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Encyclopedia > Hematocrit

The hematocrit (Ht or HCT) and packed cell volume (PCV) are measures of the proportion of blood volume that is occupied by red blood cells. It is normally between 0.42 and 0.52 for males and between 0.36 and 0.48 for women[1]. Image File history File links Illu_blood_components. ... Image File history File links Illu_blood_components. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ...

Packed cell volume diagram
Packed cell volume diagram

The packed cell volume can be determined by centrifuging. Heparinized blood in a capillary tube (also known as a microhematocrit tube) is typically centrifuged at 10,000 RPM for five minutes.[2] This separates the blood into layers. The volume of packed red blood cells, divided by the total volume of the blood sample gives the PCV. Because a tube is used this can be calculated by measuring the lengths of the layers. Image File history File links Packed_cell_volume_diagram. ... Image File history File links Packed_cell_volume_diagram. ... A laboratory centrifuge tabletop centrifuge A centrifuge is a piece of equipment that puts a substance in rotation around a fixed axis in order for the centrifugal force to separate a fluid from a fluid or from a solid substance. ... Heparin is a highly sulfated glycosaminoglycan widely used as an injectable anticoagulant. ... Capillary action or capillarity is the ability of a narrow tube to draw a liquid upwards against the force of gravity. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ...

With modern lab equipment the hematocrit is calculated by an automated analyser and not directly measured. It is determined by multiplying the red cell count by the mean cell volume. The hematocrit is slightly more accurate as the PCV includes small amounts of plasma trapped between the red cells. An estimated hematocrit as a percentage may be derived by multiplying the hemoglobin level in g/dL times three and dropping the units. [3]. The hemaglobin level is the measure used by blood banks. An automated analyser is a laboratory machine designed to measure different chemicals in a number of biological samples quickly, with minimal human assistance. ... 3-dimensional structure of hemoglobin. ... A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusions. ...

The hematocrit is not usually considered an important consideration when looking at a person's full blood count results as most people are more concerned with the hemoglobin concentration and mean cell volume. A full blood count (FBC) or complete blood count (CBC) is a test requested by a doctor or other medical professional that gives information about the cells in a patients blood. ... 3-dimensional structure of hemoglobin. ...

There have been cases where the blood for testing was inadvertently drawn from the same arm with the intravenous line running in a transfusion of packed red cells. In this sample, the hemoglobin measurement will be high because it is measuring the fluid being transfused (that is, mostly red cells) rather than the diluted serum. In this case, the hematocrit measurement will be artificially very high.

In mammals, hematocrit is independent of body size.

Elevated hematocrit

In cases of dengue fever, where the full blood count is done daily, the hematocrit is monitored as a high hematocrit is a danger sign of an increased risk of dengue shock syndrome. Dengue fever (IPA: ) and dengue hemorrhagic fever (DHF) are acute febrile diseases, found in the tropics, with a geographical spread similar to malaria. ...

Polycythemia vera is associated with elevated hematocrit Polycythemia is a condition in which there is a net increase in the total circulating erythrocyte (red blood cell) mass of the body. ...

Chronic obstructive pulmonary disease (and other pulmonary conditions associated with hypoxia) may elicit an increased production of red blood cells. This increase is mediated by the increased levels of erythropoyetin by the kidneys in response to hypoxia.

Lowered hematocrit

Lowered hematocrit can imply significant hemorrhage (for example, in an ectopic pregnancy.) To meet Wikipedias quality standards, this article or section may require cleanup. ...

See also

  Results from FactBites:
Hematocrit - Complete Blood Count (494 words)
Because the hematocrit is a percentage of red blood cells, as compared to the total volume of blood, any increase or decrease in plasma volume affects the hematocrit.
A decreased hematocrit occurs due to overhydration, which lowers the percentage of red blood cells in relation to the liquid plasma portion of blood.
A hematocrit that is done immediately after a hemorrhage usually does not show the extent of RBC loss because at the time of the hemorrhage, plasma and red blood cells are lost in equal proportions.
The UCI explained that, a 53% hematocrit limit was initially proposed (based on three standard deviations above the average hematocrit value for a normal population) but then decreased to 50% to ensure that all professional team delegates were in agreement.
A more detailed examination of the hematocrit data from all sports determined that the percentage of tests where hematocrit was greater than 50% ranged from 0.3% in netball to 25.7% in weight lifting.
Hematocrit reflects the balance between red blood cell production and destruction but is also known to be influenced by dehydration and body posture.
  More results at FactBites »



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