Cooling Post Cardiac Arrest

Why the need to cool?

  • Anoxic brain injury is a common outcome after sudden cardiac arrest.
  • Studies have shown a reduction in mortality and improved neurological outcomes after cooling.
    A European multicentre trial (HACA Study Group. New Eng J Med 2002;346:549-556) reported that cooling increased the number of patients who survived with favourable neurological outcome from 39% to 55%, and an Australian study (Bernard et al . New Eng J Med 2002; 346: 557-563) reported a similar increase from 26% to 49%.

How does cooling help?

  • Cooling reduces cerebral oxygen requirements.
  • Cerebral metabolic rate for oxygen is reduced by 6% for every 1°C reduction in brain temperature.
  • Chemical reactions associated with reperfusion injury are thought to be suppressed by mild hypothermia.
    (Resuscitation 2003; 57: 231-235)

The Evidence

On the basis of published evidence, ILCOR (International Liaison Committee on Resuscitation) made the following recommendations in October 2002:

  • Unconscious adult patients when the initial rhythm was VF and with spontaneous circulation after out of hospital cardiac arrest should be cooled.
  • Core body temperature should be cooled to 32-34oC.
  • Cooled body temperature to be maintained for 12-24 hours.

These recommendations were incorporated in the ERC Guildelines for Resuscitation 2005 with the additional comment that ‘Induced hypothermia might also benefit unconscious adult patients with spontaneous circulation after out-of-hospital cardiac arrest from a non-shockable rhythm, or cardiac arrest in hospital’