Management of Hypothermia
You may have noticed that it's getting colder outside. Moreover, some of my patients have informed me that the Almanac is predicting a hard winter. It would therefore seem appropriate to review the management of Hypothermia.
It goes without saying that the best management is prevention, so encourage your patients to dress properly in low temperatures, accounting for dampness and wind chill. Never-the-less we will continue to see cases of hypothermia in the Emergency Room.
Patients with mild hypothermia [34-36°C] require only passive rewarming with warm blankets, and external rewarming to the axillae, armpits and neck .
Patients with moderate hypothermia [30-34°C], require passive rewarming and external rewarming devices to the truncal areas.
Patients with severe hypothermia [<30°C], will require active internal rewarming :
- Warmed IV fluids [43°C]. Use normal saline and run it at 150-200 ml/hr to avoid overhydration.
- Warmed, humidified O2 [42-46°C].
- Peritoneal lavage with warmed [43°C], potassium free fluids, 2L at a time.
- Esophageal rewarming tubes are used extensively in Europe and may soon be available in North America.
The cardiac arrest situation is managed differently with the hypothermic patient. The "frozen heart" doesn't respond to defibrillation and medication the way a normothermic heart does. In fact, if the heart does not respond to the three initial defibrillations further shocks and boluses of medications should be withheld, until the core temperature reaches 30°C.
Once this temperature is attained you proceed with ACLS recognizing that the medications may accumulate and reach toxic levels, so the interval between boluses should be longer than normal. This interval, and the frequency of defibrillation attempts is somewhat empirical, but recusitation attempts should not be stopped until the patient has been rewarmed to normal or near normal temperature.
Endotracheal intubation and the placing of other tubes must be done gently, as these patients have a lower fibrillation threshold.
Also, don't forget that many episodes of hypothermia are associated with drug and alcohol abuse as well as trauma.