The growing popularity of outdoor recreation has
resulted in greater demand for an effective on-site method for treating hypothermia. Other
than for mild cases, the most effective and safest treatment for all levels of hypothermia
is the addition of heat to the body core, rather than via the periphery.
The most important phase of treatment is the
prevention of post-rescue collapse during the first 30 minutes following rescue, and
during transportation to a medical facility.
Phases and treatment of hypothermia.
After-drop
A further cooling of core temperature occurs after the victim is removed from the cold
environment. This after-drop is often responsible for post-rescue collapse.
Pre-hospital stabilization
Preventing respiratory heat loss and progressive cooling, of the heart through the tissues
is essential. This cooling if not arrested, can lead to ventricular fibrillation of the
heart. Patients who are unconscious, with a temperature below 30°C or 80°F, may not
respond to defibrillation. Thermally stabilizing a patient with suitable equipment is
necessary, both before transportation and enroute to the hospital to prevent additional
cardiac complications.
Core rewarming
This is the most effective treatment for all cases of moderate to severe hypothermia,
whether treatment occurs in the hospital or in the field.
Inhalation rewarming
As the only non-invasive hospital treatment suitable for active core rewarming in the
field, inhalation rewarming donates heat directly to the head, neck, and thoracic core
(the critical core) through inhalation of warm, water-saturated air at 43 - 45°C (107 -
122°F). This method also warms the hypothalemus, the temperature regulation center, the
respiratory center, and the cardiac center at the base of the brainstem. In many cases,
this rewarming of the central nervous system at the brainstem reverses the cold-induced
depression of the respiratory centers and improves the level of consciousness.
Beside this strategic donation of heat, inhalation
rewarming also eliminates . .
Respiratory heat loss
This accounts for 10% to 30% of the body's heat loss. This is particularly important in
rescue situations where the ambient air is cold (cooling of the core through respiration).
In summary, inhalation rewarming is highly effective
in providing "basic life support" through thermally stabilizing the core
and brain stem temperatures. It is safe for treatment for all levels of hypothermia, but is
particularly important for severe cases, because insulating alone (blankets), does not
prevent further cooling of the core.
The first half hour during rescue is the
most critical phase of hypothermia management!
Avoid having the victim assist with their own rescue!
Muscular activity by the hypothermic victim pumps
cold peripheral blood from the arms and legs into the central circulation causing the core
temperature to drop even further. Gentle handling is critical! A cold heart is particular
susceptible to ventricular fibrillation, and some victims may suffer fatal ventriculation
when jolted about during initial handling or transportation.
" The inhalation rewarming method is now our
first choice in the re-warming treatment of all stages of hypothermia in the wilderness
environment. " ( Dr. Ian Taylor, Medical Adviser to the North
Shore Rescue Team, Vancouver B.C.).
Sources:
1 Danzl, D. Accidental hypothermia. Emergency Medicine: Concepts in
Clinical Practice. Rosen et al. Mosby Publishers.
2 Hayward, J.S. et al. Thermal and cardiovascular changes during three
methods of resuscitation from mild hypothermia. Resuscitation 11:21-33.
3 Harnett, R.M. et al. A review of the literature concerning
resuscitation from hypothermia, Aviation Space Environmental Medicine. Part I
54(5):425-434. Part II 54(6):487-495.
4 Danzl, D. et al Accidental hypothermia: Always a Danger. Patient Care
17 (19):116-151, and personal communication.
5 Morrison, J.B. et al. Influence of respiratory heat transfer on
thermogenesis and heat storage after cold immersion. Clinical science 63:127-135.
6 Collis, M.L. et al. Accidental Hypothermia: A Study of Practical
Rewarming Methods. Aviation Space Environmental Medicine. 48 (7) 625-632.
7 Hayward, J.S. et al. Accidental Hypothermia: An Experimental Study of
Inhalation Rewarming. Aviation Space Environmental Medicine. 46(10):1236-1240, and
personal communication.
RES-Q-AIR