Leptomeningeal collateral vessels allow limited cerebral blood flow and brain tissue perfusion when the brain receives insufficient blood supply through an artery, via a series of anastomotic connections between cerebral arteries.
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As of 2004 there was some controversy surrounding the mechanism of dopexamine. Some held that its local effects of increased tissue perfusion were due only to increased output from the heart, while others held that were direct peripheral effects.
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The oxygen saturation of haemoglobin in the tissue (StO2) can provide information about tissue perfusion. A vascular occlusion test (VOT) can be employed to assess microvascular function. Common sites for peripheral NIRS monitoring include the thenar eminence, forearm and calf muscles.
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Using a larger sample means it takes longer for the fixative to reach the deeper tissue. Perfusion: Fixation via blood flow. The fixative is injected into the heart with the injection volume matching cardiac output. The fixative spreads through the entire body, and the tissue doesn't die until it is fixed.
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The cranium encloses a fixed- volume space that holds three components: blood, cerebrospinal fluid (CSF), and very soft tissue (the brain). While both the blood and CSF have poor compression capacity, the brain is easily compressible. Every increase of ICP can cause a change in tissue perfusion and an increase in stroke events.
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In addition to these blood vessels, the microcirculation also includes lymphatic capillaries and collecting ducts. The main functions of the microcirculation are the delivery of oxygen and nutrients and the removal of carbon dioxide (CO2). It also serves to regulate blood flow and tissue perfusion thereby affecting blood pressure and responses to inflammation which can include edema (swelling).
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The regulation of tissue perfusion occurs in microcirculation. There, arterioles control the flow of blood to the capillaries. Arterioles contract and relax, varying their diameter and vascular tone, as the vascular smooth muscle responds to diverse stimuli. Distension of the vessels due to increased blood pressure is a fundamental stimulus for muscle contraction in arteriolar walls.
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Treatment of HHS begins with reestablishing tissue perfusion using intravenous fluids. People with HHS can be dehydrated by 8 to 12 liters. Attempts to correct this usually take place over 24 hours with initial rates of normal saline often in the range of 1 L/h for the first few hours or until the condition stabilizes.
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As far as introducing the different liquidized chemicals and enzymes to an organ or tissue, perfusion and immersion decellularization techniques have been used. Perfusion decellularization is applicable when an extensive vasculature system is present in the organ or tissue. It is crucial for the ECM scaffold to be decellularized at all levels, and evenly throughout the structure.
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Thumbnail of the right hand with cuticle (left) and hangnail (top) Healthcare and pre-hospital-care providers (EMTs or paramedics) often use the fingernail beds as a cursory indicator of distal tissue perfusion of individuals who may be dehydrated or in shock.Monterey County EMS Manual . Chapter XI, Patient assessment. However, this test is not considered reliable in adults.
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Leukostasis (also called symptomatic hyperleukocytosis) is a medical emergency most commonly seen in patients with acute myeloid leukemia. It is characterized by an extremely elevated blast cell count and symptoms of decreased tissue perfusion. The pathophysiology of leukostasis is not well understood, but inadequate delivery of oxygen to the body's cells is the end result. Leukostasis is diagnosed when white cell plugs are seen in the microvasculature.
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A syringe pump for laboratory use. World Precision Instruments (WPI) SP120PZ. A syringe driver or syringe pump is a small infusion pump (some include infuse and withdraw capability), used to gradually administer small amounts of fluid (with or without medication) to a patient or for use in chemical and biomedical research. Applications include electrospinning, electrospraying, microdialysis, microfluidics, dispensing/dilution, organ/tissue perfusion and fluid circulation.
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The slowed AV node gives the ventricles more time to fill before contracting. This negative chronotropic effect is synergistic with the direct effect on cardiac pacemaker cells. The arrhythmia itself is not affected, but the pumping function of the heart improves, owing to improved filling. Overall, the heart rate is decreased while stroke volume is increased, resulting in a net increase in blood pressure, leading to increased tissue perfusion.
