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Ischemia
Ischemia
or ischaemia is a restriction in blood supply to tissues, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive).[3] Ischemia
Ischemia
is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue. It also means local anemia in a given part of a body sometimes resulting from congestion (such as vasoconstriction, thrombosis or embolism). Ischemia
Ischemia
comprises not only insufficiency of oxygen, but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia
Ischemia
can be partial (poor perfusion) or total.

Contents

1 Signs and symptoms

1.1 Cardiac ischemia 1.2 Bowel 1.3 Brain 1.4 Limb 1.5 Cutaneous

2 Causes

2.1 Occlusion 2.2 Trauma 2.3 Other

3 Pathophysiology 4 Treatment 5 Society and culture 6 Etymology and pronunciation 7 See also 8 References 9 Bibliography

Signs and symptoms[edit] Since oxygen is carried to tissues in the blood, insufficient blood supply causes tissue to become starved of oxygen. In the highly metabolically active tissues of the heart and brain, irreversible damage to tissues can occur in as little as 3–4 minutes at body temperature. The kidneys are also quickly damaged by loss of blood flow (renal ischemia). Tissues with slower metabolic rates may undergo irreversible damage after 20 minutes. Clinical manifestations of acute limb ischemia (which can be summarized as the "six P's") include pain, pallor, pulseless, paresthesia, paralysis, and poikilothermia.[4] Without immediate intervention, ischemia may progress quickly to tissue necrosis and gangrene within a few hours. Paralysis is a very late sign of acute arterial ischemia and signals the death of nerves supplying the extremity. Foot drop
Foot drop
may occur as a result of nerve damage. Because nerves are extremely sensitive to hypoxia, limb paralysis or ischemic neuropathy may persist after revascularization and may be permanent.[5] Cardiac ischemia[edit] See also: Myocardial infarction Cardiac ischemia may be asymptomatic or may cause chest pain, known as angina pectoris. It occurs when the heart muscle, or myocardium, receives insufficient blood flow. This most frequently results from atherosclerosis, which is the long-term accumulation of cholesterol-rich plaques in the coronary arteries. Ischemic heart disease is the most common cause of death in most Western countries and a major cause of hospital admissions.[6] Bowel[edit] Both large and small bowel can be affected by ischemia. Ischemia
Ischemia
of the large intestine may result in an inflammatory process known as ischemic colitis. Ischemia
Ischemia
of the small bowel is called mesenteric ischemia. Brain[edit] Main article: Stroke Brain
Brain
ischemia is insufficient blood flow to the brain, and can be acute or chronic. Acute ischemic stroke is a neurologic emergency that may be reversible if treated rapidly. Chronic ischemia of the brain may result in a form of dementia called vascular dementia. A brief episode of ischemia affecting the brain is called a transient ischemic attack (TIA) often called a mini-stroke. Limb[edit] Main article: Acute limb ischaemia Lack of blood flow to a limb results in acute limb ischemia. Cutaneous[edit] See also: Cyanosis
Cyanosis
and Gangrene Reduced blood flow to the skin layers may result in mottling or uneven, patchy discoloration of the skin Causes[edit] Ischemia
Ischemia
is a vascular disease involving an interruption in the arterial blood supply to a tissue, organ, or extremity that, if untreated, can lead to tissue death. It can be caused by embolism, thrombosis of an atherosclerotic artery, or trauma. Venous
Venous
problems like venous outflow obstruction and low-flow states can cause acute arterial ischemia. An aneurysm is one of the most frequent causes of acute arterial ischemia. Other causes are heart conditions including myocardial infarction, mitral valve disease, chronic atrial fibrillation, cardiomyopathies, and prosthesis, in all of which thrombi are prone to develop.[5] Occlusion[edit] The thrombi may dislodge and may travel anywhere in the circulatory system, where they may lead to pulmonary embolus, an acute arterial occlusion causing the oxygen and blood supply distal to the embolus to decrease suddenly. The degree and extent of symptoms depend on the size and location of the obstruction, the occurrence of clot fragmentation with embolism to smaller vessels, and the degree of peripheral arterial disease (PAD).[5]

Thromboembolism
Thromboembolism
(blood clots) Embolism (foreign bodies in the circulation, e.g. amniotic fluid embolism)

