New Injectors’ Guide to Aspirating

Aspirating is always a hot topic among our aesthetics students and social media followers.

The subject of whether aspiration is useful or not is widely debated. However, as a new injector it is crucial you learn this technique and we recommend you always aspirate.

As such, aesthetic medicine expert and Harley Academy director of education, Dr Kalpna Pindolia is here to help.

In this useful guide she explores everything you need to know about aspirating as a new injector. 

At the end, you’ll also find a word from our founder, Dr Tristan Mehta, about why it’s crucial all new aesthetics practitioners learn to aspirate as trainees – even if you later choose not to…

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Your Guide to Aspirating

What is “aspirating”?

Aspirating is the process of pulling back on the plunger, whilst in situ, where filler is to be placed. This is done to ensure the needle is not in a blood vessel and prone to blockage with filler.

You may hear the phrase “aspirate on bone” – this is simply normal aspiration when you are on bone. However, you can also aspirate in soft tissues, in fat, in the lips – anywhere. We teach that you should aspirate wherever you are injecting.

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What makes an aspirate more likely to be positive or negative? 

Here are some factors to consider:

1. Primed versus non-primed needles

If the needle is primed, or once the first injection of product is completed, any further syringe drawback will involve pulling the residual product back before any blood will aspirate. This makes aspiration less likely with primed needles, even if in a blood vessel. 

If you decide not to prime, there is more likely to be a positive aspirate. But changing the needle with each injection would mean product loss in the dead space of the discarded needles.

2. Steadiness

If the syringe is not stable and steady, the tip may move in and out of a vessel. 

3. Negative pressure achieved

A syringe full of filler will produce less negative pressure on retraction of the plunger, as there’s less drawback length compared to an emptier syringe.

4. Length of time of aspiration

Too short a time for the pull back on the syringe may mean the filler is not drawn back sufficiently to provide time for potential positive flashback.

5. Speed of aspiration

Strong negative pressure created by pulling the plunger back too far, or too quickly, whilst aspirating can cause small vessels to collapse. This can then prevent withdrawal of any blood.

6. Needle gauge and length

The thinner the needle, the more potential there is for entry into the smallest of blood vessels present. A wider bore needle will mean more blood can be aspirated quickly. Longer needles mean the aspirate has to travel a greater distance to be positive.

7. Filler viscosity

Filler viscosity, cohesivity and G prime affect the flow of the filler. The higher the G prime for instance, the less likely a positive aspirate. This is because the thick dermal filler will obstruct the hub, making it less likely that blood can enter.

8. Syringe design 

Some filler syringe plungers easily fall off during aspiration, making it difficult to do well.

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What actually happens when you get a positive aspirate? 

Getting a positive aspirate means you will see blood in the needle hub. This is why looking at the hub of the needle during aspiration is crucial. New injectors sometimes forget this part whilst trying to get used to the process. 

When blood is seen in the needle hub, there is no need to panic – in fact, a sigh of relief is allowed – as a vascular occlusion is about to be prevented!

1. Breathe!

2. Remember not to inject the filler.

3. Calmly take out the needle.

4. Firmly press the area for at least 2-3 minutes to prevent blood leakage from the vessel and bruise formation.

Now you have a filler syringe contaminated with blood. What next? 

You can extrude the filler and change the needle, should there be enough filler left to continue the procedure. Place the next injection site away from the site which has just yielded blood.

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Is aspirating the best way to prevent vascular occlusion?

There are a number of good ways to reduce the risk of vascular occlusion:

1. Inject in low volumes (boluses no more than 0.1ml)

2. Use low pressure injections (achieved by high gauge needle and cannulas)

3. Always use a cannula, where appropriate.

You can aspirate with a cannula should you wish to do so. However, if you consider the factors above, this is even less likely to yield a positive aspirate than a needle. Cannulas are used to deposit filler while moving through tissue, anyway.

Advocates of aspiration propose that aspirating should be one of several precautions taken, particularly in high-risk injection areas. This should be led with good anatomical knowledge and technique.

No one factor alone, especially aspiration, will eradicate the risk of vascular occlusion. If you choose to aspirate, that’s fine, just remember that a negative aspiration should not feel like reassurance that you are not in a vessel. 

A positive aspirate is rare but, when it happens, the above is all good information to know…

4 Top Tips For Aspirating

In conclusion, my four top tips for aspirating as a new injector are…

1. Always remember that a negative aspiration result (no blood visible) is not a reliable indicator of intravascular placement of the needle. 

2. Practice – you cannot hold a needle steady whilst aspirating unless you practice.

3. Be patient – if you are aspirating, take the time to do it well, for 8-10 seconds at least.

4. Don’t skip the usual scanning of the skin itself; always look for clinical signs of vascular occlusion, as well as looking at your needle hub, when injecting.

Should aesthetics practitioners aspirate when administering fillers?

A word from our founder, cosmetic doctor and respected facial aesthetics expert, Dr Tristan Mehta on this important – and divisive – topic…

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