Optimisation of Solute Removal and Water Usage in Paediatric Haemodialysis

Overview

Children receiving chronic haemodialysis are typically treated with dialysis machines designed for adult patients. As a result, some devices do not allow the ideal blood or dialysate flow rates to be set for paediatric use. In addition, the optimal dialysate-to-blood flow ratio for maximising solute removal while minimising water consumption remains poorly defined. The aim of this study is to quantify the dialyser extraction ratio and clearance across different dialysis modalities and a range of dialysate-to-blood flow ratios. Blood and dialysate samples are collected at the blood inlet, blood outlet, and dialysate outlet lines, and concentrations of various uraemic toxins-spanning a range of molecular weights-are measured to calculate solute clearances.

Children undergoing haemodialysis are enrolled in the study. During a mid-week dialysis session, three dialysis modalities are applied sequentially for 10-15 minutes each: haemodialysis (HD), predilution haemodiafiltration (pre-HDF), and postdilution haemodiafiltration (post-HDF). For each modality, the dialysate-to-blood flow ratio is adjusted to approximately 1.0, 1.5, and 2.0. For each setting, blood samples are collected from the blood inlet and outlet lines, and dialysate samples are taken from the spent dialysate line. All sampling is performed within the first hour of the dialysis session. All samples are analysed for a range of uraemic toxins, including small water-soluble solutes, middle molecules, and protein-bound toxins. Using inlet and outlet blood concentrations, the extraction ratio is calculated for each setting. Based on the dialysate flow rate, total water usage for a full dialysis session is estimated. Together, these calculations allow determination of the optimal dialysate-to-blood flow ratio that provides the highest dialyser clearance with the lowest relative water consumption.