Trauma[edit] Traumatic injury
Traumatic injury
to an extremity may produce partial or total occlusion of a vessel from compression, shearing, or laceration. Acute arterial occlusion may develop as a result of arterial dissection in the carotid artery or aorta or as a result of iatrogenic arterial injury (e.g., after angiography).[5] Other[edit] An inadequate flow of blood to a part of the body may be caused by any of the following:

Thoracic outlet syndrome
Thoracic outlet syndrome
(compression of the brachial plexus) Atherosclerosis
Atherosclerosis
(lipid-laden plaques obstructing the lumen of arteries) Hypoglycemia
Hypoglycemia
(lower than normal level of glucose) Tachycardia
Tachycardia
(abnormally rapid beating of the heart) Radiotherapy Hypotension (low blood pressure, e.g. in septic shock, heart failure) Outside compression of a blood vessel, e.g. by a tumor or in the case of superior mesenteric artery syndrome Sickle cell disease
Sickle cell disease
(abnormally shaped red blood cells) Induced g-forces which restrict the blood flow and force the blood to the extremities of the body, as in acrobatics and military flying Localized extreme cold, such as by frostbite or improper cold compression therapy Tourniquet
Tourniquet
application An increased level of glutamate receptor stimulation[citation needed] Arteriovenous malformations, and peripheral artery occlusive disease rupture of significant blood vessels supplying a tissue or organ. Anemia
Anemia
vasoconstricts the periphery so that red blood cells can work internally on vital organs such as the heart, brain, etc., thus causing lack of oxygen to the periphery. Premature discontinuation of any oral anticoagulant. Unconsciousness, such as due to the ingestion of excessive doses of central depressants like alcohol or opioids, can result in ischemia of the extremities due to unusual body positions that prevent normal circulation

Pathophysiology[edit]

Native records of contractile activity of the left ventricle of isolated rat heart perfused under Langendorff technique. Curve A - contractile function of the heart is greatly depressed after ischemia-reperfusion. Curve B - a set of short ischemic episodes (ischemic preconditioning) before prolonged ischemia provides functional recovery of contractile activity of the heart at reperfusion.

Main article: Ischemic cascade Ischemia
Ischemia
results in tissue damage in a process known as ischemic cascade. The damage is the result of the build-up of metabolic waste products, inability to maintain cell membranes, mitochondrial damage, and eventual leakage of autolyzing proteolytic enzymes into the cell and surrounding tissues. Restoration of blood supply to ischemic tissues can cause additional damage known as reperfusion injury that can be more damaging than the initial ischemia. Reintroduction of blood flow brings oxygen back to the tissues, causing a greater production of free radicals and reactive oxygen species that damage cells. It also brings more calcium ions to the tissues causing further calcium overloading and can result in potentially fatal cardiac arrhythmias and also accelerates cellular self-destruction. The restored blood flow also exaggerates the inflammation response of damaged tissues, causing white blood cells to destroy damaged cells that may otherwise still be viable.[7] Treatment[edit] Early treatment is essential to keep the affected limb viable. The treatment options include injection of an anticoagulant, thrombolysis, embolectomy, surgical revascularisation, or amputation. Anticoagulant therapy is initiated to prevent further enlargement of the thrombus. Continuous IV unfractionated heparin has been the traditional agent of choice.[5] If the condition of the ischemic limb is stabilized with anticoagulation, recently formed emboli may be treated with catheter-directed thrombolysis using intraarterial infusion of a thrombolytic agent (e.g., recombinant tissue plasminogen activator (tPA), streptokinase, or urokinase). A percutaneous catheter inserted into the femoral artery and threaded to the site of the clot is used to infuse the drug. Unlike anticoagulants, thrombolytic agents work directly to resolve the clot over a period of 24 to 48 hours.[5] Direct arteriotomy may be necessary to remove the clot. Surgical revascularization may be used in the setting of trauma (e.g., laceration of the artery). Amputation
Amputation
is reserved for cases where limb salvage is not possible. If the patient continues to have a risk of further embolization from some persistent source, such as chronic atrial fibrillation, treatment includes long-term oral anticoagulation to prevent further acute arterial ischemic episodes.[5] Decrease in body temperature reduces the aerobic metabolic rate of the affected cells, reducing the immediate effects of hypoxia. Reduction of body temperature also reduces the inflammation response and reperfusion injury. For frostbite injuries, limiting thawing and warming of tissues until warmer temperatures can be sustained may reduce reperfusion injury. Society and culture[edit] The Infarct Combat Project (ICP) is an international nonprofit organization founded in 1998 to fight ischemic heart diseases through education and research.[8] Etymology and pronunciation[edit] The word ischemia (/ɪsˈkiːmiə/) is from Greek ἴσχαιμος iskhaimos, "staunching blood" from ἴσχω iskhο, "keep back, restrain" and αἷμα haima, "blood". See also[edit]

