hypoperfusion


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shock

 [shok]
1. a sudden disturbance of mental equilibrium.
2. a condition of acute peripheral circulatory failure due to derangement of circulatory control or loss of circulating fluid. It is marked by hypotension and coldness of the skin, and often by tachycardia and anxiety. Untreated shock can be fatal. Called also circulatory collapse.

Mechanisms of Circulatory Shock. The essentials of shock are easier to understand if the circulatory system is thought of as a four-part mechanical device made up of a pump (the heart), a complex system of flexible tubes (the blood vessels), a circulating fluid (the blood), and a fine regulating system or “computer” (the nervous system) designed to control fluid flow and pressure. The diameter of the blood vessels is controlled by impulses from the nervous system which cause the muscular walls to contract. The nervous system also affects the rapidity and strength of the heartbeat, and thereby the blood pressure as well.



Shock, which is associated with a dangerously low blood pressure, can be produced by factors that attack the strength of the heart as a pump, decrease the volume of the blood in the system, or permit the blood vessels to increase in diameter.
Types of Circulatory Shock. There are five main types: Hypovolemic (low-volume) shock occurs whenever there is insufficient blood to fill the circulatory system. Neurogenic shock is due to disorders of the nervous system. Anaphylactic (allergic) shock and septic shock are both due to reactions that impair the muscular functioning of the blood vessels. And cardiogenic shock is caused by impaired function of the heart.
Hypovolemic (Low-Volume) Shock. This is a common type that happens when blood or plasma is lost in such quantities that the remaining blood cannot fill the circulatory system despite constriction of the blood vessels. The blood loss may be external, as when a vessel is severed by an injury, or the blood may be “lost” into spaces inside the body where it is no longer accessible to the circulatory system, as in severe gastrointestinal bleeding from ulcers, fractures of large bones with hemorrhage into surrounding tissues, or major burns that attract large quantities of blood fluids to the burn site outside blood vessels and capillaries. The treatment of hypovolemic shock requires replacement of the lost volume.
Neurogenic Shock. This type, often accompanied by fainting, may be brought on by severe pain, fright, unpleasant sights, or other strong stimuli that overwhelm the usual regulatory capacity of the nervous system. The diameter of the blood vessels increases, the heart slows, and the blood pressure falls to the point where the supply of oxygen carried by the blood to the brain is insufficient, which can bring on fainting. Placing the head lower than the body is usually sufficient to relieve this form of shock.
Anaphylactic (Allergic) Shock. This type (see also anaphylaxis) is a rare phenomenon that occurs when a person receives an injection of a foreign protein but is highly sensitive to it. The blood vessels and other tissues are affected directly by the allergic reaction. Within a few minutes, the blood pressure falls and severe dyspnea develops. The sudden deaths that in rare cases follow bee stings or injection of certain medicines are due to anaphylactic reactions.
Septic Shock. This type, resulting from bacterial infection, is being recognized with increasing frequency. Certain organisms contain a toxin that seems to act on the blood vessels when it is released into the bloodstream. The blood eventually pools within parts of the circulatory system that expand easily, causing the blood pressure to drop sharply. Gram-negative shock is a form of septic shock due to infection with gram-negative bacteria.
Cardiogenic Shock. This type may be caused by conditions that interfere with the function of the heart as a pump, such as severe myocardial infarction, severe heart failure, and certain disorders of rate and rhythm.
Pathogenesis of shock. (ARDS = adult respiratory distress syndrome, GI = gastrointestinal, IL = interleukin, TNF = tumor necrosis factor.) From Damjanov, 2000.
anaphylactic shock see anaphylactic shock.
cardiogenic shock shock resulting from primary failure of the heart in its pumping function, as in myocardial infarction, severe cardiomyopathy, or mechanical obstruction or compression of the heart; clinical characteristics are similar to those of hypovolemic shock.
colloidoclastic shock colloidoclasia.
cultural shock feelings of helplessness and discomfort experienced by an outsider attempting to comprehend or effectively adapt to a different cultural group or unfamiliar cultural context.
electric shock see electric shock.
hypovolemic shock shock resulting from insufficient blood volume for the maintenance of adequate cardiac output, blood pressure, and tissue perfusion. Without modification the term refers to absolute hypovolemic shock caused by acute hemorrhage or excessive fluid loss. Relative hypovolemic shock refers to a situation in which the blood volume is normal but insufficient because of widespread vasodilation as in neurogenic shock or septic shock. Clinical characteristics include hypotension; hyperventilation; cold, clammy, cyanotic skin; a weak and rapid pulse; oliguria; and mental confusion, combativeness, or anxiety.
insulin shock a hypoglycemic reaction to overdosage of insulin, a skipped meal, or strenuous exercise in an insulin-dependent diabetic, with tremor, dizziness, cool moist skin, hunger, and tachycardia; if untreated it may progress to coma and convulsions.
respirator shock circulatory shock due to interference with the flow of blood through the great vessels and chambers of the heart, causing pooling of blood in the veins and the abdominal organs and a resultant vascular collapse. The condition sometimes occurs as a result of increased intrathoracic pressure in patients who are being maintained on a mechanical ventilator.
septic shock shock associated with overwhelming infection, usually by gram-negative bacteria, although it may be produced by other bacteria, viruses, fungi, and protozoa. It is thought to result from the action of endotoxins or other products of the infectious agent on the vascular system causing large volumes of blood to be sequestered in the capillaries and veins; activation of the complement and kinin systems and the release of histamine, cytokines, prostaglandins, and other mediators may be involved. Clinical characteristics include initial chills and fever, warm flushed skin, increased cardiac output, and a lesser degree of hypotension than with hypovolemic shock; if therapy is ineffective, it may progress to the clinical picture associated with hypovolemic shock.
shell shock old term for posttraumatic stress disorder.
spinal shock the loss of spinal reflexes after injury of the spinal cord that appears in the muscles innervated by the cord segments situated below the site of the lesion.

