Inducing hypothermia during medical emergencies gains ground
Avery Reynolds was born with barely a whimper, black and blue from lack of oxygen, on Friday, Aug. 13, 2010. The umbilical cord encircled her legs. Doctors wrapped her in a cold blanket to induce hypothermia.
Amanda Reynolds recalls her daughter was hooked up to numerous machines; she couldn’t hold her baby for more than a week. But when she finally did, “we looked each other right in the eye .... I felt, she’s going to OK,” recalls Reynolds, who lives in Santa Monica.
Avery would spend more than six weeks in the hospital and would need physical therapy afterward. But now, “she’s right where a 10-month-old should be,” Reynolds said in June. “We’re just so thankful.”
Increasingly, doctors are using or considering the hypothermia technique for a variety of emergencies beyond full cardiac arrest. Read on:
Newborn oxygen loss
In approximately 1 in 1,000 births, babies experience restricted blood flow during labor and delivery, which may cause severe deprivation of oxygen. If infants under these conditions survive, they may suffer brain damage and conditions such as cerebral palsy.
Hypothermia is an accepted treatment but is only available in advanced neonatal intensive care units, says neonatologist Charles Simmons, chairman of pediatrics at the Cedars-Sinai Maxine Dunitz Children’s Health Center, where Avery was born. Although the method doesn’t guarantee recovery, it boosts the chances by 50%, he estimates.
In a 2005 study in the New England Journal of Medicine, doctors cooled 102 infants with potential brain damage and compared them with 106 babies kept warm. Of the cooled group, 56% survived with no or little disability. In the uncooled group, that number fell to 38%.
Stroke
Doctors are testing the use of therapeutic hypothermia with stroke patients. There are a lot of preliminary data suggesting it helps, says Dr. Patrick Lyden, the Cedars-Sinai neurologist leading the trial. He believes he’s seen the treatment work himself — but physicians haven’t tested it enough yet to be sure.
In preparation for the trial, Lyden and colleagues conducted a pilot study of 58 people, published in 2010 in the journal Stroke, showing that therapeutic cooling is safe for stroke patients. Now the Cedars team is coordinating with researchers at multiple sites to test the therapy in more than 1,000 patients.
Cooling these patients is challenging, says stroke specialist Dr. James Grotta, who is leading one arm of Lyden’s trial at the University of Texas Health Science Center in Houston.
For one thing, the treatment works best when started immediately. Yet stroke patients often don’t reach the emergency room until several hours after their symptoms start. By then, brain damage may have already occurred.
For another, stroke patients are usually awake. Hypothermia is excruciating for a conscious person, and the inevitable shivers can counter cooling efforts. Doctors must therefore use medication to sedate patients.
Grotta says he likes to combine a cooling catheter treatment (in which cold fluids are run through a catheter inserted in a vein, to chill the blood) with blowing warm air over the person’s skin, for comfort, since it’s only necessary that they be cooled on the inside.
Spinal cord injury
During the Buffalo Bills’ 2007 season opener, tight end Kevin Everett hit the ground hard. He had attempted to tackle Denver Bronco Domenik Hixon, but Everett’s head collided with Hixon’s shoulder and he dislocated his neck. This kind of injury can bruise the spinal cord, compressing nearby vessels and cutting off the blood supply.
On the way to the hospital, team physician Andrew Cappuccino, an orthopedic surgeon, infused Everett with ice-cold fluids. He repeated the treatment after a four-hour surgery to repair Everett’s neck.
The treatment would decrease swelling, and Cappuccino hoped it would also protect the player’s spine from further damage by free radicals and other chemicals released in the injured tissue.
Cappuccino had learned about hypothermia at a lecture by University of Miami neuroscientist W. Dalton Dietrich, who studies hypothermia treatment for injury to the central nervous system as part of the Miami Project to Cure Paralysis.
“It appears to be the only thing that works,” Dietrich says.
He and colleagues are testing the treatment at Jackson Memorial Hospital. Dr. Allan Levi, a neurosurgeon there who is also part of the Miami Project to Cure Paralysis, estimates that only 20% to 25% of those who survive severe spinal cord injuries are able move any part of their body below the injury site and only 2% to 3% will walk again.
Everett walked again just months after his surgery. “We have no idea if the cooling had anything to do with his great recovery,” Dietrich says. For that kind of evidence, the doctors need large clinical trials.
The Miami group has already tried the treatment in 33 people, Levi says, and published data on the first 14 in the journal Neurosurgery in 2010. At that point, 43% of subjects had achieved some movement below the injury area. The scientists are now seeking funding to run a larger trial.
Traumatic brain injury
Doctors know that cooling can reduce swelling of brain tissue and thus compression of brain blood vessels. They wonder if it might also prevent long-term brain damage. The issue is controversial, Dietrich says. “It may or may not work.”
In very small trials, hypothermia for traumatic brain injury has looked effective. But larger trials are less convincing. For example, in a study of 108 patients published in February in Lancet Neurology, people who received the treatment fared worse, on average, than those who didn’t. Of those who got hypothermia, 40% survived with moderate disability at most. In the uncooled group, the number was 55%.
Dietrich and others suspect that cooling would work but only for certain TBI patients. He thinks the best candidates would be people whose brains are bleeding. The blood fills the skull, squashing blood vessels. This restricts blood flow much like in stroke or cardiac arrest, in which therapeutic hypothermia appears to be effective.
Heart attack
In contrast to full cardiac arrest, during a heart attack only a fraction of the heart’s blood supply is blocked. Animal studies on hypothermia treatment have been encouraging, but as of yet there are few data from people.
One small, 20-person study, published in 2010 in the journal Circulation: Cardiovascular Interventions, found that cooling reduced the area of the heart damaged by the attack by 38%.