Infarction Inhibitor protein Trauma triad of death Ischemia-reperfusion injury of the appendicular musculoskeletal system

References[edit]

^ OED
OED
2nd edition, 1989. ^ Entry "ischemia" in Merriam-Webster Online Dictionary. ^ Merck & Co. Occlusive Peripheral Arterial Disease, The Merck Manual Home Health Handbook website, revised and updated March 2010. Retrieved March 4, 2012. ^ Vascular and Interventional Radiology: The Requisites (2nd Edition), John A. Kaufman & Michael J. Lee, Publisher:Elsevier - Active as of 11/13/2014 ^ a b c d e f g Lewis. S.L (2008). Medical-Surgical Nursing (7th ed.). Vascular disorder. pp. 907–908. ^ World Health Organization Department of Health Statistics and Informatics in the Information, Evidence and Research Cluster (2004). The global burden of disease 2004 update. Geneva: WHO. ISBN 92-4-156371-0.  ^ Sims N.R.; Muyderman H. (2010). "Mitochondria, oxidative metabolism and cell death in stroke". Biochimica et Biophysica Acta. 1802 (1): 80–91. doi:10.1016/j.bbadis.2009.09.003. PMID 19751827.  ^ Infarct Combat Project website; accessed October 26, 2015.

Bibliography[edit]

Elizabeth (editor). Oxford Reference: Concise Medical Dictionary (1990, 3rd ed.). Oxford University Press: Market House Books, 1987, 2nd ed., pg. 107, ISBN 0-19-281991-7, ISBN 978-0-19-281991-8

v t e

Pathology

Principles of pathology

Disease

Infection Neoplasia Cause Pathogenesis

Hemodynamics

Ischemia

Inflammation Cell damage Wound healing

Cellular adaptation Atrophy Hypertrophy Hyperplasia Dysplasia Metaplasia

Squamous Glandular

Cell death Necrosis

Coagulative necrosis Liquefactive necrosis Gangrenous necrosis Caseous necrosis Fat necrosis Fibrinoid necrosis

Programmed cell death

Apoptosis

Pyknosis Karyorrhexis Karyolysis

Accumulations pigment

Hemosiderin Lipochrome/Lipofuscin Melanin

Steatosis

Anatomical pathology

Surgical pathology Cytopathology Autopsy Molecular pathology Forensic pathology Oral and maxillofacial pathology

Gross examination Histopathology Immunohistochemistry Electron microscopy Immunofluorescence Fluorescence in situ hybridization

Clinical pathology

Clinical chemistry Hematopathology Transfusion medicine Medical microbiology Diagnostic immunology Immunopathology

Enzyme assay Mass spectrometry Chromatography Flow cytometry Blood
Blood
bank Microbiological culture Serology

v t e

Disorders of blood flow

Decreases

Clots

Thrombus Thrombosis Renal vein thrombosis

Ischemia

Brain
Brain
ischemia Ischaemic heart disease large intestine: Ischemic colitis small intestine: Mesenteric ischemia

Infarction

Types

Anemic Hemorrhagic

Location

Heart Brain Spleen Limb

Increases

Hemorrhage

Bruise/Hematoma Petechia Purpura Ecchymosis

head

Epistaxis Hemoptysis Intracranial hemorrhage Hyphema Subconjunctival hemorrhage

torso

Hemothorax Hemopericardium Pulmonary hematoma

abdomen

Gastrointestinal bleeding Haemobilia Hemoperitoneum Hematocele Hematosalpinx

joint

Hemarthrosis

Edema

Anasarca Angioedema/Lymphedema Exudate/Transudate

Cerebral edema Pulmonary edema Hydrothorax Ascites/hydroperitoneum Hydrosalpinx

Other

Hyperemia

Authority control

NDL: 00577204 N

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