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PERITONEAL MASS TRANSFER (MT) OF MINERALS AND BONE-MODULATING HORMONES IN CHILDREN ON CONTINUOUS AMBULATORY PERITONEAL DIALYSIS (CAPD)

Abstract

Abnormal mineral metabolism (MM) has profound consequences in uremic children. To evaluate the impact of CAPD on MM we performed 52 serial MT studies (x̄ 9 studies/patient) in 7 children 1 week to 16 yr. old maintained on CAPD from 1 to 18 months.

Net daily peritoneal losses averaged 18±25 mg(range +28 to -58) for Ca, 175±112 mg(-34 to -382) for P, 18±6 mg(-9 to -30) for Mg, 6±4.5 μg (-1 to -15) for 25 OH vitamin D, and 28±20 ng (-1.5 to -58) for 1,25(OH)2 D. Losses of 25 OH and 1,25(OH)2 D represented 41% and 105%, respectively, of the circulating pool. Progressive ↓ of plasma 25 OH D(37 to 22 ng/ml) and 1,25(OH)2D (74 to 17 pg/ml) was noted in 3 pats.; iPTH was readily detectable in peritoneal exchanges (352±265 μlEq/ml) and x̄ serum iPTH ↓ by 30% (394 to 280 μlEq/ml, normal 10 to 90) during x̄ 7 mo. observation. Hypermagnesemia (3.1 mg/dl) normalized (2.2 mg/dl) using low-magnesium dialysate (PD2 DianealR). Serum Ca correlated negatively with Ca MT (r= -0.61, p<0.01) and positively with % decline in serum iPTH (r= 0.81, p=0.05). Serial bone radiographs were mostly unchanged.

Thus, CAPD in children: 1) adequately removes P and Mg; 2) leads to minimal Ca losses; 3) substantially removes PTH but also vitamin D metabolites, and 4) improves hyperparathyroidism and hypermagnesemia.

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