MEDizzy - A 37-year-old male marathon runner has a syncopal episode

Feed Library Learning Discuss Leaderboard Journal

Infections due to Neisseria and others

A 37-year-old male marathon runner has a syncopal episode during the last mile of the 26.2-mile run. The outside temperature is 92° F, with almost 100% humidity. He is brought to the emergency department for presumed dehydration. The patient is awake and alert during the ambulance ride. Upon arrival at the emergency department, the patient says he is dizzy and that he has a severe headache and muscle cramps. His temperature, determined orally, is 104° F (40° C), his pulse is 115 beats/min, his respiratory rate is 24 breaths/min, and his blood pressure (taken both while sitting and standing) is 110/60 mm Hg. Which of the following would be most helpful in determining whether this patient has heatstroke or heat exhaustion?

Explanationheatstroke is associated with temperatures in excess of 105° F (40.5° C). This patient's temperature is not clearly within one range or the other; thus, the diagnosis is clouded, but there should be significant concern about heatstroke. Mental status is not a reliable indicator for differentiating between the two. Patients with heat exhaustion can have mild confusion, and patients with heatstroke do not have neurologic impairment. Dehydration with tachycardia, low blood pressure as determined orthostatically, and hemoconcentration can occur in either disorder. Two potential acid-base abnormalities in heatstroke are early respiratory alkalosis (associated with tachypnea) and late-occur- ring metabolic acidosis, resulting from an accumulation of lactic acid. Pure respiratory acidosis would not be expected, especially in a patient with normal mental status and a normal state of alertness. Heatstroke is associated with several renal abnormalities, including hematuria, myoglobinuria, proteinuria, and casts. Hemoglobinuria, a mani- festation of lysis of red cells, would not be expected as a result of heatstroke or heat exhaustion. However, it could result from the repetitive impact of this patient's feet on the road during the marathon: so-called march hemoglobinuria. Thrombocytopenia in this setting is ominous because it indicates the presence of disseminated intravascular coagulopathy (DIC), which is more common in exertional than in classic heatstroke. DIC would not be expected to be present with heat exhaustion. DIC is just one of many manifestations of organ dysfunction associated with heatstroke. The list includes acute respiratory distress syndrome, liver function abnormalities, renal failure with active sediment, and severe electrolyte derangements.