Hypophosphatemia and phosphate supplementation during continuous renal replacement therapy in children

Abstract

Severe hypophosphatemia can cause generalized muscle weakness, paralysis of the respiratory muscles, myocardial dysfunction, reduced peripheral vascular resistance, and encephalopathy. Here we conducted a prospective study to determine the incidence of hypophosphatemia in 47 children on continuous renal replacement therapy and to evaluate the efficacy and safety of adding phosphate to the replacement and dialysate solutions of 38 pediatric patients. During continuous renal replacement therapy, 68% of patients were found to have hypophosphatemia, significantly more than the 12% of patients at the beginning of therapy. There was no higher incidence of hypophosphatemia among patients requiring insulin, diuretics, parenteral nutrition, or high doses of vasoactive drugs. In the children to whom phosphate was not added to replacement and dialysate solutions, 85% presented with an incidence of hypophosphatemia and 36% required intravenous phosphate replacement, rates significantly higher than in those patients where phosphate was added to the solutions. Phosphate supplementation did not cause any instability of the mixtures or other complications. We show here that the incidence of hypophosphatemia in children on continuous renal replacement therapy is very high. Further, we show that the addition of phosphate to replacement and dialysate solutions is safe and that it reduces the incidence of hypophosphatemia and the need for intravenous phosphate treatment.

Reductions in Red Blood Cell 2,3-Diphosphoglycerate Concentration during Continuous Renal Replacment Therapy

“…One such potential adverse effect of CRRT is hypophosphatemia, a complication reported in .10% of patients undergoing CRRT (6)(7)(8)(9). We have shown that CRRT leads to net negative phosphate balance even with maintenance of normal serum phosphate levels (10).…”

Biochemical Effects of Phosphate-Containing Replacement Fluid for Continuous Venovenous Hemofiltration

“…Likewise, we demonstrated persistent relative hypocalcemia with Phoxilium. Other studies which investigated the use of a single type of CRRT fluid with or without added phosphate, did not find similar changes in systemic calcium levels [14]. Adding incremental phosphate to RF up to 2.47 mmol/l also does not lead to appreciable changes in fluid calcium levels [23].…”

“…The tendency for hyperphosphatemia despite ‘physiological’ phosphate content in RF also suggests that these patients could be highly catabolic [22], resulting in phosphate release in excess of removal. Lower CRRT fluid phosphate concentrations of 0.8 mmol/l have been investigated in a pediatric cohort with AKI, with resultant lower mean serum phosphate levels during therapy of 1.4 mmol/l [14]. The optimal CRRT fluid phosphate concentration, therefore, remains unclear.…”

“…Off-label addition of phosphate to CRRT fluid helps prevent hypophosphatemia [13,14], but runs the theoretical risk of solution incompatibility, calcium-phosphate precipitation in alkaline medium, sterile breach, and medical errors. Therefore, using a pre-prepared phosphate-containing solution is attractive and convenient.…”

Phosphate Enrichment of Dialysate for Use in Standard and Extended Haemodialysis

“…Phosphate-enriched dialysate provides an effective route of correction as it has the dual advantage of reducing phosphate leak via diffusion and provides direct supplementation into the bloodstream. Most studies on phosphate-enriched acid dialysate have been carried out in an acute care setting to prevent and treat hypophosphataemia in patients needing intensive HD regimes [5,12,13,14] or using continuous renal replacement therapy [15,16,17,18]. Addition of phosphate to the alkaline dialysate is fraught with the risk of precipitation with calcium or other divalent cations.…”