Association Between FAST Results, Transfusion, and Severe Injury in Trauma: A Multicenter Retrospective Study

The Focused Assessment with Sonography in Trauma (FAST) is used to rapidly identify intra-abdominal hemorrhage and inform early resuscitation. We evaluated whether FAST results are independently associated with emergency department (ED) transfusion and severe internal injury after accounting for physiologic and laboratory markers.

This was a multicenter retrospective cohort study of trauma patients undergoing FAST at five EDs (2021–2023). The primary outcome was ED blood transfusion. The secondary outcome was severe internal injury (solid organ, hemoperitoneum, pelvic, retroperitoneal hematoma, vascular injury, or hemothorax). Mixed-effects logistic regression with site as a random intercept estimated adjusted odds ratios (aORs), adjusting for age, sex, weight, blood pressure, heart rate, shock index, lactate, bicarbonate deficit, mechanism, and prehospital hypotension.

Among 2,214 trauma patients, FAST was positive in 327 (14.8%), indeterminate in 24 (1.1%), and negative in 1,863 (84.1%); 552 (24.9%) received ED transfusion. Transfusion occurred in 166/327 (50.8%) FAST-positive, 11/24 (45.8%) indeterminate, and 375/1,863 (20.1%) FAST-negative patients (p<0.001). In adjusted analyses, positive FAST was independently associated with transfusion (aOR 3.68; 95% CI 2.72–4.99; p<0.001), as was indeterminate FAST (aOR 3.62; 95% CI 1.32–9.96; p=0.013). Other independent predictors of transfusion included SBP <90 mmHg (aOR 6.23; p<0.001), shock index >1 (aOR 2.13; p<0.001), lactate >4 mmol/L (aOR 2.11; p<0.001), base deficit ≤−4 (aOR 2.00; p<0.001), penetrating mechanism (aOR 1.90; p<0.001), and prehospital hypotension (aOR 2.17; p<0.001). Severe internal injury occurred in 688 (31.1%) and was more common with FAST-positive (212/327, 64.8%) than FAST-negative exams (462/1,863, 24.8%) (p<0.001). After adjustment, positive FAST (aOR 4.82; 95% CI 3.65–6.37; p<0.001) and indeterminate FAST (aOR 4.49; 95% CI 1.78–11.33; p=0.001) were independently associated with severe injury.

FAST results are independent predictors of both early transfusion and severe internal injury, adding value beyond physiology and laboratory data. However, nearly one-quarter of FAST-negative patients still harbored significant injury, underscoring that FAST should complement, not replace, comprehensive clinical and laboratory assessment in early trauma triage.