Transcranial Doppler sonographic studies of cerebral autoregulation in Shy-Drager syndrome

Briebach, T.; Laubenberger, Jörg; Fischer, P

doi:10.1007/bf00314378

Cited by 22 publications

(12 citation statements)

References 20 publications

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“…Moreover, it has been shown that mean cerebral blood flow velocity dropped, with concurrent hypotension in patients with progressive autonomic failure. 16 Although it is not clear from the clinical history of these patients (Table 1) which factors may cause sympathetic hypoactivity, it may be suggested that there is yet an unknown clinical predisposition to this condition. On the other hand, it has been suggested that in some patients, sympathetic hyperactivity may modulate cerebral hypoperfusion without hypotension, 9 even in the absence of cardiopulmonary reflexes.…”

Section: Discussionmentioning

confidence: 98%

Critical limits of pressure-flow relation in the human brain.

Njemanze

1992

Stroke

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Background: This study was designed to determine the minimal mean flow velocity and pressure-flow relation necessary to preserve human consciousness.Methods: Passive upright tilt provocation was used in conjunction with transcranial Doppler in 80 patients with a history of syncope of unknown etiology. Cerebral blood flow velocity, blood pressure, and heart rate were monitored noninvasively.Results: Forty patients remained asymptomatic, and the rest had clinically induced true syncope or premonitory symptoms. In the asymptomatic group, there was a 23±16% (p=0.000) drop in mean flow velocity, but no significant changes in systolic and diastolic blood pressures. In the symptomatic patients, there was a 58+14% (/>=0.000) drop in mean flow velocity, 37±23% (p=0.000) fall in systolic pressure, and 31 ±20% (p=0.000) fall in diastolic pressure. In 80% of symptomatic patients, the critical lower limit of mean flow velocity was at -50% of resting baseline while patients were lying supine. The symptomatic group had lower mean flow velocity and blood pressure responses as compared with the asymptomatic group. The slope and intercept values of the pressure (y axis) to flow velocity (or axis) regression curves indicate a greater degree of impaired autoregulation in the symptomatic group (y=0.529x-6.11, ^=0.108, p=0.038) as compared with the asymptomatic (y=0.317 x+0.966, ^=0.14,^=0.017).Conclusions: The critical lower limit of cerebral perfusion lies at 50% below baseline supine mean flow velocity. (Stroke 1992;23:1743-1747 KEY WORDS • autoregulation • blood flow velocity • hypotension • ultrasonics

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Section: Discussionmentioning

confidence: 98%

Critical limits of pressure-flow relation in the human brain.

Njemanze

1992

Stroke

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“…Although cerebral circulation in MSA patients has been evaluated using the arteriovenous oxygen differences method (2)(3)(4), the xenon clearance technique (2,5,6), transcranial Doppler sonography (5,(7)(8)(9)(10)(11) and near-infrared (NIR) spectroscopy (7,10) (12,13)…”

Section: Orthostatic Hypotension Is a Major Problem In Patients With mentioning

confidence: 99%

Cerebral Oxygenation Monitoring for Detecting Critical Cerebral Hypoperfusion in Patients with Multiple System Atrophy during the Head-up Tilt Test

et al. 2008

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“…Others have suggested that autoregulation may actually be enhanced in patients with autonomic failure, with the lower limit of autoregulation occurring at lower than expected arterial pressures, thus enabling these patients to tolerate lower blood pressures than a normal population [7]. Although several blood flow and transcranial Doppler studies during hypotension in patients with autonomic failure have demonstrated preservation of cerebral autoregulation [3,[7][8][9][10][11][12], some studies have suggested defective autoregulation in these patients [5,6,13], in addition to one study that showed both defective and preserved autoregulation [14].The autoregulatory process for maintenance of cerebral blood flow during hypotension is cerebral vasodilation, which can be measured with transcranial Doppler ultrasonography (TCD). We examined a group of patients with autonomic failure and used TCD to assess changes in cerebral blood flow velocity during hypotension induced by head-up tilt.…”

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confidence: 98%

Autoregulatory cerebral vasodilation occurs during orthostatic hypotension in patients with primary autonomic failure

Horowitz

Kaufmann

2001

Clinical Autonomic Research

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It is unclear whether patients with autonomic failure autoregulate cerebral blood flow during hypotension. The objective in this study was to examine cerebral autoregulatory capacity in patients with autonomic failure by studying changes in middle cerebral artery blood flow velocity using transcranial Doppler ultrasonography before, during, and after tilt-induced hypotension. Nine patients with primary autonomic failure were evaluated. Mean arterial pressure and middle cerebral artery blood flow velocity were simultaneously recorded while the patients were in the supine position, during 60 degrees head-up tilt, and after they were returned to the horizontal position. The results were as follows: during tilt-induced hypotension, mean arterial pressure decreased significantly more than middle cerebral artery mean blood flow velocity (58% versus 36%, p <0.0002). After return to the horizontal position, mean arterial pressure returned to baseline, and middle cerebral artery blood flow velocity transiently increased above pretilt value (p <0.02). It is concluded that cerebral autoregulatory vasodilation occurs in patients with autonomic failure. This was demonstrated by a more pronounced decline in mean arterial pressure than in middle cerebral artery blood flow velocity during hypotension and by a transient increase in middle cerebral artery blood flow velocity (ie, hyperemic response) after blood pressure was restored.

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Transcranial Doppler sonographic studies of cerebral autoregulation in Shy-Drager syndrome

Cited by 22 publications

References 20 publications

Critical limits of pressure-flow relation in the human brain.

Critical limits of pressure-flow relation in the human brain.

Cerebral Oxygenation Monitoring for Detecting Critical Cerebral Hypoperfusion in Patients with Multiple System Atrophy during the Head-up Tilt Test

Autoregulatory cerebral vasodilation occurs during orthostatic hypotension in patients with primary autonomic failure

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