Chapter 27

As an alternative to removal of sFLCs by HCO haemodialysis, strategies have been proposed that employ FLC adsorption or a combination of haemodialysis and adsorption. Polymethylmethacrylate (PMMA) membranes are routinely used to perform standard haemodialysis, but until recently their adsorption capacity for FLCs had not been well characterised. Fabbrini et al. [575] treated 10 patients with dialysis-dependent renal failure and high levels of monoclonal sFLCs (>500 mg/L) with at least one standard 4-hour dialysis session with a Toray BK 2.1 m2 PMMA membrane. The study concluded that PMMA haemodialysis reduced κ and λ sFLCs to a similar extent (concentrations were reduced by 22.3% and 21.0%, respectively), but that the process was limited by membrane saturation. Dialyser replacement after 2 hours (termed “enhanced adsorption dialysis”) increased the overall adsorption efficiency, particularly for λ FLCs [575]. Santoro et al. [576] reported similar findings using two PMMA membranes in sequence (termed the “DELETE system”). An illustrative case is shown in Figure 27.14 .

A different strategy for FLC removal employed a plasma filter followed by a sorbent cartridge. This technique, known as coupled plasma-filtration adsorption (CPFA), has been used in the extracorporeal treatment of sepsis. In an in vitro study of FLC removal by CPFA using a number of different resins, the MDR3 resin demonstrated the best adsorptive capacity [577]. For patients treated with at least six, 4-hour CPFA sessions using MDR3, sFLC concentrations progressively decreased (p=0.05), although the dialysis protocol remains to be optimised.

Another adsorption strategy has used “SUPRA HFR”, a form of haemodiafiltration with separated convection, diffusion and adsorption stages that avoids the albumin losses seen with other HCO haemodialysis protocols. The filter comprised an HCO membrane (Synclear 0.2), followed by a low-flux polyphenylene membrane in a second diffusive stage, and a sorbent cartridge with a high affinity for FLCs. Three patients with dialysis-dependent renal failure due to biopsy-proven cast nephropathy were successfully treated with SUPRA HFR [578]. All patients showed a significant reduction of sFLCs and a complete recovery of renal function after 30, 50 and 90 days, respectively [578]. Pasquali et al. [579] reported four further patients treated with this protocol, of whom three recovered renal function.