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In those with poor tissue perfusion, boluses of isotonic crystalloid solution should be given. In children with more than 10–20% TBSA burns, and adults with more than 15% TBSA burns, formal fluid resuscitation and monitoring should follow. This should be begun pre-hospital if possible in those with burns greater than 25% TBSA. The Parkland formula can help determine the volume of intravenous fluids required over the first 24 hours.
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For coronary artery disease (ischemic heart disease), coronary artery bypass surgery and percutaneous coronary intervention (coronary balloon angioplasty) are the two primary means of revascularization. When those cannot be done, transmyocardial revascularization or percutaneous myocardial revascularization, done with a laser, may be an option. Treatment for gangrene often requires revascularization, if possible. The surgery is also indicated to treat ischemic wounds (inadequate tissue perfusion) in some forms of chronic wounds, such as diabetic ulcers.
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On a day-to-day basis a critical care nurse will commonly, "perform assessments of critical conditions, give intensive and intervention, advocate for their patients, and operate/maintain life support systems which include mechanical ventilation via endotracheal, tracheal, or nasotracheal intubation, and titration of continuous vasoactive intravenous medications in order to maintain a " mean arterial pressure that ensures adequate organ and tissue perfusion."Critical Care Nurse." DiscoverNursing.com. Johnson & Johnson Services, 3 Jan. 2013. Web.
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The cause of inadequate tissue perfusion (blood delivery to tissues) in distributive shock is a lack of normal responsiveness of blood vessels to vasoconstrictive agents and direct vasodilation. There are four types of distributive shock. The most common, septic shock, is caused by an infection, most frequently by bacteria, but viruses, fungi and parasites have been implicated. Infection sites most likely to lead to septic shock are chest, abdomen and genitourinary tract.
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For patients in hypovolemic shock due to fluid losses, the exact fluid deficit cannot be determined. Therefore, it is prudent to start with 2 liters of isotonic crystalloid solution infused rapidly as an attempt to quickly restore tissue perfusion. Fluid repletion can be monitored by measuring blood pressure, urine output, mental status, and peripheral edema. Multiple modalities exist for measuring fluid responsiveness such as ultrasound, central venous pressure monitoring, and pulse pressure fluctuation as described above.
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Mucosal PCO2 is presumed to be proportional at equilibrium and mucosal pH is calculated. PO2 and luminal pH play no role in these calculations. Proponents of this technique maintain that it is a relatively inexpensive noninvasive, tissue-specific method to evaluate the adequacy of tissue perfusion. It is of special value when used in the gastric lumen because splanchnic circulation is one of the vascular beds that is subject to early blood flow redistribution in shock states.
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Hemoglobin plays a substantial role in carrying oxygen throughout the body, and when it is deficient, anemia can result, causing 'anaemic hypoxia' if tissue perfusion is decreased. Iron deficiency is the most common cause of anemia. As iron is used in the synthesis of hemoglobin, less hemoglobin will be synthesised when there is less iron, due to insufficient intake, or poor absorption. Anemia is typically a chronic process that is compensated over time by increased levels of red blood cells via upregulated erythropoetin.
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Prolonged permissive hypotension can lead to aggravated post-injury coagulopathy (coagulation dysfunction), ischemic damage secondary to poor tissue perfusion including the brain, mitochondrial dysfunction, and lactic acidosis among others. It is also possible that other substances, such as estrogen (17 beta-estradiol) could allow for longer models of permissive hypotension. In a rat model of hemorrhagic shock, estrogen was able to reduce some of the negative effects of prolonged permissive hypotension as well as prolong long-term survival.Kozlov AV, et al.
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Critics of the technique caution that while directly measured factors are usually accurate and calculated factors correspondingly reliable, the assumption that gut mucosal pH alterations are uniquely a function of mucosal hypoxia is not. Tonometry may adequately reflect the degree of tissue perfusion, but its accuracy as an index of tissue oxygenation is less reliable. The measurement of gut mucosal carbon dioxide has been used to detect decreased blood flow. Accumulation of carbon dioxide is predominantly a result of hypoperfusion and not hypoxia.
