title: Helicopter emergency medical services (HEMS) response to out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Out-of-hospital cardiac arrest (OHCA) is a common medical emergency with significant mortality and significant neurological morbidity. Helicopter emergency medical services (HEMS) may be tasked to OHCA. We sought to assess the impact of tasking a HEMS service to OHCA and characterise the nature of these calls.
  
  
  METHODS
  Retrospective case review of all HEMS calls to Surrey and Sussex Air Ambulance, United Kingdom, over a 1-year period (1/9/2010-1/9/2011). All missions to cases of suspected OHCA, of presumed medical origin, were reviewed systematically.
  
  
  RESULTS
  HEMS was activated 89 times to suspected OHCA. This represented 11% of the total HEMS missions. In 23 cases HEMS was stood-down en-route and in 2 cases the patient had not suffered an OHCA on arrival of HEMS. 25 patients achieved return-of-spontaneous circulation (ROSC), 13 (52%) prior to HEMS arrival. The HEMS team were never first on-scene. The median time from first collapse to HEMS arrival was 31 minutes (IQR 22-40). The median time from HEMS activation to arrival on scene was 17 minutes (IQR 11.5-21). 19 patients underwent pre-hospital anaesthesia, 5 patients had electrical or chemical cardioversion and 19 patients had therapeutic hypothermia initiated by HEMS. Only 1 post-OHCA patient was transported to hospital by air. The survival to discharge rate was 6.3%.
  
  
  CONCLUSIONS
  OHCA represents a significant proportion of HEMS call outs. HEMS most commonly attend post-ROSC OHCA patients and interventions, including pre-hospital anaesthesia and therapeutic hypothermia should be targeted to this phase. HEMS are rarely first on-scene and should only be tasked as a first response to OHCA in remote locations. HEMS may be most appropriately utilised in OHCA by only attending the scene if a patient achieves ROSC.
authors.affiliation: Emergency Medicine & Pre-hospital Care, Kent, Surrey, Sussex Air Ambulance, Redhill Aerodrome, Redhill, Surrey, England. richardlyon@doctors.org.uk
authors.forename: Richard M
authors.initials: RM
authors.lastname: Lyon
authors.forename: Magnus J
authors.initials: MJ
authors.lastname: Nelson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017732:Air Ambulances / Q000706:statistics & numerical data*; D016887:Cardiopulmonary Resuscitation / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology / Q000628:therapy*; D012189:Retrospective Studies; D013997:Time Factors; D055815:Young Adult