title: The beneficial effect of mild therapeutic hypothermia depends on the time of complete circulatory standstill in patients with cardiac arrest.
abstract: OBJECTIVE
  Mild therapeutic hypothermia has shown to improve long-time survival as well as favorable functional outcome after cardiac arrest. Animal models suggest that ischemic durations beyond 8 min results in progressively worse neurologic deficits. Based on these considerations, it would be obvious that cardiac arrest survivors would benefit most from mild therapeutic hypothermia if they have reached a complete circulatory standstill of more than 8 min.
  
  
  METHODS
  In this retrospective cohort study we included cardiac arrest survivors of 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest, which remain comatose after restoration of spontaneous circulation. Data were collected from 1992 to 2010. We investigated the interaction of 'no-flow' time on the association between post arrest mild therapeutic hypothermia and good neurological outcome. 'No-flow' time was categorized into time quartiles (0, 1-2, 3-8, >8 min).
  
  
  RESULTS
  One thousand-two-hundred patients were analyzed. Hypothermia was induced in 598 patients. In spite of showing a statistically significant improvement in favorable neurologic outcome in all patients treated with mild therapeutic hypothermia (odds ratio [OR]: 1.49; 95% confidence interval [CI]: 1.14-1.93) this effect varies with 'no-flow' time. The effect is significant in patients with 'no-flow' times of more than 2 min (OR: 2.72; CI: 1.35-5.48) with the maximum benefit in those with 'no-flow' times beyond 8 min (OR: 6.15; CI: 2.23-16.99).
  
  
  CONCLUSIONS
  The beneficial effect of mild therapeutic hypothermia increases with cumulative time of complete circulatory standstill in patients with witnessed out-of-hospital cardiac arrest.
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Testori
authors.forename: Fritz
authors.initials: F
authors.lastname: Sterz
authors.forename: Michael
authors.initials: M
authors.lastname: Holzer
authors.forename: Heidrun
authors.initials: H
authors.lastname: Losert
authors.forename: Jasmin
authors.initials: J
authors.lastname: Arrich
authors.forename: Harald
authors.initials: H
authors.lastname: Herkner
authors.forename: Danica
authors.initials: D
authors.lastname: Krizanac
authors.forename: Christian
authors.initials: C
authors.lastname: Wallmüller
authors.forename: Peter
authors.initials: P
authors.lastname: Stratil
authors.forename: Andreas
authors.initials: A
authors.lastname: Schober
authors.forename: David
authors.initials: D
authors.lastname: Hörburger
authors.forename: Mathias
authors.initials: M
authors.lastname: Stöckl
authors.forename: Christoph
authors.initials: C
authors.lastname: Weiser
authors.forename: Thomas
authors.initials: T
authors.lastname: Uray
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods*; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000503:physiopathology / Q000628:therapy*; D011379:Prognosis; D012189:Retrospective Studies; D061665:Time-to-Treatment; D016896:Treatment Outcome