Accumulation of albumin-bound toxins, which have a range of detrimental effects on the liver, other organs, and patient physiology, is common in liver failure. Due to extremely low solubility in physiologic solutions, these toxins cannot be removed by conventional dialysis. Bound solute dialysis with slow continuous ultrafiltration (BSD-SCUF) has the potential of removing albumin-bound toxins.
An in-vitro system consisting of a reservoir containing surrogate blood (dialysate with 40 g/L human serum albumin (HSA) saturated with unconjugated bilirubin), the Gambro Prisma System, and a Baxter CT-110G dialyzer was employed to measure reservoir bilirubin clearance as a function of time over a 3-h experiment. BSD-SCUF variables included blood and dialysate flow rates, ultrafiltration rate, and dialysate HSA concentration in clinically relevant ranges.
Clearance of bilirubin was 5 to 10% without HSA in the dialysate stream. Clearance increased to 20–25% when HSA was added to the dialysate stream, irrespective of blood and dialysate flow rates. Notably, bilirubin clearance was not significantly different throughout the experimented ranges of HSA concentration (0.4 to 1.6 g HSA/L). Ultrafiltration rate did not affect clearance of bilirubin.
In accord with the BSD model, ultrafiltration, which removes solute at free solute concentration, does not affect bound solute clearance. Adding HSA to the dialysate stream increases bilirubin removal, independently of the blood or dialysate flow rates. The results show that toxin removal is independent of the HSA concentration in the dialysate.