Dogs and cats have an extensive potential subcutaneous space that can be used for the administration of drugs or fluids. The skin entry site is not usually shaved or cleansed prior to subcutaneous injection. The hair may be wetted with alcohol to better define the skin surface so the injection is not given in the haircoat.

 Needle size for subcutaneus injection ranges from 18 to 25 gauge. Use a needle size appropriate to the patient size and viscosity and volume of the fluid being injected. Subcutaneous injections can be given anywhere over the dorsal cervical, thoracic or lumbar regions. If giving large volumes of fluid, deposit 10 to 20 ml/kg at each site. In states of extreme dehydration, blood flow to and subsequently absorption from the subcutaneous site is diminished. Do not use this route in severely dehydrated animals.

To enter the subcutaneous space, pick up a fold of skin and insert the needle under the skin, parallel to the long axis of the skin fold. If the needle is inserted across the fold of skin, the needle may penetrate both folds of skin and the injection will be deposited on the haircoat (or sprayed at the person holding the animal).

After inserting the needle into the subcutaneous space, aspirate by pulling back the plunger of the syringe. If you aspirate air, the needle has penetrated both skin folds and needs to be repositioned. Once the needle is in the subcutaneous space, you can release the skin fold or you can keep the skin tented as you administer the fluid. You can deposit the fluid in the subcutaneous space as rapidly as it can be ejected from the syringe.

When administering a large volume of subcutaneous fluids, use a flexible delivery system instead of a needle rigidly attached to a syringe. Pictured is a hypodermic needle attached to a fluid extension set and then to the syringe containing the fluids to be administered.

A butterfly catheter can also be used

If more than one syringeful of fluid is to be administered, use different needles to aspirate fluids from the sterile fluid container and to administer fluids to the patient to prevent contamination of the fluid container.

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