Therapeutic hypothermia: Keeping cool in emergencies
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.
Right after treatment, the woman was confused and so aggressive that the doctors sent her off to rehab in protective restraints. But the only lasting effects were a slight memory loss.
Harrison, eager to promote the technique that so impressed him, founded the American Society of Hypothermic Medicine, which began recruiting members this year.
This year has also seen the inaugural issue of the scientific journal Therapeutic Hypothermia and Temperature Management. A survey of 58 emergency physicians in the new journal reported that 38 use therapeutic hypothermia in cases of cardiac arrest. The authors noted that doctors interested in hypothermia were probably more likely to fill out the survey, so it’s likely that a lower percentage of doctors in the general population use the technique.
Of the physicians who hadn’t embraced the cold treatment, some were planning to do so soon. Others responded that they had never thought about it, or they felt it was still unproved.
For a hospital to adopt therapeutic hypothermia, it often takes a champion for change. “People are just used to what they’re used to,” laments Mayer, who pushed to make hypothermia an option across New York City. He’d noticed that when Columbia first started offering hypothermia, other hospitals would send certain cases his way — generally doctors, nurses or their spouses. “It wasn’t being offered for Joe Six-pack, the man on the street,” he says.
Through the efforts of Mayer and the New York Fire Department, the city made a rule in 2009 that paramedics must take cardiac arrest patients to a hypothermia-ready hospital. There are similar policies in several other cities, including Boston, Seattle and London.
In Los Angeles County, at least 33 out of the 73 acute-care hospitals are hypothermia-ready, says Dr. Bill Koenig, medical director of the county’s emergency medical services agency. Since January, the agency has required paramedics to take cardiac arrest patients to one of those centers.
In 2010, California Assemblyman Anthony Portantino (D-La Cañada Flintridge) introduced a bill to require emergency rooms statewide to implement hypothermia procedures. The bill died in committee; several health groups opposed a mandate on emergency department procedures because medicine is an ever-changing field.
Hypothermia is not actually all that difficult, says Dr. Lance Becker, director of the Center for Resuscitation Science at the University of Pennsylvania Medical School in Philadelphia, which runs a training center for the treatment.
“What it really takes is a team,” Becker says. Doctors and nurses in several departments — the emergency room, cardiology, intensive care and radiology — must work together, along with hospital administrators, to ensure that patients remain safely cooled as they rotate through the different units. “That’s the biggest obstacle,” Becker says.
The therapy works better for some patients than others. Success rates in the 2002 studies were high partly because the investigators cherry-picked candidates. They limited their subjects to those in ventricular fibrillation, meaning their hearts were beating abnormally — quivering — but were not fully stopped. Such people are most likely to survive cardiac arrest anyway.
People whose hearts are at a standstill “typically have an even more dismal outcome,” Shah says. Nonetheless, he and other doctors say, it’s worth trying hypothermia on these kinds of cases as well.
Hypothermia does have side effects, including a higher risk of infection and bleeding. But given the low chances of recovery without it, “you don’t have a lot to lose by trying,” Stein says. “I think you’re on more thin ice if you don’t.”
Earlier this year, U.S. Air Force doctors in Iraq decided to do just that: try.
On March 29, a soldier was found unconscious with his heart stopped; it’s thought that he tried to use a fire extinguisher and it slammed him in the chest. Medics restarted his heart and sent him to the Air Force Theater Hospital in Joint Base Balad, north of Baghdad.
The medical team there had never performed therapeutic hypothermia, but Dr. Maj. Daniel Carlson of Walter Reed Army Medical Center in Washington, D.C., thought the patient would be an ideal candidate, according to Air Force Public Affairs.
The physicians followed instructions on the University of Pennsylvania website. Dining hall workers collected ice, then medical staff stuffed it into baggies and packed them around the patient. A medical technician hauled a 50-pound fan from the gym to the patient’s room to keep it cool. The doctors flushed his system with ice-chilled fluids to chill him from the inside.
Twelve hours later, the team transferred the soldier to a medical center in Germany. They endured an unheated flight to help their patient stay at 90 degrees.
When the soldier was rewarmed, he woke up talking right away. “He even asked to use the ‘commode,’” reported Col. Paul Gourley, commander of the 332nd Expeditionary Medical Operations Squadron, in an Air Force press release. “When a patient gets ornery, that’s a good thing.”
The adoption of hypothermia by physicians has been, and continues to be, slower than some doctors would like. And yet proponents say it takes only one successful treatment — with a recovered patient awake and talking — to make a doctor a believer.
“You’re hooked,” Mayer says. “You’ll never go back.”
