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Hypovolemia Fluid Loss

Pathophysiology of Hypovolemia

Hypovolemic (hypo=low + volemic=volume) shock due to water loss can be the endpoint of many illnesses, but the common element is the lack of fluid within the body (Hypovolemia).

Hypovolemic shock, also known as hemorrhagic shock, is a life-threatening condition that results when you lose more than 20 percent (one-fifth) of your body’s blood or fluid supply. This severe fluid loss makes it impossible for the heart to pump a sufficient amount of blood to your body. Hypovolemic shock can lead to organ failure. This condition requires immediate emergency medical attention.

Hypovolemia is characterized by sodium (salt) depletion and thus differs from dehydration, which is defined as excessive loss of body water.

There needs to be enough red blood cells and water in the blood for the heart to push the fluids around within the blood vessels. When the body becomes dehydrated, there may be enough red blood cells, but the total volume of fluid is decreased, and pressure within the system decreases.

The human body responds to acute hemorrhage by activating the following major physiologic systems:

Hypovolemia

Release of norepinephrine / epinephrine

Tachycardia, Increased cardiac contractility, venous and arteriolar constriction, and decreased capillary hydrostatic pressure

Decreased blood Flow – Skin, Muscle, Gastro Intestinal Tract, and Kidney

Increased Blood Flow – Brain and Heart + Flow of fluid from interstitium to blood vessles

The Autotransfusion Effect

Further decompensation – Decreased perfusion of brain,

Coronary arteries – Anaerobic Matabolism

Lactic acidosis, decreased cardiac function, dysrrhythmias

Subsequently – Decreased ATP synthesis with intracellular energy failure

Increased intracellular sodium and water – Swelling

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Release of lysozomal enzymes – Increased cell permeability

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Enzyme release (Histamine, Serotonin, Kinins, Prostaglandine) – Increased Vascular Permeability

Multiple System Organ Failure

Progressive Cardiac Failure – Myocardial depressant factor

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Increased lung water with atelecatasis and hemorrhage –  Adult Respiratory Distress Syndrome

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Hepatobiliary and Pancreatic Failure – Hyperglycemia

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Decreased Gastro-Intestinal mobility – Stress Ulcers

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Decreased urine output and renal failure

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Impaired white blood cell and clotting functions, function, Infection,

Disseminated intravascular coagulation