Review Question - QID 217171

This patient presents with disorientation, hyperthermia, hypotension, tachycardia, tachypnea, and rhabdomyolysis (urinalysis positive for blood without red blood cells) in the setting of physical activity in the heat, which is indicative of exertional heat stroke.

Exertional heat stroke is characterized by severe hyperthermia (core temperature >104°F [40°C]) and signs of end-organ failure in the setting of physical activity on a hot and humid day. The most common manifestation is CNS dysfunction, including disorientation, irritability, headache, behavioral or emotional disturbances, coma, or seizure. Patients can also have hypotension, tachycardia, tachypnea, nausea, vomiting, weakness, or profuse sweating. Rhabdomyolysis can also occur as a consequence of tissue damage, resulting in excess myoglobin in the urine that is detected as blood in the absence of red blood cells. Diagnosis is clinical, and treatment consists initially of management of the "ABCs" (airway, breathing, circulation) and fluid resuscitation for hypotension. This is followed by rapid cooling measures consisting of evaporative and convective cooling in which water is sprayed on the naked patient and fans blow air over the moist skin.

Casa et al. review the etiology and treatment of exertional heat stroke. They highlight the increased risk of mortality due to misdiagnosis, delayed treatment, inefficient cooling, or rapid return to play. They recommend measuring core temperature with a rectal thermometer in suspected cases to avoid a delay in diagnosis.

Incorrect Answers:
Answer 1: Heat exhaustion can present similarly to heat stroke with dehydration, weakness, profuse sweating, muscle cramps, and tachycardia, but core temperature is typically lower in heat exhaustion (101-104°F [38.3-40.0°C]) and CNS dysfunction is not present.

Answer 3: Hypertrophic obstructive cardiomyopathy (HOCM) often presents with sudden collapse in young athletes due to cardiac outflow tract obstruction. A systolic murmur can be heard on physical exam. The most common presentation is syncope upon exertion, although sudden cardiac death is possible. However, HOCM does not cause signs of myoglobinuria on urinalysis.

Answer 4: Malignant hyperthermia is caused by inhalation of volatile anesthetics and presents with severe hyperthermia and characteristic muscular rigidity. This patient has normal muscle tone. In addition, he has not been recently exposed to volatile anesthetics.

Answer 5: Serotonin syndrome can present with fever, autonomic instability (e.g., hypotension, tachycardia), and altered mental status but usually involves myoclonus and/or hyperreflexia. Although this patient is on a serotonergic medication, the patient has normal reflexes.

Bullet Summary:
Exertional heat stroke presents with hyperthermia (core temperature >104°F [40°C]) and signs of central nervous system dysfunction such as confusion, coma, or seizure.