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Therapeutic hypothermia: Keeping cool in emergencies

The technique, which lowers a patient's body temperature to stave off brain damage, is gaining in popularity, but some doctors are slow to adopt it.

August 22, 2011|By Amber Dance, Special to the Los Angeles Times
  • Surgeons have used cooling ever since the 1950s, packing the heart with slushy ice to protect the brain during operations.
Surgeons have used cooling ever since the 1950s, packing the heart with… (Jose J. Santos / Los Angeles…)

Alaina Dixon barely remembers the end of the last Houston marathon, on an unusually hot and humid Jan. 30. The 26-year-old interior designer collapsed 200 feet from the finish line: Her heart had stopped. Paramedics shocked her twice to restart it, then rushed her to the hospital.

Doctors would later discover and fix the congenital heart defect that probably caused Dixon's collapse. But in the minutes and hours following the incident, their focus was on an entirely different organ: her brain.

So they put her on ice.

At St. Luke's Episcopal Hospital, nurses wrapped her in cold gel pads and filled her IV bag with chilly fluids. Her core body temperature dropped from a normal 98.6 degrees Fahrenheit to about 91. Seven months later, Dixon is back much as she was. She hasn't noticed any trouble thinking since she recovered. And with her heart now repaired, she says she'd run a marathon again.

Such emergency cooling, known as therapeutic hypothermia, is growing in popularity as a treatment for cardiac arrest. In fact, "it's the single most important advance in resuscitation science in the last 10 years or so," says Dr. Prediman Shah, director of cardiology at the Cedars-Sinai Heart Institute. At the same time, doctors are slowly expanding cooling's uses for other crises: Infants who didn't get enough oxygen during birth are now routinely cooled to protect their brains, and studies are underway to test the potential of cooling for treating victims of stroke or heart attack, as well as those who have suffered traumatic injury to the brain or spinal cord.

Through such cooling, doctors can prevent the long-term brain damage that usually results as the brain recovers from a short period without oxygen.

Therapeutic hypothermia has a long history. The ancient Greek physician Hippocrates packed wounds with snow. Centuries later, during the Napoleonic wars, an army surgeon noticed that wounded soldiers who stayed warm fared worse than those who slept in a chillier bunk.

Surgeons have used cooling ever since the 1950s, packing the heart with slushy ice to protect the brain during operations. But even though the American Heart Assn. has recommended therapeutic hypothermia for cardiac arrest since 2003, emergency rooms have been slow to adopt the technique. "It's only hit the mainstream in the last three years," says Dr. Stephan Mayer, head of the neurology critical care unit at Columbia University Medical Center in New York.

There are about 295,000 out-of-hospital cardiac arrests in the U.S. annually, according to a 2011 report from the American Heart Assn. Without hypothermia, the prognosis is downright "dismal," Shah says. Of those 295,000, 23.8% will survive long enough to reach a hospital and only 7.6% will be discharged alive, according to a 2010 review in the journal Circulation.

When the heart stops, so does blood flow to the brain, depriving it of the oxygen and sugar it needs to perform. That's bad enough.

But most of the damage happens later, after the blood returns. At that point, the nerve cells "go nuts," Mayer says. They spit out toxic neurotransmitters. They fill up with calcium, potentially activating cellular suicide. The sudden oxygen influx causes formation of free radicals, which shred cell membranes.

Chilling patients to between 89.6 and 93.2 degrees slows this brain damage process, giving them a better shot at recovery. "Cooling the brain is like throwing water on the fire," Mayer says.

Two 2002 papers in the New England Journal of Medicine provided key evidence that the treatment works. One study, led by Dr. Stephen Bernard, a critical care physician at the Alfred Hospital in Melbourne, Australia, reported that of 77 cardiac arrest patients, 49% of those who underwent hypothermia were able to leave the hospital, walking and talking, and resume their normal lives. In the uncooled group, only 26% had such good results.

The other study, conducted in several European countries, examined 273 people who had cardiac arrest. In the cooled group, 55% recovered, compared with 39% in the normal-temperature group.

More recently, the authors of a June 12 paper in the journal Circulation reported on their implementation of hypothermia across the Minneapolis area. Among survivors, the percentage of patients with good brain function went up from 77% to 92% after cooling protocols were added.

"It's just shameful how slow we've been to make hypothermia a standard procedure," says Dr. Susan Stein, a pulmonary and critical care physician at Olive View-UCLA Medical Center.

Dr. Eric Harrison, director of cardiology for IASIS, a nationwide healthcare system, was an early convert. He recalls one 76-year-old woman he treated for cardiac arrest in 2002, just months after the New England Journal of Medicine articles came out. She arrived at the hospital, heart restarted but bent backward with her head toward her heels — an indicator of severe brain damage. Physicians cooled her with ice packs and a cooling blanket.

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