Haematocrit stuff

Question 1

What is the PCV?

Answer 1

PCV= packed cell volume (also known as haematocrit). This is reported as a % of the total blood volume.

You will normally perform this procedure using blood collected in EDTA anticoagulant.

Question 2

What are the steps for performing a haematocrit?

Answer 2

Loading the sample and centrifugation

1. Mix the blood carefully first (invert it 4-5 times)
2. Fill the capillary tube 2/3-2/4 full (dip it in the blood and let it fill by capillary action –jiggling it may help as may laying the tube at an oblique angle). It doesn’t matter which end you fill it from.
3. Wipe the outside of the tube with a tissue
4. Seal one end of the tube with the clay/plasticine provided
5. Place your tube in the centrifuge slot with the plugged end on the outside of the rotor and the base of the tube resting against the outer rim of the slot (otherwise it will fly into the end to the rotor as it spins, your plug will come out and your tube will probably shatter spraying blood all over the centrifuge)
6. You need to balance the centrifuge (each tube should have one opposite it –you would normally do a pair of tubes for each blood sample)
7. Secure the rotor cover
8. Close the lid
9. Start the centrifuge ( on our centrifuges you will spin the samples for 4 min but each centrifuge is different and you will need to check the speed and time the sample should be spun for and the size of micro-haematocrit tubes that fit the slots –this is usually in the centrifuges documentation)
10. Wait till the centrifuge has stopped
11. Open the lid and rotor cover and take your samples out

Question 3

How should you read your PCV after centrifuging?

Answer 3

1. Place the tube in the slot in the PCV reader
2. You should have the top of your clay plug positioned on the bottom line.
3. You should slide your tube along until the top of the serum is at the top line
4. Adjust the sliding (white) line until it is at the top of the cellular fraction
5. Read off the PCV (where your white line intersects the PCV scale).

Question 4

What serum colours may you get and should look for? What may they represent?

Answer 4

Red = probably haemolysed

Yellow = icteric (you may see this in liver failure or some anaemias – bilirubin is yellow)

White/milky = lipaemic (there is a lot of fat in the sample –this may be normal if the animal has just eaten)

Note whether you can see a buffy coat (white cell layer) or not, in normal samples this is often difficult to see

Question 5

How do you measure specific gravity and total protein after doing you haematocrit?

Answer 5

1. First check the refractometer is set at zero with distilled water.
2. If if it is not zeroed, adjust the blue white interface to read zero on the appropriate scale using the adjustment screw on top of the refractometer.
3. Use the diamond blade to score the haematocrit tube just above the buffy coat.
4. Using both hands break the tube.
5. Use the pipette bulb to push out the liquid as drop on the face of the refractometer.

Read of axis arrow points to in pic.