A 32-year-old man is brought to the emergency department after his coworkers found him confused, disoriented, and bleeding from the nose. The patient's medical history is significant for an episode of major depression. He is currently taking no medication. According to his friends, he was in his normal state of health this morning when he came to work. He then spent the morning cutting several bushes and trees to clean the area for a new road construction. Temperature is 42 C (108 F), blood pressure is 110/70 mm Hg, respirations are 16/min, and pulse is 120/min and regular. BMI is 40 kg/m². The patient's skin is warm and dry, and his neck is supple with no stiffness. The pupils are symmetric, midsize, and reactive to light. There is active bleeding from the right nostril. Deep tendon reflexes are symmetric. No Babinski sign is present. The patient moves all the extremities but is unable to speak or follow simple commands. Skin on his extremities has several scratch marks, likely from thorn injuries. Which of the following is the most likely diagnosis?

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11ec25c8_d147_e73e_bc81_8b8389d781f0_MD0003_00 This patient with severe hyperthermia, encephalopathy, and epistaxis that developed while working outside has exertional heat stroke (EHS). EHS is characterized by core temperature ≥40 C (104 F) with CNS dysfunction (eg, altered mental status). Unlike nonexertional heat stroke, which typically affects individuals at the extremes of age who are incapable of obtaining adequate fluids and removing themselves from a hot environment, EHS occurs most commonly in those exposed to hot/humid environments while performing extreme physical activity (eg, landscaping, as with this patient). Risk factors include obesity, poor physical fitness, lack of acclimatization, and certain medications/drugs (eg, anticholinergics, alcohol, amphetamines) that impair thermoregulation. In addition to CNS dysfunction, other common manifestations of EHS include tachycardia, tachypnea, and flushing. Diaphoresis may or may not be present, depending on fluid status, and hypotension may occur. Complications include rhabdomyolysis, disseminated intravascular coagulation (DIC) (resulting in coagulopathic bleeding, as seen in this patient with epistaxis), and end-organ dysfunction (ie, renal/hepatic failure). Management includes patient stabilization (eg, airway, breathing, circulation), rapid cooling techniques (eg, ice water immersion), fluid resuscitation, and treatment of end-organ dysfunction. (Choice A) Anticholinergic toxicity can cause confusion, tachycardia, and temperature elevations; however, severe hyperthermia ≥40 C (104 F) is unexpected. Furthermore, most patients have other signs of anticholinergic toxicity (eg, pupillary dilation, flushing). (Choice C) Malignant hyperthermia affects genetically susceptible individuals during anesthesia involving agents like halothane and succinylcholine. Diffuse muscle rigidity is also expected. (Choice D) Meningococcal meningitis can cause fever and mental status changes and is associated with DIC. However, it would be expected to cause neck stiffness and petechial rash. Furthermore, it would be unlikely to cause such high fevers or develop so rapidly in a patient who was in his normal state of health this morning. (Choice E) Salicylate toxicity causes fever and mental status changes; however, patients typically present with nausea and vomiting. Furthermore, significant hyperpnea is typically seen due to activation of the medullary respiratory center. Educational objective: Heat stroke is characterized by core temperature ≥40 C (104 F) with CNS dysfunction (eg, altered mental status). It occurs most commonly in those exposed to hot/humid environments while performing extreme activities. Complications include rhabdomyolysis, disseminated intravascular coagulation, and end-organ dysfunction.

A 32-Year-Old Man Is Brought to the Emergency Department After