetised and placed on pressure‑controlled ventilation. They were instrumented for continuous haemodynamic monitoring. They then underwent smoke inhalation injury, followed two hours later by veno‑venous ECMO. Sheep were randomised to threegroups: control (no transfusion (n = 8)), fresh RBC (n = 8) and stored RBC (n = 8) transfusion occurring six hours after ECMO initiation. Blood samples were taken regularly, and 24 h post‑ECMO, animals were sacrificed. Post‑mortem samples of lung and kidney were collected for post‑mortem analyses.

Results

Following ECMO initiation and transfusion, pulmonary artery pressure increased in the stored RBC group. His topathological analysis also demonstrated a significantly elevated lung injury in this group. This lung injury was characterised by greater extravasation of inflammatory cells as well as bronchiole damage and oedema. Renal histopathology showed no significant differences between groups. Alanine aminotransferase, aspartate aminotransferase and bilirubin levels increased in a time dependent manner post‑transfusion but there were no treatment‑associated differences. During experimentation, the coagulation profile changed with firmer clots forming more quickly. Differences were observed between both transfusion groups and controls.

Conclusions