RESPONSE OF VASOACTIVE SUBSTANCES TO REDUCTION OF BLOOD-VOLUME DURINGHEMODIALYSIS IN HYPOTENSIVE PATIENTS

Hypotension is a frequent complication in patients subjected to regula r hemodialysis. Insufficient regulation of blood pressure following di alysis with ultrafiltration has been attributed to a lack in hormone a ctivation. To determine whether altered production of vasoactive hormo nes is involved in the breakdown of blood pressure regulation during h emodialysis (HD), blood volume (BV), atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (Aldo), norepinephrine (NE), epinephrine (Epi), intact immunoreactive parathyroid hormone (iPTH) a nd arginine vasopressin (AVP) were examined. The relative BV was measu red by continuous hemoglobinometry during the HD period of about 240 m in. The total decrease in BV at the end of treatment was 23.5 +/- 4.8% of the pretreatment value. Systolic blood pressure (SBP) was 99.6 +/- 23.0 mmHg before dialysis compared with 74.6 +/- 18.8 mmHg at the end of dialysis and heart rate (HR) increased from 76.3 +/- 5.5/min befor e to 92.0 +/- 10.0/min at the end of dialysis. Despite the wide range of interindividual variance, the hormonal changes indicate that hypote nsive patients under HD develop reduced sensitivity of the angiotensin -renin, adrenergic and AVP systems to volumetric stimuli. A paradoxica l activation in iPTH and PRA independent Aldo secretions is apparent.