Use of Re-warming in Hypothermia

Re-warming is the most important part of management of hypothermia. Re-warming can be done actively or passively. The type of re-warming (passive or active) depends on the type of hypothermia (acute primary or secondary hypothermia) and severity (mild, moderate or severe) of the symptoms.

Passive external re-warming:

This is best suited for previously healthy individuals who suddenly develop acute, mild and primary accidental hypothermia. Passive re-warming is done by covering and insulating the patient of hypothermia in a warm environment. If head is also covered passive re-warming can achieve temperature increase of 0.5-2 degree Centigrade per hour. In most of the cases of acute, mild and primary accidental hypothermia this increase is usually adequate/sufficient. For successful passive re-warming the patient should have adequate glycogen store to support thermogenesis (heat production).

Active re-warming:

This can be active external re-warming or active core re-warming. This is providing of extra heat from external source for re-warming a patient of hypothermia. Active re-warming is required in case of body temperature below 32 degree Centigrade, extremes of ages (neonates and elderly individuals), CNS dysfunction, hormone insufficiency, or in case of suspicion of secondary hypothermia. Active external re-warming can be achieved by forced-air heating blankets (best method), radiant heat sources and hot packs. Heated tubs (monitoring difficult) and electrical blankets should not be used because vasoconstricted skin can easily burn.

Active core re-warming can be done in many ways. Airway re-warming can be done by using humidified oxygen at 40-45 degree Centigrade via musk. This do not provide much heat but reduce respiratory heat loss and can provide additional 1-2 degree Centigrade to overall heat required.

Intravenous crystalloids can be heated at 40-42 degree Centigrade and infused. But sufficient heat can be provided only during massive volume resuscitation. Heated fluid or blood can be efficiently delivered with countercurrent in-line heat exchanger.

Irrigation of stomach and bladder can be done with heated liquid, but delivers/transfer minimal heat due to small surface area. Peritoneal lavage can be done with heated (40-45 degree Centigrade) fluid. Hypothermia patients with cardiac arrest can be re-warmed with thoracic lavage.

In general, hypothermia patients (especially those with severe hypothermia) may require more than one method of delivering heat to raise core body temperature rapidly and safely.

NB: In addition there is extracorporeal blood re-warming options available for severely hypothermic patients (especially for individuals with severe primary accidental hypothermia), such as continuous arterio-venous re-warming (CAVR), hemo-dialysis, venovenous, cardiopulmonary bypass etc.

 


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2 Comments

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