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Chapter 12 Laboratory Skills 233

Top lid

Inside lid

Slots for
PCV tubes

FIGURE 12.18 Hematocrit centrifuge lids and slots.

the patient’s name on a piece of paper with the tube
location. This is especially important if running several
samples at the same time. Put the inside cover on the
tray (Figure 12.18) and tighten it down with either your
fingers or the lid plyers that is usually attached to the
FIGURE 12.17 Hematocrit tubes and tray of clay sealant. centrifuge with a chain. If you forget to put this cover on,
the tubes will spin out of the slots and be busted into a
fine bloody powder. Close the outside lid (Figure 12.18)
tube will be put into the hub of the needle to draw out and set the centrifuge for 5 minutes.
just enough blood to fill the tube. Once the centrifuge has come to a complete stop,
Supplies required for a PCV include two hematocrit open the first and second lids and remove the tubes.
tubes, a tray of clay sealant (Figure 12.17), a Kem Wipe, Place them beside the PCV card reader and the refrac-
the PCV card reader, the refractometer, and a lens paper. tometer for the technician to read. If there are multiple
Cap the blood sample and gently mix it once again. patients, make sure to keep everyone’s sample separate.
Then hold both PCV tubes between your index finger Some clinics may allow the assistant to read the PCV and
and thumb on your dominant hand. Slide both tubes perform the plasma protein. If so, the following are the
into the blood and hold them and the sample almost instructions for these two tests.
horizontally in order for the blood to flow into the tubes. The tubes will have changed from a homogeneous
Once they have filled to about three‐quarters full move red color to one with three different colored layers
your index finger over the top of the tubes to prevent the (Figure 12.19). From the bottom up, the clay sealant,
blood from flowing out. Set the blood sample down and a dark red layer composed of red blood cells, just
wipe the end of the tubes off with the Kem Wipe. Then above that and often barely visible a white line is seen.
plunge the ends of the tubes into the clay to seal them. This is called the buffy coat and is composed of white
Remove the tubes from the clay and put them into the blood cells and platelets. Above that is the clear to
hematocrit centrifuge. The hematocrit centrifuge will golden liquid which is the plasma. If the color is dark
have slots to put the tubes into. To balance the centri- yellow, pink or red, or white alert the technician or
fuge, put one tube with the sealed end towards the veterinarian.
outside of the circle and then directly across the circle To determine the PCV, a microhematocrit reader or
from the first tube lay the second tube into the slot, again PCV card is used. The card can be linear or circular in
with the clay end toward the outside (Figure 12.18), oth- form. With either type of reader, align the top edge of
erwise the blood will be spun out of the tubes. Note the the sealant on the zero line (Figure 12.19) and the top
number on the slot in which the tubes are placed. Write edge of the plasma on the 100 line. The line running