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.
Bouchama
A
A
Department of Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
Cafege
A
A
Robertson
W
W
al-Dossary
S
S
el-Yazigi
A
A
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