Mechanisms of hypophosphatemia in humans with heatstroke.
Hypophosphatemia is common in heatstroke, but little is known about its mechanism. We investigated 10 consecutive patients with heatstroke (mean age 58 +/- 2 yr) whose mean rectal temperature at admission was 42.3 +/- 0.2 degrees C. Eight patients presented with hypophosphatemia [0.48 +/- 0.08 mmol/l, normal range (NR) 0.8-1.4 mmol/l], associated with increased fractional excretion of phosphate (19.8 +/- 6.4%, NR 6-20%) relative to plasma phosphate levels and reduced renal threshold for phosphate (0.55 +/- 0.08 mmol/l glomerular filtrate, NR 0.8-1.4 mmol/l). Plasma parathyroid hormone (75.0 +/- 5 pmol/l) and calcium (2.24 +/- 0.02 mmol/l) levels and fractional excretion of calcium were normal (1.66 +/- 0.27%). There was no evidence of uricosuria or aminoaciduria, and only one patient had glucosuria. Arterial carbon dioxide was decreased in eight patients (28 +/- 1.1 Torr); however, none had elevated blood pH (7.35 +/- 0.02). The results suggest that heatstroke-related hypophosphatemia is associated with abnormal phosphaturia independent of the parathyroid hormone level, and there is no evidence of tubular dysfunction.
Department of Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
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Bouchama
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Cafege
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Robertson
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al-Dossary
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el-Yazigi
D000368:Aged; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D002118:Calcium / Q000097:blood; D004573:Electrolytes / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006359:Heat Exhaustion / Q000097:blood*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood*; D011674:Pulse / Q000502:physiology; D012119:Respiration / Q000502:physiology
D004573:Electrolytes; D010281:Parathyroid Hormone; D010710:Phosphates; D002118:Calcium