To Aspirate or to not Aspirate?

That is the question.

It can be widely agreed that dermal filler treatments require constant reassessment of practice for improving and safe-guarding the rapidly evolving aesthetic field. While some consider aspiration one such protocol for increased safety, others will argue it’s dubious reliability, while some will go so far as to posit that the use of aspiration as a safety measure is potentially harmful as it disallows the use of other harm reduction measures. We will examine evidence for both sides of the argument.

To Aspirate?

All injectors are ultimately aligned in the avoidance of intravascular incidents and no single method guarantees safety. If the use of pre-injection aspiration is preferred by a practitioner, the following should be kept in mind, as outlined by the “The 10-Point Plan 2021: Updated Concepts for Improved Procedural Safety During Facial Filler Treatments”: 

  1. Negative aspiration does not guarantee safe injection – slow, careful, low-volume injection is mandatory.
  2. Adequate aspiration time should be allowed (5 −7 seconds).
  3. Waiting times for visualizing flashback may be affected by physiochemical and rheological properties, with some products requiring longer negative pressure.
  4. Not all injectors are equally able to maintain a steady needle position on bone, reducing the effectiveness of aspiration as a harm reduction measure.
  5. Awareness of bevel angle (eg, 45 degrees vs perpendicular) in relation to tissue plane and vascularity is vital.
  6. With the needle in perpendicular position, the bevel tip still may be in a dangerous vascular plane despite a stable needle tip on bone, as in the forehead or temple (aSTA).
  7. Intravascular placement is possible with a cannula, especially with < 25G, and in the presence of underlying fibrosis or skin tethering.
  8. Insightful knowledge of vascular anatomy is mandatory, especially pertaining to “z-axis” or vessel depth.
  9. Constant vigilance of watershed areas such as nasal tip and glabella is mandatory as these areas often demonstrate early, fleeting blanching.
  10. Pain is not invariably present with intravascular injection.

Above list as quoted in: Heydenrych I, De Boulle K, Kapoor KM, Bertossi D. The 10-Point Plan 2021: Updated Concepts for Improved Procedural Safety During Facial Filler Treatments. Clin Cosmet Investig Dermatol. 2021;14:779-814 https://doi.org/10.2147/CCID.S315711 

Or to not Aspirate?

However, comprehensive analysis of published literature on inadvertent intravascular injection of hyaluronic acid investigating if the aspiration technique confers safety for the patient and practitioner did not appear to yield any correlation. Other factors played a more important role, such as understanding injection anatomy and good techniques, and the study “Aspiration Before Tissue Filler—An Exercise in Futility and Unsafe Practice” by Drs Goodman et al goes so far as to conclude that “if there is any doubt about the sensitivity or reliability of a negative aspiration, there is no role for its utilization” (Goodman SITE). 

The same study goes on to outline the issues around negative aspiration as a safety measure due to the following reasons:

  1. The likelihood of a false negative aspiration is high, for a variety of reasons including:
    1. Insufficient negative pressure, especially in smaller vessels.
    2. Exceptionally quick pullback aspiration will have insufficient pressure to the filler column back into the syringe on aspiration.
    3. Smaller caliber vessels may collapse under the pressure and reopen when pressure is released.
    4. After a reassuring negative aspiration, subsequent bolus injection may allow retrograde filling of the smaller upstream arteries leading to major vessels. On reaching significant vessels, the downstream flow may block the intricate tributaries and on the release of the plunger, this filler column may reverse direction with the reestablishment of normal arterial flow, both causing a variety of potentially serious issues.
  2. Currently, deep injections on bone are considered safer practice in the mid-face, deep pyriform space, and temple because they bypass the middle lamella where mimetic or masticatory muscles and major vessels are found. However, foramina are found in the supraperiosteal plane in the mid-face which have been known to create issues.
  3. Vertical needle insertion may lead to multiple layer injection, involving more superficial vasculature.
  4. Larger bore needles are considered beneficial for decreasing false-negative aspirations, however the longer bevel length poses potential problems due to the possibility of entering multiple layers on vertical injection.
  5. Priming or not priming the needle: 
    1. it seems that priming the needle will lead to a more direct transmission of pressure in a hydraulic sense, however;
    2. not priming removes the need to suck the intraluminal filler back up the needle. This may allow a vacuum to form in the hub, which will fill with blood quickly if a vessel is impaled or transited if negative pressure is transmitted through retraction of the plunger.
    3. Relying on an unprimed needle obligates the injector to withdraw after every single injection point and replace the needle with another unprimed needle which is both impractical and leads to a concentration on bolus injection to limit how many needles and injection points are to be used. 

