Impairment of cerebral autoregulation in diabetic patients with cardiovascular autonomic neuropathy and orthostatic hypotension.

AIMS: Impaired cerebrovascular reactivity and autoregulation has been previously reported in patients with diabetes mellitus. However, the contribution of cardiovascular diabetic autonomic neuropathy and orthostatic hypotension to the pathogenesis of such disturbances is not known. The purpose of this study was to evaluate cerebral blood flow velocity in response to standing in patients with diabetes and cardiovascular autonomic neuropathy with or without orthostatic hypotension.

METHODS: We studied 27 patients with diabetes--eight had cardiovascular autonomic neuropathy and orthostatic hypotension (age 46.4 +/- 13.5 years, diabetes duration 25.0 +/- 11.0 years), seven had autonomic neuropathy without hypotension (age 47.3 +/- 12.7 years, diabetes duration 26.4 +/- 12.1 years), and 12 had no evidence of autonomic neuropathy (age 44.1 +/- 13.8 years, diabetes duration 17.1 +/- 10.2 years)-and 12 control subjects (age 42.6 +/- 9.7 years). Flow velocity was recorded in the right middle cerebral artery using transcranial Doppler sonography in the supine position and after active standing.

RESULTS: Cerebral flow velocity in the supine position was not different between the groups studied. Active standing resulted in a significant drop of mean and diastolic flow velocities in autonomic neuropathy patients with orthostatic hypotension, while there were no such changes in the other groups. The relative changes in mean flow velocity 1 min after standing up were -22.7 +/- 16.25% in patients with neuropathy and orthostatic hypotension, +0.02 +/- 9.8% in those with neuropathy without hypotension, -2.8 +/- 14.05% in patients without neuropathy, and -9.2 +/- 15.1% in controls.

CONCLUSIONS: Patients with diabetes and cardiovascular autonomic neuropathy with orthostatic hypotension show instability in cerebral blood flow upon active standing, which suggests impaired cerebral autoregulation.