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Clinical Hemorheology and... 2020Microcirculatory shock is a condition defined by the presence of tissue hypoperfusion despite the normalization of systemic and regional blood flow. Currently, more...
Microcirculatory shock is a condition defined by the presence of tissue hypoperfusion despite the normalization of systemic and regional blood flow. Currently, more evidence shows that intrinsic septic shock is microcirculatory shock, which results in septic shock that is difficult to resuscitate. At present, treatments are aimed at recovering macro-circulation functions and include fluid resuscitation, vasoactive drugs, positive inotropic drugs, de-obstruction, and even mechanical assistance to improve oxygen delivery. However, the application of these treatments to more accurately improve microcirculation or avoid further microcirculatory damage is more important in clinics. In this article, we discuss the need for microcirculation protection and microcirculation-guided protection strategies in hemodynamic therapies.
Topics: Fluid Therapy; Hemodynamics; Humans; Microcirculation
PubMed: 31903987
DOI: 10.3233/CH-190784 -
Best Practice & Research. Clinical... Dec 2016The microcirculation is altered in sepsis, and the degree and persistence of these alterations are associated with outcome. When there are significant alterations of the... (Review)
Review
The microcirculation is altered in sepsis, and the degree and persistence of these alterations are associated with outcome. When there are significant alterations of the systemic circulation, as in shock, the microcirculation is always altered. However, sometimes global variables can be restored to normal while the microcirculation remains altered. Monitoring the microcirculation has, therefore, been proposed as a more precise means of assessing the effects of therapy. In this review, we will discuss the limitations of global haemodynamic variables such as mean arterial pressure, cardiac output and mixed venous oxygen saturation as markers of microcirculatory abnormalities. We will also consider how these differences can be revealed during therapy.
Topics: Arterial Pressure; Cardiac Output; Hemodynamics; Humans; Microcirculation; Monitoring, Physiologic
PubMed: 27931643
DOI: 10.1016/j.bpa.2016.10.006 -
Circulation Research Jan 2016The microcirculation is responsible for orchestrating adjustments in vascular tone to match local tissue perfusion with oxygen demand. Beyond this metabolic dilation,... (Review)
Review
The microcirculation is responsible for orchestrating adjustments in vascular tone to match local tissue perfusion with oxygen demand. Beyond this metabolic dilation, the microvasculature plays a critical role in modulating vascular tone by endothelial release of an unusually diverse family of compounds including nitric oxide, other reactive oxygen species, and arachidonic acid metabolites. Animal models have provided excellent insight into mechanisms of vasoregulation in health and disease. However, there are unique aspects of the human microcirculation that serve as the focus of this review. The concept is put forth that vasculoparenchymal communication is multimodal, with vascular release of nitric oxide eliciting dilation and preserving normal parenchymal function by inhibiting inflammation and proliferation. Likewise, in disease or stress, endothelial release of reactive oxygen species mediates both dilation and parenchymal inflammation leading to cellular dysfunction, thrombosis, and fibrosis. Some pathways responsible for this stress-induced shift in mediator of vasodilation are proposed. This paradigm may help explain why microvascular dysfunction is such a powerful predictor of cardiovascular events and help identify new approaches to treatment and prevention.
Topics: Animals; Blood Circulation; Cardiovascular Diseases; Endothelium, Vascular; Humans; Microcirculation; Vasodilation
PubMed: 26837746
DOI: 10.1161/CIRCRESAHA.115.305364 -
Current Cardiology Reviews 2022Invasive assessment of coronary physiology has radically changed the paradigm of myocardial revascularization in patients with coronary artery disease. Despite the... (Review)
Review
Invasive assessment of coronary physiology has radically changed the paradigm of myocardial revascularization in patients with coronary artery disease. Despite the prognostic improvement associated with ischemia-driven revascularization strategy, functional assessment of angiographic intermediate epicardial stenosis remains largely underused in clinical practice. Multiple tools have been developed or are under development in order to reduce the invasiveness, cost, and extra procedural time associated with the invasive assessment of coronary physiology. Besides epicardial stenosis, a growing body of evidence highlights the role of coronary microcirculation in regulating coronary flow with consequent pathophysiological and clinical and prognostic implications. Adequate assessment of coronary microcirculation function and integrity has then become another component of the decision-making algorithm for optimal diagnosis and treatment of coronary syndromes. This review aims at providing a comprehensive description of tools and techniques currently available in the catheterization laboratory to obtain a thorough and complete functional assessment of the entire coronary tree (both for the epicardial and microvascular compartments).
Topics: Coronary Angiography; Coronary Artery Disease; Coronary Stenosis; Fractional Flow Reserve, Myocardial; Humans; Microcirculation; Percutaneous Coronary Intervention
PubMed: 34521331
DOI: 10.2174/1573403X17666210908114154 -
Frontiers in Endocrinology 2021The pancreas is regarded as consisting of two separate organ systems, the endocrine and exocrine pancreas. While treatment of a disease with either an endocrine or... (Review)
Review
The pancreas is regarded as consisting of two separate organ systems, the endocrine and exocrine pancreas. While treatment of a disease with either an endocrine or exocrine pathogenesis may affect the function of the entire pancreas, the pancreatic diseases have been treated by clinicians in different medical disciplines, including endocrinologists and gastroenterologists. Islet microcirculation has long been considered to be regulated independently from that of the exocrine pancreas. A new model proposes that pancreatic islet blood flow is integrated with the surrounding exocrine capillary network. This recent model may provide revived or contrasting hypotheses to test, since the pancreatic microcirculation has critical implications for the regulation of islet hormones as well as acinar pancreas functions. In this mini-review, practical applications of and studies of islet microcirculation are described with a specific emphasis on large-scale data analysis to ensure sufficient sample size accounting for known islet heterogeneity. For small animal studies, intravital microscopy based on two-photon excitation microscopes is a powerful tool that enables capturing the flow direction and speed of individual fluorescent-labeled red blood cells. Complementarily, for structural analysis of blood vessels, the recent technical advancements of confocal microscopy and tissue clearing have enabled us to image the three-dimensional network structure in thick tissue slices.
Topics: Animals; Cytological Techniques; Hemodynamics; Humans; In Vitro Techniques; Islets of Langerhans; Microcirculation; Models, Biological
PubMed: 34040578
DOI: 10.3389/fendo.2021.602620 -
The International Journal of Lower... Jun 2023Dynamic optical coherence tomography (D-OCT) is a relatively new technique that may be used to study the substructures in the retina, in the skin and its... (Review)
Review
Dynamic optical coherence tomography (D-OCT) is a relatively new technique that may be used to study the substructures in the retina, in the skin and its microcirculation. Furthermore, D-OCT is a validated method of imaging blood flow in skin microcirculation. The skin around venous and mixed arterio-venous ulcers was imaged and found to have tortuous vessels assumed to be angiogenic sprouts, and classified as dots, blobs, coils, clumps, lines, and curves. When these images were analyzed and measurements of vessel density were made, it was observed that the prevalence of coils and clumps in wound borders was significantly greater compared with those at wound centers. This reinforced the belief of inward growth of vessels from wound edge toward wound center which, in turn, reposed confidence in following the wound edge to study healing. D-OCT imaging permits the structure and the function of the microcirculation to be imaged, and vessel density measured. This offers a new vista of skin microcirculation and using it, to better understand angiogenesis in chronic wounds.
Topics: Humans; Tomography, Optical Coherence; Skin; Wound Healing; Microcirculation; Veins
PubMed: 33960852
DOI: 10.1177/15347346211017334 -
The Canadian Journal of Cardiology May 2020Large conduit arteries and the microcirculation participate in the mechanisms of elevation of blood pressure (BP). Large vessels play roles predominantly in older... (Review)
Review
Large conduit arteries and the microcirculation participate in the mechanisms of elevation of blood pressure (BP). Large vessels play roles predominantly in older subjects, with stiffening progressing after middle age leading to increases in systolic BP found in most humans with aging. Systolic BP elevation and increased pulsatility penetrate deeper into the distal vasculature, leading to microcirculatory injury, remodelling, and associated endothelial dysfunction. The result is target organ damage in the heart, brain, and kidney. In younger individuals genetically predisposed to high BP, increased salt intake or other exogenous or endogenous risk factors for hypertension, including overweight and excess alcohol intake, lead to enhanced sympathetic activity and vasoconstriction. Enhanced vasoconstrictor responses and myogenic tone become persistent when embedded in an increased extracellular matrix, resulting in remodelling of resistance arteries with a narrowed lumen and increased media-lumen ratio. Stimulation of the renin-angiotensin-aldosterone and endothelin systems and inflammatory and immune activation, to which gut microbiome dysbiosis may contribute as a result of salt intake, also participate in the injury and remodelling of the microcirculation and endothelial dysfunction. Inflammation of perivascular fat and loss of anticontractile factors play roles as well in microvessel remodelling. Exaggerated myogenic tone leads to closure of terminal arterioles, collapse of capillaries and venules, functional rarefaction, and eventually to anatomic rarefaction, compromising tissue perfusion. The remodelling of the microcirculation raises resistance to flow, and accordingly raises BP in a feedback process that over years results in stiffening of conduit arteries and systo-diastolic or predominantly systolic hypertension and, more rarely, predominantly diastolic hypertension. Thus, at different stages of life and the evolution of hypertension, large vessels and the microcirculation interact to contribute to BP elevation.