hypoperfusion

/hy·po·per·fu·sion/ (-per-fu´zhun) decreased blood flow through an organ, as in hypovolemic shock; if prolonged, it may result in permanent cellular dysfunction and death.

hypoperfusion

(hi?po-per-fu'zhon) [ hypo- + perfusion]
Inadequate blood flow to a single organ or through the entire circulatory system.
Synonym: circulatory collapse

hypoperfusion

decreased blood flood through an organ, as in circulatory shock; if prolonged, it may result in permanent cellular dysfunction and death.
References in periodicals archive ?
Chronic brain hypoperfusion due to multi-vessel extracranial atherosclerotic disease: A potentially reversible cause of cognitive impairment.
Alternations of septal-hippocampal system in the adult Wistar rat with spatial memory impairments induced by chronic cerebral hypoperfusion.
In abdominal tomography performed at this stage, the presence of CT hypoperfusion complex in the patient indicates that the patient is in shock and there must be an appropriate treatment for this exigency.
Detection of mesial temporal lobe hypoperfusion in patients with temporal lobe epilepsy by use of arterial spin labeled perfusion MR imaging," American Journal of Neuroradiology, vol.
The results of his study show that such a technique is successful in preventing the digital hypoperfusion syndrome and venous hypertension despite the fact that in his study 22% of the patients were diabetic patients [4].
IDH-related enteral hypoperfusion increases intestinal permeability to inflammatory stimuli, such as endotoxin, while BP reduction through dialysis results in localized hypoperfusion, reducing capillary arteriolar wall tension and localized edema (Klar et al.
3] Structural heart disease results in global cerebral hypoperfusion by decreasing the cardiac output and subsequently the systemic BP.
Vascular cognitive impairment and Alzheimer's disease: role of cerebral hypoperfusion and oxidative stress.
Although the literature significantly lacks a comparable control group, (4) it has been proven that migraine with aura has the highest risk for subclinical infarction in the cerebellum probably due to hypoperfusion in the posterior circulation of the brain.
baseline anxiety or anxiety related to a procedure or test) or a pathological change related to hypoperfusion or hypoxia (Dennison, 2013).
8) demonstrated hypoperfusion of the left medial frontal area in a patient with a right superior cerebellar artery territory infarction via SPECT analysis.
At baseline, flow velocity at the level of the affected ear was significantly lower in comparison with the other ear showing cochlear hypoperfusion.