Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter IV: Cold Injury

Field Management Of Hypothermics

United States Department of Defense

Individuals must be stripped of their wet clothing; insulated; given warm, sweet drinks; and encouraged to do large-muscle activities that will warm them up. Warming the core with external heat is an extremely difficult physiologic problem. Conscious individuals will shiver and initiate rewarming. If other muscle activity is added, they will warm up quickly. Replacement of fluids is essential to improve peripheral circulation, cutaneous perfusion, and cardiac output. Comatose individuals must be handled carefully, as rough handling can produce ventricular fibrillation arrest. The airway should be patent. Wet clothes should be carefully stripped. They should be well covered and insulated. They should shell be transported as rapidly as possible to definitive medical care. Positive pressure ventilation is advised but chest compression is not. Such compressions may convert sinus bradycardia to ventricular fibrillation.

Field rewarming procedures for the comatose individual are time consuming. If possible, it is better to move the casualty to a nearby medical facility. A heated, humidified oxygen rewarming device, if available, may be effective, but is certainly not a major method of heat input for the comatose hypothermic victim. Management throughout the evacuation chain involves improving cardiac output, decreasing blood viscosity, adding heat to the core, improving acid-base balance, and the hyperkalemia.

Treatment of imbalances in these parameters depends on the level of sophistication at each treatment site. Hospital management should include active core rewarming utilizing peritoneal dialysis, arterio-venous shunts, or peripheral rewarming involving torso water immersion. Rewarming blankets are slow but may be the only rewarming devices available. Volume replacement is essential to decrease viscosity and increase cardiac output. Low central venous pressures are advisable early and are increased slowly as there is an indication of the ability to hold fluid in the vascular space.

Lactate-free and potassium-free fluids are advisable, as lactate conversion to pyruvate by the liver does not occur below 32°C and hyperkalemia probably already exists. Hyperkalemia is improved by fluid replacement and glucose and insulin infusions. Sodium bicarbonate is indicated early to begin correction of acidosis. However, overzealous correction is ill advised. The patient should be kept mildly acidotic throughout the treatment process. Improved ventilation during the resuscitation can improve pH significantly. Antiarrthymic drugs are contraindicated. Excessive early manipulation can result in cardiac arrest. This complication is managed by continuing the rewarming process, along with half-rate, closed-chest cardiac massage until the temperature reaches 31° or 32°C, at which point electrical conversion is more likely to be successful. The patient with severe acidosis and hyperkalemia should not be rewarmed past 30°C. Post rewarming complications include pneumonia, pancreatitis, intravascular thromboses, gastric erosions, and acute tubular necrosis. Pneumonitis is by far the most common problem. It is managed by pulmonary toilet and appropriate antibiotics.

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Operational Medicine 2001

Health Care in Military Settings

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