RESPONSE OF VASOACTIVE SUBSTANCES TO INTERMITTENT ULTRAFILTRATION IN NORMOTENSIVE HEMODIALYSIS-PATIENTS

The changes in blood volume (BV), atrial natriuretic peptide (ANP), pl asma renin activity (PRA), aldosterone (Aldo), norepinephrine (NE), ep inephrine (Epi), parathyroid hormone (PTH), arginine vasopressin (AVP) and the cyclic nucleotides cAMP and cGMP were measured during a fluct uating BV cycle in 15 patients with end-stage renal failure maintained on chronic hemodialysis (HD). HD consisted of 4 periods of about 60 m in each. The first half of each HD period consisted of ultrafiltration (UF) greater than 1,000 ml/h, and the second half consisted of no UF. Changes in relative BV were measured using continous hemoglobinometry . Total BV at the end of treatment was 74.3 +/- 6.9% of the pretreatme nt volume. A significant positive correlation between BV and the level s of ANP, PTH, Epi and cGMP and an inverse correlation between BV and PRA, Aldo, AVP and NE were demonstrated. While mean values of NE and A VP levels were directly related to actual changes in BV, individual va lues did not homogeneously reflect this relationship. The cyclic nucle otides cGMP and cAMP did not follow immediate BV changes, but showed a significant decrease correlated with diminished BV. Based on a pre-po stdialysis analysis, significant changes in PRA and Aldo were missing. It seems possible that vascular stability in dialysis patients may be maintained by the response of NE and AVP, and not by the renin-aldost erone system. The changes in ANP and cGMP values correlated most signi ficantly (r = 0.38 and r = 0.51, p < 0.005) with the changes in BV, bu t no single variable could explain the blood pressure regulation durin g HD with intermittent rapid UF.