FAILURE OF ARGININE-VASOPRESSIN AND OTHER PRESSOR HORMONES TO INCREASE IN SEVERE RECURRENT DIALYSIS HYPOTENSION

Background. Recurrent dialysis hypotension is common in long-term dial ysis 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 episode s of dialysis hypotension (BP syst. <70 mmHg). We also tested autonomi c function (amyl nitrate inhalation, cold presser test) during the int erdialytic interval. Results. We observed that systolic blood pressure decreased from 127+/-8 (at the end of the first hour of dialysis; tak en as control state) to 64+/-1 mmHg (symptomatic hypotension) in 23 pa tients. In six of the 23 patients hypotension was accompanied by nause a, which is a known direct stimulus of AVP. In these six patients, pla sma 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 nau sea, AVP fell moderately in nine and increased in eight. Taken togethe r, this group of 17 hypotensive patients failed to show significant AV P 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 hypoten sion (compared to healthy controls) showed blunted baroreflex response (assessed by amyl nitrate inhalation) but intact sympathetic outflow (assessed by cold presser test). Conclusion. The observations of AVP a re taken as further evidence of defects in the afferent rather than th e efferent limb of autonomic reflexes in dialysis patients with recurr ent dialysis hypotension.