Background: Recurrent dialysis hypotension is common in long-term dialysis patients. Arginine-vasopressin (AVP) is a potent vasoconstrictor hormone, release of which is stimulated in hypotension.
Study design: We measured AVP as well as adrenaline and noradrenaline in 23 patients with recurrent dialysis hypotension during severe symptomatic episodes of dialysis hypotension (BP syst. < 70 mmHg). We also tested autonomic function (amyl nitrate inhalation, cold pressor test) during the interdialytic interval.
Results: We observed that systolic blood pressure decreased from 127 +/- 8 (at the end of the first hour of dialysis; taken as control state) to 64 +/- 1 mmHg (symptomatic hypotension) in 23 patients. In six of the 23 patients hypotension was accompanied by nausea, which is a known direct stimulus of AVP. In these six patients, plasma AVP showed a large increase: control state, 6.2 +/- 0.9; hypotension, 130.4 +/- 51.1 pg/ml; P < 0.5). Of the remaining 17 patients without nausea, AVP fell moderately in nine and increased in eight. Taken together, this group of 17 hypotensive patients failed to show significant AVP stimulation: control state, 9.0 +/- 1.4; hypotension, 13.8 +/- 3.8 pg/ml, NS). Adrenaline and noradrenaline did not change during hypotension. During autonomic testing the patients with recurrent dialysis hypotension (compared to healthy controls) showed blunted baroreflex response (assessed by amyl nitrate inhalation) but intact sympathetic outflow (assessed by cold pressor test).
Conclusion: The observations of AVP are taken as further evidence of defects in the afferent rather than the efferent limb of autonomic reflexes in dialysis patients with recurrent dialysis hypotension.