The most severe of the heat-related illnesses, characterized by high fevers (over 104°F [40°C]), neurological impairment, and, frequently, death.
SYN: SEE: sunstroke

In the U.S., an average of 650 people die of heat-related illnesses each year. The incidence increases in the summer.

Heatstroke is a failure of the body’s heat-regulating mechanisms during or after exposure to heat and high relative humidity (normally air temperatures of higher than 79°F (26.1°C) and relative humidity greater than 70%). In young healthy people it most often follows strenuous physical activity; in inactive individuals or older adults, it is commonly related to cardiovascular disease or use of drugs that influence body temperature regulation.

Heatstroke is marked by high body temperature (over 104°F [40°C]); headache; numbness and tingling; confusion preceding sudden onset of seizures, delirium, or coma; tachycardia; rapid respiratory rate; and increased blood pressure followed by hypotension. Multiple organ system failure is common. On presentation to the hospital, patients with non-activity-related heatstroke may have hot, dry, red skin; the skin of active people may still be damp from perspiration, but sweating will cease as the condition worsens.

There are no specific diagnostic tests for heatstroke, and its diagnosis is clinically established. Diseases that mimic heatstroke (sepsis, neuroleptic malignant syndrome, febrile drug reactions) should be sought and excluded. Patients who die of heatstroke often have very elevated serum lactate, troponin, and creatinine levels, abnormalities of liver function and coagulation, advanced age, general debility, or multiple existing medical conditions.

Heat-related illnesses (heat cramps, heat exhaustion, heatstroke) are preventable through education of the public. Athletes, soldiers, and laborers are taught to recognize the signs and symptoms of heat problems and the importance of prevention, e.g., by avoiding prolonged exposure to heat, and by increasing their electrolyte and water intake, and prompt treatment of symptoms. High-risk patients (older adults, obese, diabetic, or alcoholic, those with cardiac disease and other chronic debilitating illnesses, and those taking phenothiazines or anticholinergics) are advised to take the following precautions: wear loose-fitting, lightweight clothing; take frequent rest breaks, esp. during strenuous activities; ingest adequate amounts of fluids, including electrolyte drinks; avoid hot, humid environments, if possible; use proper room cooling (fans and open windows) or air conditioners and seek air-conditioned areas for relief.

Effective, immediate treatment in an inpatient setting to lower the body core temperature can save the patient’s life, but delayed treatment markedly increases mortality. Airway, breathing, and circulation should be monitored and maintained. The patient’s clothes should be removed immediately and the patient actively cooled with water, ice packs, or a hypothermia blanket. The patient should be observed for signs of fluid and electrolyte imbalance rhabdomyolysis, cardiac arrhythmias, and renal failure. Intensive care is the standard of care.

The patient suspected of heatstroke is assessed for airway patency, breathing adequacy, circulation, mental status using the AVPU (alert, voice, pain, unresponsive) scale, and other associated signs and symptoms such as shock, weakness, dizziness, nausea, vomiting, blurred vision, infection, and skin findings. Vital signs are obtained, and the caregiver monitors the patient’s temperature with a rectal or core probe; initially it may be extremely elevated. In the hospital setting, laboratory studies, including blood chemistry, arterial blood gases, urinalysis, complete blood count, and appropriate cultures are obtained to aid in treatment management. Cooling procedures are promptly instituted in the field and continued in the hospital. Intravenous therapy is begun to replace fluids in the dehydrated patient and high-concentration oxygen is administered. Fluid intake and urinary output are monitored. A nasogastric tube is inserted to prevent aspiration; an indwelling urinary catheter may also be required. Seizure activity is controlled or prevented with diazepam. Dobutamine is used to correct cardiogenic shock. Invasive hemodynamic monitoring, endotracheal intubation and ventilation, or emergency dialysis may be needed in severe instances. If necessary, the patient is referred to a social service agency for assistance with home cooling. Patients who have experienced heatstroke should be warned that they may experience hypersensitivity to high temperatures for several months.

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