Hypothermia is a medical emergency that requires immediate care. While it’s most common in winter when temperatures can drop significantly, it also can occur at milder temperatures if you’re chilled from rain, sweat, or submersion in cold water.
Luke N. Apisa, MD, a Mass General Brigham emergency medicine doctor, is an expert in hypothermia prevention and care. At Massachusetts General Hospital, he serves on the faculty of the Emergency Department’s Division of Wilderness Medicine. The division focuses on the practice of resource-limited medicine under austere conditions, including emergency care in wilderness areas, medical care in response to rural and urban disasters, and care in other challenging settings.
In this article, Dr. Apisa describes how hypothermia commonly develops, how to best stay alert to signs and symptoms, and how keep a person with hypothermia healthy and safe.
“Hypothermia is as simple as having inadequate means to keep your body warm when the temperature outside is colder than your body's internal temperature,“ explains Dr. Apisa. “Our internal body temperature is almost 99 degrees Fahrenheit, so the vast majority of environments we encounter are continuously draining heat from the body. The body is in a constant push-and-pull with the environment to maintain core temperature. Nutrition, insulation, and radiant heat from the sun are just some of the ways that we maintain euthermia (an appropriate body temperature) in spite of the environment.”
Body temperature hovers around 98.6°F (37°C) and hypothermia occurs when it drops below 95°F (35°C). If you’re exposed to cold temperatures, your body can lose heat faster than it’s produced. Hypothermia most often occurs at very cold temperatures. But if you’re chilled from rain, sweat, or submersion in cold water, hypothermia can occur even at cool temperatures above 40°F. Lengthy exposures to cold air or water use up your body’s stored energy over time, and this leads to lower body temperature.
“Our body is extraordinarily good at finding means of compensating for cold temperatures,” says Dr. Apisa. “Not only do we produce our own heat from calories that we consume, but our innate desire to get out of the cold is a survival response. Shelter and insulation are key means of preventing hypothermia. People will rarely voluntarily stay out in a cold area until hypothermia sets in. In a big city like Boston, where shelter is often all around us, the hypothermia we see tends to be in undomiciled patients without access to shelter, or in patients with a substance in their system (usually alcohol) that impaired their ability to respond to that innate desire to find warmth.“
Hypothermia is dangerous because cold environments are widespread and hypothermia can set in rapidly in low temperatures, especially if your body is wet.
If your body temperature drops too low, one late-stage complication of hypothermia is that it can affect the brain. A person with hypothermia may be unable to think clearly or move well. This makes hypothermia especially dangerous, because you may not know that it’s happening. You may not realize that you need to take action to prevent serious health complications or even death.
In most cases, the lack of awareness that leads to fatal hypothermia doesn’t stem from the hypothermia itself. Instead, the person has typically consumed something that affects their judgment, such as alcohol.
Anyone can develop hypothermia, but patients with hypothermia are often:
Hypothermia is a medical emergency. If you have any of the symptoms below or observe these signs of hypothermia in another person, check body temperature if you can. If it’s below 95°F, get medical care immediately.
Warning signs of hypothermia in adults include:
Signs of hypothermia in babies may include:
Hypothermia in the late stage involves a person who is totally unresponsive. They may be unconscious and may not seem to have a pulse or to be breathing. “If you see someone who’s totally unresponsive, particularly in a city or in an urban environment where you can call for help, the first rule of thumb is always to call 911,” advises Dr. Apisa. “There is no substitute for activating emergency services and getting them there. That's what’s going to get them healthiest, quickest.”
Perform CPR, even if the person appears dead. CPR should continue until the person responds or medical aid arrives. In some cases, hypothermia victims who appear to be dead can be successfully resuscitated.
Here’s what you can do:
“If a person is shivering and seems quite cold, and suddenly stops shivering despite not getting any warmer, maybe they're starting to get a little confused, they’re progressing to moderate hypothermia and that's a true medical emergency,” says Dr. Apisa.
If you’re at increased risk of hypothermia or know someone who is, contact your local department of public health. Many provide community outreach programs and social support services including: