Failure of arginine-vasopressin and other pressor hormones to increase in severe recurrent dialysis hypotension

BACKGROUND.: Recurrent dialysis hypotension is common in long-term dialysispatients. Argininevasopressin (AVP) is a potent vasoconstrictorhormone, release of which is stimulated in hypotension. STUDY DESIGN.: We measured AVP as well as adrenaline and noradrenaline in 23patients with recurrent dialysis hypotension during severe symptomaticepisodes of dialysis hypotension (BP syst. < 70 mmHg). Wealso tested autonomic function (amyl nitrate inhalation, coldpressor 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; takenas control state) to 64 ± 1 mmHg (symptomatic hypotension)in 23 patients. In six of the 23 patients hypotension was accompaniedby nausea, which is a known direct stimulus of AVP. In thesesix 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, AVPfell moderately in nine and increased in eight. Taken together,this group of 17 hypotensive patients failed to show significantAVP stimulation: control state, 9.0 ± 1.4; hypotension,13.8 ± 3.8 pg/ml, NS). Adrenaline and noradrenaline didnot change during hypotension. During autonomic testing thepatients with recurrent dialysis hypotension (compared to healthycontrols) showed blunted baroreflex response (assessed by amylnitrate inhalation) but intact sympathetic outflow (assessedby cold pressor test). CONCLUSIONS.: The observations of AVP are taken as further evidence of defectsin the afferent rather than the efferent limb of autonomic reflexesin dialysis patients with recurrent dialysis hypotension.