How many seconds should you aspirate for when injecting fillers?

Should you aspirate, or not? If you do aspirate, how many seconds of aspiration is safe and effective when you are injecting different dermal fillers? If you have watched experts and manufacturer-endorsed key opinion leaders (KOLs) demonstrating injection techniques for dermal fillers at high profile aesthetic conferences, where some aspirate and some do not, you will no doubt be rightly confused as to the safe methods of practice in medical aesthetics.

Thankfully, Dr Tim Pearce did an experiment to find out more about aspirating by injecting his own brachial vein with eight different soft tissue filler products, using both needle and cannula, and timed how long it took each one to get a flashback of blood into the syringe of dermal filler. In this blog, he will break down the test results, explain his findings, and tell you how you can do a simple test yourself, using milk!

Dr Tim will be discussing more medical aesthetic training tips as part of his upcoming webinar series, so if you’re looking to increase your CPD-certified learning and want to learn more skills to make you a better clinician, then step one is to register for the free webinars by Dr Tim.

Should you aspirate or not when injecting dermal fillers?

This all comes down to your training – those who are taught to aspirate often feel uncomfortable, or at the very least confused, when watching peers and experts who do not follow this approach, especially given their experiences and education from those who do aspirate. Likewise, there are those who have been taught not to aspirate who go on to feel judged or guilty for not doing so, when in the company of others who do aspirate!

Dr Tim does not think that the approach of ‘not aspirating’ makes you automatically unsafe, and conversely, nor does he think that ‘aspirating’ makes you automatically safe.

There is a propagation of a very ‘black and white’ thinking within aesthetic medicine which does nothing but feed the constant confusion and endless debate on the matter. There are so many factors that affect the safety of injecting, aside from the action of aspirating or not, many of which are also required to control any risk.

There are aesthetic clinicians, including trainers and KOLs, who will be quick to tell you that there is no evidence that aspirating works, but those who do aspirate and have seen their syringes fill with a flashback of blood are understandably confused by such a stance.

In recent times, there was also a view that once you had commenced injecting the filler, the needle was primed and would become filled with product, thus aspirating would no longer work, or that you would need to aspirate for at least 10 seconds or more to have any hope of aspirating blood back through the needle again.

This reasoning was being used to argue against aspirating, and Dr Tim notes that there is a considerable amount of truth to it. He learnt quite quickly in his own aesthetic learning that there are dermal filler products that simply do not aspirate, for example, undiluted calcium hydroxylapatite. Similarly, trying to aspirate a thick hyaluronic acid filler with a 31G needle or cannula is totally pointless and would require a very long wait for the product to make its way back into the cylinder of the syringe for you to see any blood, simply due to the physical properties of the product.

Dr Tim Pearce performs an aspiration experiment to see how long you should aspirate when injecting different fillers?

Many aesthetic clinicians have started advocating for a published minimum time for aspiration tests, and Dr Tim regularly gets asked this question. It is not a simple question to answer because you just do not know without testing your combination of dermal filler product and instrument – needle or cannula, and syringe – all of which affect the ease of retrograde flow.

So, guess what Dr Tim did? Yes, he tested it on his own brachial vein in 2018.

The premise for the experiment was to test a range of dermal filler, needle, and cannula combinations to see if they would detect placement in a vessel. It is important to test every combination because the physics of flow is directly affected by each component. Poiseuille’s law describes the flow of fluid in a tube. The flow is related to several factors – the viscosity of the fluid (the dermal filler and the blood), the pressure gradient across the needle or cannula, and the length and diameter of the needle or cannula. If you try this experiment yourself, everyone’s set-up will be unique, you will not be able to get concrete guidance from someone else.

Dr Tim tested five dermal filler brands, eight different products, and three different devices – cannula, BD syringe, and the manufacturers’ supplied 27- and 31-gauge needles.

The results showed that all fillers tested with a 27G needle did give a positive aspiration within 10 seconds, but most were less than 5 seconds.

The length of time varied from almost instantaneous with products like Juvéderm Volbella, to nearly half a minute with Stylage XXL using a 31G needle, and for some, it did not aspirate at all. Dr Tim believes that aspiration is futile if you are using certain combinations, for example, Juvéderm Ultra 3 and Belotero Intense with a 31G needle do not allow for positive aspirations, even with Juvéderm Ultra 2, it took 20 seconds, which is too long to be useful in a busy clinic.

He also notes that you can aspirate blood with some products with a 25G, 38mm cannula, but this is the least likely instrument to allow for positives. BD syringes do allow for aspiration to work and are more sensitive than aspirating with a normal syringe with a 31G needle.

For more information, why not download all the results and watch Dr Tim’s video on his Aspirating experiment test results: How quickly does your filler brand aspirate…if at all?.

The problem with this test is that your chosen combination of filler and instrument will likely not be on Dr Tim’s non-exhaustive list of tested combinations, so what should you do?

He has spent some time looking for common compounds that have a similar viscosity to blood – so that you do not have to, in his words, “stab yourself in the arm like I did” to test each filler product that you are likely to use.

He discovered that full cream milk is like blood, they are both colloids with a viscosity is in a very similar range. It may not be exact, but it is an easily accessible liquid for testing purposes. If you have a little bit of filler product left in a syringe at the end of a procedure, that is going to be disposed, then it will be ideal for this experiment – simply attach a clean needle, store it, and gather a small collection ready for testing using milk. Consider filming your tests as this allows you to time the experiments more accurately.

Dr Tim would love to hear your thoughts on aspirating, and see any experiments that you have a go at, so let him know what you think by dropping a comment on social media, or tag him on your videos, you can find Dr Tim Pearce on Instagram.

For more insights, he has another recently published blog called Does aspirating work? for you to read.

Aesthetics Mastery Show

How many seconds of aspiration is safe when you’re injecting dermal fillers?

Dr Tim shares the results of an experiment in which his brachial vein was injected with 8 different filler brands and a number of different instruments. We timed how long it took to get a flashback. This helps us to better understand how long you need to aspirate for.  Watch the full Aesthetics Mastery Show here.

The show has active discussion from aesthetics professionals. Some of the latest comments include:

“If you’ve gotten a flash before, you KNOW that feeling… Like you just avoided a potential disaster. It makes it scarier to not aspirate in certain regions after it happens.”

Anne Onymous

“One time I was to fill a nose dorsum (high g-prime filler, 30G needle) and immediately after aspirating, there came the blood.”

Dr Luiz Pirès

Read more and add your own comments on our YouTube channel.

Are you still anxious about delivering cosmetic injectables safely?

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Filler Complications eLearning Courses

If you want to increase your confidence by learning how to handle complications, Dr Tim Pearce offers two comprehensive courses that are highly rated by our delegates:

• Botulinum Toxin Complications Mastery
• Dermal Filler Complications Mastery

Both give CPD and certificates on completion.

In addition, browse our FREE downloadable resources on complications.

Dr Tim Pearce eLearning

Dr Tim Pearce MBChB BSc (Hons) MRCGP founded his eLearning concept in 2016 in order to provide readily accessible BOTOX® and dermal filler online courses for fellow Medical Aesthetics practitioners. His objective was to raise standards within the industry – a principle which remains just as relevant today.

Our exclusive video-led courses are designed to build confidence, knowledge and technique at every stage, working from foundation level to advanced treatments and management of complications.

Thousands of delegates have benefited from the courses and we’re highly rated on Trustpilot. For more information or to discuss which course is right for you, please get in touch with our friendly team.