Cerebral autoregulation dynamics in humans.
نویسندگان
چکیده
We studied the response of cerebral blood flow to acute step decreases in arterial blood pressure noninvasively and nonpharmacologically in 10 normal volunteers during normocapnia, hypocapnia, and hypercapnia. The step (approximately 20 mm Hg) was induced by rapidly deflating thigh blood pressure cuffs following a 2-minute inflation above systolic blood pressure. Instantaneous arterial blood pressure was measured by a new servo-cuff method, and cerebral blood flow changes were assessed by transcranial Doppler recording of middle cerebral artery blood flow velocity. In hypocapnia, full restoration of blood flow to the pretest level was seen as early as 4.1 seconds after the step decrease in blood pressure, while the response was slower in normocapnia and hypercapnia. The time course of cerebrovascular resistance was calculated from blood pressure and blood flow recordings, and rate of regulation was determined as the normalized change in cerebrovascular resistance per second during 2.5 seconds just after the step decrease in blood pressure. The reference for normalization was the calculated change in cerebrovascular resistance that would have nullified the effects of the step decrease in arterial blood pressure on cerebral blood flow. The rate of regulation was 0.38, 0.20, and 0.11/sec in hypocapnia, normocapnia, and hypercapnia, respectively. There was a highly significant inverse relation between rate of regulation and PaCO2 (p less than 0.001), indicating that the response rate of cerebral autoregulation in awake normal humans is profoundly dependent on vascular tone.
منابع مشابه
Cerebellar autoregulation dynamics in humans.
Knowledge on autoregulation of cerebellar blood flow in humans is scarce. This study investigated whether cerebellar autoregulation dynamics and CO(2) reactivity differ from those of the supratentorial circulation. In 56 healthy young adults, transcranial Doppler (TCD) monitoring of the posterior inferior cerebellar artery (PICA) and, simultaneously, of the contralateral middle cerebral artery ...
متن کاملWhy is the neural control of cerebral autoregulation so controversial?
Cerebral autoregulation refers to the mechanisms that act to keep cerebral blood flow (CBF) constant during changes in blood pressure. The mechanisms of cerebral autoregulation, especially in humans, are poorly understood but are undoubtedly multifactorial and likely reflect many redundant pathways that potentially differ between species. Whether sympathetic nervous activity influences CBF and/...
متن کاملEffect of inhibition of nitric oxide synthase on dynamic cerebral autoregulation in humans.
Cerebral blood flow is maintained constant over a range of cerebral perfusion pressures by cerebral autoregulation. Impaired cerebral autoregulation may be important in the pathogenesis of cerebral ischaemia. The mechanisms mediating normal cerebral autoregulation in humans are poorly understood. We used a recently described transcranial Doppler technique, which allows non-invasive measurement ...
متن کاملMathematical model of the interaction between baroreflex and cerebral autoregulation
Baroreflex (BR) and cerebral autoregulation (CA) are two important mechanisms regulating blood pressure and flow. However, the functional relationship between BR and CA in humans is unknown. Since BR impairment is an adverse prognostic indicator for both cardiac and cerebrovascular diseases it would be of clinical interest to better understand the relationship between BR and CA. Motivated by th...
متن کاملComparison of flow and velocity during dynamic autoregulation testing in humans.
BACKGROUND AND PURPOSE We compared relative changes in middle cerebral artery velocity and internal carotid artery flow during autoregulation testing to test the validity of using transcranial Doppler recordings of middle cerebral artery velocity to evaluate cerebral autoregulation in humans. METHODS Seven human volunteers had dynamic autoregulation tested during surgical procedures that incl...
متن کاملCerebral autoregulation and gas exchange studied using a human cardiopulmonary model.
The goal of this work is to study the cerebral autoregulation, brain gas exchange, and their interaction by means of a mathematical model. We have previously developed a model of the human cardiopulmonary (CP) system, which included the whole body circulatory system, lung and peripheral tissue gas exchange, and the central nervous system control of arterial pressure and ventilation. In this stu...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Stroke
دوره 20 1 شماره
صفحات -
تاریخ انتشار 1989