Development and validation of a pre-hospital "Red Flag" alert for activation of intra-hospital haemorrhage control response in blunt trauma

Background: Haemorrhagic shock is the leading cause of early preventable death in severe trauma. Delayed treatment is a recognized prognostic factor that can be prevented by efficient organization of care. This study aimed to develop and validate Red Flag, a binary alert identifying blunt trauma patients with high risk of severe haemorrhage (SH), to be used by the pre-hospital trauma team in order to trigger an adequate intra-hospital standardized haemorrhage control response: massive transfusion protocol and/or immediate haemostatic procedures. Methods: A multicentre retrospective study of prospectively collected data from a trauma registry (Traumabase (R)) was performed. SH was defined as: packed red blood cell (RBC) transfusion in the trauma room, or transfusion >= 4 RBC in the first 6 h, or lactate >= 5 mmol/L, or immediate haemostatic surgery, or interventional radiology and/or death of haemorrhagic shock. Pre-hospital characteristics were selected using a multiple logistic regression model in a derivation cohort to develop a Red Flag binary alert whose performances were confirmed in a validation cohort. Results: Among the 3675 patients of the derivation cohort, 672 (18%) had SH. The final prediction model included five pre-hospital variables: Shock Index >= 1, mean arterial blood pressure <= 70 mmHg, point of care haemoglobin <= 13 g/dl, unstable pelvis and pre-hospital intubation. The Red Flag alert was triggered by the presence of any combination of at least two criteria. Its predictive performances were sensitivity 75% (72-79%), specificity 79% (77-80%) and area under the receiver operating characteristic curve 0.83 (0.81-0.84) in the derivation cohort, and were not significantly different in the independent validation cohort of 2999 patients. Conclusion: The Red Flag alert developed and validated in this study has high performance to accurately predict or exclude SH.