Topics: Arteries; Blood Pressure; Humans; Hypertension; Microcirculation; Phenotype; Vascular Remodeling; Vascular Stiffness
PubMed: 32389338
DOI: 10.1016/j.cjca.2020.02.003 -
Microcirculation (New York, N.Y. : 1994) Apr 2017Endothelial cells express a diverse array of ion channels including members of the strong inward rectifier family composed of K 2 subunits. These two-membrane spanning... (Review)
Review
Endothelial cells express a diverse array of ion channels including members of the strong inward rectifier family composed of K 2 subunits. These two-membrane spanning domain channels are modulated by their lipid environment, and exist in macromolecular signaling complexes with receptors, protein kinases and other ion channels. Inward rectifier K channel (K ) currents display a region of negative slope conductance at membrane potentials positive to the K equilibrium potential that allows outward current through the channels to be activated by membrane hyperpolarization, permitting K to amplify hyperpolarization induced by other K channels and ion transporters. Increases in extracellular K concentration activate K allowing them to sense extracellular K concentration and transduce this change into membrane hyperpolarization. These properties position K to participate in the mechanism of action of hyperpolarizing vasodilators and contribute to cell-cell conduction of hyperpolarization along the wall of microvessels. The expression of K in capillaries in electrically active tissues may allow K to sense extracellular K , contributing to functional hyperemia. Understanding the regulation of expression and function of microvascular endothelial K will improve our understanding of the control of blood flow in the microcirculation in health and disease and may provide new targets for the development of therapeutics in the future.
Topics: Animals; Endothelium, Vascular; Humans; Membrane Microdomains; Membrane Potentials; Microcirculation; Microvessels; Potassium Channels, Inwardly Rectifying; Protein Subunits; Regional Blood Flow; Signal Transduction
PubMed: 27652592
DOI: 10.1111/micc.12319 -
Transfusion and Apheresis Science :... Dec 2017Early identification of sepsis followed by diagnostic blood cultures and prompt administration of appropriate intravenous antibiotics covering all likely pathogen... (Review)
Review
Early identification of sepsis followed by diagnostic blood cultures and prompt administration of appropriate intravenous antibiotics covering all likely pathogen remains the corner stone in the initial management of sepsis. Source control, obtained by harvesting microbiological cultures and removal or drainage of the infected foci, is mandatory. However, optimization of hemodynamically unstable patients including volume support supplemented with vasopressor, inotropic and transfusion of red blood cells (RBCs) in case of persistent hypoperfusion have the potential to reduce morbidity and mortality. Given the imbalance between the ability of the cardiovascular system to deliver enough oxygen to meet the oxygen demand, transfusion of RBCs should theoretically provide the ideal solution to the challenge. However, both changes in the septic patients' RBCs induced by endogenous factors as well as the storage lesion affecting transfused RBCs have negative effects on the microcirculation. RBC morphology, distribution of fatty acids on the membrane surface, RBC deformability needed for capillary circulation and the nitrogen oxide (NO) signaling systems are involved. Although these deteriorating effects develop during storage, transfusion of fresh RBCs has not proven to be beneficial, possibly due to limitations of the studies performed. Until better evidence exists, transfusion guidelines recommend a restrictive strategy of RBC transfusion i.e. transfuse when hemoglobin (Hb)<7g/dL in septic patients.
Topics: Blood Transfusion; Humans; Microcirculation; Sepsis
PubMed: 29158076
DOI: 10.1016/j.transci.2017.11.020 -
Anesthesia and Analgesia Jan 2021
Review
Topics: Critical Care; Hemodynamics; Humans; Microcirculation; Resuscitation
PubMed: 33177325
DOI: 10.1213/ANE.0000000000005272