In the last article, I discussed localized cold exposure syndromes in which a specific body part becomes cold but the rest of the body remains warmer. This article discusses generalized cold exposure, hypothermia, caused by a drop in the body’s core temperature. Both localized and generalized cold exposure syndromes can exist in a patient at the same time, but treatment is quite different: Localized cold exposure is treated with immediate re-warming, while hypothermia must be slowly reversed.
How hypothermia develops
Hypothermia can occur when we are exposed to temperatures below that of our skin, which averages 92 degrees Fahrenheit.
Factors influencing hypothermia development
- Severity of exposure (how cold it is)
- Physical medium of exposure (water exposure cools the body
- 35 times faster than air)
- Exposure duration
- Degree of protection (clothing) worn or available
- Body type and size
Clinical hypothermia is present when the deep, or core, body temperature falls below 35 degrees Celsius (95 degrees Fahrenheit), meaning when we have lost about 2 degrees Celsius (35.6 degrees Fahrenheit). With continued cooling, consciousness becomes progressively impaired then lost, followed by death.
The signs and symptoms of hypothermia can be easy to recognize in others but hard to see in ourselves. As the body’s core temperature drops to less than 98 degrees, our skin becomes pale, we may develop a headache, and shivering commences. When core temperature falls below 95 degrees Fahrenheit, we may start having trouble thinking clearly, shivering stops, coordination becomes impaired and completing tasks becomes difficult. At less than 86 degrees Fahrenheit, we enter a moribund state where signs of death are present. Death occurs below 82 degrees Fahrenheit.
All phases of hypothermia require treatment. Handle patients with a minimum of movement. If vomiting occurs, make sure the patient vomits in a downward direction to avoid aspiration (suffocation). Do not massage. Massage makes the inner body colder by forcing cold blood in. Re-warm the patient slowly by immersing only the torso in a 105- to 110-degree Fahrenheit water bath. Onboard, an electric blanket or nude body contact with a warm individual under a regular blanket works best. A nude body on each side of the victim may be needed in severe cases. Do not give alcohol or stimulants. Provide warm liquids only. Provide emotional support and reassurance; a strong will to live greatly enhances survival. Be aware that initiating treatment for severe hypothermia does not ensure survival. Rapid re-warming can lead to a sudden death syndrome, which can sometimes be reversed by cardiopulmonary resuscitation. If possible, re-warming should be done in a medical facility. CPR knowledge is helpful, and I encourage everyone to take a CPR course.
If you have to enter cold water, always go feet first. This reduces cold shock and allows for cold adaptation. Wear plenty of protection; clothes trap the air and warmed water around your body, reducing the circulation of cold water. Never dive into cold water as this can cause acute vertigo, disorientation, vomiting and cramps. Do not eat or drink (especially alcohol) before going into cold water. If you must enter the water in an emergency, wear as many articles of clothing as practical and always wear a life jacket. If you find yourself in the water, cold and awaiting rescue, assume the HELP (Heat Escape Lessening Posture) position. To assume this posture, cross your feet and bring your knees up to your chest with your arms pulled into your sides across your knees. In a group, huddle in groups of two or three. Huddling can extend survival time by 50 percent or more. Survival times noted on the graph are for people in the HELP position. Swimming or treading water markedly reduces survival time and, in general, the time you can spend in the water without getting hypothermia.
Four stages of cold-water immersion
The major threats of cold-water immersion are drowning, hypothermia, and collapse just before, during or after rescue. Understanding the four stages of immersion and their associated risks can help you deal with them.
Stage 1: Initial cold-water immersion responses
The initial responses to cold-water immersion are
- inability to hold your breath
- involuntary gasp, followed by uncontrollable breathing
- increased stress on your heart
Caused by the sudden fall in skin temperature, these responses last only about three minutes before abating.
Points to remember
- A fit person has a smaller initial response to cold-water immersion and a smaller chance of experiencing heart problems.
- Wearing an appropriate, properly fitted life jacket decreases your risk by keeping your airway clear of the water and reducing the need for movement during this critical period.
- Wearing appropriate protective clothing decreases the risk by slowing the rate of skin cooling and reducing the severity of the initial response.
- If you experience initial responses, stay still for the first few minutes, doing as little as possible until you have regained control of your breathing: A life jacket will help you do this.
- Start possible self-rescue immediately after the initial responses (if experienced) and before hypothermia sets in.
Stage 2: Short-term immersion effects
During this phase, cooling of the muscles and nerves close to the surface of the skin—particularly in the limbs—can lead to inability to perform physical tasks. Your swimming ability becomes significantly impaired. (Swimming accelerates the rate of cooling in any event.)
Points to remember
- Essential survival action that requires grip strength or manual dexterity—such as adjusting your clothing or life jacket, locating a life jacket whistle, or turning on a light—should be taken as soon as possible after the initial responses to cold water immersion have passed.
- Do not attempt to swim except to reach a fellow survivor or nearby shore, craft, or other floating object you can hold or climb onto. Stay calm. Evaluate your options. Can you reach a shore or floating object with less-than-normal swimming ability? If not, stay where you are, conserve body heat and await rescue.
Stage 3: Long-term immersion effects
Long-term immersion effects include a fall in deep body temperature (a cooling of your vital organs such as your heart, lungs and brain) to hypothermic levels. The rate at which your core body temperature falls depends on many factors, including your clothing, physique and amount of movement (swimming, for example).
Points to remember
- Wear several layers of clothing, including a head covering, especially under a waterproof outer layer such as an immersion suit.
- Keep still; wearing a life jacket reduces the need to move (tread water).
Stage 4: The rescue phase
A significant percentage of people die just before rescue, during rescue or just after rescue. Factors may include
- the way they are rescued
- relaxing too soon
- a loss of buoyancy due to actions such as waving, which may release air trapped in clothing; wearing a life jacket removes this threat
Points to remember
- Stay still. Blow a whistle or shout to attract attention, but don’t wave unless you are wearing a life jacket or have another flotation aid.
- Maintain your determination to survive. Do not relax too soon.
I’m ready to answer your questions in an upcoming column. Don’t be shy; email questions to Gbottino@aol.com.
Gino Bottino, M.D., has had wide experience in medical practice and emergency medical matters. A member of United States Power Squadrons First Aid Support Team (FAST) and the Safety Committee, Gino also has a background in competitive sail racing and is familiar with health-related problems afloat.