| The hematocrit is a measure of the
red blood cell mass, expressed as a percentage.
Blood is placed in a test tube and centrifuged to separate the heavier
red blood cells from the lighter serum and plasma. The percentage of the
blood volume occupied by the mass of red cells is the hematocrit.
Increased in the Presence of:
- Hemoconcentration
- COPD (chronic obstructive pulmonary disease)
- CHF (congestive heart failure)
- Smokers
- Pre-eclampsia
Decreased in the Presence of:
- Anemia
- Leukemia
- Hyperthryroidism
- Chronic liver disease
- Hemolysis:
- Transfusion reaction
- Drug/chemical reaction
- Infection
- Burns
- Mechanical disruption (artificial heart valves)
- Systemic Disease
Special Considerations
- Smokers typically have elevated hematocrits in response to
chronic, low-grade carbon monoxide poisoning and other mild
respiratory ailments. Because of the carbon monoxide binding, they may
still be functionally anemic, even though their hematocrit levels look
good.
- Adaptation to high altitudes includes moderate elevation of
hematocrit.
- During the initial phases of an acute hemorrhage, the hematocrit generally doesn't change very much. Later, as extracellular
fluid is mobilized and IV fluids are incorporated, there is a
dilutional effect that will lead to a reduced hematocrit. This
fall in hematocrit may take several hours to develop.
|
Normal Values*
| |
Packed Cell Volume |
|
Men |
40%-54% |
| Women |
37%-47% |
| Pregnancy |
33%-44% |
| Newborn |
50%-62% |
*These are general values taken from a variety of sources. The
actual normal values may vary from lab to lab and from one type of testing
protocol to another.
|