Comparative Studies between Hemofiltration and Hemodialysis on Urea and Isotope-Labelled Sodium Kinetics

Abstract

Comparative studies on urea and sodium kinetics were performed between hemodialysis (HD) and hemofiltration (HF). 10 patients on HF were examined and 11 patients on HD were then selected to match the HF group on the basis of age, body weight and height. The urea concentration of serum, cerebrospinal fluid (CSF) and total urea removed were measured during HD and HF. The slope of regression line of the serum urea concentration during the 5 h of treatment was significantly higher for HD, while the total urea removed was comparable between the two. On the contrary, CSF reduction in urea was significantly greater after HF, resulting in a smaller urea concentration gradient between serum and CSF. The sodium kinetics during the procedures were estimated using 22Na. Although the total 22Na removed was significantly larger in HF than in HD and body weight loss was comparable between the two groups, the slope of regression line for 22Na was significantly less with HF whereas total serum Na levels for HF equaled HD. The above results indicate that urea and sodium equilibrated more efficiently between the compartments of body fluid in HF. This resulted in a smaller decrease in osmolality as well as in solute concentration gradients between plasma and CSF.