Journal of Applied Physiology, Vol 71, Issue 1 328-332, Copyright © 1991 by American Physiological Society
Mechanisms of hypophosphatemia in humans with heatstroke
A. Bouchama, A. Cafege, W. Robertson, S. al-Dossary and A. el-Yazigi
Department of Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
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.
