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Chapter 11 Clinical Techniques 203

Bevel

(Lumen interior)
Shaft

FIGURE 11.29 Monoject™ brand needle sizes.

Hub Prepackaged, individually sterilized needles are avail-
able in boxes of 100 and each size is color coded.
However, the colors are not uniform across manufac-
turers. Figure 11.29 shows the Monoject™ brand of
colors. Learn what brand your clinic utilizes and then
FIGURE 11.28 Part of a hypodermic needle. memorize the color code so that in an emergency you
don’t have to stop to read each needle cap for size. Some
clinics may purchase syringe and needle combos, this
will bend over creating a burr. They also must be disin- tends to speed up set‐up, but it can be a waste if the
fected properly and sterilized between herds. needle size doesn’t match the need.
Needles come in a variety of sizes and lengths. The Guidelines for needle selection; use the smallest
lumen or circumference of a needle is measured as a gauge needle possible to accommodate the solution. If it
gauge and the larger the number the smaller the circum- is hard to pull a solution into the syringe then try a larger
ference (Figure 11.29). For example, a 25‐gauge needle gauge. If you must pass a needle through thick skin use a
is smaller than a 14 gauge needle. Selection of size is larger gauge. Use a smaller gauge if you are working on
based upon the size of the animal and the thickness of small‐sized and young animals. Blood tends to be thick
the solution to be delivered. If the solution to be given is and will become damaged if the gauge selected is too
thick like penicillin or euthanasia solution, then a larger small, usually a 22–20 gauge, 1 inch needle for dogs and
lumen is selected. If the solution is watery then select a cats is appropriate. An 18–20 gauge, 1½ inch needle is
smaller gauge. Blood cells can be destroyed if pulled appropriate for blood collection on livestock and horses.
through too small a gauge so if drawing blood try to use
the largest gauge recommended for the size of patient.
Recommended gauges for each animal group are as Preparing Syringe and Needle
follows: 30–25 gauge needles are often used on pocket for Use
pets or birds. The lengths are between 5/8 to ½ inch.
Small kittens and puppies can handle a 25–22 gauge Determine the appropriate syringe for the volume of
needle at 5/8 to 1 inch length. Adult dogs and cats can medication required. Select the appropriate needle
handle 22–20 gauge, 1 inch in length is most commonly based upon the size of the animal and the thickness of
used. Livestock and horses can handle a 20–16 gauge the solution being given or drawn out. Check the seals
needle and usually at 1½ inch in length. The most on both the syringe case and needle cover. If they have
common lengths used in veterinary medicine are 5/8, ¾, been broken you cannot be sure they haven’t been used,
1, 1½, and 2 inches. Shorter needles are used for more discard those appropriately and select another.
superficial injections. Longer needles are used for Break the seal on the syringe case and take the top off
deeper injections. but leave the syringe in the case until you have broken