Subcutaneous Fluid Therapy Lab
Presenter: Kathryn Benson
NCSU College of Vet Medicine
Hydration assessment
Hydration can be subjectively assessed by clinical appearance, or objectively assessed by weight. Percentage of
dehydration is the percentage of the animal’s weight lost in water.
% Dehydration
<5
5
6-8
10-12
>12
Clinical signs
Normal on examination
Slightly dry or tacky mucous membranes
Dry/tacky mucous membranes + skin tents/wrinkles
Same as above + sunken eyes, lethargic
animal usually dies
Skin tenting:
 Normal: Skin takes less than 1 second to return to normal position following skin tent
 Abnormal: Skin takes greater than 1 second to return to normal position following skin tent. As
hydration status worsens, skin will take an increasingly longer amount of time to return to normal
position.
 Mammals: Tent skin between shoulder blades (“scruff”) or over the back
 Birds: Tent skin on feet or legs. Please note: some birds are too small to perform the skin tenting
assessment.
o Dehydrated birds will have a flattened or sunken abdomen with wrinkled and sometimes flaky
skin.
Mucous membrane assessment: This is checked by opening the mouth and looking at the gums of mammals,
the inside of the mouth in birds, or the inside of the eyelids. Most animals will have a pale pink to pink color,
but many animals, especially birds, have a natural variation in color. Well-hydrated animals will have smooth
and slippery mucous membranes (feel the inside of your own mouth for comparison). If there is stringy or
ropey saliva, or the mucous membranes feel dry and tacky, the animal is dehydrated. This technique is clearly
not practical for all animals, since they may bite or get too stressed.
Eyes: as an animal becomes severely dehydrated, their eyes will actually sink back in their sockets.
How much to give:
● Never give more than 5% of their body weight SQ at one time.
● When in doubt, be conservative with SQ and give more fluids orally (you can never over-hydrate an
animal through their gut).
● Animals normally lose a certain amount of fluid to metabolic processes throughout the day, these are
met by their maintenance fluid requirements. Good general rules for maintenance fluid requirements for
various species are:
o Small Mammals: 50-100 ml/kg/day
o Avian: 50 ml/kg/day
o Reptiles: 10-15 ml/kg/day
 In addition to their maintenance fluid requirements you also need to address the percent dehydration
with your SQ fluid therapy. Please see the PowerPoint Presentation for an example of the math.
All about needles
All needles have numbers associated with them to tell you how big they are in diameter and how long they are.
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Learning the “needle code” will help you pick up the right size needle for the animal you have. Gauge (G) is
the measure of a needle’s diameter, and is the first number listed in a needle’s code. The length is always given
just after the gauge. For example, a 22G 1” is a 22-gauge, 1-inch needle.
A needle’s diameter gets larger as the gauge number gets smaller. For example, an 18G needle has a much
larger diameter than a 27G needle. Larger needles work well for administering larger volumes of fluids, but
you also need to take the size of your patient into account and match it to the size of your needle. You would
not want to use an 18G needle to give SQ fluids to a baby robin, but it would work in a bobcat or larger animal.
27G works well in small birds, 25G is probably the largest you would want to use. 22-25G works well in
waterfowl and raptors. 21G-27G work well in mammals, depending on their size and age.
Now for that pesky second number: the length. Generally speaking, you should NOT try to use 2 inch needles.
These are unwieldy and too long to control for most wildlife seen in NC (unless you choose to rehab bears).
You can again match the length of your needle to the size of your patient. Thus, you would probably prefer a
27G 1/2” needle for small song birds (notice the number after the G is ½” meaning one-half inch) or for baby
mammals, but can go up to 1” for most of the other wildlife.
Supplies required
Needles – appropriate size for your animal (gauge and length)
Bag of sterile fluids – Isotonic fluids, such as Lactated Ringers, Normosol-R, Normal Saline
Syringe (or fluid line for larger animals, bobcat size or larger)
Warm water bath to warm fluids – ALWAYS warm fluids to body temperature by soaking drawn fluids in a
warm water bath before injecting into an animal
Giving SubQ fluids to your patient
Tent the skin
Insert the needle bevel up. Push needle through the skin (you will feel a pop) and into the subcutaneous space.
Make sure you insert the needle parallel to the skin. If you go in at an angle, you may hit the muscle with your
needle and that will be painful for your patient.
Take care not to push the needle completely through the skin and out the other side.
Once you begin to administer fluids, you will see a bulge developing in the skin.
Location to administer SubQ fluids
 Mammals: between shoulder blades, along back in loose skin
 Birds: groin, or between shoulder blades (be careful not to puncture air sac!)
 Reptiles: groin, axilla, lower back
Needle do’s and don’ts
1. NEVER uncap a needle with your mouth! (people get disease from animals by doing this)
2. IF you uncap a needle with your mouth anyway (and ignore point 1), NEVER try to recap the needle while
still holding the cap with your mouth!
3. To safely recap a needle, place the cap on the table, counter, or other flat, stable surface and use the needle to
scoop up the cap, then use your fingers to lock the cap back on.
4. Do NOT use a needle more than once.
5. ALWAYS use a clean, sterile needle to draw fluids from a fluid bag.
6. ALWAYS dispose of needles in a sturdy container with a sturdy lid, such as a plastic milk jug, glass jar, or
specifically designed “sharps” container from your local vet clinic or hospital. Dispose of the filled, capped
container into the trash.
*Thank you to Austin Duncan, Alicia Cawlfield, and Erin Galemore for their contributions to the lab notes.
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