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Respiratory, endocrine, cardiac, and renal topics
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
Consideration of the length of time over which the hypertension has developed is very important [12]. Cerebral autoregulation keeps cerebral blood flow relatively constant within systemic BP limits but over time this range is altered in hypertension. If BP is lowered too rapidly there is a real danger of relative hypotensive damage to watershed areas, particularly visual cortex, cerebellum and end-arteries (ciliary arteries to optic nerve and spinal arteries). Visual loss may be permanent. Thus, the principle of slow reduction of severe, chronic hypertension is paramount.
Neurophysiology: Age-related changes
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Dinu Chandran, Smriti Badhwar, Manpreet Kaur
Cerebral autoregulation is a homeostatic mechanism to regulate and maintain a fairly constant brain blood flow over wide ranges of arterial blood pressure; in other words, the perfusion pressure (33). The perfusion pressure of cerebral circulation is defined as the difference between mean arterial blood pressure (MAP) and the ICP. The quantitative relationship between CPP, CBF, and CVR is given as follows: therefore, where CPP = MAP − ICP, MAP is the mean arterial blood pressure, and ICP is the intracranial pressure.
SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
The rate of cerebral blood flow remains essentially stable, up to a point, with changing blood pressure owing to local autoregulation of flow. Autoregulation is very well developed in the brain; a fall in blood pressure causes the resistance vessels to dilate and thereby maintain flow. Cerebral autoregulation seems to involve both myogenic and metabolic mechanisms.
Liberating carotid arteries: measuring arterial pressure through femoral artery in mice
Published in Clinical and Experimental Hypertension, 2019
Li Wu, Wanrong Lin, Xian Fu, Xianliang Li, Xuelong Li, Youfu Li, Weijin Zhang, Jian Guo, Qingchun Gao
Monitoring the physiological parameters of experimental animals is the base in animal researches. One key variable that must be monitored and evaluated, especially for the cardio-cerebrovascular pathophysiology researches, is arterial pressure. Accurate blood pressure (BP) measuring is crucial not only for the assessment of the condition of the animal during experiment process, but also for determining the cardio-cerebrovascular function and studying pathological conditions such as impaired cerebral autoregulation (1). Cerebral autoregulation is the intrinsic ability of the brain to maintain constant cerebral blood flow in response to changes of systemic BP; therefore, it is necessary for the homeostasis of central nervous system, and impaired cerebral autoregulation has been found to be involved in the pathophysiology of various cardio-cerebrovascular diseases, such as hypertension, ischemic stroke, brain trauma, etc. (2).
Vitamin D deficiency and androgen excess result eutrophic remodeling and reduced myogenic adaptation in small cerebral arterioles in female rats
Published in Gynecological Endocrinology, 2019
Leila Hadjadj, Éva Pál, Anna Monori-Kiss, Réka Eszter Sziva, Ágnes Korsós-Novák, Eszter Mária Horváth, Rita Benkő, Attila Magyar, Péter Magyar, Zoltán Benyó, György L. Nádasy, Szabolcs Várbíró
With mechanism of cerebral autoregulation, brain vasculature is able to maintain constant mean cerebral arterial pressure despite of immediate systolic blood pressure changes. Small cerebral arterioles play an essential role in autoregulation with instant changes in their myogenic activity. At upper threshold of autoregulation (>150 mmHg) a forced dilatation of cerebral vessels occurs [11,12]. The loss of myogenic tone during forced dilatation results lower cerebrovascular resistance, but increases hydrostatic pressure on the cerebral endothelium. This mechanism could lead to acute vascular edema and growth of wall thickness. In case of chronic hypertension, remodeling of the vascular wall, decreased myogenic adaptation, and shift of the autoregulatory range could be observed as an end effect.
Long-term effects of multiple concussions on prefrontal cortex oxygenation during repeated squat-stands in retired contact sport athletes
Published in Brain Injury, 2022
Luke W. Sirant, Jyotpal Singh, Steve Martin, Catherine A. Gaul, Lynneth Stuart-Hill, Darren G. Candow, Cameron Mang, J. Patrick Neary
Cerebral autoregulation is the ability of the brain to control and maintain a constant cerebral blood flow through changes in cerebral perfusion pressure and cerebrovascular resistance (21). Controlling cerebral blood flow is critical to maintaining homeostasis and avoiding damage to the sensitive cells in the brain. There have been reports of long-term impairments in some of these mechanisms in those with a history of concussion, and specifically that of hemodynamic dysfunctions in dynamic cerebral autoregulation (dCA) (22). Using a squat-stand protocol (10-s squat; 10-s stand; 0.05 Hz) has been shown to stimulate the baroreflex and by using this intervention method it is possible to activate dCA and monitor changes in cerebral circulation that can occur in a setting of changing cerebral perfusion pressure (14,23). Blood (velocity) flow changes in those with a concussion have been noted using transcranial Doppler; however, there is still information missing related to the changes in prefrontal cortex oxygenation. Prefrontal cortex oxygenation changes have been noted in acute concussion when utilizing a 20 second breath hold cerebrovascular reactivity inducing task (18), and as such, assessing these similar mechanics can potentially provide greater insight to oxygenation changes during a dCA activating task, i.e., squat-stand. Previous studies have noted changes in blood pressure measures and heart rate variability in acute concussion patients using similar methodology (14), but no studies have used this methodology while measuring prefrontal cerebral oxygenation. It is also important to note that significant impairments in prefrontal cortex oxygenation have been noted in individuals exposed to normobaric hypoxia during a repeated squat-stand maneuver (24).