32-Microglobulin removal

Substances with an unexpectedly low CSF concentration are either selectively removed from the CSF between the ventricles and lumbar sac (e.g., glycine) or are metabolized (e.g., sorbitol). Substances with an unexpectedly high CSF concentration (e.g. ascorbate, /32-microglobulin, or neuron-specific enolase) either originate from the central nervous system or reach the CSF space by carrier-mediated transport. Through the albumin ratio (RAib), the size of a locally synthesized (i.e., intrathecal) fraction can be calculated (F2, R3). 

Tsuruoka S, Osono E, Nishiki K, Kawaguchi A, Arai T, Furuyoshi S, Saito T, Takata S, Sugimoto K, Kurihara S, Fujimura A. Removal of digoxin by column for specific adsorption of beta(2)-microglobulin a potential use for digoxin intoxication. Clin Pharmacol Ther 2001 69(6) 422-30. 

In practice a combination of dialysis and filtration is used, haemodiafiltration. Haemodiafiltration (HDF) is a combination of diffusion and convection. Diffusion is mainly effective for the removal of small waste molecules such as urea and creatinine. Larger molecules, for example beta-2-microglobuline, may only be removed from the blood by convection. For sufficient convective transport per HDF treatment an equivalent of 60 L of plasma is filtrated. At the same time the same volume is given back to the patient in the form of substitution solution. The substitution solution enters the circulation of the patient. This is the same process as the administration of an infusion, which is why some European Inspectorates regards solutions for HDF as parenterals. 

While adsorption of endotoxins and cytokines is clearly desirable, one cotrld argue that adsorptive properties of a dialyzer are not important for removal of solutes such as P2-microglobulin because it does not matter to the patient whether a toxin goes down the drain or is adsorbed within the membrane wall. 

Ronco, C., Brendolan, A., Winchester, J. F., Golds, E., Clemmer, J., Polaschegg, H. D., Muller, T. E., Davankov, V., Ts5fumpa, M., Pavlova, L., Pavlov, M., La Gieca, G., and Levin, N. W. (2001). First clinical experience with an adjunctive hemoperfusion device designed specifically to remove beta 2-microglobulin in hemodialysis. Contrib. Nephrol, 166-173. 

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