Intramuscular Injection: Sites, Landmarks and the Z-Track Technique

Intramuscular injection puts drug into a well-perfused muscle for faster absorption than the subcutaneous route. The technique is straightforward; the site selection is where harm happens, and it is the part interns are most often taught badly by imitation.

At a glance

Finding the ventrogluteal site

This is done with your hand on the patient, not by looking. Place the palm of your hand on the greater trochanter of the hip you are injecting, with your index finger pointing towards the anterior superior iliac spine. Spread your middle finger back along the iliac crest. The triangle between your index and middle fingers, above the palm, is the target.

Every one of those landmarks is bone you can feel. That is the point — it works on patients of any body habitus, whereas estimating quadrants of a buttock by eye does not.

Why the buttock fell out of favour

The dorsogluteal site was taught for decades and is still used. The problem is that the sciatic nerve and superior gluteal vessels lie close enough that a misjudged injection can strike them, and the subcutaneous layer over the buttock is often thicker than expected, so the drug may not reach muscle at all. Sciatic nerve injury from injection is uncommon but it is devastating and permanent, and there is a site without that risk. That is the whole argument.

How it is done

1. Confirm patient, drug, dose, route, time and allergies. Check the preparation is licensed for intramuscular use.
2. Position the patient so the muscle is relaxed — a tensed muscle hurts more and resists the needle.
3. Locate the site by palpating the bony landmarks.
4. Clean the skin per local policy and let it dry.
5. For the Z-track: pull the skin and subcutaneous tissue laterally with the side of your non-dominant hand and hold it there.
6. Insert the needle at ninety degrees to the skin, in one decisive movement, deep enough to be in muscle.
7. Inject at a steady, unhurried rate.
8. Wait briefly before withdrawing so the drug disperses rather than following the needle out.
9. Withdraw, then release the displaced skin. The tissue planes slide back over one another and seal the track.
10. Do not rub. Apply gentle pressure only.
11. Dispose of the sharp yourself, immediately.
12. Document drug, dose, route, site and time.

What the Z-track is actually for

When you insert a needle straight through skin, subcutaneous fat and into muscle, you leave a straight channel. Some drugs will track back up it and reach subcutaneous tissue and skin, causing irritation, pain and in some cases staining. Displacing the skin laterally before insertion means that when you let go, the layers no longer line up, and the channel is broken. It is a mechanical solution to a mechanical problem, and it costs nothing to do routinely.

What can go wrong

What seniors actually ask

• Show me where you would put your hand to find that site.
• Why not the buttock?
• What is the Z-track for?
• What would you do if the patient shouted with electric pain as you inserted?

Last-minute checklist

• Ventrogluteal by preference; landmarks palpated, not estimated
• Muscle relaxed by positioning before you start
• Skin displaced laterally and held for Z-track
• Ninety degrees, decisive, deep enough to reach muscle
• Pause before withdrawing, then release the skin
• Radiating electric pain means stop and escalate
• Site documented

References

• Your hospital’s medicines administration policy
• The current national formulary entry for the specific drug