Neurocritical Care Interventions

Hypothermia

Induced hypothermia involves lowering body temperature in order to prevent brain injury. It’s main application is in the prevention of brain injury following a cardiac arrest, or sudden stoppage of heart activity, (as what might happen after a large heart attack). The reason cardiac arrest can cause a brain injury is because with heart stoppage there is a sudden cessation of blood flow to the brain. While the rest of the body can survive with a temporary stoppage of blood flow, the rest of the brain is quite vulnerable. For every second that blood flow stops, 32,000 brain cells die, or 1.9 million brain cells a minute. The goal of hypothermia is to protect the brain from rapid cell death after emergency responders and physicians have gotten the heart going again.

Hypothermia protects the brain by decreasing temperature to the point where brain metabolism slows down significantly. In other words, with colder temperatures the brain cells slow down, or temporarily shut down, to the point that they don’t need as much oxygen. Therefore, they can survive a temporary decrease in oxygen.

The goal in induced hypothermia is to cool the patient to 32 to 34 degrees Celsius (89.6 to 93.2 degrees Fahrenheit). Hypothermia is induced by administering chilled fluids into the blood. Then a device is used to maintain the new, low, temperature. This device is either a pad placed on top of the skin or a catheter placed in a large vein in the groin. The goal temperature is maintained for 24 hours. The patient is then rewarmed over a 24 hour period.

Hypothermia may also be of benefit in controlling brain swelling. It may be used in patients where maximal medical therapy has failed to reduce brain pressure.