title: The effect of prehospital time related variables on mortality following severe thoracic trauma.
abstract: OBJECTIVE
  The aims of this study is firstly to analyse the impact of prehospital time related variables on mortality, in a specific subset of HEMS patients and secondly to demonstrate any interactions between time related variables and factors taking place in the prehospital setting.
  
  
  METHODS
  Retrospective analysis of 688 consecutive London HEMS transfers with severe thoracic trauma and mean injury severity score (ISS) of 35, during a 9-year period (1994-2002). We have analysed the effect of the following time related variables on mortality: activation time, arrival on scene time (AoS), stay on scene time (SoS), total time (ToT), rush-hour time (RhT) and leisure-hour time (LhT). We have also investigated the interaction of the above mentioned variables with observations and interventions taken place on scene and at accident and emergency department (A&E) following adjustment for type and severity of injury. For statistical analysis the time variables were grouped into quintiles.
  
  
  RESULTS
  Six hundred eighty eight victims (510 males) with mean age of 38.5 ± 17.5 had total survival rate of 59.6%. The mean AoS and SoS were 11.6 ± 5.8 min and 36.6 ± 16.8 min, respectively. ToT>65 min, as in quintiles III, IV and V with mean ToT of 65.3 min, 74.9 min and 102.7 min respectively, had an influence on mortality with calculated adjusted OR of 1.37 (95%CI=0.47-3.94), 3.36 (95%CI = 1.22-9.23) and 1.43 (95%CI = 0.52-3.92) respectively with concomitant adjustment for type of injury, severity of injury, age, physiological variables on scene and on scene emergency thoracotomy (ET). ET on scene was an independent predictor for mortality (OR 3.94, 95%CI = 1.03-15.06). SoS of more than 34 min can lead to harmful changes on patients' pathophysiological status. ISS has no significant effect on AoS or SoS. RhT and LhT have no significant effect on mortality and they did not influence the AoS and SoS.
  
  
  CONCLUSIONS
  This study suggests that time related variables have a complex and heterogeneous effect on mortality. Thoracic trauma victims usually have high ISS, in such population, ToT <65 min may be associated with lower possibility of death. Neither AoS nor SoS was influenced by time of incident or severity of injury.
authors.affiliation: Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Emaddin
authors.initials: E
authors.lastname: Kidher
authors.forename: George
authors.initials: G
authors.lastname: Krasopoulos
authors.forename: Tim
authors.initials: T
authors.lastname: Coats
authors.forename: Alexandros
authors.initials: A
authors.lastname: Charitou
authors.forename: Patrick
authors.initials: P
authors.lastname: Magee
authors.forename: Rakesh
authors.initials: R
authors.lastname: Uppal
authors.forename: Thanos
authors.initials: T
authors.lastname: Athanasiou
mesh_terms: D000328:Adult; D000465:Algorithms; D004632:Emergency Medical Services / Q000458:organization & administration*; D004638:Emergency Treatment / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015601:Injury Severity Score; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D015996:Survival Rate; D013898:Thoracic Injuries / Q000401:mortality* / Q000503:physiopathology / Q000601:surgery; D013908:Thoracotomy / Q000401:mortality* / Q000706:statistics & numerical data; D013997:Time Factors