hypovolemic shock

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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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

hy·po·vo·le·mic shock

shock caused by a reduction in volume of blood, as from hemorrhage or dehydration.
Farlex Partner Medical Dictionary © Farlex 2012

hypovolemic shock

Critical care A rapid fall in BP due to a ±20% ↓ of blood volume Etiology GI tract and other internal or external hemorrhage, loss of blood volume and body fluids–eg, diarrhea, vomiting, intestinal blockage, inflammation, burns, etc. See Shock, Volume depletion.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

hy·po·vo·le·mic shock

(hī'pō-vŏ-lē'mik shok)
Shock caused by a reduction in volume of blood, as from hemorrhage or dehydration.
Synonym(s): hypovolaemic shock.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Hypovolemic shock

Shock caused by a lack of circulating blood.
Mentioned in: Thoracentesis
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Most common cause of hypovolemic shock was acute diarrhoeal disease which accounted for 90% of hypovolemic shock.
In our patient, the probable cause of hypovolemic shock could be severe pain and poor compliance with her medications.
Upon arrival, the patient was in hypovolemic shock with intense pallor, filiform peripheral pulses, and cold extremities.
Results of the compounds PMZ-2010 and PMZ-1620 being developed for hypovolemic shock and stroke, respectively, were presented at the Society of Critical Care Medicine annual meeting January 21-24, 2017 in Honolulu, Hawaii.
The sudden death of the mare of the present report was most likely due to hypovolemic shock as a consequence of hemoperitoneum.
On arrival to the NSICU, he was in hypovolemic shock (overall 3.4 L negative fluid balance in past few hours) from clear polyuria.
We present a very interesting case of a patient in hypovolemic shock secondary to a gastrointestinal (GI) bleed with black esophagus that, due to contraindications, required total parenteral nutrition (TPN) resulting in complete resolution of the esophageal mucosa necrosis.
The mortality risk was felt to be resultant to overwhelming hypovolemic shock at presentation, but this report lacked inclusion of initial resuscitation measures during diagnostic evaluation in its suggested flowchart to optimize treatment [6, 11].
The onset of AKI following wasp stings is known to be caused by hypotension resulting from anaphylactic or hypovolemic shock, acute tubular necrosis, acute interstitial nephritis, and pigment nephropathy (resulting from rhabdomyolysis and hemolysis) [7-9].
Hypovolemic shock, characterized by inadequate plasma or blood volume, can result from blood or other significant body fluid losses.
Hypovolemic shock evaluated by sonographic measurement of the inferior vena cava during resuscitation in trauma patients.
Treatment with doxycycline (100 mg/12 h) was initiated; 2 days later her fever abated, but hypovolemic shock resulting from hemorrhage necessitated mechanical ventilatory assistance.