Effect of osmolar changes on plasma arginine vasopressin (PAVP) in dialysis patients

The effect of changes in plasma osmolality and changes in plasma arginine vasopressin (PAVP) were analyzed in 10 stable chronic hemodialysis patients utilizing four protocols. During regular hemodialysis opposing influences on PAVP (decrease in blood pressure and intravascular volume and increase in serum calcium) resulted in no significant change in PAVP (by analysis of variance). In the second protocol low dialysate calcium (2.5 meq/l) isovolemic hemodialysis was used. PAVP and serum osmolality levels declined from 2.0 +/- 0.4 to 1.4 +/- 0.2 microU/ml (p less than 0.05), and 285 +/- 2.5 mOsm/l to 275 +/- 3.2 mOsm/l respectively. Removal of PAVP by hemodialysis did not occur as evidenced by no difference in arterial-venous PAVP levels and no "rebound" of PAVP for three hours after completion of dialysis (second protocol). Isovolemic low calcium high dialysate sodium (145 meq/l) hemodialysis was utilized in the third protocol. Serum osmolality and PAVP did not change. Addition of a very high dialysate sodium (155 meq/l) to isovolemic low calcium hemodialysis resulted in an increase in plasma sodium, osmolality and AVP (139.7 +/- 0.62 to 144 +/- 0.67 meq/l, 294 +/- 2.79 to 304.3 +/- 2.4 mOsm/l and 1.8 +/- 0.3 to 2.7 +/- 0.5 microU/ml (p less than 0.05 for each) respectively. In conclusion, PAVP responds to changes in plasma osmolality in chronic hemodialysis patients.