The patient with acute neurological problems
Peate Ian, Dutton Helen in Acute Nursing Care, 2020
The cerebral blood vessels and the blood contained within them take up approximately 10 per cent of the space within the skull. Blood vessel diameter affects the amount of space that the blood vessels occupy within the brain. Blood vessels may dilate due to increased blood volume or because of metabolic factors influencing blood vessel tone, for example, pH, PaO2, and PaCO2. Hypoxia, hypercapnia and acidosis cause vasodilation of blood vessels, increasing ICP. The reverse is also true: hypocapnia and alkalosis cause vasoconstriction, reducing cerebral blood flow. As a result of these effects on the cerebral blood vessels, the partial pressure of carbon dioxide in arterial blood gas (PaCO2) is monitored closely and maintained within normal limits between 4.6–6kPa for optimal cerebral blood flow (Carney et al. 2016).
The patient with acute neurological problems
Ian Peate, Helen Dutton in Acute Nursing Care, 2014
The cerebral blood vessels and the blood contained within them take up approximately 10 per cent of the space within the skull. Blood vessel diameter affects the amount of space that the blood vessels occupy within the brain. Blood vessels may dilate due to increased blood volume or because of metabolic factors influencing blood vessel tone, for example, pH, PaO2, and PaCO2. Hypoxia, hyper-capnoea and acidosis cause vasodilation of systemic blood vessels, increasing ICP. The reverse is also true: hypocapnoea and alkalosis cause systemic vasoconstriction, reducing cerebral blood flow. Because of the effects of blood gases on cerebral blood vessels it is normal practice to control blood gases within strict limits in order to control ICP.
Neuronal Mechanisms of Cutaneous Blood Flow
Geoffrey Burnstock, Susan G. Griffith in Nonadrenergic Innervation of Blood Vessels, 2019
Among the neuropeptides involved in the regulation of the blood vessel tone, SP has been investigated in most detail. It is present in approximately 30 regions of the mammalian central nervous system and in the intestinal tract (for review see References 21 and 22). It also occurs in a certain group of nonmyelinated sensory nerve fibers which are involved in the control of cutaneous blood vessels. Like all primary sensory neurons, these SP-containing neurons are pseudounipolar neurons; their perikarya lie in the spinal ganglia23 or in corresponding ganglia of the cranial nerves.24 As nociceptive impulses are transmitted via the central endings of SP neurons in the brain, they are classified as pain fibers. Release of SP from the central endings of these neurons is an important link in the “damage report” to the brain.25
High beat-to-beat blood pressure variability in atrial fibrillation compared to sinus rhythm
Published in Blood Pressure, 2018
Joakim Olbers, Adam Gille, Petter Ljungman, Mårten Rosenqvist, Jan Östergren, Nils Witt
Blood pressure and blood pressure variability is influenced by several different factors and has been studied extensively in regular sinus rhythm. Respiration, heart rate variability, cardiac output, total peripheral resistance and the autonomous nervous system interact in an intricate manner and influences the physiological fluctuation in BP [6–8]. Vascular resistance is a major determinant of blood pressure [9] and an irregular heart rhythm leading to increased beat-to-beat BP variability may have an influence on vascular tone. It has been previously shown that irregular atrial pacing simulating AF leads to a 70% increase in sympathetic nerve activity (SNA) as compared to regular pacing [10]. A higher degree of irregularity in pacing correlated with higher SNA [11]. The increase in SNA is thought to be mediated through arterial baroreflexes [10]. Hypothetically, the large fluctuation in BP that we observed in AF contributes to a physiological response with increased SNA leading to variable changes in vascular tone. The sympathetic nervous system plays a fundamental role in both short-term and long-term regulation of the cardiovascular system [9]. In the short-term it mainly acts by inducing vasoconstriction through increased sympathetic neural activity [9]. In the long-term, increased SNA may hypothetically provide a link between AF and myocardial ischemia [12]. Adding further complexity, irregular rhythm has been shown to result in rate-independent depression of left ventricular function [13], possibly affecting stroke volume and BP.
The effects of particle size, shape, density and flow characteristics on particle margination to vascular walls in cardiovascular diseases
Published in Expert Opinion on Drug Delivery, 2018
Hang T. Ta, Nghia P. Truong, Andrew K. Whittaker, Thomas P. Davis, Karlheinz Peter
The blood flow pattern changes during the development of atherosclerosis [33]. Understanding blood flow is important for the design and engineering of an optimally targeted vascular nanoparticle for atherosclerosis. The extent of blood flow within a vessel is directly proportional to pressure gradients and inversely proportional to vascular resistance. Small changes in vessel diameter due to a growing atherosclerotic plaque can lead to substantial changes in vascular resistance, thus changing the flow pattern significantly. Blood flow is known to have a laminar pattern characterized by a parabolic flow profile (Figure 1, left and right) [33,34]. When blood flow transitions from a laminar, parabolic flow to a turbulent flow, the blood flows across the vessel (no longer along it), and vortices are formed which significantly increase the overall flow resistance (Figure 1, middle). Turbulent/recirculating flow, a direct function of blood velocity and inversely related to viscosity, occurs when there are changes in the structure of a vessel, such as an obstruction (Figure 1, middle), a sharp turn, or a rough surface [35,36]. In laminar flow, the wall shear stress is high while in disturbed flow it is lower. The areas of the vasculature prone to developing atherosclerotic changes tend to be large vessels and exhibit disturbed blood flow profiles [37], including high pulsatility (regulated by the cardiac cycle), low net shear due to reverse flow, and recirculation eddies near areas of bifurcation or high curvature [38].
Doppler ultrasonography of the ophthalmic artery in perimenopausal and postmenopausal women: a new approach
Published in Climacteric, 2020
A. L. P. Saramago, A. L. D. Diniz
One of the ways to assess the behavior of blood vessels in the body and their alterations is through the Doppler study of blood flow, which quantifies the impedance and vascular resistance as well as the speed of blood displacement in most vascular territories. An example is the ophthalmic artery (OA), one of the orbital vessels. Doppler velocimetry of the orbital vessel has been described in the literature for over 30 years and is feasible and reproducible8,9. Probably, under normal conditions, what happens in this vascular territory may be partly extrapolated to other cerebral vascular territories, due to the shared anatomical characteristics, given that they are direct and indirect branches of the internal carotid artery10,11. The focus of the present study was to value assessment of the flow velocity waveform (FVW) of the OA as a means of quantifying the possible hemodynamic effects caused by HT. This could be an important pillar for the study of the action of new drugs during this perimenopause period.
Related Knowledge Centers
- Blood Pressure
- Pulmonary Circulation
- Central Venous Pressure
- Circulatory System
- Blood
- Cardiac Output
- Hemodynamics
- Mean Arterial Pressure
- Vasodilation
- Vasoconstriction