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Septic shock is a subclass of distributive shock, a condition in which abnormal distribution of blood flow in the smallest blood vessels results in inadequate blood supply to the body tissues, resulting in ischemia and organ dysfunction. Septic shock refers specifically to distributive shock due to sepsis as a result of infection. Septic shock may be defined as sepsis-induced low blood pressure that persists despite treatment with intravenous fluids. Low blood pressure reduces tissue perfusion pressure, causing the tissue hypoxia that is characteristic of shock.
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In case of cardiogenic shock or acute hemorrhagic shock resulted from heart failure or from a large volume of blood loss, respectively, body deals with which by constricting peripheral vessels for the sake of reversing low arterial pressure that causes inadequate tissue perfusion. Nevertheless, in vasodilatory shock, peripheral vascular smooth muscle finds it difficult to constrict. In refractory vasodilatory shock, peripheral vascular smooth muscle even finds itself poorly respond to therapy with vasopressor drugs. Vasopressin deficiency may play an important role in vasodilatory shock.
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Hemorheology, also spelled haemorheology (from the Greek ‘αἷμα, haima "blood" and rheology [from Greek ῥέω rhéō, "flow" and -λoγία, -logia, "study of"]), or blood rheology, is the study of flow properties of blood and its elements of plasma and cells. Proper tissue perfusion can occur only when blood's rheological properties are within certain levels. Alterations of these properties play significant roles in disease processes. Blood viscosity is determined by plasma viscosity, hematocrit (volume fraction of red blood cell, which constitute 99.9% of the cellular elements) and mechanical properties of red blood cells.
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Gastric tonometry describes the measurement of the carbon dioxide level inside the stomach in order to assess the degree of blood flow to the stomach and bowel. Gastric tonometry has been introduced as a novel method of monitoring tissue perfusion in critically ill patients. Tonometry is based on the principle that at equilibrium the partial pressure of a diffusible gas such as CO2 is the same in both the wall and lumen of a viscus. The technique therefore can estimate gut mucosal PCO2 by measuring gut luminal PCO2 at equilibrium.
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Leukocytes may be normal, increased, or decreased. PCV and total protein are usually both increased due to fluid loss, and the horse displays a prerenal azotemia. On the chemistry panel, liver enzymes such as GGT, ALP, AST are increased, likely due to ascending infection from the common bile duct, endotoxin absorption, and hypoperfusion. A metabolic acidosis with a high anion gap is often seen due to loss of bicarbonate in gastric reflux and an increase in lactic acid in the blood, secondary to hypovolemia and decreased tissue perfusion.
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The main functions of the microcirculation are the delivery of oxygen and nutrients and the removal of carbon dioxide (CO2). It also serves to regulate blood flow and tissue perfusion thereby affecting blood pressure and responses to inflammation which can include edema (swelling). Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes. The endothelium provides a smooth surface for the flow of blood and regulates the movement of water and dissolved materials in the interstitial plasma between the blood and the tissues.
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With a broader understanding of the pathophysiology of hemorrhagic shock, treatment in trauma has expanded from a simple massive transfusion method to a more comprehensive management strategy of "damage control resuscitation". The concept of damage control resuscitation focuses on permissive hypotension, hemostatic resuscitation, and hemorrhage control to adequately treat the "lethal triad" of coagulopathy, acidosis, and hypothermia that occurs in trauma. Hypotensive resuscitation has been suggested for the hemorrhagic shock patient without head trauma. The aim is to achieve a systolic blood pressure of 90 mmHg in order to maintain tissue perfusion without inducing re-bleeding from recently clotted vessels.
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Because the introduction of a nasogastric tube is almost routine in critically ill patients, the measurement of gastric carbon dioxide can be an easy method to monitor tissue perfusion. The gastric mucosal pH is measured according to an equation that assumes that arterial bicarbonate is equal to intramucosal bicarbonate, an argument that is not always valid. Given that the gastric mucosal carbon dioxide is the directly measured value, whereas the gastric mucosal pH is the derived and possibly inaccurate value, studies that used gastric pH to monitor perfusion may be inherently flawed. Most studies have failed to effectively affect gastric pH and for this reason failed to produce improvements in outcome.
