EXUDATIVE MINERAL LOSSES AFTER SERIOUS BURNS - A CLUE TO THE ALTERATIONS OF MAGNESIUM AND PHOSPHATE-METABOLISM

Hypomagnesemia and hypophosphatemia are frequent after severe bums; ho wever, increased urinary excretion does not sufficiently explain the m agnitude of the mineral depletion. We measured the mineral content of cutaneous exudates during the first week after injury. Sixteen patient s aged 34 +/- 9 y ((x) over bar +/- SD) with thermal burns were studie d prospectively and divided in 3 groups according to the extent of the ir burn injury and the presence or absence of mineral supplements: gro up 1 (n = 5), burns covering 26 +/- 5% of body surface; group 2 (n = 6 ), burns covering 41 +/- 10%; and group 3 (n = 5), bums covering 42 +/ - 6% with prescription of magnesium and phosphate supplements. Cutaneo us exudates were extracted from the textiles (surgical drapes, dressin gs, sheets, etc) surrounding the patients from day 1 to day 7 after in jury. Mean magnesium serum concentrations decreased below reference ra nges in 12 patients between days 1 and 4 and normalized thereafter. Ph osphate, normal on day 0, was low during the first week. Albumin conce ntrations, normal on day 0, decreased and remained low. Urinary magnes ium and phosphate excretion were within reference ranges and not large r in group 3. Mean daily cutaneous losses were 16 mmol Mg/d and 11 mmo l P/d (largest in group 2). Exudative magnesium losses were correlated with burn severity (r = 0.709, P = 0.003). Cutaneous magnesium losses were nearly four times larger than urinary losses whereas cutaneous p hosphate losses were smaller than urinary phosphate losses. Mean daily losses of both magnesium and phosphate were more than the recommended dietary allowances. Exudative losses combined with urinary losses lar gely explained the increased mineral requirements after burn injury.