Is aspiration necessary before injecting into the deltoid muscle for an Intramuscular (IM) injection?

From the Guidelines

No, aspiration before injecting for an intramuscular (IM) injection in the deltoid muscle is not necessary, as the risk of inadvertent intravascular injection is extremely low due to the few large blood vessels in the deltoid muscle 1. When administering an IM injection in the deltoid, you should simply clean the site with alcohol, insert the needle at a 90-degree angle, inject the medication, and withdraw the needle.

Key Points to Consider

• The deltoid muscle has few large blood vessels, making the risk of inadvertent intravascular injection extremely low 1.
• Aspiration causes additional pain, prolongs the procedure unnecessarily, and may cause tissue damage from needle movement.
• Modern injection technique focuses on proper site selection, appropriate needle length (typically 1-1.5 inches for adults), and correct anatomical landmarks to ensure safe administration.
• The deltoid injection site is identified by locating the acromion process and inserting the needle 2-3 finger widths below this point in the middle of the lateral aspect of the upper arm.

Evidence-Based Recommendation

The most recent and highest quality study, although not directly addressing IM injections in the deltoid muscle, provides guidance on injection techniques 1. However, the key takeaway from the provided evidence is that aspiration is not always necessary, and the focus should be on proper site selection and technique to minimize risks.

Important Considerations

• Even if aspiration were performed, it's not always reliable in detecting intravascular placement.
• The Centers for Disease Control and Prevention’s “General recommendations on immunization recommendations of the Advisory Committee on Immunization Practices” does not support or recommend aspiration for vaccine injections, stating that no large blood vessels exist at the recommended injection sites 1.

From the Research

Aspiration in Intramuscular Injections

• The necessity of aspiration before injecting into the deltoid muscle for an Intramuscular (IM) injection has been debated in various studies 2, 3, 4, 5.
• A systematic literature review found that aspirating during the intramuscular injection procedure is not always necessary, especially in the deltoid, ventrogluteal, and vastus lateralis sites 2.
• The review also found that the majority of health professionals do not aspirate for the recommended 5-10 seconds, and that administering an injection faster without aspiration is less painful than injecting slowly and aspirating 2.
• Another study found that the middle of the vastus lateralis is an appropriate site for intramuscular injections due to the low risk of vascular or nerve damage 6.

Deltoid Muscle Injection Sites

• A study aimed to establish a new appropriate intramuscular injection site in the deltoid muscle, and found that the intersection between the anteroposterior axillary line and the perpendicular line from the mid-acromion was the most appropriate site for IM injections 3.
• The study also found that the depth of needle insertions was 5 mm greater than the subcutaneous thickness at a 90° angle, which was sufficient to penetrate subcutaneous tissue in both sexes 3.
• Another study recommended that the deltoid intramuscular injection (IMI) must be given at or below the level of the midpoint of the deltoid muscle, but never in the upper half, and suggested a site 4 fingerbreadths/9 cm below the mid-acromion point as the safest site to avoid injury to any underlying neurovascular structures 5.

Best Practices for Intramuscular Injections

• A review of medically attended injection site events data found that nerve palsies, musculoskeletal injuries, and cutaneous reactions can occur due to inappropriate site of injection, needle over or under penetration, local sepsis, and vascular complications 4.
• The review aimed to formulate best vaccination practice procedures for deltoid intramuscular injection of vaccines through the collation and analysis of medically attended injection site events 4.
• A cadaveric pilot study found that the mean distances of the axillary nerve and posterior circumflex humeral artery from the mid-acromial point are 8.19±0.616 and 8.66±0.968 cm, respectively, and recommended a site 4 fingerbreadths/9 cm below the mid-acromion point as the safest site for IM injections 5.