A 74-year-old man is brought to the emergency department after he was found unconscious in a hot sauna at his home. The family is unsure how long he has been there, but he was not seen for at least 3 hours. The patient was in his usual state of health until this incident. His medical history is significant for hypertension. The patient usually drinks 2 or 3 glasses of whiskey every night but has been drinking more for the last 3 months, since his wife's death. Temperature is 41 C (106 F), blood pressure is 90/60 mm Hg, pulse is 130/min and regular, and respirations are 22/min. BMI is 43 kg/m². The patient appears restless and not oriented. His pupils are 4 mm, symmetric, and reactive to light. Lung examination shows rales at both lung bases. The patient's abdomen is soft and nontender, and normal bowel sounds are present. There is no neck stiffness. His skin is warm. Reflexes are 1+ in the upper and lower extremities. Muscle tone and bulk is decreased. His initial laboratory results are as follows: Which of the following is the most likely cause of the patient's current condition?

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11ec25c8_d1d3_37ea_bc81_1fe0f35277e0_MD0003_00 This elderly patient with obesity has hyperthermia and altered mental status (AMS) after being found in a hot sauna. These clinical features are consistent with nonexertional (classic) heat stroke (NHS), characterized by a temperature ≥40 C (104 F) with CNS dysfunction (eg, encephalopathy). NHS typically occurs in elderly patients due to age-related changes that impair the normal thermoregulatory response (eg, tonic peripheral vasoconstriction, fewer sweat glands). Other risk factors include obesity, alcohol, and certain medications (eg, diuretics, as this patient with hypertension may be receiving). High humidity, which occurs in wet saunas, further increases the risk, because >75% atmospheric humidity impairs evaporative cooling from sweat. In addition to hyperthermia and CNS dysfunction, further manifestations may include tachycardia, tachypnea, and hypotension. Diaphoresis may or may not occur, depending on volume status. Complications include acute disseminated intravascular coagulation (DIC) (prolonged coagulation markers), pulmonary edema (rales), and hepatic or renal failure. Laboratory analysis may also reflect hemoconcentration (ie, elevated hemoglobin and leukocyte counts) due to dehydration. Management includes rapid cooling; evaporative techniques (eg, spraying lukewarm water while fans blow air on the patient's skin) are best tolerated in the elderly, as well as fluid resuscitation and management of end-organ complications. (In contrast, in exertional heat stroke [eg, following strenuous exercise in a hot, humid environment], ice water immersion should be considered rather than evaporative techniques.) (Choice A) Alcohol withdrawal can cause tachycardia and occasional fever but typically causes delirium, hallucinations, and seizures rather than syncope. In addition, hypertension, not hypotension, is expected, and DIC is atypical. (Choice C) A hypothalamic stroke may disrupt normal neural thermoregulatory mechanisms and result in neurogenic fever. However, an expanding hypothalamic hemorrhage would likely result in herniation with Cushing triad (bradycardia, Cheyne-Stokes breathing, hypertension). DIC and pulmonary edema are not typical. (Choice D) Malignant hyperthermia can cause elevated temperature, AMS, and DIC but is usually triggered by certain anesthetic agents (eg, halothane); furthermore, patients have diffuse muscular rigidity. (Choice E) Severe sepsis causes fever, tachycardia, tachypnea, and leukocytosis and may result in AMS and DIC. However, this patient was in his normal state of health hours prior, and although meningitis may cause a rapid decompensation, his examination does not demonstrate meningismus. Furthermore, temperatures >40 C (104 F) are atypical, and NHS is more likely in the setting of prolonged heat exposure. Educational objective: Nonexertional (classic) heat stroke most commonly affects elderly patients and is characterized by body temperature ≥40 C (104 F) with CNS dysfunction (eg, encephalopathy). Other common manifestations include tachycardia, tachypnea, hypotension, and end-organ dysfunction (eg, diffuse intravascular coagulopathy, pulmonary edema). References: American College of Sports Medicine roundtable on exertional heat stroke-return to duty/return to play: conference proceedings. (http://www.ncbi.nlm.nih.gov/pubmed/20827100)

A 74-Year-Old Man Is Brought to the Emergency Department After