Enhanced pre-hospital medical interventions facilitated by air ambulances (HEMS) appear to correlate with an improved likelihood of survival following severe trauma. A recent analysis of survival statistics from a specific regional service in South East England suggests that such services are associated with saving an additional five lives per hundred major trauma cases, exceeding expected outcomes. The comprehensive findings have been made available online in the esteemed Emergency Medicine Journal.
Researchers have noted that international consensus on the survival impact of Helicopter Emergency Medical Services (HEMS) in major trauma scenarios has been elusive. This has been attributed to variations in study methodologies, insufficient participant numbers, and a lack of standardized outcome definitions. Furthermore, it remains unclear which specific patient demographics are most likely to derive substantial benefit from these critical care services.
To address these questions, the investigative team conducted a retrospective examination of the outcomes for 3225 trauma patients who received pre-hospital care from a single HEMS unit. This unit provided services across the regions of Kent, Surrey, and Sussex between the years 2013 and 2022.
A specialized statistical methodology was employed to ascertain the probability of survival (a Ws analysis). This technique was meticulously designed to account for variations in patient conditions (case-mix) and to identify factors predicting mortality within a 30-day timeframe post-incident.
Additionally, the study delved into the identification of unexpected determinants of survival. Particular attention was given to the rates of return of spontaneous circulation (ROSC) in cases of traumatic cardiac arrest. This condition describes the cessation of heart function following severe physical trauma, such as major hemorrhage or thoracic injuries.
Across the entire cohort, 2125 individuals successfully survived beyond the 30-day mark following their trauma incident. This figure represents an observed survival rate of 85%, compared to an anticipated rate of 81%. This translates to an additional five survivors for every hundred patients treated, equating to an estimated 115 lives saved annually, based on the average caseload handled by the HEMS service.
The patient subgroup identified as most likely to benefit from HEMS were those with severe injuries and a moderate probability of survival (ranging from 25% to 45%). Within this group, an unexpected 35% achieved survival for more than 30 days.
For individuals whose survival probability was deemed low (less than 50%) due to the severity of their injuries, a remarkable 39% demonstrated unexpected survival over the 30-day period.
Key indicators associated with unexpected survival included advanced age and a higher initial score on the Glasgow Coma Scale. This scale, which ranges from 3 to 15, is a standardized measure of consciousness level following brain injury.
The administration of pre-hospital emergency anesthesia, a procedure that induces a comatose state in trauma patients and can only be performed by highly specialized medical teams such as HEMS, was found to be independently linked to superior survival rates in this particular patient segment.
Within the subset of 1316 patients experiencing traumatic cardiac arrest, 356 individuals (approximately 27%) achieved a return of spontaneous circulation while being transported to the hospital. Conversely, 960 patients were declared deceased at the scene of the incident.
Of the 356 patients who were alive upon arrival, 30-day survival data were available for 185 (about 52%). Of these, 46 (25%) remained alive after the 30-day observation period, while 139 individuals succumbed during their hospital stay. The analysis indicated a progressive increase in the probability of return of spontaneous circulation, rising by 6% year-over-year from 2013 to 2022.
The researchers have issued a cautionary note, emphasizing that their quantitative estimates represent “excess survival” when contrasted with modeled projections, rather than definitively establishing a direct causal link with HEMS interventions. They also operate under the assumption of consistent service performance and patient case-mix over the study period, acknowledging that these conditions may not always hold true in real-world scenarios.
Despite these caveats, the research team asserts that their findings eloquently illustrate “the potential magnitude of clinical benefit,” aligning consistently with previously documented economic and societal advantages reported in earlier studies.
In conclusion, the authors state: “These findings offer compelling substantiation for ongoing investment in HEMS, particularly for individuals sustaining severe injuries. However, further comparative investigations against alternative care modalities are imperative to conclusively ascertain causal efficacy.”
