Baroreceptor Activity in Normotensive and Hypertensive Uremic Patients

Baroreceptor activity and postural blood volume changes were evaluated in four normotensive and nine hypertensive uremic patients before and after bilateral nephrectomy. Baroreceptor activity, reflected by the slope of linear regression of R-R interval with drug-induced systolic blood pressure elevation, was significantly lower in hypertensive than in normotensive patients. Six of nine patients had normal blood pressure following bilateral nephrectomy; however, the mean slopes of all nine patients, irrespective of postnephrectomy blood pressure, approached that of normotensive uremic patients. The slopes of both normotensive and hypertensive patients, before and after bilateral nephrectomy, were significantly less than normal controls. Similar results were found in lowering blood pressure with amyl nitrite. Depressed baroreceptor activity is suggested to be secondary to neuropathy of the autonomic nervous system, chronic hypertension, heart disease, and anemia. It is speculated that this reduced baroreceptor sensitivity may accentuate the postural symptoms primarly induced by volume reduction on hemodialysis. There is no evidence in this study that depressed baroreceptor activity, as opposed to a reset baroreceptor, is a cause of hypertension in patients with chronic renal failure.