How to Perform a PCV/TP | VETgirl Veterinary Continuing Education Videos

Cost

Free for Elite Members

Related Disciplines:

In this VETgirl online veterinary continuing education video, Amy Johnson, BS, LVT, RLATG, CVJ, VETgirl’s Senior CE Manager and Michaela Witcher, MS, CVT review how to perform a packed cell volume (PCV) and total protein (TP) in veterinary medicine (see our VETgirl blog on The Difference Between Total Protein vs. Total Solids HERE!). In VETgirl’s opinion, any patient on IV fluids should ideally have a minimum of a PCV/TS every day to evaluate hydration status and degree of hemodilution. Performing a PCV/TP off a blood sample is easy to perform, and results are available within minutes. Veterinary support staff, including tech assistants, triage, and veterinary technicians, must feel comfortable performing this commonly performed clinical pathology test.

Introduction:
In this VETgirl video, we will guide you through the process of performing a packed cell volume (PCV) and total protein (TP) on a veterinary patient. These are common laboratory values collected on patients to evaluate their hydration status, detect anemia, and measure proteins in the blood. Together, these tests offer a quick snapshot of the patient’s health and can further guide diagnostic and treatment decisions.

NOTE – The terms microhematocrit tube, hematocrit tube, and crit tube will all be used interchangeably.

Sample Collection:
When blood is collected from a patient, and the tubes filled will be based on what laboratory tests will need to be performed along with the PCV/TP. A PCV/TP can be performed from a lavender-top tube (LTT), a green-top tube (GTT), or a hematocrit tube directly from the needle hub in the patient’s vein.

NOTE: If using a hematocrit tube directly from the patient, you will want to use a red-ringed hematocrit tube. The red ring indicates that the tube contains heparin, an anticoagulant that prevents the blood from clotting.

For information on blood tubes and what they could be used for, check out THIS VETgirl Video.

Sample Preparation:
If blood clots in your tubes, it will invalidate the result. So, it is important to make sure there is no clotting. Once samples are collected, no matter what tube they are in, make sure to gently invert them a couple of times to mix the blood sample with the anticoagulant in the tube. If you can’t run the tests immediately, putting the samples on a machine that will gently invert them is helpful. If the blood does clot in your tubes, you will need to collect a new sample.

Supplies:
What you will need:
• Your blood sample
• Hematocrit tubes
• Clay to plug one end of the tube
• Centrifuge
• Hematocrit reader card
• Refractometer
• Distilled water
• Wipes

Crit Tube Selection & Filling:
If you are filling your crit tube from a green top tube or lavender top tube you will want to make sure to use the correct crit tube. When filling from another blood tube with anticoagulant, you will want to use the blue-ringed hematocrit tubes, as they do not contain anticoagulant. We want to avoid doubling up on the anticoagulant. If you are collecting directly from a vessel using the needle hub, you will use the red-ringed hematocrit tube to prevent the blood from clotting.

Make sure that your sample has been inverted gently a couple of times to adequately mix the sample before starting. To fill the crit tubes, place one end in the patient’s blood, carefully tilt the tube, and allow the surface tension to pull the blood into the tube. Allow it to fill approximately 2/3rds of the way and then place your finger over the end of the tube to plug it before removing the crit tube from the blood. Place the open end of the tube in the clay to plug it. We generally fill 2 crit tubes for a couple of reasons:
• We need two tubes across from each other in the centrifuge to balance it – make sure they are filled with the same amount for balancing
• You may have one tube blow out in the centrifuge, and this will allow you to still have a sample without having to fill and re-spin another sample

A tip to help with the tubes blowing out is to pull it out of the clay and place it in again 1-2 times. The extra clay in the plug will help decrease the likelihood of it blowing out of the tube while spinning in the centrifuge.

Place the hematocrit tubes in the microcentrifuge with the clay plug towards the outside gasket and fitted against the gasket rim. Balance the centrifuge with a tube filled to the same level. Screw down the safety plate and close the lid. Centrifuge at speed and time set forth in your practice’s protocol. Every centrifuge is different, which means protocols will vary.

PCV
Once your tubes have completed spinning and the centrifuge has come to a stop, you will remove them from the centrifuge. You will now be able to see the blood cells packed at the bottom of the tube and plasma at the top. You will take your tube and line it up on the hematocrit reader card. The line where the clay meets the blood needs to be on the zero line at the bottom of the card, and the top of the plasma lined up on the 100 line at the top of the card. You will need to slide your tube along the slant of the top line to get them both to line up. Once you have your tube in place, you will read the line where the blood and plasma meet as your PCV percentage.

This dog has a PCV of 58%

Plasma Evaluation
The plasma color evaluation is another assessment usually done in conjunction with the PCV and TP. When the spun hematocrit tube is up against a white background, we note the color and evaluate as:

Straw/clear – Normal
Red – hemolytic
Yellow – Icteric

This dog’s plasma is slightly hemolytic

Total Protein
The refractometer will read the patient’s total protein. You should always start by cleaning the refractometer with distilled water and wiping it dry. Next, you will take your hematocrit tube and break it in half. You do this by putting your thumbs and first fingers on the tube just above the blood cells. Once the tube has been broken, ensure there are no blood cells in the plasma half of the tube. From the top half of the tube with the plasma in it, take the unbroken end of the tube and drop the plasma on the refractometer. Ensure no glass shards are in the plasma before closing the lid.

When you look into your refractometer, you will see several scales. Make sure to read the scale marked as g/dl. In this example, the refractometer has three scales, with the correct one being marked as Serum or plasma protein. Keep in mind that all refractometers are different. You will read the line where the blue and white meet.

This dog’s TP is 7.1 g/dl

Not a VETgirl ELITE member? Get your learning on with the #1 veterinary CE resource – clinically relevant, practical, and accessible 24/7 on your own time! Don’t miss out – click HERE to check out your options, including our new  14-day, no-commitment ELITE Trial.

Only VETgirl members can leave comments. Sign In or Join VETgirl now!