A stroke
—also known as a "brain attack"
—occurs when the blood supply to a part of the brain is suddenly interrupted by a blood clot (called an ischemic stroke) or when a blood vessel in the brain bursts, leaking blood into the spaces surrounding the brain cells (called a hemorrhagic stroke). When this occurs, blood flow to the brain's cells is hindered. With the loss of its supply of oxygen and energy, the brain cannot function properly, and its cells begin to die.
Stroke is the third leading cause of death in the United States, and the leading cause of serious, long-term disability. About 700,000 Americans have strokes each year.
What is hypothermia?
Hypothermia is an experimental treatment that involves lowering the body temperature of a person who has suffered a stroke. The goal is to limit the size of the lesion, or area of damaged tissue, by protecting the brain tissue near the site of the stroke. Limiting tissue damage can lead to improved outcomes and quality of life for stroke victims.
How does hypothermia work?
It is not known exactly how hypothermia works to reduce tissue death following a stroke. Scientists researching this technique theorize that hypothermia's protective benefits come from slowing the body's metabolism (use of energy), which in turn reduces the chemical reactions that lead to brain cell death. Cooling also is known to reduce inflammation (swelling and irritation), another cause of brain injury after a stroke. Hypothermia also may protect against further damage to brain cells that can occur when clot-busting drugs, such as tissue plasminogen activator (tPA), are used to restore blood flow (called reperfusion).
Who is a candidate for hypothermia?
Hypothermia may be used to treat people who have suffered an acute (sudden and severe) ischemic stroke. (About 85 percent of all strokes are ischemic.) Special imaging techniques
—such as magnetic resonance imaging (MRI) and computed axial tomography (CAT) scanning
—are used to identify stroke patients who have areas of brain tissue that are at risk for damage but that may be saved through therapies such as tPA and hypothermia. To be eligible for hypothermia, a person must be available for treatment within a specific period of time (currently within 12 hours of the start of the stroke).
How is hypothermia done?
The core body temperature is lowered to about 33 degrees Celsius (about 92 degrees Fahrenheit). Hypothermia can be achieved by use of surface cooling using special cooling blankets. Alternatively, hypothermia may be achieved by inserting a special catheter (small tube) with a cooling device into a vein in the groin. The device can be cooled to a specific setting to cool the blood as it circulates. The patient may remain awake during hypothermia treatment; however, he or she may be given relaxing medication to minimize shivering. All patients treated with hypothermia are carefully monitored in an intensive care unit.
What complications are associated with hypothermia?
The mild to moderate level of hypothermia that is used to treat acute ischemic stroke is generally well tolerated. However, there are potential complications, including:
- Slowing of the heart rate or other heart rhythm changes
- Decrease in blood pressure
- Infections
- Electrolyte imbalances
- Deep venous thrombosis (blood clot) at the site of catheter insertion
What is the outcome for people treated with hypothermia?
Cleveland Clinic is involved in an ongoing study
, called Cooling for Acute Ischemic Brain Damage (COOL AID)
, which is investigating the use of hypothermia as a treatment for acute ischemic stroke. Preliminary results are promising, suggesting that hypothermia may reduce tissue damage by as much as 20 percent.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.This document was last reviewed on: 10/3/2005
