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Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. [1] This may be due to either a loss of both salt and water or a decrease in blood volume. [2] [3] Hypovolemia refers to the loss of extracellular fluid and should not be confused with dehydration. [4]
With regard to severe burns, fluids may pool on the burn site (i.e. fluid lying outside of the interstitial tissue, exposed to evaporation) and cause depletion of the fluids. With pancreatitis or ileus, fluids may "leak out" into the peritoneal cavity, also causing depletion of the intracellular, interstitial or vascular compartments.
Intravascular volume depletion is divided into three types based on the blood sodium level: Isonatremic (normal blood sodium levels) Example: a child with diarrhea, because both water and sodium are lost in diarrhea.
The term "dehydration" has sometimes been used incorrectly as a proxy for the separate, related condition of hypovolemia, which specifically refers to a decrease in volume of blood plasma. [3] The two are regulated through independent mechanisms in humans; [ 3 ] the distinction is important in guiding treatment.
Volume contraction is a decrease in the volume of body fluid, including the dissolved substances that maintain osmotic balance . The loss of the water component of body fluid is specifically termed dehydration .
In ecology, pressure-volume curves describe the relationship between total water potential (Ψt) and relative water content (R) of living organisms. These values are widely used in research on plant-water relations and provide valuable information on the turgor , osmotic and elastic properties of plant tissues .
EABV can be reduced, therefore, by factors which reduce actual arterial blood volume (hemorrhage, dehydration), increase arterial vascular capacitance (cirrhosis, sepsis) or reduce cardiac output (congestive heart failure). EABV can be reduced in the setting of low, normal, or high actual blood volume.
The excluded volume of a hard sphere is eight times its volume—however, for a two-molecule system, this volume is distributed among the two particles, giving the conventional result of four times the volume; [2] this is an important quantity in the Van der Waals equation of state. The calculation of the excluded volume for particles with non ...