Helicopter emergency medical service dispatch in older trauma: time to reconsider the trigger?

Background Helicopter Emergency Medical Services (HEMS) respond to serious trauma and medical emergencies. Geographical disparity and the regionalisation of trauma systems can complicate accurate HEMS dispatch. We sought to evaluate HEMS dispatch sensitivity in older trauma patients by analysing critical care interventions and conveyance in a well-established trauma system. Methods All trauma patients aged ≥65 years that were attended by the Air Ambulance Kent Surrey Sussex over a 6-year period from 1 July 2013 to 30 June 2019 were included. Patient characteristics, critical care interventions and hospital disposition were stratified by dispatch type (immediate, interrogate and crew request). Results 1321 trauma patients aged ≥65 were included. Median age was 75 years [IQR 69-89]. HEMS dispatch was by immediate (32.0%), interrogation (43.5%) and at the request of ambulance clinicians (24.5%). Older age was associated with a longer dispatch interval and was significantly longer in the crew request category (37 min [34-39]) compared to immediate dispatch (6 min [5-6] (p = .001). Dispatch by crew request was common in patients with falls 2 m more often resulted in immediate dispatch (p = .001). Immediate dispatch to isolated head injured patients often resulted in pre-hospital emergency anaesthesia (PHEA) (39%). However, over a third of head injured patients attended after dispatch by crew request received PHEA (36%) and a large proportion were triaged to major trauma centres (69%). Conclusions Many patients who do not fulfil the criteria for immediate HEMS dispatch need advanced clinical interventions and subsequent tertiary level care at a major trauma centre. Further studies should evaluate if HEMS activation criteria, nuanced by age-dependant triggers for mechanism and physiological parameters, optimise dispatch sensitivity and HEMS utilisation.