Determination Of Packed Cell Volume (PCV) | Physiology Practical

Afnan September 21, 2017

Determination of Haematocrit or Packed Cell Volume (PCV).

Theory:

Packed cell volume (PCV) is the proportion of bloodoccupied by RBCs, expressed in percentage. It is thevolume of RBCs packed at the bottom of a hematocrittube when the blood is centrifuged. It is also called hematocrit value or erythrocyte volume fraction (EVF).

SIGNIFICANCE OF DETERMINING PCV

Determination of PCV helps in:
1. Diagnosis and treatment of anemia
2. Diagnosis and treatment of polycythemia
3. Determination of extent of dehydration and recoveryfrom dehydration after treatment
4. Decision of blood transfusion.

NORMAL VALUES OF PCV

Normal PCV:
In males = 40% to 45%
In females = 38% to 42%

VARIATIONS IN PCV

PCV increases in:
1. Polycythemia
2. Dehydration
3. Dengue shock syndrome

DECREASE IN PCV

PCV decreases in:
1. Anemia
2. Cirrhosis of liver (Chapter 40)
3. Pregnancy
4. Hemorrhage

Requirements:

Microhaematocrit tube, centrifuge, Lancet, anti coagulant, Clay, Cotton soaked in alcohol.

Procedure:

  1. Wash your hand with soap and allow it to dry.
  2. Clean the tip of your finger with alcohol swab.
  3. Prick the pulp of your finger with lancet.
  4. Add small amount of anti coagulant to the Microhaematocrit tube.
  5. Discard the first drop of blood. And collect another big drop of blood.
  6. Take a Microhaematocrit tube and touch it with a drop of blood.
  7. Tube will be filled by capillary action up to 3/4
  8. Seal ends of the tube with clay.
  9. Place capillary tubes in the grooves on the base plate of centrifuge.
  10. Balance these Microhaematocrit tube with the blank capillary tube at the other side.
  11. Cover it with the lid of the centrifuge and adjust the timer at 15 minutes and 3000 rpm,swith on the machine.
  12. After the machine stop remove the lid and calculate the haematocrit.

Precautions:

      1. Avoid air bubbles in the tube.
      2. The lid should be properly tight.
      3. Sterilized lancet and Microhaematocrit tube should be used.

Observations and Figures.

After centrifugation 3 different types of portion were observed.In the microhematocrit tube.
1-The first red part is that of erythrocytes having a length of 2.5cm
2-Second layer consist of leuckocytes and platelets
3-Third part is largest part consisting of plasma.The length of whole blood was found to be 7 cm.
PCV=2.6/7x100


PVC=37.14%
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