In addition to cardiovagal dysfunction, baroreflex-mediated sympathetic modulation of the blood vessels is impaired in type II diabetic patients.

Aims/hypothesis Assessment of cerebral regulation in diabetic patients is often problematic because of the presence of cardiac autonomic neuropathy. We evaluated the technique of oscillatory neck suction at 0

Aims/hypothesis Patients with diabetes mellitus have an increased risk of stroke and other cerebrovascular complications. The purpose of this study was to evaluate the autoregulation of cerebral blood flow in diabetic patients using a simple method that could easily be applied to the clinical routine screening of diabetic patients. Methods We studied ten patients with type 2 diabetes mellitus and 11 healthy volunteer control participants. Continuous and non-invasive measurements of blood pressure and cerebral blood flow velocity were performed during deep breathing at 0.1 Hz (six breaths per minute). Cerebral autoregulation was assessed from the phase shift angle between breathing-induced 0.1 Hz oscillations in mean blood pressure and cerebral blood flow velocity. ResultsThe controls and patients all showed positive phase shift angles between breathing-induced 0.1 Hz blood pressure and cerebral blood flow velocity oscillations. However, the phase shift angle was significantly reduced (p<0.05) in the patients (48±9°) compared with the controls (80±12°). The gain between 0.1 Hz oscillations in blood pressure and cerebral blood flow velocity did not differ significantly between the patients and controls. Conclusions/interpretation The reduced phase shift angle between oscillations in mean blood pressure and cerebral blood flow velocity during deep breathing suggests altered cerebral autoregulation in patients with diabetes and might contribute to an increased risk of cerebrovascular disorders.

In diabetic patients, vascular disease and autonomic dysfunction might compromise cerebral autoregulation and contribute to orthostatic intolerance. The aim of our study was to determine whether impaired cerebral autoregulation contributes to orthostatic intolerance during lower body negative pressure in diabetic patients.Thirteen patients with early-stage type 2 diabetes were studied. We continuously recorded RR-interval, mean blood pressure and mean middle cerebral artery blood flow velocity at rest and during lower body negative pressure applied at −20 and −40 mm Hg. Spectral powers of RR-interval, blood pressure and cerebral blood flow velocity were analyzed in the sympathetically mediated low (LF: 0.04-0.15 Hz) and the high (HF: 0.15-0.5 Hz) frequency ranges. Cerebral autoregulation was assessed from the transfer function gain and phase shift between LF oscillations of blood pressure and cerebral blood flow velocity. In the diabetic patients, lower body negative pressure decreased the RRinterval, i.e. increased heart rate, while blood pressure and cerebral blood flow velocity decreased. Transfer function gain and phase shift remained stable.Lower body negative pressure did not induce the normal increase in sympathetically mediated LF-powers of blood pressure and cerebral blood flow velocity in our patients indicating sympathetic dysfunction. The stable phase shift, however, suggests intact cerebral autoregulation. The dying back pathology in diabetic neuropathy may explain an earlier and greater impairment of peripheral vasomotor than cerebrovascular control, thus maintaining cerebral blood flow constant and protecting patients from symptoms of presyncope.

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