Calcium and phosphate balance in adolescents on home nocturnal haemodialysis

Abstract

Studies in adults show superior serum phosphate and parathyroid hormone (PTH) control on slow nocturnal haemodialysis (NHD) compared with conventional haemodialysis. We studied the progress of four children aged 12, 13, 14 and 16 years after they had been initiated on NHD. The follow-up period ranged from 6 months to 20 months. Biochemical indices of bone metabolism were collected prospectively. All four children were initially dialysed against a 1.5 mmol/l calcium bath. In two patients, owing to biochemical hypocalcaemic episodes, the dialysate calcium concentration was increased to 1.75 mmol/l. One patient became hypercalcaemic and received calcitonin for bone pain secondary to osteoporosis and was dialysed against a 1.0 mmol/l calcium bath. Including an evaluation of dietary intake, all four patients had a net positive calcium balance, ranging from 5.1 mmol/m2 body surface area (BSA) per day to 24.3 mmol/m2 BSA per day. A significant reduction in the pre-dialysis phosphate level was observed in all four patients, such that none required dietary restrictions or phosphate binders, and dialysate phosphate supplements of 0.8-2.03 mmol/l were employed to prevent hypophosphataemia. The (CaxPO4) dropped below 4.4 mmol(2) l(-2) in all four patients. Concurrently, significant reductions in intact PTH levels were seen in all four patients, but the level dropped to below normal range in two. In our cohort of patients, NHD rapidly lowered plasma phosphate and PTH levels, and additional dialysate phosphate and possibly calcium may be necessary to prevent bone demineralisation due to chronic losses and to prevent oversuppression of PTH.

Mineral metabolism and bone abnormalities in children with chronic renal failure

“…Conventional peritoneal and intermittent hemodialysis are not as effective as daily nocturnal hemodialysis in reducing phosphorus levels. However, the latter procedure is not yet feasible in very small children [51].…”

Impact of Water Quality and Dialysis Fluid Composition on Dialysis Practice

“…Contrary to the observations of Kopple and Coburn [22] , who noted interdialytic calcium depletion, more recent studies indicate that haemodialysis patients are in positive calcium balance between dialysis treatments [23,24] . To minimize the impact on vascular calcification of such a positive balance, calcium removal during dialysis is a potential option which necessitates a kinetic approach [25] .…”

Can dialysis modality influence cardiovascular outcome?

“…At the present time, HDF and QHD are only practiced in a handful of paediatric centres worldwide. Anecdotal reports children on daily HDF showing improved growth [27] and better phosphate clearance, normalisation of PTH and nutrition in children on QHD [28] suggest that intensified dialysis may indeed improve cardiovascular outcomes, with reported survival rates of patients on QHD comparable to those of deceased donor transplantation [29]. In HDF, both the convective and diffusive clearance of uraemic toxins across a wide molecular weight range, better tolerance of and greater fluid removal, biocompatibility of high-flux dialysis membranes and 'ultrapure' dialysis water together improve survival by 35 % in adults on HDF [30].…”