Oxalate clearance by haemodialysis - a comparison of seven dialysers

Background. In patients with primary hyperoxaluria (PH) and oliguric end-stage renal disease, oxalate removal is largely dependent on the clearance by dialysis. Data on the oxalate clearance of newer dialyser types are scarce or absent. Therefore, we measured oxalate clearances of seven dialysers in a single 52-year-old female patient with PH. Since haemodiafiltration (HDF) has been advocated to increase oxalate clearance, we also assessed the effect of different predilution flows. The goal of the study was to select the dialyser and pre-dilution flow combination with the highest oxalate clearance. Methods. Oxalate clearances were assessed by simultaneously taking afferent blood and efferent dialysate samples at 30, 60, 120 and 180 min after the start of haernodialysis. Blood flow and dialysate flow were 350 and 500 ml/min, respectively. All dialysers were tested at a pre-dilution flow of 2 I/h. Six dialysers were also tested at either a pre-dilution flow of 4.5 I/h or without HDF, depending on the ultrafiltration coefficient of the dialyser. Results. Oxalate clearances differed markedly between the tested dialysers, ranging from 144 +/- 10 to 220 +/- 12 ml/min. The highest oxalate clearances were achieved with HdF 100S (219 +/- 10 ml/min) and Sureflux FB-2 IOU (220 12 ml/min) at a pre-dilution flow of 2 I/h. Higher pre-dilution flows (2 l/h vs no HDF or 4.5 vs 2.0 l/h) yielded similar oxalate clearances. Conclusion. The highest oxalate clearances were achieved with a high-flux polysulfone and a cellulose triacetate dialyser with a large surface area. Higher pre-dilution flows did not augment oxalate clearance.