Middle molecular weight substances and uremic polyneuropathy.

A group of 25 uremic patients on regular hemodialysis was examined during 12 months after six-hour dialyses twice a week were changed to five-hour dialyses thrice a week. Twelve of the patients suffered from polyneuropathy, while 13 did not show signs of this uremic complication. The effect was studied of the increase of the amount of dialyses on the severity of polyneuropathy, checked by neurological and electromyographic methods, as well as on the serum levels of uremic middle molecular weight substances (MMS). Sera of the patients were subjected to gel filtration on Sephadex G-15 columns. This analysis resolved MMS into five distinct fractions in the range of middle molecular weight. Sera of the patients with polyneuropathy contained more of MMS in the 2nd and 4th fractions than those without signs of polyneuropathy. During 12 months of treatment with three hemodialyses a week, a significant improvement of polyneuropathy, together with a pronounced decrease of the serum levels of the 2nd and 4th MMS fractions were evidenced. A statistically significant negative linear relationship of polyneuropathy signs and the serum levels of MMS in these two fractions was registered.