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Cool the body, protect the brain

Cooling patients who have had a heart attack and lost consciousness may reduce deaths and brain damage

Donald McNeil New York Times

In the hope of saving thousands of people who have had a heart attack and also lost consciousness, a special committee of the "American Heart Association" recommends lowering their body temperature, after CPR has been performed on them and their hearts have started working again. According to the association, cooling the body makes it possible to bring the patients back to life slowly and gradually, thus reducing the brain damage that may be caused to them. However, an orderly protocol for cooling treatment has not yet been published.

Studies in Europe and Australia have shown that among patients who suffered a heart attack and coma, whose body was cooled to a temperature of 34-31.6 degrees Celsius and who were left in this state for up to 24 hours, fewer deaths and brain damage were recorded than among those who suffered a heart attack and coma and who were quickly resuscitated.

"This is a very exciting discovery. Many patients will be able to benefit from it," believes Dr. Terry Vanden Hoek, a lecturer in emergency medicine at the University of Chicago and the author of the American Heart Association's recommendation, which was recently published in the association's journal, "Circulation", but we have only touched the tip of the iceberg. We hope to find more effective ways to cool the patients."

About 680 Americans a day who have a heart attack also suffer from cardiac arrest (myocardial infarction) - a condition in which the heart stops beating and begins to flutter (fibrillation). If the heart rate is not quickly regulated with the help of a defibrillator (a device that produces electrical shocks), the patient's brain will begin to die from lack of oxygen - which indeed occurs in about 95% of patients in complete cardiac arrest outside hospitals. In the US, a large public program was launched to install portable defibrillators in airplanes, office buildings and other public places, to increase the chance of saving lives.

After a few minutes without blood circulation, the patient's condition deteriorates and he enters a coma. In such a situation, even if the heart starts beating again, the patient often dies or suffers severe brain damage. Doctors believe that most of the damage caused to patients who have been resuscitated occurs when oxygenated blood flows to the brain again, resulting in free radicals that attack brain cells and create inflammation, which further worsens the brain damage. Cold slows down this process and may reduce or prevent the damage.

Many questions have yet to be fully answered: How to cool the patients quickly but safely? Should we start cooling the patient's body already in the ambulance? How long should patients remain in a state of "medical hypothermia"?

The European researchers, who set themselves the goal of reaching the required temperature within four hours, used a cold mattress with a cover that diffuses cold air. The Australian team of researchers used ice packs. In any case, it takes up to eight hours to cool the patient, said Dr. Vanden Hoek.

The cooling process must be done carefully, says Mary Fran Hazinski, a CPR instructor at Vanderbilt University Medical Center. According to her, sometimes the patient needs to be injected with a muscle relaxant to prevent tremors. Shivering, a natural response to the cold, "is an attempt by the body to increase oxygen consumption, and this contradicts what we are trying to do."

Among the new cooling techniques currently being tested are cooling helmets; injection of cooled physiological solutions into the patient's veins; Inserting catheters with very cooled liquids into the patient's arteries; Inserting crushed ice into the stomach using a probe; or even breathing through cooled gases.

The idea that cooling can help those who have had a heart attack or stroke has been around since the 50s. Russian doctors who performed open-heart surgery without access to heart-lung machines cooled the patients with ice until the circulation stopped.

The committee of the American Heart Association writes in its recommendations on cooling patients that the hypothermia method was banned in the USA because it was considered a difficult procedure to perform. Even in 2000, when the association updated the medical guidelines for the treatment of patients who suffered a heart attack, the evidence for the benefits of the procedure was still considered to be inconclusive. However, since 2000, experiments have been carried out in dogs and pigs, and new studies in humans have also indicated clear advantages to the procedure.

273 patients participated in the European study. 55% of the patients who were cooled during the resuscitation lived in maximum independence six months after the treatment, compared to 39% of the patients who were not cooled. 41% of patients who underwent cooling during CPR died, compared to 55% of patients who were not cooled. Only 67 patients participated in the Australian study, but its results indicated an even more distinct advantage for patients who were cooled. About 51% of those who underwent the cooling process died, compared to 68% of the patients who did not undergo the process.

The brain savant

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