Should we aspirate to check for blood during intralesional injections in patients of various demographics and conditions?

Aspiration During Intralesional Injections

For intralesional injections, you should NOT routinely aspirate to check for blood, but you must avoid specific high-risk anatomical sites where vascular compromise is a concern.

Key Recommendation

The primary safety measure for intralesional injections is anatomical site selection rather than aspiration technique. 1 The IDSA/ASTMH guidelines explicitly state that intralesional pentavalent antimonial injections "should not be used on fingers, nose, ears, eyelids, near the lips, or anywhere vascular compromise could be of concern." 1

Rationale for Not Routinely Aspirating

The evidence supporting routine aspiration for intralesional injections is weak:

• Anatomical considerations: When proper injection sites are selected (avoiding areas with major vessels), aspiration becomes unnecessary because no large blood vessels exist at recommended sites 2

• Technical limitations: The intralesional technique involves injecting into the dermis under pressure using small-gauge needles (25-27G), where the injection "may be met with resistance" 1. This resistance and the dermal location make blood aspiration technically unreliable

• False-negative rates: Research on dermal injections shows aspiration has a false-negative rate up to 47%, meaning blood may not appear even when the needle is intravascular 3, 4

Proper Intralesional Injection Technique

Instead of relying on aspiration, follow this algorithm:

1. Site selection first: Avoid fingers, nose, ears, eyelids, lips, and any area where vascular compromise is possible 1

2. Cleanse the area with Betadine or soap and water 1

3. Use appropriate equipment: 25-27G needle, approaching at a right angle initially 1

4. Inject into dermis: Infiltrate in a V-shaped pattern under pressure, treating the entire lesion plus 1-2 mm of surrounding normal-appearing skin until blanching is seen 1

5. Monitor for blanching: This visual endpoint confirms proper dermal placement and adequate infiltration 1

When Aspiration IS Indicated

Aspiration remains important in other injection contexts:

• Local anesthetics: Always aspirate before injecting anesthetics (like EMLA cream used before intralesional injections) to prevent local anesthetic systemic toxicity 3

• Intramuscular injections of medications with different IV versus IM safety profiles: If a medication has different administration rates, doses, or concerns when given IM versus IV, aspiration should be implemented 5

Common Pitfalls to Avoid

• Don't confuse intralesional with intramuscular technique: The CDC recommendation against aspiration for vaccines 2 does not directly apply to intralesional injections, which have different anatomical considerations

• Don't rely solely on aspiration for safety: Even if you choose to aspirate, the high false-negative rate means absence of blood does not guarantee extravascular placement 3, 4

• Don't inject in high-risk anatomical zones: This is more important than any aspiration technique 1