Physicians have long used cooling methods to help patients wake up after suffering a cardiac arrest, and researchers from Aarhus University in Denmark are exploring how to make the approach even more effective.
Past research has shown that some cardiac arrest patients who do not immediately wake up after hospitalization have benefited from being cooled down to 91.4 degrees (33 degrees Celsius) for 24 hours. But in the Aarhus study, data shows the process can be more effective if patients are cooled for 48 hours.
The study, published in JAMA, could help clarify how best to prevent severe brain damage after cardiac arrest. It included 355 out-of-hospital cardiac arrest patients aged 18 to 80.
Because the results of the study were not statistically significant, the researchers are unable to concretely conclude that the longer cooling period is the best way to prevent brain damage. However, they have determined that it won’t make things worse.
"We cannot rule out that there is a smaller clinical benefit of cooling down patients for two days, and the indications are that patients under the age of 60 in particular may benefit from the extra 24 hours,” said Hans Kirkegaard, a professor at Aarhus University, in a statement. “But a statistically significant result will require a randomized and blinded study with 3,000 contributing patients, and we do not have the opportunity to undertake such a study.”
Half of the patients in the study were cooled down to 91.4 degrees for 24 hours, while the other half were cooled to the same temperature for 48 hours. Then the researchers followed the survivors and measured cerebral performance after six months.
Assessments showed that patients who were cooled for 48 hours had better brain function than those only cooled for 24.
"This has definitely contributed to a very low mortality rate, which is 27 percent in the 48-hour group and 34 percent in the other group,” Kirkegaard said. “Another factor that contributes to the low mortality rate is that most patients undergo an examination and, if necessary, treatment of their coronary arteries immediately after arriving at the hospital.”