Field Management of Hypothermia

Consider the following scenario: You and your family are enjoyed an impromptu swim in a protected cove. After the early morning dip, you notice your young niece whose lips look slightly blue. She is huddled in a towel and still wearing a rash guard over her swimsuit. A breeze has picked up, and her hair is wet. You ask her if she's warm enough, and she just shrugs her shoulders. You mention that she might be warmer if she changes out of her wet items. "Yeah, I tried," she mumbles, "but I couldn't get them over my head."

Thermal Challenge: Hypothermia

Mild hypothermia is marked by shivering and a group of symptoms that can collectively be referred to as "the umbles." These include fumbling, mumbling and grumbling, which characterize a combination of lethargy, apathy and a decline in motor function. Fine motor skills are the first to go, and tasks like zipping up a jacket or tying shoes become difficult. The patient may neglect to take steps to minimize further heat loss, such as removing a wet swimsuit. Although it's often thought of as a cold water boating risk, hypothermia is particularly problematic at sea, even in warm weather, because of the way it can subtly steal one's ability to think clearly and make good decisions.

How to Prevent and Treat Hypothermia

To successfully prevent or treat hypothermia, attention should be given to each of the four mechanisms of heat transfer:

• Conductive heat loss can be minimized by insulating the patient from direct contact with anything colder than he is. Place a dry wetsuit, boat cushion or foam sleeping pad between the patient and the ground (or the boat deck) to reduce heat loss into it. Layers of clothing or blankets are useful for insulating a person against cold air. Sleeping bags and down jackets are excellent examples of this approach to insulation; they are essential equipment in cold environments because they have significant loft for their weight and create substantial space for trapping heat around the body.
• Convective heat loss can be minimized by creating a stable microclimate around the body. Clothing made of nylon, other synthetic materials or tightly knit fabrics limit air flow and effectively reduce convective heat loss. By keeping the same air near the body, the patient doesn't have to keep reheating the air around him. This is similar to the way a wetsuit reduces convective heat loss in water.
• Evaporative heat loss is often subtle. Even a small amount of moisture on the skin can make it very hard for a cold person to warm up. Replace damp underlayers, and dry the skin thoroughly before adding more layers.
• Some fabrics are specially designed to minimize radiative heat loss, including those used in the "space blankets" often found in first aid kits. A reflective blanket on its own, though, is inadequate for warmth in a cold environment since it offers little protection against conductive or convective heat loss.

In addition to managing heat loss, it is a good idea to promote heat generation. Encourage the patient to eat and, if she is able, perform light exercise. Sweet foods in particular offer calories the body can use quickly. Out of concern for maintaining an airway, give a patient food only if she is able to eat it without assistance.

Warning Signs of Moderate Hypothermia

If cold stress becomes hypothermia and is not addressed in the early stages, the patient will begin to experience uncontrollable shivering and a decline in gross motor skills. These are signs that moderate hypothermia has begun. The patient's coordination will be impaired, ultimately manifesting as stumbling or an inability to walk. At this point, the need for intervention is critical. It may still be possible to rewarm this patient in the field; efforts should begin in earnest.

Warning Signs of Severe Hypothermia

A patient with severe hypothermia will have lost the ability to shiver. Many basic body functions will slow down due to diminished core temperature. This patient may be unresponsive, and the heart rate may not be palpable. Respirations may be slow and faint. The objective of care should be to prevent further heat loss. Wrap the patient in as many insulating layers as are available, and use a tarp or tent fly to ensure that the patient and the insulating layers remain dry. Initiate an evacuation immediately, but take care to handle the patient gently. Violent movement could send the patient's heart into a potentially fatal rhythm. This combined with the possible difficulty identifying a heartbeat means that great care must be taken when assessing signs of life in severely hypothermic people. Chest compressions are appropriate only when signs of life are truly absent. Rescue breaths can be given freely, if needed.

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