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Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, [1] usually referring to the delivery of blood to a capillary bed in tissue. Perfusion may also refer to fixation via perfusion, used in histological studies.
Reperfusion injury, sometimes called ischemia-reperfusion injury (IRI) or reoxygenation injury, is the tissue damage caused when blood supply returns to tissue (re-+ perfusion) after a period of ischemia or lack of oxygen (anoxia or hypoxia).
Ischemia, meaning insufficient blood flow to a tissue, can also result in hypoxia in the affected tissues. This is called 'ischemic hypoxia'. Ischemia can be caused by an embolism, a heart attack that decreases overall blood flow, trauma to a tissue that results in damage reducing perfusion, and a variety of other causes.
Tissue hypoxia refers to low levels of oxygen in the tissues of the body and the term hypoxia is a general term for low levels of oxygen. [2] Hypoxemia is usually caused by pulmonary disease whereas tissue oxygenation requires additionally adequate circulation of blood and perfusion of tissue to meet metabolic demands. [4]
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. [4] There are four types of distributive shock.
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. Permissive hypotension is a means of restricting fluid administration until hemorrhage is controlled while accepting a short period of suboptimal end-organ perfusion.
Hypothermia due to decreased perfusion and evaporation of sweat; Thirst and dry mouth, due to fluid depletion; Cold and mottled skin (livedo reticularis), especially extremities, due to insufficient perfusion of the skin; The severity of hemorrhagic shock can be graded on a 1–4 scale on the physical signs.
In the cases of cardiogenic shock resulting from heart failure or acute hemorrhagic shock caused by a large volume of blood loss, the body constricts peripheral vessels to reverse the low arterial pressure that causes inadequate tissue perfusion. [22] With vasodilatory shock, it is difficult for the peripheral vascular smooth muscle to ...