Hemodialysis hypotension is not the result of uremic peripheral autonomic neuropathy

Five chronic hemodialysis patients with persistent hypotension during dialysis (MAP: 74.2 +/- 3.1 mm Hg) were given a number of standard tests of autonomic nervous system function and compared with eight normotensive hemodialysis patients (MAP: 96.4 +/- 3.4 mm Hg). Tests of efferent sympathetic nerves were normal in both groups, as were plasma catecholamine levels and the cold pressor test. The response to Valsalva maneuver and the venoconstriction reflex were generally abnormal and did not differentiate between the two groups. When adjusted for age and MAP, the baroreceptor slope to a high-pressure stimulus was diminished only in the hypotensive subjects. This result reinforces the previously described finding that many uremic patients do not develop a normal cardioacceleration during hypotension. Although reduced baroreceptor sensitivity may be a factor in the chronic hypotension of some hemodialysis patients, autonomic dysfunction alone is not a sufficient explanation of this phenomenon.