Writing in the July issue of the American Journal of Physiology-Heart and Circulatory Physiology, researchers found no significant difference in the amount of oxygen available to the heart between rats exposed to one hour of severe hypothermia and rats exposed to five hours. However, the rats in the five-hour group were more likely to experience fatal heart failure during rewarming.
The issue is important because the rewarming of victims of severe hypothermia almost always causes heart failure of varying severity, but little is known about why that happens, said Torkjel Tveita, the study's senior researcher. Tveita is an anesthesiologist who treats victims of hypothermia, including fishermen who have fallen into the frigid Norwegian waters, and cross-country skiers marooned in bad weather.
"We still do not know the pathophysiological mechanism of hypothermia, which is necessary to developing the best way to rewarm hypothermia victims," Tveita explained. This study -- which examined the effect hypothermia had on the heart, not on other vital organs such as the brain -- is a step in that direction.
Timofei V. Kondratiev, Kristina Flemming, Eivind S.P. Myhre, Mikhail A. Sovershaev and Tveita did the study "Is oxygen supply a limiting factor for survival during rewarming from profound hypothermia?" The study is published by The American Physiological Society. The researchers are from the University of Tromsø (Norway) and University Hospital of North Norway.
"Due to the limited amount of oxygen the body needs when hypothermic, I want to stress the importance of starting and continuing cardiopulmonary resuscitation (CPR) efforts with all victims of hypothermia," Tveita said. Doctors typically cease CPR efforts in a normothermic patient after 30 minutes. Bu
Source:American Physiological Society