Volume status
Encyclopedia
In medicine, intravascular volume status refers to the volume of blood in a patient's circulatory system, and is essentially the blood plasma
component of the overall volume status of the body, which otherwise includes both intracellular fluid and extracellular fluid
. Still, the intravascular component is usually of primary interest, and volume status is sometimes used synonymously with intravascular volume status.
It is related to the patient's state of hydration, but is not identical to it. For instance, intravascular volume depletion can exist in an adequately hydrated person if there is loss of water into interstitial tissue (e.g. due to hyponatremia
or liver failure
).
of intravascular fluid (blood plasma
) is termed hypovolemia
, and its signs include, in order of severity:
(high blood volume) include:
is diarrhea or vomiting. The other causes are usually divided into renal and extrarenal causes. Renal causes include overuse of diuretics, or trauma or disease of the kidney. Extrarenal causes include bleeding, burns, and any causes of edema
(e.g. congestive heart failure, liver failure, etc.).
Intravascular volume depletion is divided into three types based on the blood sodium level:
can occur during surgery, if water rather than isotonic saline is used to wash the incision. It can also occur if there is inadequate urination, e.g. with certain kidney diseases.
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
component of the overall volume status of the body, which otherwise includes both intracellular fluid and extracellular fluid
Extracellular fluid
Extracellular fluid usually denotes all body fluid outside of cells. The remainder is called intracellular fluid.In some animals, including mammals, the extracellular fluid can be divided into two major subcompartments, interstitial fluid and blood plasma...
. Still, the intravascular component is usually of primary interest, and volume status is sometimes used synonymously with intravascular volume status.
It is related to the patient's state of hydration, but is not identical to it. For instance, intravascular volume depletion can exist in an adequately hydrated person if there is loss of water into interstitial tissue (e.g. due to hyponatremia
Hyponatremia
Hyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...
or liver failure
Liver failure
Acute liver failure is the appearance of severe complications rapidly after the first signs of liver disease , and indicates that the liver has sustained severe damage . The complications are hepatic encephalopathy and impaired protein synthesis...
).
Intravascular volume depletion
Volume contractionVolume contraction
Volume contraction is a decrease in body fluid volume, also including any concomitant loss of osmolytes. The loss of the water component of body fluid is specifically termed dehydration.-By body fluid compartment:...
of intravascular fluid (blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
) is termed hypovolemia
Hypovolemia
In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
, and its signs include, in order of severity:
- a fast pulse
- infrequent and low volume urination
- dry mucous membranes (e.g. a dry tongue)
- poor capillary refill (e.g. when the patient's fingertip is pressed, the skin turns white, but upon release, the skin does not return to pink as fast as it should - usually >2 seconds)
- decreased skin turgor (e.g. the skin remains "tented" when it is pinched)
- a weak pulse
- orthostatic hypotensionOrthostatic hypotensionOrthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...
(dizziness upon standing up from a seated or reclining position, due to a drop in cerebral blood pressure) - orthostatic increase in pulse rate
- cool extremities (e.g. cool fingers)
Intravascular volume overload
Signs of intravascular volume overloadHypervolemia
Hypervolemia, or fluid overload, is the medical condition where there is too much fluid in the blood.The opposite condition is hypovolemia, which is too little fluid volume in the blood.-Causes:Excessive sodium or fluid intake:* IV therapy...
(high blood volume) include:
- an elevated Jugular venous pressureJugular venous pressureThe jugular venous pressure is the indirectly observed pressure over the venous system...
(JVP)
Volume Measurement
Blood volume may be measured with the BVA-100 blood volume analyzer from Daxor Corporation.Intravascular volume depletion
The most common cause of hypovolemiaHypovolemia
In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
is diarrhea or vomiting. The other causes are usually divided into renal and extrarenal causes. Renal causes include overuse of diuretics, or trauma or disease of the kidney. Extrarenal causes include bleeding, burns, and any causes of edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
(e.g. congestive heart failure, liver failure, etc.).
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.
- HyponatremicHyponatremiaHyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...
(abnormally low blood sodium levels). Example: a child with diarrhea who has been given tap water to replete diarrheal losses. Water is replenished, but sodium is not, so water flows out of the vasculature into the interstitial tissue. - HypernatremicHypernatremiaHypernatremia or hypernatraemia is an electrolyte disturbance that is defined by an elevated sodium level in the blood. Hypernatremia is generally not caused by an excess of sodium, but rather by a relative deficit of free water in the body...
(abnormally high blood sodium levels). Example: a child with diarrhea who has been given salty soup to drink, or insufficiently diluted infant formula. Here sodium has been replenished, but not enough water has been provided with it.
Intravascular volume overload
Intravascular volume overloadHypervolemia
Hypervolemia, or fluid overload, is the medical condition where there is too much fluid in the blood.The opposite condition is hypovolemia, which is too little fluid volume in the blood.-Causes:Excessive sodium or fluid intake:* IV therapy...
can occur during surgery, if water rather than isotonic saline is used to wash the incision. It can also occur if there is inadequate urination, e.g. with certain kidney diseases.