Evaluation and Treatment of Hypothermia, Colin K. Grissom, M.D.
page 9
contact adds no advantage to rewarming a mildly hypothermic patient who is vigorously
shivering (Giesbrecht 1994). External rewarming will increase skin temperature and
inhibit shivering. External rewarming will only provide a benefit to shivering patients if
the amount of heat donated exceeds the amount of shivering heat production that is
inhibited. In the non-shivering patient, however, active external rewarming should be
applied in the field. Forced air warming (Bair Hugger) or immersion of distal arms and
legs in warm water (arteriovenous anastomoses rewarming) are effective rewarming
methods for hypothermia but require special equipment in the pre-hospital setting
(Giesbrecht 1998; Vanggaard 1999).
Rewarming Moderate Hypothermia
A patient with a decreased level of consciousness and weak, or absent, shivering
requires active rewarming. The goal of field treatment is to limit afterdrop and transport
the patient to a hospital. Forced air warming, as with a Bair Hugger, is an efficient means
of rewarming in the hospital but requires special equipment in the field. If endotracheal
intubation is indicated, then heated (40
°C) humidified oxygen should be used for
ventilation. Heated, humidified oxygen can also be delivered by facemask, but is less
effective. For core body temperatures below 30
°C body cavity lavage may be used as a
rewarming method, but in the patient with a perfusing rhythm rewarming can be achieved
without invasive methods utilizing body cavity lavage (Vassal 2001). The combination of
forced air rewarming (Bair Hugger), heated humidified oxygen, and warmed IV fluids is
effective in rewarming moderate hypothermia as long as a perfusing cardiac rhythm is
present (Koller 1997). IV fluids should be heated to about 40
°C. Although
administration of warmed IV fluids is not an efficient method of rewarming unless large
volume resuscitation is required, cold IV fluids may cause worsening hypothermia.
Rewarming Severe Hypothermia
Treatment of the patient with severe hypothermia, but who still has a pulse and
respirations, includes all previously mentioned methods and selected methods of
extracorporeal rewarming. The goal of field treatment of severe hypothermia is to limit
afterdrop and transport the patient to a hospital for rewarming. For the severely
hypothermic asystolic patient, extracorporeal rewarming with cardiopulmonary bypass
may be the only way to rewarm successfully. This requires a hospital with cardiac
surgery capability, and should be considered in the disposition of a severely hypothermic
patient in circulatory arrest transported from a wilderness environment. A report from
Switzerland of 15 survivors among 32 patients with severe hypothermia and circulatory
arrest treated with extracorporeal circulation suggests that neurologic outcome is good
(Walpoth 1997). A recent case report from Norway describes a 29 year old female skier
rescued after acute hypothermia whose core body temperature was 13.7
°C just prior to
rewarming with extracorporeal circulation (Gilbert 2000). She had good neurologic
outcome after a long critical illness and is the survivor with the lowest known core body
temperature after accidental hypothermia.