Ready? Keep steady.

Perhaps most importantly, aspiration raises issues as it pertains to the movement of the injecting instrument, both as complete stillness is difficult to maneuver, and in that it results in the neglect of other harm-mitigation techniques that require it; “the practitioner must therefore decide between the following contradictory techniques of injection: moving or aspirating. One cannot hold both positions” (Goodman, G.J. et al, 2021). There are several arguments that the movement of the instrument in and out of vessels increases safety. It is believed to reduce the chance of inadvertently injecting an embolic bolus of filler within a single vessel, and with continual movement, any filler injected within a vessel should be small enough to dissipate harmlessly in the circulation. Commonplace bruising is a sign that injectors are in and out of vessels all the time, regardless of injection method; “the caliber of most named facial vessels is only in the order of 1 to 2 mm and movement would likely mean only a fleeting intravascular presence (unless the vessel is cannulated)” (Goodman, G.J. et al, 2021). Movement has been commonly employed over the years for retrograde and anterograde filling, ferning, fanning, and linear threading techniques. Moreover, practitioners who support a static approach rarely follow this concept when injecting other highly mobile areas such as the lips as it is highly impractical, if not impossible to aspirate and stay still with each injection point. 

Using small amplitude movements (a couple of millimeters of oscillation within the plane chosen for injection), still allows for a deposit without delivering a static bolus. The placement of the injecting instrument can also be crucial, especially when injecting on the bone; “safety may be enhanced by injecting at a non-vertical angle (at the smallest acute angle possible with the bevel surface down facing towards the bony plane) to reduce the chance of the needle bevel occupying multiple tissue planes and enabling the practitioner to move the needle if they choose to do so during the injection process” (Goodman, G.J. et al, 2021). This movement should reduce the chance of a large inadvertent intravascular bolus of filler, limiting potential ramifications such as visual loss. 

Some would argue that aspiration is a good safety precaution, while others do not find adequate evidence supporting this claim. A positive aspiration can be seen as simply a transference of the risk from one area of perceived trouble to another, shifting with it the dangers associated with a false negative, assuming a negative aspiration is attained at the next site. One could argue other factors play a larger part in increased safety, such as intentional movement at the injection site, type of instrument used, substantial anatomical understanding, and the depth, timing, pressure and direction of the injection, to name a few. As a practitioner, perhaps consider the strengths and weaknesses of your own technique, the location of the injection performed, and keep on top of the latest publications and evidence to ensure the maximum safety for your patients and yourself. 

 

References

Goodman, G. J., Magnusson, M.R., Callan P., Roberts, S., Hart, S., Lin, F., Rahman, E., McDonald, C.B., Liew, S., Porter, C., Corduff, N., & Clague, M. (2021). Aspiration Before Tissue Filler—An Exercise in Futility and Unsafe Practice, Aesthetic Surgery Journal, Volume 42, Issue 1, January 2022, Pages 89–101, https://doi.org/10.1093/asj/sjab036 

Goodman GJ, Magnusson MR, Callan P, et al. Neither Positive Nor Negative Aspiration Before Filler Injection Should Be Relied Upon as a Safety Maneuver. Aesthet Surg J. 2021;41(4):NP134-NP136. Doi: 10.1093/asj/sjaa215

Heydenrych I, De Boulle K, Kapoor KM, Bertossi D. The 10-Point Plan 2021: Updated Concepts for Improved Procedural Safety During Facial Filler Treatments. Clin Cosmet Investig Dermatol. 2021;14:779-814 https://doi.org/10.2147/CCID.S315711

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