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This adaptation may malfunction: too small a diameter of the resistance vessels relates to insufficient tissue perfusion as well as hypertension. The vascular wall consists of amongst others the vascular smooth muscle cells, endothelial cells that line the lumen, and elastic fibers and other extracellular matrix elements. Physical forces form an important part of the adaptation mechanisms of small arteries: Blood pressure causes distension of the matrix elements, but also induces contraction of the smooth muscle cells and production of more cells and more matrix. Blood flow is sensed by the endothelial cells, which release factors such as nitric oxide that cause relaxation and remodeling towards larger diameters.
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Leukocytes Symptomatic Hyperleukocytosis (Leukostasis) is defined by a tremendously high blast cell count along with symptoms of decreased tissue perfusion. Leukostasis is associated with people who suffer from bone and blood disorders and is very common among people suffering from acute myeloid leukemia or chronic myeloid leukemia. Leukostasis is a pathologic diagnosis that inhibits efficient flow to the microvasculature of the body. Continued and untreated leukostasis presents respiratory and neurological distress simultaneously and is a medical emergency, with untreated patient mortality rates reaching a minimum of 20 and a maximum of 40 percent.. A leukemia blood cell count greater than 50 x 10^9/ L (50,000 / microL) or 100 x 10^9 L / (100,000/ microL) signifies hyperleuckocytosis.
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Because cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important component of how efficiently the heart can meet the body's demands for the maintenance of adequate tissue perfusion. Body tissues require continuous oxygen delivery which requires the sustained transport of oxygen to the tissues by the systemic circulation of oxygenated blood at an adequate pressure from the left ventricle of the heart via the aorta and arteries. Oxygen delivery (DO2 mls/min) is the resultant of blood flow (cardiac output CO) times the blood oxygen content (CaO2). Mathematically this is calculated as follows: Oxygen delivery = cardiac output × arterial oxygen content DO2 = CO × CaO2.
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With more detailed observations and information on fetal tissue perfusion and metabolism, better predictions on development can be made. For pregnancies in which genetic abnormalities may be present, PUBS can be used to construct a karyotype, usually within 48 hours, and detect irregular chromosomal patterns. Karyotypes are able to confirm or detect monosomies, trisomies, or missing portions of chromosomes to give a detailed picture of the severity of the genetic defect as well as predicting developmental future. PUBS is also indicated in the cases of twins with accumulation of amniotic fluid and substantially different growth rates (at least 10%), if the fetus is expected to be breaking down red blood cells improperly, and in the alleviation of hydrops fetalis, a build-up of fluid in at least 2 parts of the fetus.
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No particular ventilator mode is known to improve mortality in acute respiratory distress syndrome (ARDS). Some practitioners favor airway pressure release ventilation when treating ARDS. Well documented advantages to APRV ventilation include decreased airway pressures, decreased minute ventilation, decreased dead-space ventilation, promotion of spontaneous breathing, almost 24-hour-a-day alveolar recruitment, decreased use of sedation, near elimination of neuromuscular blockade, optimized arterial blood gas results, mechanical restoration of FRC (functional residual capacity), a positive effect on cardiac output (due to the negative inflection from the elevated baseline with each spontaneous breath), increased organ and tissue perfusion and potential for increased urine output secondary to increased kidney perfusion. A patient with ARDS, on average, spends between 8 and 11 days on a mechanical ventilator; APRV may reduce this time significantly and thus may conserve valuable resources.
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Pre-shock is also known as compensated shock, or cryptic shock describes the state in which the human body is still capable of offsetting the abnormally reduced tissue perfusion by exerting compensatory mechanism. For instance, in a solely hypovolemia without formally entering shock state, the body is able to constrict peripheral vessels, accelerate heart rate, and boost myocardial contractility to compensate for the negative impacts out of a certain percentage reduction in total effective arterial blood volume. Thus, the person, particularly for those non-elderly who have higher physical reserve, might not be symptomatic of such blood loss accounted for certain amount of total blood volume in the body and might even manifest a normal systolic pressure as well as diastolic pressure. Taken together, tachycardia, a modest change in overall blood pressure in either trend—increase or decrease--, or hyperlactatemia that is not deemed to be moderate to severe, are the likely only early signs of clinical shock.
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