The Wilderness Emergency Medical Services Institute

ADVANCED TREATMENT OF HYPOTHERMIA

In the last year or so, controversy has been increasing about the best way to care for the victim of hypothermia. The use of the warm gas inhalator has come under scrutiny - does it really increase the victim's chance of survival?

To clarify this issue, I met with Dr. David Frimm, a physiologist with the Canadian Armed Forces' Defence and Civil Institute of Environmental Medicine. For several years, Dr. Frimm and his associates have been engaged in testing various methods of hypothermia treatment. His disclosures were startling.

(Addendum: I should mention that Dr. Frimm's team is responsible for testing the survival gear made for Canadian sailors and pilots in the North Atlantic Ocean, one of the coldest bodies of water in the world.)

In tests conducted by the DCIEM, moderate hypothermia was induced in armed forces volunteers by immersion in a refrigerated water tank. A warm gas inhalator, commercially produced in England, was being evaluated. The experimenters found that wrapping the victim in a single wool army blanket was just as effective as the warm gas inhalator for rewarming, and also that the patient compliance was poor with the warm gas inhalator.

To be effective, the warm air or oxygen must be delivered with 100% humidification. Many subjects found this very uncomfortable, and preferred to warm in room air rather than breathe the warm, moist air. When dry warmed air was tested, it was found to actually result in a heat loss from the victim.

What, then, is the best treatment for hypothermia? First, in mild or moderate hypothermia, the usual external rewarming methods taught in basic cave rescue courses will be adequate. These methods are also quite acceptable for the treatment of acute hypothermia resulting from relatively brief immersion in cold water. The criteria here is that the patient's rectal temperature is not below 91 degrees F.

In chronic or severe hypothermia, the situation is somewhat different. The patient is in a state of impending metabolic bakruptcy, and is subject to volume depletion, electrolyte imbalance, cardiac arrhythmias, and other sequelae.

However, hypothermia in a sense contributes to its own treatment, since the patient is in a "metabolic icebox". In the absence of other injuries, the patient will tend to remain stable (although critical), allowing time to plan and act.

Care, therefore, is directed to advanced monitoring, and prevention of further heat loss. Active rewarming will cause the patient to quickly become unstable, and changes will be fast and furious. If possible, active rewarming should be delayed until the patient can be taken to an advanced medical facility; that is, one with a well-equipped Emergency Department and Intensive care Unit.

(Web Site Administrator's Note - Since this article was written about ten years ago, thinking has changed. It is now realized that it is almost impossible in the field to rewarm a patient enough to reach the unstable state mentioned above. Thus, active rewarming is now encouraged. See the WEMSI course notes for further information. -BFR.)

In some cases, it may be possible to bring a medical team and equipment to the cave entrance or even into the cave, if circumstances demand. This is a judgment call which will have to be made by the medical team leader and the surface coordinator. Remember that helicopter evacuation can greatly reduce surface travelling times, especially in hilly areas.

General supportive measures, such as intravenous volume replacement, by cut-down or a CVP line, if necessary, should be started as early as possible.

The following algorithm will help in the decisions to be made.

Additional Guidelines for Medical care:

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