Use of Systemic Blood Urea Nitrogen Levels

Urea rebound refers to an early postdialysis phenomenon in which urea returns to the systemic circulation, raising the blood level to a near plateau over a period of 0.5 to 1 hour [1]. The urea involved is believed to have come from either the intracellular compartment by means of diffusion resulting from the dialysis-induced concentration gradient [2,3], or tissues poorly perfused as a result of a dialysis-induced vasoconstriction [4]. Because of urea rebound, blood urea nitrogen (BUN) levels of systemic blood samples obtained 30 minutes after the completion of a hemodialysis treatment (+30-min BUN) are higher than those collected promptly after a dialysis session is over [1,5–11]. Recently, however, it has been shown that the BUN concentrations of systemic blood specimens obtained 30 minutes prior to the end of a dialysis session (–30-min BUN) are similar in value to their 30-minute postdialysis (+30-min BUN) counterparts [12,13]. In an attempt to determine whether such a relationship between BUN concentrations exists in patients dialyzed six times per week, as well as in those dialyzed three-times weekly, the present study was carried out. Preliminary results have been reported previously [14]. Materials and methods