Plasma vasopressin, catecholamines and atrial natriuretic factor during hemodialysis and sequential ultrafiltration.

In 13 patients with chronic renal failure on maintenance hemodialysis, plasma vasopressin, atrial natriuretic factor, catecholamines and renin activity were measured during ordinary hemodialysis with fluid removal, and during isolated isoosmotic ultrafiltration and a subsequent isovolemic hemodialysis. Concomitant with a significant fall in serum osmolality, plasma vasopressin decreased significantly from 6.3 +/- 0.8 to 3.8 +/- 0.4 pg/ml (p < 0.05). Predialytic plasma vasopressin was significantly correlated to serum osmolality (r = 0.62, p = 0.001). No such relationship was observed after dialysis. During isolated ultrafiltration (1.25 +/- 0.13 L) through 1 hour, no change in either osmolality or vasopressin was observed, whereas atrial natriuretic factor decreased (700 +/- 136 to 564 +/- 115 pg/ml, p < 0.05). Atrial natriuretic factor was excessively high at all times, and may explain the low plasma renin activity observed in these patients even after fluid removal. No consistent changes were observed in the catecholamines during hemodialysis or ultrafiltration alone, despite marked changes in blood pressure and heart rate. Thus, even in patients with chronic renal failure osmotic regulation of vasopressin seems intact, and volume reduction through ultrafiltration causes a decrease in atrial natriuretic factor.