Hypothermia has been applied therapeutically since antiquity. The Greek physician Hippocrates, the namesake of the Hippocratic Oath and arguably the world’s first modern doctor, advocated the packing of wounded soldiers in snow and ice. Centuries later, Napoleonic surgeon Baron Dominique Jean Larrey recorded that officers, who were kept closer to the fire, survived less often than the minimally pampered infantrymen.
The first medical article concerning hypothermia was published in 1945. This study focused on the effects of hypothermia on patients suffering from severe head injury. In the 1950s, hypothermia received its first medical application, being used in intracerebal aneurysm surgery to create a bloodless field. Most early research focused on hypothermia at body temperatures between 20–25°C (68–77°F). This extreme drop in body temperature can trigger a host of side effects, which has made the use of deep hypothermia impractical in most clinical situations.
Many medical applications have been investigated, including stroke, traumatic cardiac arrest, cardiac failure, postoperative tachycardia, anoxic brain injury, newborn hypoxic-ischemic encephalopathy, hepatic encephalopathy, bacterial meningitis, acute respiratory distress syndrome, near-drowning, and traumatic head injury as noted above.1 The use of mild hypothermia in certain cardiac arrest patients is becoming routinely applied and recommended in guidelines across the world.
Mild hypothermia has also been studied in acute myocardial infarctions (AMI). In the early 2000s, a few companies investigated endovascular cooling technologies in large AMIs known as ST segment elevation myocardial infarctions (STEMIs). Their goal was to reduce the final infarct size by lowering body temperature to mild TH temperatures prior to reopening the blocked artery.
Unfortunately, those approaches didn’t cool quickly enough and, in their clinical trials, the investigators often reopened the blocked artery before the patients reached the therapeutic temperature of less than 35°C. While those trials failed, the trials provided very useful insight. In the patients that did reach a temperature of less than 35°C prior to blood flow restoration, there appeared to be a substantial reduction of infarct size, leading some to conclude that a faster cooling method might prove beneficial in AMI patients. Velomedix is investigating a new, much quicker cooling technology in hopes of demonstrating improved clinical outcomes first in heart attack patients and potentially in others thereafter.
- Varon J, et al. Therapeutic Hypothermia: Past, Present, and Future. Chest. 2008 May; 133(5):1267-74.