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Use of Venous Pressuras a Probe for Waterfall-Like Behavior in the Coronary Bed
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
I am pleased that you are looking at the venous side as well as the arterial side of the bed. But what about autoregulation? Isn’t it possible that autoregulatory vasodilation occurs when venous pressure is raised and that is why flow remains constant?
The nervous system and the eye
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
James A.R. Nicoll, William Stewart, Fiona Roberts
Neurons require a continuous, adequate supply of oxygen and glucose, which depends on cardiorespiratory function and CBF; this is determined by the cerebral perfusion pressure (the difference between the systemic arterial blood pressure and the cerebral venous pressure). An autoregulatory mechanism maintains a relatively constant CBF in spite of changes in perfusion pressure, even when systemic arterial pressure falls as low as 6.65 kPa (50 mm Hg) provided that the patient is in the horizontal position. At arterial pressures lower than this, CBF can fall rapidly. Autoregulation may be impaired in hypertension, hypoxia or hypercapnia, or in many acute conditions producing brain damage, e.g. TBI and stroke.
Neural Control of the Intestinal Circulation and its Interaction With Autoregulation
Published in Irving H. Zucker, Joseph P. Gilmore, Reflex Control of the Circulation, 2020
Gerald A. Meininger, Harris J. Granger
By definition autoregulation is the ability of an organ to maintain a relatively constant blood flow in the presence of changes in perfusion pressure. This is accomplished by intrinsic vascular responses that probably involve a combination of metabolic, myogenic and/or endothelial mechanisms. Whatever the exact cause, evidence has indicated that the mechanisms responsible for intestinal autoregulation of blood flow continue to operate in the presence of neural and humoral vasoconstriction (Meininger and Trzeciakowski, 1988). A consequence of this observation is that a component of the vascular resistance residing in a vascular bed at any given moment will be a function of the autoregulation in that vascular bed. The autoregulatory ability of a vascular bed can be defined by its pressure-flow relationship. From knowledge of the pressure-flow relationship a very simplified view of the interaction is to assume that any change in arterial pressure brought about by the pressor response would cause the normal operating point on the pressure-flow curve to shift along that curve until the point defined by the new arterial pressure is reached. As such a component of the change in vascular resistance will be due to an autoregulatory adjustment to the change in arterial pressure.
Mechanistic links between systemic hypertension and open angle glaucoma
Published in Clinical and Experimental Optometry, 2022
Ying-kun Cui, Li Pan, Tim Lam, Chun-yi Wen, Chi-wai Do
However, under physiological conditions, there is a lack of a linear relationship between ocular perfusion pressure and ocular blood flow.43 This is attributed to the ability of maintaining a relatively constant ocular blood flow despite fluctuating ocular perfusion pressure, which is known as autoregulation.42 Autoregulation is a complicated process and refers to the intrinsic property of organs to maintain a constant blood flow in response to changes in perfusion pressure. It is controlled by both myogenic and metabolic mechanisms. Since the retina has no autonomic innervation, the blood supply to the inner retina is regulated by local vascular mechanisms. In the myogenic mechanism, the smooth muscle cells in the blood vessels contract when being stretched. This process is possibly mediated by activating voltage-gated Ca2+ channels, resulting in an increased vascular resistance due to vasoconstriction.44
A randomized controlled study comparing high-dose insulin to vasopressors or combination therapy in a porcine model of refractory propranolol-induced cardiogenic shock
Published in Clinical Toxicology, 2019
Katherine G. Katzung, Jenna M. Leroy, Sean P. Boley, Samuel J. Stellpflug, Joel S. Holger, Kristin M. Engebretsen
Knowing this, we were surprised to find that by adding NE (a medication known to cause vasoconstriction in end-organ capillary beds) to HDI therapy led to improved brain tissue oxygenation. The reason for this is unclear. The answer may be related to balancing increased perfusion via cerebral microcapillary vasodilation with the autoregulation phenomenon of cerebral perfusion. Autoregulation of cerebral blood flow is the ability of the brain to maintain relatively constant blood flow and as a result, maintain cerebral oxygenation despite changes in cerebral perfusion pressure [22,23]. In humans, literature suggests that cerebral blood flow is maintained provided that the cerebral perfusion pressure is within 50–150 mmHg [24,25]. In refractory PICS, the MAP falls below the lower limit of autoregulation and cerebral ischemia occurs [26]. While insulin may maintain the vasodilation in the brain to avoid microcapillary ischemia, the peripheral vasoconstriction and resultant increased MAP affected by the addition of the vasopressor may better maintain the animal in this range of autoregulation and stave off a drop in cerebral perfusion pressure.
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).