Is Aspiration Necessary for Safe Dermal Filler Injections?

‘Do you aspirate?’ is the most common question we’re ask on our training courses and live injecting webinars! Its clearly a hot topic and often contentious in the world of aesthetics.

What is Aspiration in Dermal Filler Injection?

Aspirating when injecting dermal fillers, often referred to as the aspiration technique, is a practice used in aesthetic procedures to enhance safety. This technique involves pulling back on the syringe plunger before injecting. The idea is that if the tip of the needle has been placed in a blood vessel, there will be a flashback of blood into the syringe, known as a “positive aspirate.” If blood is aspirated and you were inside a blood vessel, injecting the filler could lead to a vascular occlusion and subsequent tissue necrosis. A “negative aspirate” (no blood on drawing back) indicates that the needle tip is not in a vessel and is therefore safer to inject. Overall, the aspiration technique is used in aesthetic procedures as a safety tool aimed at reducing the risk of intravascular injection.

Role of Aspiration in Preventing Vascular Occlusion

Vascular occlusion is one of the most feared complications and any tool to help reduce the frequency of these incidents for aesthetic practitioners is helpful! But what are the considerations in this debate and how should aspiration be utilised in day-to-day practice?

Key Considerations for Aspiration in Dermal Filler Injections

• The first is that using aspiration is not a 100% reliable tool and can yield false negative results, meaning that blood may not always be aspirated even when a blood vessel is inadvertently punctured. It can therefore give false reassure to the injector during procedures. Several studies have shown that aspiration might not be possible even if the needle tip is within a vessel and that the reliability of the test is poor (studies reporting 33-63% reliability2) which makes interpreting the result of an aspiration test difficult 2,3.
• The next consideration is when to aspirate. For the safety tool to be effective, the needle tip must not move during the filler injection at the aspiration location. We know that when injecting dermal fillers, the pressure/volume of the product being injected will often move the needle tip, and the practitioner will also often move the needle to deliver the filler (unless using a bolus technique). Once the needle tip has been moved, the aspiration test is no longer accurate. Does this mean that the injector should continuously aspirate and inject throughout each thread of filler for the tool to be effective in preventing a filler injection complication?
• The product rheology (properties of the dermal filler such as elasticity and flow) may also impact the aspiration technique in terms of the amount of time needed to draw back on the plunger and how far you pull it back. Especially when using high density filler, it is challenging to achieve a positive aspirate of blood into the syringe. Once the needle has been primed (filler has been pushed through the needle and no longer filled with air) the effectiveness of aspiration also reduces.
• Another consideration is that aspiration is used to reduce the risk of a direct occlusion when filler is placed intravascularly. However, there are other mechanisms such as external vessel compression (indirect occlusion) and vascular spasm which are unlikely to be reduced in frequency with aspiration.

My concern when training new practitioners like doctors, dentists, and nurses is that there is excess focus and over reliance on aspiration rather than consider the bigger picture of the procedure. Aspiration can also be technically challenging for less experienced injectors again reducing its effectiveness.

Safety Tips for Injectors

My top tips for injectors are to prioritise these factors when injecting to maximise safety:

• Ensure sound knowledge of vascular anatomy of the face
• Avoid overfilling, use small volumes of dermal filler
• Inject slowly
• Continuously assess the patient/local tissues (skin changes, blanching, pain levels) throughout injector
• Use injected local anaesthetics (e.g. lidocaine) and/or adrenaline with caution as can mask signs of a vascular occlusion
• Consider using a blunt-ended cannula in higher risk areas
• Be cautious when treating patients who have undergone rhinoplasty or other facial surgical procedures as the vasculature may be altered
• Use reversible hyaluronic acid dermal fillers that can be managed with hyaluronidase the in the event of a vascular occlusion

A Broader Approach to Safety

Aspiration is a tool that can be used when injecting dermal filler, but assessment of safety cannot be reduced to the idea that an injector who aspirates equals a safe injector. At Derma Medical we encourage a range of clinical tools to maximise safety whilst delivering the best aesthetic outcomes.