The Prehospital Resuscitation On Helicopter Study (PROHS) is a pragmatic, multicenter, prospective observational study of air ambulance-based prehospital resuscitation regimens currently utilized at the participating sites. Patients will be enrolled at participating sites that currently have blood products available on air ambulances and other sites that do not. This study will not change the current prehospital standard of care for resuscitation. The primary outcome will be in-hospital mortality and the primary unit of analysis will be the patient. Other outcomes of interest will include time to hemostasis, hospital length-of-stay, number of ventilator-free and ICU-free days, incidence of major surgical procedures, complications (transfusion-related acute lung injury [TRALI], acute kidney injury [AKI], multiple organ failure [MOF], acute respiratory distress syndrome [ARDS], sepsis, intra-abdominal complications, thromboembolic complications, compartment syndromes), lifesaving interventions, the amount and type of blood products and concentrates transfused (including prehospital), wastage of prehospital blood products and concentrates, use of external and internal hemostatic devices, and functional status at discharge/discharge destination.

All patients arriving to the participating center's trauma emergency department via helicopter directly from the scene will be screened and initial data collected. Of that group, all patients who meet the "highest risk" category (based on vital signs, type of injury, use of tourniquet, and/or intubation) or received blood during transport will be followed through "direct observation" through the initial resuscitation period and then indirectly through medical chart review until hospital discharge or 30 days after admission (whichever occurs first).

Inclusion Criteria:

Criteria for "at risk" population

• Patients with traumatic injuries received directly from the scene via air ambulance service (did not receive a lifesaving intervention at an outside hospital or healthcare facility)
• Estimated age of 15 or older or greater than/equal to a weight of 50 kg, if age unknown Criteria for "highest risk" population
• Meet at least one of the following during prehospital care: HR >120 bpm, SBP ≤90 mmHg, penetrating truncal injury, tourniquet application, pelvic binder application or intubation.
• Received blood products during transport (for those facilities with blood product availability)

Exclusion Criteria:

• Prisoners (defined as those received directly from a correctional facility.

The target population for this study is trauma patients who are transported to one of the participating Level I trauma centers via air ambulance, directly from the scene, and meet the eligibility criteria.