Are trauma centers penalized for improved prehospital resuscitation?: The effect of prehospital transfusion on arrival vitals and predicted mortality.

Background: Prediction models for survival in trauma rely on arrival vital signs to generate survival probabilities. Hospitals are benchmarked on expected and observed outcomes. Prehospital blood (PB) transfusion has been shown to improve mortality, which may affect survival prediction modeling. We hypothesize that the use of PB increases the predicted survival derived from probability models compared with non-blood-based resuscitation.
Methods: All adult trauma patients presenting to a level 1 trauma center requiring emergency release blood transfusion from January 2017 to December 2021 were reviewed. Patients were grouped into those receiving PB or those who did not (no PB). Prehospital Trauma and Injury Severity Score (TRISS) and shock index were compared with those at presentation to hospital. Univariate and multivariate regressions were performed to identify factors associated with changes in survival probability at presentation.
Results: In total, 2117 patients were reviewed (PB, 1,011; no PB, 1,106). Patients receiving PB were younger (35 vs. 40 years, p < 0.001), more likely to have blunt mechanism (71% vs. 65%, p = 0.002), and more severely injured (Injury Severity Score, 27 vs. 25; p < 0.001) and had higher rates of prehospital hypotension (44% vs. 19%, p < 0.001) and shock index (1.10 vs. 0.87, p < 0.001). Upon arrival, PB patients had lower rates of ED hypotension (34% vs. 39%, p = 0.01), and significant improvements in arrival TRISS scores (+0.09 vs. -0.02, p < 0.001) and shock index (+0.10 vs. -0.07, p < 0.001) compared with prehospital. On multivariate analysis, PB was associated with a threefold increase in unexpected survivors (odds ratio, 3.28; 95% confidence interval, 2.23-4.60).
Conclusion: The use of PB was associated with improved probability of survival and an increase in unexpected survivors. Applying TRISS and shock index at hospital arrival does not account for en route hemostatic resuscitation, causing patients to arrive with improved vitals despite severity of injury. Caution should be used when implementing survival probability calculations using arrival vitals in centers with prehospital transfusion capability.
Level of Evidence: Therapeutic/Care Management; Level IV.
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