Alternative models of consent in out-of-hospital transfusion trials: a CAN-PATT position statement supporting exception from prospective consent with opt-out notification.

Out-of-hospital blood transfusion (OHBT) trials in trauma face unique ethical and operational challenges. Patients are often incapacitated, time-critical interventions preclude traditional consent, and surrogate decision-makers are rarely accessible in the out-of-hospital environment. The Canadian Prehospital and Transport Transfusion Network (CAN-PATT) supports the use of alternative models of consent to enable rigorous evaluation of OHBT strategies. This position statement outlines the ethical and regulatory justification for an exception from prospective consent with opt-out notification model used in the SWiFT Canada (Study of Whole Blood in Frontline Trauma) pilot randomized controlled trial. Grounded in the Tri-Council Policy Statement 2 (TCPS2) Article 3.8 governing research in medical emergencies, the SWiFT Canada model uses multi-modal notification and post-enrollment withdrawal options to balance feasibility with respect for autonomy. We argue this approach is essential to advance evidence-based transfusion practice in Canadian out-of-hospital care and serves as a national template for emergency research.