An analysis of multiple studies has shown hypothermia therapy (HT) provides critical benefits for people who suffer cardiac arrest, though it remains under-utilized by hospitals and emergency medical service crews, according to researchers.
Not only did the analysis indicate HT may increase survival among cardiac arrest patients, the therapy also may have protective effects on the brain.
In one study, for example, the survival rate at six months following cardiac arrest was 59 percent for patients who had undergone HT compared to 45 percent among patients who had not.
Meanwhile, 55 percent of patients who had undergone HT showed favorable neurological outcomes – such as the brain returning to complete or at least partial function – compared to 39 percent of non-HT patients.
“Every cardiac arrest patient or cardiac patient who has suffered a neurological event should be cooled absolutely."
When a person goes into cardiac arrest, the heart stops pumping, which causes blood to stop circulating to the brain and can lead to neurological damage. However, HT appears to slow the rate of damage and protect the brain from further negative effects when blood begins recirculating.
The results of the analysis fall in line with current medical guidelines: HT has been included in the American Heart Association's guidelines for cardiac arrest care for nearly a decade.
“Every cardiac arrest patient or cardiac patient who has suffered a neurological event should be cooled absolutely,” said study researcher Dr. Ron Waksman, associate chair of cardiology at the Washington Hospital Center in the nation’s capitol. Ideal application of HT involves cooling the body to 32 to 34 degrees Celsius for 12 to 24 hours.
However, Waksman, who is also professor of medicine and cardiology at Georgetown University, said despite scientific support, the therapy is still not used by enough doctors and emergency medical service crews.
“I think it’s the minority of ambulances that apply HT and have the equipment for it,” Waksman said, adding that there’s no national registry to track HT application. “We have to increase awareness because it can save people in terms of neurological events. It’s in the guidelines, but it's just not being used.”
Typically, patients who suffer cardiac arrest and undergo CPR have two minutes of no blood supply to the brain, according to Waksman. Even if their heart is restored to normal function, they may suffer from brain damage or memory loss.
“Once you suffer cardiac arrest, there is ongoing damage in the brain,” Waksman said. “The reason for brain damage is lack of oxygen because there is no circulation to the brain.”
After four to five minutes, the brain suffers damage, and even if you reintroduce oxygen to the cells, it can continue to create damage because you’re pumping oxygen onto tissue that has already suffered, he added. HT minimizes the metabolic processes that can potentially induce more damage.
While HT can slow the rate of and minimize damage, it does not heal damage that has already occurred. Therefore, the treatment works best when applied early.
“Time is really important – first, you have to intubate the patient and restore circulation, but once you do that, the next step is to do cold infusion,” Waksman said. “It’s a very non-expensive methodology, which can be done out of the hospital by putting the patient in ice cubes. A medical team can even start with cold infusion.”
But only medical professionals should apply HT, he added. “Laymen should not be pouring ice on cardiac arrest patients in the street.”
The risks of HT include bleeding, infection or shivering during treatment, but are far outweighed by the potential benefits, according to Waksman.
“Those [risks] are relatively mitigated by being able to restore full brain functionality versus being incapacitated or on disability for the rest of your life due to neurological damage,” he said.