Removal of endogenous middle molecules by hemoperfusion.

In four regular dialysis patients, the removal of uremic middle molecules was studied during a three-hour hemoperfusion using a column containing 300 gm of activated carbon encapsulated with cellulose. Middle molecules in plasma were determined by high-speed gel filtration followed by gradient elution chromatography. Different adsorption characteristics were shown for the four middle molecule fractions measured. The initial clearances for middle molecule fractions were about 120 ml/min; clearances were 20-50 ml/min after two hours, and less than 25 ml/min, with release of some middle molecule fractions from the column, after three hours. The findings suggest that saturation of the column occurs after two to three hours of perfusion. Thus, prolongation of the perfusion time beyond two hours appears to be of little benefit. The reduction of middle molecules in plasma by a three-hour hemoperfusion was in magnitude, similar to that obtained by three-hour dialysis with a large surface area dialyzer or high-flux membrane.