Hematocrit (HCT) or Packed Cell Volume (PCV)

Hematocrit (HCT) or Packed Cell Volume (PCV)

Hematocrit (HCT) or Packed Cell Volume (PCV)

● Hematocrit, also known as packed cell volume (PCV), is a measurement that indicates the percentage of red blood cells (erythrocytes) in the total volume of blood.

● It is commonly used to assess the oxygen-carrying capacity of the blood and to diagnose certain medical conditions.

● Hematocrit is the volume of packed red cells in a particular specimen of blood calculated as a percentage of the total volume of blood.

● Hematocrit (HCT) and packed cell volume (PCV) are used to measure red blood cell mass.

● It is generally a part of the complete blood count (CBC) test.

● The PCV test measures how much of the blood consists of cells.

● Hematocrit may be measured by centrifugation or automated methods.

● A PCV of 40% means that there are 40 milliliters of cells in 100 milliliters of blood.

Hematocrit (HCT)

● A calculated value obtained from modern automated hematology analyzers.

● It is the product of the mean cell volume (MCV) and the red blood cell (RBC) count, both of which are directly measured by the analyzer.

● The formula used to calculate the HCT is as follows:

HCT = (MCV x RBC count)÷10

Packed cell volume (PCV)

● This is a directly measured value obtained from centrifuging blood in a micro-hematocrit tube in a micro-hematocrit centrifuge.

● The PCV is measured as the height of the red cell column in a micro-hematocrit tube after centrifugation.

● It is the quickest and most readily available measure of the red blood cell component of blood

Measurement:

Hematocrit is measured by centrifuging a blood sample in a narrow capillary tube.

The blood components separate based on their densities, with red blood cells settling at the bottom, followed by a thin layer of white blood cells and platelets, and finally, plasma at the top.

The height of the packed red blood cells is then measured and expressed as a percentage of the total blood volume.

Clinical significance:

The hematocrit value is a valuable diagnostic tool in various medical situations.

It helps in evaluating anemia, polycythemia (abnormally high red blood cell count), dehydration, and certain other blood disorders.

It also aids in monitoring the response to treatment for anemia and assessing blood loss or fluid shifts.

Normal Ranges of Packed cell volume (PCV)

● Male adult: 42 –52%

Female adult: 35 – 47%

Pregnant females: 33- 38%

● Newborn: 42- 64%

● 1 – 5 years: 31- 44%

● 5 – 10 years: 35– 44%

● 11 – 18 years: 37 – 48% (male), 34 – 44% (female)

Indications of Packed cell volume (PCV)

● Hematocrit shows that a patient has anemia, erythrocytosis, or changes in plasma volume.     

● Hematocrit value is used as a cutoff to determine the amount of requirement for transfusion.

Interpretation of Packed cell volume (PCV)

● Hematocrit is raised with an increase in the number of red blood cells or a decrease in plasma volume.

● Hematocrit falls in decreased erythropoiesis or hemolysis and hemorrhage where plasma volume is increased.

Increased Levels of Packed cell volume (PCV)

● Polycythemia vera

● Burns

● COPD

● Congenital heart disease

● Dehydration

● Eclampsia

Decreased Levels of Packed cell volume (PCV)

● Anemia

● Hemoglobinopathy

● Bone marrow failure

● Hemorrhage

● Hemolytic reaction

● Normal pregnancy

● Multiple myeloma

● Leukemia or lymphoma

● Nutritional deficiencies of iron or vitamin (B12 or
folate) and mineral deficiencies

● Recent or long-term blood loss

Interfering Factors of Packed cell volume (PCV)

Altitude: People living in high altitudes have a high HCT.

Pregnancy: Hemodilution of pregnancy causes decreased HCT.

Age: Lower HCT is seen in men and women over the age of 60.

Dehydration: Severe dehydration causes a false increase in HCT.

Interpretation:

● A low hematocrit value may indicate conditions such as iron deficiency anemia, vitamin B12 or folate deficiency anemia, chronic inflammation, or blood loss.

● High hematocrit values can be seen in cases of polycythemia vera, lung disease, congenital heart disease, or dehydration.

Limitations:

● Although hematocrit provides valuable information about the blood’s composition, it does not provide a complete picture of the overall health.

● Other blood tests, such as hemoglobin levels and red blood cell indices, are often used in conjunction with hematocrit to provide a more comprehensive assessment.

Clinical considerations

● Hematocrit is commonly used in routine blood tests and can be interpreted alongside other blood parameters to aid in the diagnosis and monitoring of various conditions.

● Changes in hematocrit values over time can help healthcare professionals evaluate the effectiveness of treatments or interventions.

Nursing Implications of Packed cell volume (PCV)

● Manage fatigue avoid complications of anemia, maintain adequate nutrition, maintain adequate perfusion, and encourage compliance with prescribed therapy.

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