INTRODUCTION
The packed cell volume measurement is a relatively simple and quick test on blood, which can prove useful in the assessment of conditions such as anaemia and dehydration.

EQUIPMENT

• Lab coat.
• Microcentrifuge.
• EDTA blood sample.
• Capillary tubes.
• Plastic sealing compound.
• Gauze swab.
• Microhaematocrit reader.

METHOD

1. Put on your lab coat; ensure that long hair is tied back and any jewellery removed.
2. Ensure that you have a flat, clean, dry surface upon which to work.
3. Draw blood from the EDTA tube into the capillary tube by capillary action to three quarters of the length of the tube.
4. Insert one end of the capillary tube into the plastic sealing compound and twist it as it is withdrawn to form a stopper.
5. Wipe the tube clean with a gauze swab.
6. Place the capillary tube in the microcentrifuge with the plastic plug pointing outwards and fitted against the gasket rim.
7. Balance the centrifuge with a tube filled to the same level.
8. Screw down the safety plate and close the lid.
9. Centrifuge for 5 minutes at 2500rpm.
10. Open the lid, switch off the power and remove the tubes.
11. Read the result against the microhaematocrit reader.
12. If a reader is not available, use the following calculation:
    
    PCV = height of red blood cell column x 100% divided by total height of blood column.
    
    NORMAL PCV VALUES:
    Dog = 37-55%
    Cat = 30-45%
    Remember that greyhounds have a higher PCV than other dogs.
    
    NOTE: In general, for each 1% increase in PCV a fluid loss of approximately 10mls/kg has occurred. This can only ever be an estimation unless the normal PCV of the patient is known. Therefore PCV should always be considered in conjunction with the total protein of plasma.
    
    RAISED PCV: Indicative of dehydration or true polycythaemia.
    LOWERED PCV: Indicative of hypoplastic anaemia or recent haemorrhage.