Diffusion kinetics of urea, creatinine and uric acid in blood during hemodialysis. Clinical implications

In order to elucidate some conflicting data reported in the literature the diffusion kinetics between red blood cells (RBC) and plasma during dialysis were studied for urea, creatinine and uric acid. Several complementary studies were performed. According to our results urea diffuses very rapidly from RBC to plasma and is almost at equilibrium at the dialyser outlet; thus the extraction of urea during dialysis is from both plasma and RBC. On the other hand creatinine and uric acid hardly diffuse at all from RBC to plasma during blood transit through the hemodialyser and these solutes are thus extracted mainly from plasma