HOW THERAPEUTIC HYPOTHERMIA WORKS
Within the first 20 seconds of cardiac arrest, tissues start to deplete their reserves of oxygen, and toxins build up in
Cooling the body after cardiac arrest reduces the
brain’s metabolic rate,
slowing reactions that
cause cell damage. For each 1°C drop
in core temperature,
the brain’s metabolic rate decreases by 6-7 per cent.
After resuscitation, patients are kept cold and unconscious for 12-24 hours. This prevents brain damage when patients are revived.
Drugs prevent shivering, which raises body temperature.
Once stable, the patient is
warmed slowly – sometimes by as little as
0.1°C every hour.
After being sufficiently warmed, the patient is revived. Patients who’ve been hypothermic for many hours will often show signs of fever, or
develop respiratory infections.
The sooner patients can be cooled the better, although cooling patients after they have been resuscitated can still
Doctors use cooling
blankets, pads or ice-cold instruments to reduce the body temperature to 33-36°C. Cruder
temporary measures, such as applying bags of frozen food, have also been employed.
If blood flow is restored, tissue damage in the brain continues. Such ‘reperfusion injury’ is thought to be caused by the production of free radicals when blood returns to oxygen-depleted