Wilderness and Rescue Medicine 8th Edition

141

Section V: Environmental Medicine

Most authorities recommend that CPR be per- formed on all patients without a palpable pulse. However, we believe that performing CPR on a hypothermic patient during a backcountry evacu- ation is counterproductive and may be harmful, especially if it delays access to definitive care. In addition, chest compressions may cause a very slow but functional cardiac rhythm to decay into ventricular fibrillation. For these reasons, we rec- ommend attempting only rewarming and PPV during a litter or toboggan transport. If you are waiting at a helicopter landing zone or trailhead, continuous CPR may be beneficial. As the science of hypothermia resuscitation con- tinues to evolve, several cases have documented success with high quality CPR and timely access to advanced medical care. How long CPR can con- tinue pending helicopter or ambulance transport will likely be determined by resources and rescuer endurance. If evacuation from the field is impossible, rewarming a severely hypothermic patient in place can be attempted. Find shelter and apply heat to the patient any way that you can, but try to avoid aggressive external rewarming like immersion in a hot spring or exposure to a hot engine room. This may produce vasodilatation and shock. Add sugar orally if the patient rewarms enough to protect the airway. Dextrose can also be added to an IV. If you succeed in improving level of consciousness and mental status, recognize that metabolic derangement may be significant and evacuation to medical care is still the ideal plan. If the patient is in apparent cardiac arrest, try to warm them enough to produce detectable vital signs. Perform CPR if you have the resources to do so. If no pulse or other life signs (including organized electrical activity on a monitor) are observed after 30 minutes of external heat and warmed PPV, the effort can be discontinued.

Treatment of Severe Hypothermia The ideal treatment for severe hypothermia is invasive controlled rewarming in a hospital, preferably a Level 1 trauma center. Take the time to package the patient properly before initiat- ing a gentle but urgent evacuation. This should include heat sources such as warm water bottles or a chemical or charcoal heat pack applied to the thorax, with at least one layer of clothing protect- ing the skin. This minimizes heat loss and may begin rewarming, improving the stability of the cardiovascular system. Rough handling can cause the cold heart to go into ventricular fibrillation. Keep the patient horizontal. Positive pressure ventilation with humidified, heated air will help reduce heat lost to respiration. Because the patient’s oxygen demand and produc- tion of CO 2 is decreased, the rate can be reduced to about six breaths per minute. The best source of heated and humidified air in the backcountry is probably going to be your own breath supplied through a pocket mask. If available, intravenous normal saline warmed to 40°C and delivered through an insulated system can restore fluid volume without contributing to heat loss. In extremely cold patients, pulse and respira- tion may not be detectable. It is quite possible to mistake severe hypothermia for death. Anecdotal experience and animal studies suggest that even patients in apparent cardiopulmonary arrest may be salvageable if the body core temperature is above 10°C and definitive medical care can be accessed within a reasonable time. However, any significant risk to rescuers will not be justified by the low probability of success.

General Principles

Severe Hypothermia

Evacuation: • Package with added heat source to begin rewarming • Urgent but gentle evacuation to hospital maintained in horizontal position • PPV with heated and humidified O2 • Warmed IV if available • No chest compressions if it will delay transport or put rescuers at risk.

© 2018 WMA