Researchers say it has been difficult to draw firm conclusions from international studies on Helicopter Emergency Medical Services (HEMS) and trauma survival. Differences in study methods, small patient numbers, and the lack of shared outcome definitions have limited comparisons. Another unresolved question has been identifying which types of patients benefit the most from helicopter-based emergency care.

Nearly a Decade of Trauma Data Analyzed

To explore these issues, researchers reviewed outcomes for 3225 trauma patients who received pre-hospital care from a single HEMS team. The service operates across Kent, Surrey, and Sussex, and the data covered the years from 2013 to 2022.

The team used a statistical method to estimate each patient's chance of survival (Ws analysis). This approach adjusted for differences in injury severity and patient characteristics, and it also examined factors linked to death within 30 days.

Unexpected Survival and Cardiac Arrest Outcomes

The researchers also examined cases where patients survived against expectations, along with outcomes in traumatic cardiac arrest, when the heart stops beating after severe injury such as major bleeding or chest trauma. A key focus was whether circulation returned before reaching the hospital, known as return of spontaneous circulation.

Out of all patients studied, 2125 survived for at least 30 days after their injury. This represented an actual survival rate of 85% compared with an expected rate of 81%. The difference amounts to five extra survivors per 100 patients and could equal as many as 115 additional lives saved each year based on the service's typical caseload.

Which Patients Benefited the Most

Patients with severe injuries and a moderate (25-45%) predicted chance of survival showed some of the largest gains. In this group, 35% survived for 30 days even though survival was not expected.

Survival was also higher than predicted among patients with a low probability of survival (less than 50%). Despite the seriousness of their injuries, 39% of these patients survived for at least 30 days.

Factors Associated With Better Survival

Younger age and a higher initial Glasgow Coma Scale score were strong predictors of unexpected survival. The Glasgow Coma Scale is a 3 to 15 point measure used to assess consciousness after a brain injury.

Another important factor was pre-hospital emergency anesthesia. This intervention places patients into an induced coma and can only be delivered by advanced medical teams such as HEMS. It was independently linked to improved survival in severely injured patients.

Outcomes in Traumatic Cardiac Arrest

Among 1316 patients who experienced traumatic cardiac arrest, 356 (27%) regained circulation while being transported to the hospital. The remaining 960 patients were declared dead at the scene.

For the 356 patients who initially survived, 30-day outcome data were available for 185 (52%). Of those, 46 (25%) were still alive after 30 days, while 139 died after arriving at the hospital. The analysis showed that the likelihood of circulation returning increased by 6% each year between 2013 and 2022.

Study Limitations and Cautious Conclusions

The researchers emphasize that their results reflect survival rates that were higher than statistical predictions, not direct proof that HEMS caused the improved outcomes. Their estimates also assume that patient characteristics and service performance remained consistent over time, which may not always be the case.

Even so, the team says the findings highlight "the potential magnitude of clinical benefit, consistent with previous economic and social benefits demonstrated in previous studies."

They conclude: "These findings provide supportive evidence for continued investment in HEMS, particularly for severely injured patients, though comparative studies with alternative care pathways are needed to establish causal effectiveness."