Use of a sampler to collect spent dialysate in hemodialysis: a technical note

Precise quantification of dialysis efficiency requires assessment of solute mass transfer through analysis of spent dialysate. Total dialysate collection is impractical and difficult to implement in routine practice, while partial dialysate collection methods remain insufficiently validated. We evaluated the reliability of the Theraflux® sampler, a standalone device designed to automatically collect 1% of spent dialysate during hemodialysis sessions.

This observational study was conducted in a French dialysis center between November 2021 and February 2022. Twenty chronic dialysis patients were initially enrolled; 16 patients undergoing hemodiafiltration were included in the final analysis. A total of 126 dialysis sessions were analyzed. The total dialysate volume estimated by the Theraflux® sampler was compared with the volume calculated by the dialysis machine. Agreement between measurements was assessed using repeated-measures Bland-Altman analysis.

The median difference between dialysis machine-calculated dialysate volume and sampler-reported volume was 8.3 L (IQR 4.3-14.8), corresponding to a median discrepancy of 7.4% (IQR 4.5-11.6%). The sampler collected a median of 1.02% (IQR 1.00-1.07%) of total dialysate according to dialysis machine calculations and 0.96% (IQR 0.96-0.97%) according to sampler-derived values. Twelve sessions (9.4%) were identified as outliers. Excluding outliers improved agreement without reducing the average bias.

The Theraflux® sampler demonstrated satisfactory reliability for partial spent dialysate collection during hemodiafiltration sessions. Its automated sampling system substantially reduces the logistical burden associated with total dialysate collection and may facilitate future studies assessing toxin mass transfer and albumin loss in routine clinical practice.