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Specialized Circulations in Susceptible Tissues
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
In this situation, issues of mean flow and the “brain in a box” assume high importance. By compressing blood vessels, elevated intracranial pressures will increase resistance and reduce mean cerebral blood flow unless mean blood pressure is elevated (Kolias et al., 2016; Godoy et al., 2018). Harvey Cushing (1901) was the first to study this. He described how acute major cerebral lesions cause elevated arterial pressure and regarded this as compensatory, i.e. essential to maintain cerebral blood flow. Cushing’s work formed the basis of views still current in many places that elevated blood pressure in patients with stroke should not be treated. (“Essential” hypertension supposedly required high blood pressure for adequate tissue perfusion.) Compression of vessels is inevitable when the brain cannot expand. Compression of blood vessels in the brain will only intensify the problems already described in the cerebral micro-vasculature, since narrowing of these vessels increases flow pulsations and reduces mean flow at the same time.
Cardiovascular, Hemodynamic, and Critical Care Considerations in the Patient With Necrotizing Enterocolitis
Published in David J. Hackam, Necrotizing Enterocolitis, 2021
Christine C. Pazandak, Zachary A. Vesoulis, Misty Good
The medication choices for hypotension should be driven by the underlying pathophysiology. Poor tissue perfusion may result from poor cardiac contractility, inadequate ventricular filling, intravascular volume depletion (from acute blood loss or capillary leak), or inadequate response to catecholamines (adrenal insufficiency). Sufficient investigation should be undertaken to determine the underlying cause(s) for the hypotension in order to tailor the management strategy to the specific patient. Interventions might include parenteral fluid, inotropic or chronotropic agents, and corticosteroids.
Integrated Cardiovascular Responses
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Septic shock is a severe vascular disturbance in response to bacteraemia. Toxins from the infective agents (usually Gram negative bacteria and sometimes Gram positive bacteria, fungi and viruses) release mediators from cells of the immune and vascular systems. These mediators cause generalized vasodilatation with increased vascular permeability and myocardial depression (Table 32.4). This leads to hypotension and poor tissue perfusion and hypoxia. Hypoxia and mediators released by hypoxia cause capillary damage which leads to further leakage and worsening the hypovolaemia. The roles of the mediators implicated in septic shock are summarized in Table 32.3. Prostaglandins and leukotrienes released from activated neutrophils, mast cells, platelets and many other cells increase vascular permeability, leading to oedema, and cause a reduction in circulating volume. They also activate leukocytes which release mediators that cause pulmonary vasoconstriction which exacerbates hypoxia.
Phases of fluid management and the roles of human albumin solution in perioperative and critically ill patients
Published in Current Medical Research and Opinion, 2020
Giving fluid therapy to restore and maintain tissue perfusion is standard practice for patients with critical illness or those undergoing surgery1. Significant risks of fluid therapies are related to under- or over-administration, as well as their pharmacological side effects. Every day, more than 20% of patients in intensive care units (ICUs) are treated with intravenous fluids; more than 30% receive fluids for volume resuscitation on day 12. In the past, colloid solutions have been used more frequently than crystalloid solutions for volume resuscitation; however, colloids cost more and some are potentially harmful3. Today, more crystalloid solutions are used, often buffered solutions instead of saline, and solutions of the natural colloid albumin are favored over synthetic colloid solutions, particularly hydroxyethyl starch (HES)4–7.
Retinal Tissue Perfusion in Patients with Multiple Sclerosis
Published in Current Eye Research, 2019
Yi Liu, Silvia Delgado, Hong Jiang, Ying Lin, Jeffrey Hernandez, Yuqing Deng, Giovana Rosa Gameiro, Jianhua Wang
As the decreased tissue thickness resulting from retinal neurodegeneration in patients with MS may change the demand for blood flow, it remains unknown whether the decreased blood flow is a consequence of the decreased tissue volume. Tissue perfusion is important in maintaining the organ function and is defined as a certain blood volume flowing through a given tissue volume over a period of time.5,38 Retinal blood flow in the macula can be measured and decreased retinal blood flow under diseased conditions has been reported.20,39 In addition, macular tissue volume can be readily measured using optical coherence tomography.40–42 With both the blood flow and perfused tissue volume available, retinal tissue perfusion (RTP) can be calculated as the blood flow divided by the tissue volume which the blood flow perfuses.43 We hypothesize that retinal hypoperfusion occurs in MS. The goal of the present study was to determine the RTP in patients with MS.
A systematic review of diagnostic techniques to determine tissue perfusion in patients with peripheral arterial disease
Published in Expert Review of Medical Devices, 2019
Kirsten F. Ma, Simone F. Kleiss, Richte C.L. Schuurmann, Reinoud P.H. Bokkers, Çagdas Ünlü, Jean-Paul P.M. De Vries
Study details were extracted from the articles using a predefined abstract form and categorized according to diagnostic tests for measuring tissue perfusion. The following data were extracted: study design, number of patients and healthy controls, the method of assessing PAD, characteristics of the measurement protocol, and outcome. The outcome of interest was the differences in tissue perfusion between PAD patients and healthy controls. The technical properties and clinical application within PAD are described for each technique. Statistical comparison and accuracy of the diagnostic techniques was scored if available in the included studies. Data were collected using Review Manager 5.3. software (The Nordic Cochrane Centre, the Cochrane Collaboration, 2014, Copenhagen, Denmark). Quality assessment of the studies was performed according to the Quality Assessment of Diagnostic Accuracy studies (QUADAS-2) method [9].