Subcutaneous injection

MOUSE

The mouse should be restrained in the normal manner. With your fingers, lift the skin to make a “tent”. Disinfect the injection site and insert needle into the subcutaneous tissue. Aspirate prior to making the injection. Proper placement should yield no aspirate. Inject.

*  Most common injection site is the loose skin around the neck and shoulder area.

Subcutaneous

Subcutaneous injections are used often to inject anesthetics or to administer fluids for hydration during anesthesia recovery. The subcutaneous route of injection is often abbreviated as SC or SQ. The amount of fluid injected should be limited to volumes that will not overly stretch the skin (which would be uncomfortable) or that will not over-hydrate the animal unnecessarily. Typical volumes injected subcutaneously are in the range of 1 ml or less.

Procedure
  1. Lift the skin over the back to form a tent.
  2. When injecting an awake mouse, place the mouse on the wire lid so it can hang on with its front paws during the injection. Scruff the skin over the back and tent it up. Your hand is both restraining the mouse and presenting the area to be injected.
  3. Insert the needle at the tent base, being careful to avoid directing the needle at your fingers. Your fingers should be at top of the tent, safely above the point of the needle’s entry. Hold the needle parallel to the animal’s body to also avoid puncturing underlying structures.
  4. Aspirate to ensure that the needle has not entered a blood vessel.
  5. Inject the full volume at a moderate rate.
  6. Withdraw the needle and then press the skin to seal the needle’s exit hole in the skin and to prevent the fluid from leaking out.
  7. Check the animal for any bleeding.
  8. Because the fluid has been deposited in the subcutaneous space, you can see and feel the bubble of fluid, called a bleb.
  9. Note: Mice will generally not object to a subcutaneous injection when they are allowed to grasp the wire lid.

RAT

Restrain the rat by grasping the base of the tail with one hand and with the other, flatten the rat against the table. With your fingers, lift the skin to make a “tent”. Disinfect injection site and insert needle into the subcutaneous tissue. Aspirate. You should not aspirate anything. Inject.

* Most common injection site is the loose skin around neck and shoulder area.
*** The recommended needle size for SQ injections is 23-25 gauge.

Information from AALAS Learning Library