Abstract
Appropriate use of helicopter emergency medical service (HEMS) is important in ensuring that patients with critical illness or injury receive adequate treatment. To investigate the association between use of HEMS compared with use of ground EMS (GEMS) and mortality overall and in a subgroup of patients with critical illness or injury. This register-based, nationwide cohort study used data retrieved from Danish registries from October 1, 2014, to April 30, 2018. Patients receiving GEMS originated from dispatched HEMS missions for which a helicopter was unavailable. For the primary analysis, patients from accepted HEMS missions and patients from missions in which HEMS was dispatched but unavailable were included. The secondary analysis included patients assigned a hospital International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) diagnosis considered a critical illness or injury. These patients were selected via a consensus-based agreement among all authors by reviewing the Danish version of the World Health Organization's ICD-10 classification. Data were analyzed from March to June 2020. Dispatch of HEMS vs GEMS unit (primary analysis) and treatment and transport by HEMS vs GEMS unit among patients with critical illness or injury (secondary analysis). One-year mortality was retrieved from the Danish Civil Registration System. Among 10 618 patients (median [interquartile range] age, 60 [42-72] years; 6834 [64.4%] men) included in the primary analysis, 9480 patients (89.3%) received HEMS and 1138 patients (10.7%) received GEMS. Median (interquartile range) age was 60 (42-72) years, and 6834 patients (64.4%) were men. Adjusted cumulative 1-year mortality was 23.2% (95% CI, 22.4%-24.1%) among patients receiving HEMS vs 24.5% (95% CI, 21.9%-27.1%) among patients receiving GEMS. The difference in mortality risk for HEMS compared with GEMS was not statistically significant (hazard ratio, 0.94 [95% CI, 0.84-1.06]). Among 2260 patients with critical illness or injury receiving HEMS, compared with 315 patients with critical illness or injury receiving GEMS, adjusted cumulative 1-year mortality was 25.1% (95% CI, 23.5%-26.7%) vs 27.1% (95% CI, 22.0%-32.1%). The difference in mortality risk for HEMs compared with GEMs was not statistically significant (hazard ratio, 0.91 [95% CI, 0.73-1.14]). This study found that 1 year after dispatch, the use of HEMS, compared with the use of GEMS, was not associated with a statistically significant difference in mortality overall or mortality among patients with critical illness or injury. Further research is needed to determine whether optimized dispatch systems may be associated with further improvements in survival among selected patients.
Highlights
Helicopter emergency medical service (HEMS) is part of many prehospital health care systems
The difference in mortality risk for helicopter emergency medical service (HEMS) compared with ground EMS (GEMS) was not statistically significant
This study found that 1 year after dispatch, the use of HEMS, compared with the use of GEMS, was not associated with a statistically significant difference in mortality overall or mortality among patients with critical illness or injury
Summary
Helicopter emergency medical service (HEMS) is part of many prehospital health care systems. The main purpose of most European HEMS units is to bring advanced critical care to patients and provide rapid transportation to definitive care. We previously found that approximately two-thirds of patients attended to by physicianparamedic–staffed Danish HEMS have severe illness or injury and that the diagnostic groups most commonly seen consist of patients with time-critical conditions, such as cardiovascular emergencies, neurovascular emergencies, and severe trauma. A group of patients triaged by the emergency medical dispatch centers (EMDCs) to be in need of HEMS was left to be attended solely by ground EMS (GEMS) units. The allocation of transportation modality based on weather conditions provided the opportunity to compare outcomes in patients with a different level of exposure (HEMS vs GEMS), mimicking what might have been achieved by a scientific randomized allocation of patients
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