Therapeutic hypothermia after cardiac arrest. ARC and NZRC Guideline 2010.

All studies of post-cardiac arrest therapeutic hypothermia have included only patients in coma. One trial defined coma as “not responding to verbal commands”. The other trials defined coma similarly, used GCS 8, or did not provide a clear definition. One randomized trial and a pseudo-randomised trial demonstrated improved neurological outcome at hospital discharge or at 6 months after hospital discharge in comatose patients after out-ofhospital ventricular fibrillation cardiac arrest. Cooling was initiated within minutes to hours after return of spontaneous circulation and a temperature range of 32–34°C was maintained for 12–24 hours. Two studies with historical control groups showed improvement in neurological outcome after therapeutic hypothermia for comatose survivors of ventricular fibrillation cardiac arrest. One systematic review demonstrated that conventional cooling methods were more likely to reach a best cerebral performance category score of 1 or 2 (five point scale where one is good and five is brain death) with a relative risk of 1.55 995% CI 1.22–1.96) and more likely to survive to hospital discharge (relative risk of 1.35 95% CI 1.1 to 1.65) compared with standard post resuscitation care. One small (n = 30) randomized trial showed reduced plasma lactate values and oxygen extraction ratios in a group (n = 16) of comatose survivors after cardiac arrest with asystole or pulseless electrical activity who were cooled with a cooling cap. Six studies with historical control groups showed benefit using therapeutic hypothermia in comatose survivors of out-of-hospital cardiac arrest after all rhythm arrests. One study with historical controls showed better neurological outcome after ventricular fibrillation cardiac arrest but no difference after cardiac arrest from other rhythms. Two non-randomised studies with concurrent controls indicated possible benefit of hypothermia following cardiac arrest from other initial rhythms inand out-of-hospital. One registry study that included almost 1000 cooled comatose patients following cardiac arrest from all rhythms, the survival with good outcome at six months was 56% after initial VT/VF, 21% after initial asystole and 23% after initial PEA.