ADRENERGIC REGULATION OF BLOOD-PRESSURE IN CHRONIC RENAL-FAILURE

Previous investigations suggested that significant hypotension during hemodialysis may result from abnormalities of sympathetic nervous system activity. To further evaluate these phenomena, plasma dopamine .beta.-hydroxylase (D.beta.H) and cold pressor test (proposed indexes of efferent sympathetic nervous system activity) and amyl nitrite inhalation (an index of the entire baroreceptor reflex arc) were studied in 2 groups of patients: [group I], patients exhibiting a mean arterial pressure decrease to less than 70 mm Hg during less than 10% of dialyses; [group II] (hemodialysis hypotension), patients with a mean arterial pressure decrease to less than 70 mm Hg during more than 90% of dialyses. The groups were similar with respect to plasma renin activity, renin response to ultrafiltration, age, duration of dialysis, nerve conduction velocity, plasma protein concentration, hematocrit, dialysis weight change, resting heart rate, sex, race, blood pressure and hear rate response to cold pressor test, and 125I-albumin plasma volume. Supine mean arterial pressure was higher in patients with hemodialysis hypotension than in patients without hemodialysis hypotension (group I) both before and after dialysis. Plasma D.beta.H activity was significantly higher in patients with hemodialysis hypotension (group II) than in group I both before and after dialysis. Amyl nitrite inhalation, expressed as change in .DELTA.R-R (pulse change) interval/mean arterial pressure decrease, was less in hemodialysis hypotension patients. Hemodialysis hypotension may result from a lesion in the baroreceptors, cardiopulmonary receptors, or visceral afferent nerves. Elevated mean arterial pressure in patients with hemodialysis hypotension may be neurogenic in origin, as reflected by plasma D.beta.H activity, and appears similar to the hypertension that follows baroreceptor deafferentation of experimental animals.