All heat-related illness is treated with rehydration (oral, unless there is a diminished level of consciousness or trouble swallowing), removal from heat sources, and, in the case of life-threatening hyperthermia, rapid reduction in body temperature. Unless the patient has severe hyperthermia, he or she will live.
Moving patients into the shade (passive cooling) can externally decrease the ambient temperature; however, this is most effective when temperatures are <20°C (<68°F). Place the patient on an insulating barrier such as a sleeping pad or a sleeping bag to reduce heat conduction from the ground. Optimize air circulation (convection) by loosening or removing clothing.
Oral and IV hydration are equally effective in replenishing water deficiencies. Use whatever method is safe and available. Use the patient’s blood pressure, heart rate, urine color, and urine output to guide the patient’s response to fluids.
The treatment for acute, severe hyperthermia, such as might be found in heat stroke, can be done with minimal equipment. First, remove the heat source and quickly cool the patient. Delay cooling efforts only when you need to treat airway and breathing problems. If the patient is in cardiovascular collapse, begin cooling first before treating the cardiac problem. In a hyperthermic individual with an altered mental state, initiate cooling immediately, even if no thermometer is available.
To cool the patient, remove most or all his or her clothing and cover with a thin sheet of cloth. An alternative is to wrap the patient in wet towels or douse their loose clothes with any available liquid and generate as much breeze over the cloth as possible. Use a fan, if available, or do it by hand (conductive/evaporative cooling). The idea is to evaporate the water in the cloth, which cools as the water evaporates. This can lower the patient’s temperature 0.04° C/min to 0.08°C/min. A helicopter’s downdraft may drop the temperature about 0.10°C/min. Be careful not to continue cooling too long; the target active cooling temperature is about 39°C.
Cold-water immersion therapy, when available, is the optimal field treatment to cool heat stroke patients. It lowers body temperature by about 0.20°C/min. To do this, remove the patient’s clothes and equipment, then immerse the trunk and extremities in a cold-water bath or another convenient body of water. Protect the patient’s airway. If a body of water is not available, repeatedly douse the person with cold water or ice or snow if available. Shivering is not an immediate problem in heat stroke patients.
Chemical cold packs or ice packs have minimal benefit in heat reduction unless they cover the entire body. Medications do not help in heat stroke.29
Hypothermia is a significant problem for infants and small children, the elderly, those with prolonged cold exposure, and major trauma and burn patients.30 “Hypothermia secondary to hemorrhagic shock is as bad a problem now (2004 Iraq war) as it was in 1918.”31
The easiest way to treat hypothermia is to prevent it. Use insulation to protect patients when they are being transported or otherwise are at risk of hypothermia. Good insulation includes paper, such as newspapers or paper bags. Even better is corrugated cardboard, such as from boxes, because it has an air layer sandwiched between the paper sheets.
The first step in treating these patients is to remove any wet clothing and dry the patient. Use layered material to insulate the patient from the cold, including sleeping bags, plastic sheets, blankets, bubble-wrap, and foam pads. Then begin passive or active rewarming. Both can be done in most resource-poor environments.
Passive and Active External Rewarming
There are many passive rewarming techniques. If core temperature is >90°F (32°C), for example, remove any wet clothing, cover the patient in insulating material, and, if possible, warm the room to >72°F (22°C).32 Further “field expedient” (US Army term) rewarming techniques include placing patients in cardboard boxes and administering warm fluids. The fluids are often warmed by “placing a lightbulb in a cardboard box to warm IV fluids up to 40°C, the innovative use of the meals-ready-to-eat (MREs) warming units for warming a liter of Ringer lactate to 44°C, a hand-held hair dryer and a cardboard box unit that can be placed over casualties in a bed, which allows efficient warming when bed huggers are not available, and, finally, a radiator that was pulled off the wall and stuck under a sheet next to the casualty.”31
Another method for passive rewarming is to put hypothermic patients into body bags, leaving their face free and cutting holes for the arms. The arm openings are used for IV lines and monitoring cables, if available. Use tape to seal the openings around the extremities to prevent the egress of warmed air.
Active external rewarming should be limited to putting the person in a sleeping bag or other insulated container along with a warm person, and applying insulated hot water bags or bottles to their axillae and groin. Insulate the hot water bags with mittens or cloth. Additional active external rewarming drops the patient’s core temperature (“afterdrop” or “rewarming shock”) because it transfers blood from the core to the suddenly dilated periphery.
Warming the head is as effective as, but often less comfortable than, warming the torso and produces no differences in shivering heat production, afterdrop, or rate of rewarming. In field conditions, warming the head may be preferable if: (a) exposing the patient’s torso to the cold is contraindicated, such as when it is already wrapped in insulation; (b) excessive movement is contraindicated; or (c) if the torso is otherwise inaccessible due to other emergency interventions.33
Use active core rewarming for moderate-to-severe hypothermia with core temperatures <90°F (32°C). The effects of these techniques are additive, so they should be used simultaneously whenever possible. Depending on your situation, all can be done in austere environments.
Deliver warm, up to 45°C (113°F), humidified oxygen. It must be humidified to warm sufficiently. This technique works better when using an endotracheal tube rather than using a mask, but the difference is not enough to warrant intubating the patient.
