Selecting the needle gauge:
19 g to 25 g needle is used for intramuscular injections. Needles smaller than 22 gauge may break or bend upon entering the muscle (in adults). 25 g commonly used in children.
Selecting the needle length:
Use a 1 – 2 inch needle depending on the size of the site chosen. On adults, a 1-inch needle is used in the deltoid and vastus lateralis muscles. A 1.5 inch is most commonly used for the gluteus medius although a 1-inch may be used on small patients.
Selecting the syringe:
A 2 to 5 ml syringe is used. On pediatric patients, a tuberculin syringe is commonly used to measure small doses.
Located in the upper arm, the deltoid muscle is easily accessible. It is a small muscle and cannot receive more than 2 ml of nonirritating medication. While this muscle is adequate in a well developed arm, it has limited use in small adults and children.
Locating the Deltoid Site: The deltoid site is located in the middle of the upper arm. The boundaries are 2-3 fingerbreadths below the acromion process, and roughly opposite the axilla.
Vastus Lateralis Site:
The vastus lateralis muscle, located in the middle third of the upper, outer thigh, is relatively free from major nerves and blood vessels. It is accessible in the Fowlers, supine, or dorsal recumbent position. This site is preferred in infants and small children whose deltoid and gluteal muscles are undeveloped. It is well suited for large or obese patients.
On an adult, the boundaries of the site and 1 hand breadth above the knee, 1 Handbreadth below the greater trochanter, mid-anterior thigh and mid-lateral thigh. Inject 1 inch into the muscle.
On infants and children look for the anterior surface of the midlateral thigh. The muscle is more visible if the child’s leg is extended. Inject well into the muscle.
This site is the posterior approach to the gluteus medius muscle and is commonly used. This is a large muscle that can receive a greater amount of more irritating medication than the deltoid. The maximum dose for one site in a well developed person is 5 ml. The patient may be prone or standing with his weight on the opposite side.
Locating the Dorsogluteal Site: Divide the buttock into quadrants using the upper iliac crest, the inner crease of the buttock, the lower edge of the buttock and the side of the patient as your boundaries. Identify the upper outer quadrant. The injection is given into the upper, outer area of this quadrant.
This is the side approach to the gluteus medius muscle. It has fewer nerves and vessels than the dorsogluteal area and may be given if the patient is in the supine, prone, Sims, or lithotomy position.
Locating the Ventrogluteal Site: Place the palm of your hand on the greater trochanter. Point one finger toward the anterior superior iliac spine and the adjacent finger toward the crest of the ilium. The injection site is the middle or lower aspect of the triangle formed by the fingers (approximately 1 inch below the iliac spine).