Metabolic and electrolyte abnormalities during heat exhaustion.

Accepted 27 September 1995 An 81-year-old man, resident of a poorly ventilated, ineffectively air-conditioned inner city apartment, presented during a heat wave (environmental temperature 80°-93°F and humidity 70%-80%) with hyperthermia, confusion and dehydration. The patient had mild hypertension, depression and urinary incontinence and was taking hydrochlorothiazide/methyldopa, nortriptyline and oxybutynin. On admission, tympanic temperature was 39.4°C, pulse rate 124 beats/min, respiration 24 breaths/min and blood pressure 156/86 mmHg. On initial examination lung fields were clear, the patient had a holosystolic murmur, and central nervous system examination was unremarkable except for confusion. Dehydration was characterised by haemoglobin 19.7 g/dl, haematocrit 53.9%, blood urea nitrogen 12.5 mmol/l and creatinine 141.4 jmol/l. Serum electrolytes were: sodium 133 mmol/l, potassium 2.9 mmolI and phosphate 0.5 mmol/l. Arterial blood gas analysis (pH 7.5, pCO2 40 mmHg, PO2 62 mmHg and HCO3 31 mmol/l) was consistent with metabolic alkalosis. Serial electrocardiograms showed anterior T-wave evolution consistent with myocardial injury. An initial creatine phosphokinase (CPK) level of 4234 IU peaked to 32 800 IU; CPK-MB isoenzyme was also elevated to 43.3 ng/ml and MB index was 0.1%. Chest X-ray and computed tomography (CT) scan of the head were unremarkable. Echocardiogram showed severe mitral regurgitation and moderately reduced left ventricular function with apical akinesis. Blood, urine and sputum cultures failed to reveal a source of infection. The patient was admitted to the coronary care unit; hyperthermia was initially managed with cold sponging which resulted in a temperature drop from 39.4°C to 37°C in four hours. The patient's mental status improved and electrolytes were corrected (table). On day 5, he was transferred to a medical ward and discharged home on day 10 in a stable condition.