Infuse crystalloid warmed to 40°C to 42°C (104°F to 108°F). Insert a peritoneal lavage catheter (see the “Diagnostic Peritoneal Lavage” section in Chapter 24), and infuse isotonic dialysate (1.5% dextrose with potassium) at 40°C to 45°C (104°F to 113°F). Alternatively, use normal saline or lactated Ringer’s as the dialysate. Infuse 10 to 20 mL/kg; retain it for 20 to 30 minutes and then aspirate it.34
Irrigate through a nasogastric or rectal tube, using crystalloid no warmer than 45°C (113°F). Infuse ≤300-mL aliquots in an adult; aspirate and replace that volume every 15 minutes. Don’t bother irrigating a urethral catheter; there is not enough surface area to make much difference. Warmed fluid can also be lavaged through large-bore thoracostomy tubes, with one placed anteriorly (second or third interspace, mid-clavicular line) and the other posteriorly on the same side (fifth or sixth interspace, posterior axillary line). Run 40°C to 42°C (104°F to 107.6°F) crystalloid into the anterior tube, and drain it out of the posterior tube. If only one tube is used, use 200- to 300-mL aliquots.34
As with hypothermia, it is far better to prevent than to treat frostbite. If frostbite or any of its precursors, such as “frostnip,” occur, remove any jewelry and make a decision whether to thaw the body part immediately. If there is a possibility it could refreeze, keep it frozen until it can be kept thawed. If it thaws spontaneously, prevent the area from being refrozen, because that will worsen the injury. Do not purposefully keep tissue frozen, because that can result in greater tissue damage and morbidity.
Administer fluids, ibuprofen/nonsteroidal anti-inflammatory drugs (NSAIDS), and pain control, if possible.
If the proper equipment and methods are available and definitive care is >2 hours away, attempt to rapidly rewarm the affected part using a water bath at 37°C to 39°C (98.6°F to 102.2°F). If a thermometer is not available, ensure a safe water temperature by placing an uninjured hand in the water for at least 30 seconds to confirm that the water temperature is tolerable and will not cause burn injury. Continually, but carefully, warm the water to maintain the target temperature. Circulate the water around the injured part without letting the skin touch the hot sides of the container.35 Because the nose and ears are often involved, soaking or carefully using chemical warmers over a thin cloth, rather than immersion, may be required. Administer analgesics during rewarming and as needed afterward. Using anti-inflammatory medications such as ibuprofen 12 mg/kg/day and topical Aloe vera may decrease tissue loss.36
Rewarming is complete when the involved part takes on a red/purple appearance and becomes soft and pliable to the touch. This takes about 30 minutes, depending on the extent and depth of the injury. Once rewarming is complete, let the body part air dry or gently blot it dry with a soft cloth. Then dress the part with bulky, clean, and dry dressings, if available, applying dressings between the toes and fingers. Do not routinely debride blisters until definitive care is available, and, if possible, elevate the extremity above the level of the heart to decrease dependent edema. Boots (or inner boots) may need to be worn continuously to compress swelling. If at all possible, the patient should not use a frozen or thawed extremity for walking, climbing, or other maneuvers until definitive care is reached. However, each case requires assessing the risks and benefits. Boots that are removed may not be able to be replaced if walking or climbing is absolutely necessary in order to self-evacuate.35
High-altitude illness can affect anyone ascending to ≥8000 feet (~2500 m), especially if he or she has not taken time to acclimatize en route. Its occurrence cannot be predicted, and it can affect people who have been to that altitude previously without symptoms. When disasters occur at high altitudes, rescuers who are flown in to help are at particular risk, with high-altitude pulmonary edema (HAPE) occurring in ~16% of rescuers flown directly from sea level to 14,500 feet.37
The appropriate acetazolamide dosage for prophylaxis against acute mountain sickness (AMS) remains uncertain, as does the comparative effectiveness of dexamethasone with high doses of acetazolamide. Current recommendations to prevent AMS or high-altitude cerebral edema (HACE) are acetazolamide 125 to 250 mg twice per day (bid). During early acclimatization, acetazolamide reduces the ability to exercise hard and increases fatigue, especially in older individuals.38 If acetazolamide produces unacceptable side effects or is contraindicated, use dexamethasone 4 mg two or three times per day. To prevent HAPE, use nifedipine 30-mg slow-release formulation bid. If this is not available or cannot be tolerated, use a phosphodiesterase-5 inhibitor (e.g., tadalafil 10 mg bid) or dexamethasone 8 mg bid. Inhaled salmeterol (125 mcg bid) is less effective than the other options.
The diagnosis of high-altitude illness is clinical. AMS is diagnosed when victims have a headache accompanied by other nonspecific symptoms. HACE victims have AMS symptoms plus altered mental status and ataxia. HAPE victims have inappropriate dyspnea progressing to frank pulmonary edema. The treatment of HACE and severe AMS is to descend as soon as possible or to use a hyperbaric bag and administer oxygen (2-4 L/min) and dexamethasone 8 mg initially, followed by 4 mg/6 hr (IV, intramuscular [IM], by mouth [PO]). For HAPE, use descent and oxygen plus slow-release nifedipine 60 to 80 mg/24 hr divided into several doses.39