Mannitol and HS cause an increase in cerebrospinal fluid osmolality, and are associated with similar brain relaxation scores and arteriovenous oxygen and lactate difference during craniotomy.

There is little information on gender differences in cerebral autoregulation. The purpose of this study was to compare autoregulation of the anterior and posterior circulations using the tilt test method in healthy boys and girls who were 10 -16 y of age. Transcranial Doppler was used to measure middle cerebral artery and basilar artery flow velocities (Vmca and Vbas). Cerebral autoregulation (ARI) of the middle cerebral (ARImca) and basilar arteries (ARIbas) was examined using the tilt test method. An ARI Ͻ0.4 indicates impaired autoregulation. Among the 13 boys and 13 girls, Vmca and Vbas were higher in girls. All children demonstrated intact autoregulation, but boys had higher ARImca than girls, whereas girls had higher ARIbas than boys. Girls demonstrated greater autoregulation in the basilar artery, whereas boys demonstrated greater autoregulation in the middle cerebral artery. Girls had higher flow velocities in both vessels. This study provides normative data on cerebral autoregulation of the poste- Autoregulation of cerebral blood flow (CBF) is a physiologic and homeostatic process that maintains nearly constant CBF over a range of mean arterial pressures (MAPs). Disease states, including traumatic brain injury, can impair cerebral autoregulation, rendering the brain susceptible to inadequate (cerebral ischemia) or excessive (cerebral hyperemia) CBF (1). Despite its critical role in maintaining CBF, there is limited information on cerebral autoregulation in healthy children.Little has been published on pediatric cerebral autoregulation in children outside the clinical arena of neurogenic syncope (2-4). In one study that examined dynamic cerebral autoregulation in awake adolescent study participants, the time to return of middle cerebral artery flow velocity (Vmca) to normal after a transient hypotensive stimulus was reported to be more in healthy adolescents compared with their healthy adult counterparts (5). However, in a subsequent evaluation of cerebral autoregulation in children versus adults during general anesthesia using static autoregulation testing, the investigators reported no age-related differences in autoregulatory capacity and no difference in cerebral autoregulation compared with adults (6). Because both of these studies examined cerebral autoregulation of the anterior circulation only, differences in cerebral autoregulation between the anterior and posterior circulation in children could not be evaluated. In addition, to our knowledge, there is no information regarding cerebral autoregulation of the posterior circulation in children, no information on gender differences in cerebral autoregulation in children, and finally no normative data on cerebral autoregulation using the tilt test method. Therefore, the purpose of this study was to 1) provide normative data on cerebral autoregulation using the tilt test method, 2) describe cerebral autoregulation of the posterior cerebral circulation, and 3) examine gender-related differences in autoregulatory capacity in healthy, awake boys and girl...

Transcranial Doppler ultrasonography appears to be highly predictive of an angiographically demonstrated vasospasm in the MCA and ACA; however, its diagnostic accuracy was lower with regard to vasospasm in the BA. Single-photon emission computed tomography was not predictive of a vasospasm in any of the vascular territories assessed.

Although there are several settings in which transcranial Doppler has well established usefulness, there are many more in which it is likely valuable, such as traumatic brain injury, ischemic stroke, and fulminant hepatic failure. Further research is needed in these fields to elucidate the exact role for transcranial Doppler.

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