Search Results

You are looking at 1 - 10 of 958 items for :

  • "autoregulation" x
  • Refine by Access: all x
Clear All
Restricted access

Marek Czosnyka, Piotr Smielewski, Stefan Piechnik, Luzius A. Steiner, and John D. Pickard

C erebral autoregulation is one of the major mechanisms responsible for brain protection in circumstances in which CPP may become unstable. 15, 26, 32 Maintaining CPP above 70 mm Hg by using CPP-oriented therapy is a realistic target, 35 but changes in CPP often may be too rapid for timely intervention to prevent temporary falls in pressure. Elevations of ICP, variations in ABP, and other factors may lead to ischemic insults when autoregulation is defective. Disturbed autoregulation has been demonstrated to occur after head injury. 5–7, 15, 28, 34 In

Restricted access

Elisabeth C. Jünger, David W. Newell, Gerald A. Grant, Anthony M. Avellino, Saadi Ghatan, Colleen M. Douville, Arthur M. Lam, Rune Aaslid, and H. Richard Winn

T he cerebral circulation has a capacity to maintain blood flow at a relatively constant level during changes in blood pressure. This phenomenon, known as cerebral autoregulation, is usually observed between a mean arterial blood pressure (MABP) of approximately 50 and 150 mm Hg. 14, 26 Cerebral autoregulation can be impaired or absent following severe closed head injury. 4–6, 8, 9, 21, 22, 25, 26 Impairments in autoregulation may contribute by several mechanisms to secondary neuronal injury following head injury. Lowered cerebral perfusion pressure (CPP

Restricted access

Andras A. Kemeny, Jan A. Jakubowski, Anthony A. Jefferson, and Emil Pasztor

product reaching its destination is proportional not only to secretion but also to local blood flow. Measurement of pituitary blood flow by the commonly used diffusible indicator, rubidium-86, or radiolabeled microsphere technique is unreliable because of the special angiostructure in this gland, 10 and does not allow for dynamic studies. In our present study, the hydrogen clearance method 1 was used, with a direct approach to the pituitary gland, 7, 13, 14 to establish the limits of autoregulation in the adenohypophysis of rats. Materials and Methods Twenty

Restricted access

Eric A. Schmidt, Marek Czosnyka, Luzius A. Steiner, Marcella Balestreri, Piotr Smielewski, Stefan K. Piechnik, Basil F. Matta, and John D. Pickard

A utoregulation is the physiological mechanism that maintains a relatively constant CBF over a wide range of CPPs. Autoregulation has been demonstrated to be impaired after TBI. 8, 24 This impairment contributes to the brain's vulnerability to secondary brain injury. An alteration in autoregulation is presently addressed as a clinical issue, and may be measured at the bedside by using different methods. 3, 5, 10, 14, 15, 17, 22 The clinical usefulness of these methods to improve the treatment of patients with head injury, however, remains to be demonstrated

Restricted access

Joseph M. K. Lam, John N. K. Hsiang, and Wai S. Poon

(CBF) over a wide range of CPPs. This ability, called autoregulation of CBF, may be impaired in the injured brain. The loss of autoregulation renders the brain more susceptible to systemic insults, such as derangement of blood pressure. 4 The success of the various strategies for CPP management depends on the accurate determination of the status of autoregulation. Moreover, the autoregulatory status may vary with time as patients deteriorate or recover, hence the need for continuous assessment of autoregulation. However, there is a paucity of satisfactory methods

Restricted access

Marek Czosnyka, Marcella Balestreri, Luzius Steiner, Piotr Smielewski, Peter J. Hutchinson, Basil Matta, and John D. Pickard

generally, multiple markers that have been shown to be associated with worse outcome after head injury 6, 24, 28 may have a specific age dependency. We sought to investigate a selected subset of brain monitoring variables, focusing on the relationship between brain pressures and blood flow, which possibly contribute to the high incidence of unfavorable outcomes in elderly patients after head trauma. The age dependence of ICP, CPP, blood FV through basal cerebral arteries, and various indices used to describe pressure autoregulation and cerebrovascular reactivity were

Restricted access

Gerrit J. Bouma and J. Paul Muizelaar

I ntravascular volume expansion, alone or in combination with induced hypertension, has been proposed to be useful in the prevention and treatment of focal cerebral ischemia caused by arterial occlusive disorders or by vasospasm after subarachnoid hemorrhage. The beneficial effect of this treatment on regional cerebral blood flow (rCBF), neuroelectrical activity, and clinical symptoms has been demonstrated both in laboratory investigations 13, 28, 31, 35 and in clinical situations, 12, 23, 29 and has been related to impaired autoregulation in ischemic brain

Restricted access

Gill E. Sviri, Rune Aaslid, Colleen M. Douville, Anne Moore, and David W. Newell

C erebral autoregulation is a complex intrinsic control mechanism that maintains a constant cerebral blood flow by constantly changing in the cerebral vascular resistance in response to changing arterial BP or CPP. This mechanism was found to be impaired after brain injury; even minor 1 , 3 and impaired AR has been suggested to be associated with variety of cerebrovascular abnormalities found after injury. 10 Impaired AR may increase the vulnerability of the brain to secondary ischemic insult resulting from reduction in the BP or elevated ICP. 3 , 4 , 5

Restricted access

Howard J. Senter and Joan L. Venes

severe cord injury. A recent study in this laboratory not only confirmed the presence of ischemia in the lateral white matter after severe thoracic cord trauma, but suggested that there was a consistent time delay between injury and demonstrable ischemia. 26 That study suggested that, although blood pressure fell within a few minutes after trauma, SCBF remained normal until 1 to 2 hours later. The present study investigates the hypothesis that ischemia of delayed onset is related to the loss of autoregulation. Materials and Methods Preparation of Animals

Restricted access

Anthony A. Figaji, Eugene Zwane, A. Graham Fieggen, Andrew C. Argent, Peter D. Le Roux, Peter Siesjo, and Jonathan C. Peter

P ressure autoregulation in the healthy or diseased brain has been extensively studied since the earliest descriptions of the response of cerebral vessels to changes in BP. 15 , 27 Autoregulation is an important neuroprotective mechanism that varies pial arteriolar caliber when BP changes to maintain a (relatively) constant CBF. Normally, autoregulation is active within a MABP range of 50–150 mm Hg, 34 and responds within seconds of the BP change. 32 However, autoregulation may be impaired after TBI, and several studies suggest that this impairment is a