Helicopter emergency medical service in out-of-hospital cardiac arrest--a 10-year population-based study

In 1988, Norway established a countrywide, physician staffed helicopter emergency medical service (HEMS). The medical benefit remains controversial. The aim of this study was to estimate the population incidence of HEMS involvement in out-of-hospital cardiac arrest, report the patient outcome and evaluate the contribution of HEMS to survival.

We studied HEMS operations in central Norway (population 364,000) during a 10-year period (1988-1997). Missions were classified according to type and quality of intervention done by the primary care providers. HEMS witnessed cardiac arrests were not considered. Patient outcome was determined as survival to hospital discharge with cerebral performance category (CPC) score. The contribution made by HEMS in each survivor was assessed from the timing of return of spontaneous circulation (ROSC) and from subsequent need for advanced medical intervention. The relation between survival and HEMS response time was investigated by ordinal correlation.

A total of 541 requests (14.9 per 100,000 inhabitants per year) were identified, of which 424 missions were completed. Overall survival to discharge was 36/541 (6.6%), yielding a population survival incidence of 1 per 100,000 per year. Ninety-five percent of survivors made a favourable cerebral outcome (CPC 1 or 2). General practitioners/ambulance personnel resuscitated 29 out of 36 survivors. The remainder achieved ROSC after HEMS arrival. Case by case, HEMS assistance was considered possibly important in 17 survivors. We found no relation between survival and HEMS response time (P=0.77).

Survival following out-of-hospital cardiac arrest assisted by HEMS in this region is low, but not negligible. While primary care is most important, HEMS may possibly contribute to the additional survival of 0.19 to 0.46 patients per 100,000 per year. This benefit appears to be independent of HEMS response time.