DYSREGULATION OF CALCIUM HOMEOSTASIS AFTER SEVERE BURN INJURY IN CHILDREN - POSSIBLE ROLE OF MAGNESIUM DEPLETION

Objective: To determine the cause and extent of hypocalcemia observed in children after severe burns. Design: We studied 10 children with bu rns covering 57% +/- 17% (SD) body surface area, ages 9.6 +/- 4.7 year s, who were admitted consecutively during a 6-month period. Diet suppl ied a minimum of 2.7 gm/m(2) of calcium, 0.3 gm/m(2) of magnesium, and 2.2 gm/m(2) phosphate. Blood specimens were obtained daily for 10 +/- 5 days for the following tests: (1) simultaneous analysis for ionized calcium, magnesium, and intact parathyroid hormone (group A); (2) two of these children, randomly selected, had serial 2-hour determination s on a single day (group B); (3) a modified Ellsworth-Howard test., co nsisting of a 10-minute infusion of synthetic parathyroid hormone 18 /- 10 days postburn and associated changes in urinary cyclic adenosine monophosphate excretion and renal threshold phosphate concentration ( group C). Three of these children, when nor-momagnesemic, also receive d a standard magnesium infusion to determine magnesium retention (grou p D). Data were analyzed with chi-square, regression analysis, and non parametric testing as appropriate. Results: All patients showed sustai ned hypocalcemia and hypomagnesemia; intact parathyroid hormone respon se was inappropriately low and response to synthetic parathyroid hormo ne infusion was blunted. Lowest ionized calcium levels were associated with hypomagnesemia. Conclusion: Hypoparathyroidism and blunted renal response to parathyroid hormone suggest that magnesium depletion may contribute to their pathogenesis. Magnesium repletion and monitoring a re recommended.