What happens to the PCV immediately after blood loss?

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:           o Transfusion reaction           o Drug/chemical reaction           o Infection           o Burns           o Mechanical disruption (artificial heart valves)     * Systemic Disease           o Cancer           o Lupus           o Sardoidosis

Packed Cell Volume Men             40%-54% Women          37%-47% Pregnancy    33%-44% Newborn     50%-62%

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.

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Source: www.brooksidepress.org