Recently my wife and kids visited friends in Vermont. I remained in Fairfield due to professional obligations.
While checking the weather reports frequently, I wondered how they were getting along. That’s when I received an emailed video of my son sledding down a frozen hill, shirtless and wearing shorts, screaming in delight. Fortunately, humans are pretty tough and can tolerate cold exposure quite well, if they are young, healthy and well hydrated. When it comes to the ridiculously low temperatures, recently reaching 30 below zero in northern Minnesota, all bets are off. The medical term for low body temperature is hypothermia.
One of the premier medical textbooks addressing cold exposure issues is Auerbach’s “Wilderness Medicine.” This textbook divides cases of hypothermia into accidental, homicidal and suicidal categories, a common forensic classification approach.
More 600 Americans die annually due to hypothermia. Surprisingly, this condition occurs in all locations, even Florida. I recall treating a woman for hypothermia who fell into the San Francisco Bay years ago, and the weather was not particularly cold. Indeed, body temperatures may take a nosedive even on a balmy day in the 70s, particularly in persons who are chronically ill, very young or elderly. Thyroid disease, Parkinson’s disease, and infections, for example, may impair thermoregulation.
While practicing in a mental health facility, I often encountered cases of low or high body temperature attributed to chronic use of psychiatric medications. Evaluating a patient with hypothermia, therefore, may require detective work. A clinician must identify predisposing conditions, while simultaneously correcting the acute body temperature challenge.
Auerbach describes stages of hypothermia. Normal body temperature varies between 36.0 and 37.1 degrees Celsius, or 96.9 to 98.9 Fahrenheit, upon awakening in the morning (temperature rises in the afternoon). Medical science is moving increasingly toward the more rational metric system, but I will use Fahrenheit numbers more familiar to our readers.
Mild hypothermia, with body temperature above 91.4, may elicit shivering, poor judgment and maladaptive behavior. Loss of coordination of the hands may impair one’s capacity to take life-saving actions, such as lighting a camp fire. Moderate hypothermia, from 84.2 to 89.6 degrees, causes loss of shivering response, and decreased mental status or even stupor. Severe hypothermia, 71.6 to 82.4 degrees, may cause irregular heart beat patterns, such as life-threatening ventricular fibrillation. Profound hypothermia, with core temperatures below 68.0 degrees, is associated with an 80 percent likelihood of lacking a palpable pulse.
The lowest recorded body temperature associated with long-term survival was 48.2 degrees. Drowning patients, particularly children, can sometimes survive profound hypothermia with aggressive resuscitation. Core body temperatures are more reliable than oral temperatures in assessing hypothermia. Tympanic membrane monitors, for example, reflect core body temperature.
Emergency department evaluation of a patient with hypothermia typically involves blood tests, various warming modalities, correction of any metabolic conditions and addressing underlying contributory factors, such as diabetes, thyroid disease or infection. Indeed, emergency medicine is now a distinct field of medical specialization, and an acutely hypothermic patient might well be managed by an interdisciplinary team, also including intensive care specialists.
If possible, however, it is best to prevent hypothermia. Informing others of our travel plans, dressing appropriately and maintain emergency supplies in our vehicles and homes are all reasonable precautions.
Persons suffering from cold exposure may at times engage in “paradoxical undressing,” disrobing in the face of freezing ambient temperatures. Forensic pathologists are aware of this behavioral entity, which probably reflects central nervous system disruption.
NFL fans, particularly in northern climates, seem prone to similar behavior, removing their shirts and donning body paint, and goofy hats. Unfortunately, medical science cannot explain every phenomenon.
Stay safe, and warm, this winter season.
Scott T. Anderson, MD, PhD ([email protected]) is Clinical Professor of Medicine, UC Davis. This article is informational, and does not constitute medical advice.