Hypophosphatemia-induced hypercalcemia during acute renal failure

Looking at calcimimetics impact on hypercalcemia of immobilization: Hypotheses and a case study

For the treatment of secondary hyperparathyroidism (HPTH-II) in dialysis patients and hypercalcemia in patients with parathyroid carcinoma. Calcimimetics are a new class of drugs approved in the European Community and the United States by the Food and Drug Administration that were designed to suppress parathyroid hormone (PTH) levels with a simultaneous reduction in serum calcium and phosphorus levels, and calcium phosphorus product (Ca x P). Hypocalcemia is a frequent finding during the correction phase of the HPTH-II with calcimimetics. By contrast, the appearance of a hypercalcemia has yet to be described. In this paper, we report a case of severe hypercalcemia of immobilization in a 40-year-old hemodialyzed woman treated by cinacalcet HCl for a severe HPTH-II (PTH>1,000 pg/mL). A kidney transplantation recipient 1983 to 1995, she was diagnosed with Charcot-Marie Tooth disease in 1991. She had multiple orthopedic interventions for kidney-related osteoarticular problems probably favored by the kidney graft and the immunosuppressive treatment. While she was receiving the maximum dose of 180 mg/day of cinacalcet HCl and PTH at 443 pg/mL, she needed to be hospitalized for a right hip prothesis. Two weeks after the intervention she developed a symptomatic hypercalcemia of 3.57 mmol/L which was resistant to several measures including lowering the calcium concentration in the dialysate, withdrawing all vitamin D and calcium supplementation and the administration of calcitonin. Her serum calcium level was finally stabilized in the 2.37-2.95 mmol/L by administration of a single intravenous dose of pamidronate. This observation illustrates that the pharmacological activation of the parathyroid CaR and other putative CaR on bone cells by calcimimetics did not protect against the occurrence of hypercalcemia of immobilization favored by a severe HPTH-II in a hemodialysis patient.

Acute dialysis hypercalcemia and dialysis phosphate loss

During maintenance hemodialysis in patients with chronic renal failure, acute elevations of the plasma calcium are common, although of doubtful significance. Because the mechanisms for this hypercalcemia are unclear, calcium, magnesium, and inorganic phosphate mass transfer data was collected during routine hemodialysis. While the increase in the plasma calcium did not significantly correlate with the gain of calcium from the dialysate nor with the dialysate calcium concentration, there was a significant positive correlation between the degree of hypercalcemia and the loss of body phosphate (r = 0.66, P less than 0.05, n = 15). Hemodialysis without ultrafiltration and concomitant hemoconcentration depressed the dialysis hypercalcemia by 46% (P less than 0.001). However, continuous infusion of 33.5 mmol of phosphate during a 5-hour dialysis period, which reduced the plasma phosphate fall (1.53 +/- 0.16 to 0.87 +/- 0.08 mmol/L, P less than 0.01, in the control group; compared with 1.59 +/- 0.19 to 1.35 +/- 0.11 mmol/L, not significant [NS], in the phosphate infusion group) abolished the hypercalcemia (2.38 +/- 0.07 to 2.54 +/- 0.04 mmol/L, P less than 0.01, in the control group and 2.39 +/- 0.06 to 2.41 +/- 0.04 mmol/L, NS, in the phosphate infusion group). It is suggested that during routine hemodialysis, the loss of inorganic phosphate from the body is excessive, and that phosphate as well as calcium is released from the intracellular pool in response to the rapid fall in the plasma phosphate concentration. Such rapid, repetitive, and excessive losses of phosphate, particularly from bone, may be an important cause of renal osteodystrophy.