Predicting the Prehospital Blood Transfusion Need in a Large Metropolitan Center

Prehospital blood transfusion (PHBT) has been associated with reduced mortality for trauma patients in hemorrhagic shock. However, there are currently no standardized prehospital criteria to identify patients who may benefit from PHBT. We designed this study to assess the positive predictive value (PPV) of a set of PHBT criteria to identify patients requiring emergent transfusion within four hours of emergency department (ED) arrival.

We conducted an observational retrospective cohort study of all trauma patients ≥ 15 years-old who were transported by emergency medical services (EMS) between November 1st, 2021 and September 30th, 2023 to a trauma center prior to the implementation of PHBT protocols in LAC. We retrospectively applied the PHBT criteria: systolic blood pressure (SBP) < 70mmHg, a simultaneous reading of SBP < 90 mmHg and heart rate (HR) ≥ 110 beats per minute (BPM), or EMS-witnessed traumatic arrest. We excluded patients with cardiac arrest prior to EMS arrival, isolated head injury, or ground-level fall as the only mechanism of injury. Our primary outcome was the PPV of the PHBT criteria as a whole as well as each individual PHBT criterion for emergent transfusion need, which we defined as the proportion of trauma patients requiring in-hospital transfusion within four hours of ED arrival.

Of the 25,473 trauma patients, 905 met one or more PHBT criterion with no exclusion. These patients were primarily male (76%, n = 688) with a median age of 35 (IQR 27-47) and most suffered blunt trauma (68%, n = 618). Overall, 475 (52%) received blood within four hours of hospital arrival. The PHBT criterion of SBP < 90 mmHg and HR ≥ 110 BPM was found to have the highest PPV (56%, 95% CI 52-60%) for in-hospital transfusion within four hours. PPV for the other PHBT criteria ranged between 51-53%.

The PHBT criteria of SBP < 90 mmHg and HR ≥ 110 bpm had the greatest PPV for transfusion within four hours of ED arrival. This information may be used to further optimize criteria for PHBT and identify patients most likely to benefit.