Page 246 - Zoo Animal Learning and Training

230 Tasks for the Veterinary Assistant

sample must sit undisturbed for 10–20 minutes until the
blood is fully clotted. The top is removed and an appli- Reflection
cator stick is run around the inside circumference of the
tube, this breaks the clots away from the glass wall of the Envision yourself helping with a blood draw.
tube. Then the tube can be placed in a centrifuge and You are restraining the patient. Write down the
spun for about 10 minutes. procedure as it unfolds, then re‐read what you
For plasma and serum samples, the tube is carefully wrote down in comparison to the description
removed from the centrifuge, the cover is removed and in Chapter 8. Did your memory agree with the
using a pipette the liquid is extracted from the cell por- procedure? If not, re‐write the steps to cement the
tion of the sample. Care must be taken to not suck up procedure in your mind.
red blood cells as the liquid is removed. This will con-
taminate the sample. Serum and plasma should be
removed from the tube as soon as possible. The cells
within the solid portion of the tube will continue to uti- Blood Sample Handling
lize the components within the liquid, altering the test
results. Many tests require either plasma or serum and it Improper handling can result in rendering the sample
will say which in the instructions with the test kits. unfit for analysis. Rough handling or use of a needle that
To collect the blood using vacuum tubes, a holder is too small can cause hemolysis. Hemolysis is the rup-
and a blood drawing needle is used (Figure 12.14). The ture of red blood cells which imparts a red color to the
needle has two pointed ends. The shortest end, often serum or plasma. Hemolysis may interfere with some test
with a rubber sleeve for multiple tubes, turns into the results; consult the instructions that accompany each
top of the holder. The other end of the needle has a cap test.
that should remain in place until it is time for the blood Tips to prevent hemolysis:
draw. The vacuum tube is slid into the holder and
impaled upon the needle just until the top of the tube 1. Use a needle at least 22 gauge or bigger on either a
cap reaches a line on the holder. If you push it on too far syringe or in a vacuum tube holder.
the tube will lose its vacuum and not work properly. 2. Handle blood gently. Rock back and forth collection
Other supplies to gather are a couple extra tubes just in tube to mix with anticoagulant; do not shake blood.
case, cotton balls, one wetted with water and a dry one, 3. Avoid excess pressure when dispensing blood into a
and an ink or sharpie pen to write on the tube. vacuum tube from a syringe.
Once the tube is filled, if it has an anticoagulant it
must be gently rocked back and forth 3–5 times to mix Complete Blood Count
the blood with the anticoagulant. Then it can be marked
with the patient’s name, owner’s last name, date, time, The complete blood count, referred to as the CBC, is
and the initials of the venipuncturist. Red topped tubes run using whole blood collected in a lavender or green
can be marked right away and then propped at an angle topped tube. It is composed of a group of tests that is
to facilitate clotting. Purple topped tubes can be placed used in wellness exams, as a screening test before sur-
in the refrigerator for 12–24 hours before the blood cells gery, and as a tool to evaluate disease states.
start to deteriorate. Red topped tubes must be processed The individual tests of the CBC are:
as soon as the clot forms. 1. Total white blood cell count (WBC)
Some clinics use a needle and syringe to draw blood 2. Total red blood cell count (RBC)
samples and then transfer the blood to a vacuum tube. 3. Total platelet count
This requires speed and gentleness! Blood starts to clot 4. Hemoglobin
the instant it leaves the body, so the blood must be drawn 5. Hematocrit or packed cell volume, referred to as the
quickly which isn’t always easy to do when the patient is PCV
tiny! Once sufficient sample is drawn, the needle is 6. RBC indices such as the mean cell volume (MCV)
removed from the syringe and the cap from the vacuum 7. Differential
tube is removed. The blood is gently dispensed into the 8. Plasma protein.
tube and if there is an anticoagulant, the cap replaced
and the tube is rocked gently to mix. The sample must Some of the tests that make up a CBC can be run man-
be checked for clots before use. This is done by passing ually but the rest require a hematology analyzer. CBCs
one or two applicator sticks into the sample and swirling run on analyzers are often called hemograms. The tests
them gently to capture any clots. They will look like that can be done manually are the PCV, the differential,
bumps on the sticks and if present cannot be used as the and the plasma protein. The PCV reflects the percentage
clots will have changed the makeup of the sample and of RBCs in whole blood. The differential is done on a
will not represent the patient’s state of health. blood smear to determine the percentages of the various