The mechanism of symptomatic postural hypotension in the elderly.

To study the mechanism of symptomatic postural hypotension in the elderly, we collected 11 such patients to further divide them into group 1 with central nervous system (CNS) involvement and group 2 without CNS involvement. Group 1 was the so-called Shy-Drager syndrome, and group 2 was the elderly postural hypotension not secondary to the medications or other systemic diseases. All patients had various degree of autonomic dysfunction and heterogenous defects in the reflex arc of autonomic nervous system (ANS). Both groups also had normal plasma volume but reduced blood volume. Patients in group 1 had normal level of plasma norepinephrine in recumbent posture, but failed to increase normally after standing (p less than 0.05, as compared the percentage rising with that of the controls). Patients in group 2 had near normal level of plasma norepinephrine in recumbent posture and could rise normally after standing. They also had normal level of plasma epinephrine in recumbent posture, but failed to rise normally after standing (p less than 0.05 as compared with the controls). These findings suggested that impaired responsiveness of end organs as blood vessels and adrenal medulla is one of the major causes responsible for the symptomatic postural hypotension in the elderly without CNS involvement.