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Does the evidence support the use of mild hypothermia after cardiac arrest? Yes

BMJ 2011; 343 doi: (Published 23 September 2011) Cite this as: BMJ 2011;343:d5830
  1. Jerry P Nolan, consultant in anaesthesia and intensive care medicine1,
  2. Jasmeet Soar, consultant in anaesthesia and intensive care medicine2
  1. 1Royal United Hospital NHS Trust, Bath BA2 7AJ, UK
  2. 2Southmead Hospital, North Bristol NHS Trust, Bristol, UK
  1. Correspondence to: J P Nolan jerry.nolan{at}

Several guidelines recommend hypothermia for comatose patients who have had a cardiac arrest outside hospital. Jerry Nolan and Jasmeet Soar believe the data support this advice, but Andrew Walden, Niklas Nielsen, and Matt Wise (doi:10.1136/bmj.d5889) question the quality of the evidence

The use of mild hypothermia in comatose survivors of cardiac arrest has been shown to improve neurological outcome in both animals and humans.1 2 The evidence of benefit is strongest for people who have had a ventricular fibrillation cardiac arrest outside hospital, but data are beginning to emerge supporting its use in other types of arrest.

Supportive evidence

A randomised trial3 and a pseudorandomised (by day of the month) trial4 of cooling unconscious patients to 32-34ºC after ventricular fibrillation cardiac arrest outside hospital both recorded benefits.3 4 The randomised Hypothermia After Cardiac Arrest (HACA) study enrolled 275 patients (8% of those assessed).3 Those in the hypothermia group were sedated, paralysed, ventilated, and surface cooled to 32-34°C for 24 hours. Seventy five (55%) of the 136 in the hypothermia group showed a favourable neurological outcome at 6 months compared with 54 (39%) of 137 in the normothermia …

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