Saline Aspiration Negative Intravascular Test: Mitigating Risk with Facial Fillers
Injectable fillers are among the most common nonsurgical cosmetic procedures, with significant growth yearly. Knowledge of rheological and mechanical characteristics of fillers, facial anatomy and injection technique are essential for safety. Concepts such as the use of cannula versus needle, aspiration before injection and facial danger zones have been well discussed; injectors should always have the concept of ‘’no safe zones’’ when performing facial fillers. In case of accidental intravascular puncture, the pressure inside the vessel may not be sufficient to push blood into the syringe due to the characteristics of the filler product (i.e., thick gel may not allow an adequate flash when aspirating); this is especially true for calcium hydroxyapatite (CaHA), hyaluronic acid (HA) fillers with high G* (complex modulus) or fat. Since viscoelastic properties of normal saline are much lower than those of fillers, aspiration with saline prior to filler injection may decrease the risk of a false negative aspiration and subsequent catastrophic effects. The risk of accidental intravascular puncture has been calculated to be between 1:6410 to 1:40882 syringes among expert injectors, however, the consequences of intravascular injection can be catastrophic even with experienced plastic surgeons or dermatologists. Indeed, among a study of 370 dermatologists with vast experience, 28% reported a vascular occlusion; risk was lower with cannula. We discuss a technique to add an additional safety step to the procedure with saline aspiration prior to injection. This is essentially the reverse of a Seldinger technique used for vascular access, wherein the goal is to check that one is inside a vessel initially by aspirating with a saline-filled syringe. In our technique, we aspirate to check that we are outside of a major vessel, which we term Saline Aspiration Negative Intravascular Test (SANIT). This may be especially useful in areas where a bolus is to be injected for volume gain or a lifting effect, such as the nose, glabella, temporal and zygomatic regions, the chin or mandible. In this abstract we present the author’s (PSP) technique which adds an additional safety step to the process of filler injection, with both CaHA, HA and fat, in order to decrease risk of intravascular injection.
Methods/Technique:
Normal skin cleansing and topical anesthesia with prilocaine/lidocaine cream are performed; the facial subunits to be treated are marked. A 3mL Luer lock syringe is filled with 2mL of 0.9% normal saline and a 27G needle, which is turned one half rotation. When a cannula is to be used, the Luer lock syringe is attached to a 27G 4cm single hole disposable cannula. After skin puncture, the 3mL syringe is advanced with the plunger pulled back (negative pressure). Progress is made to the desired depth of injection, all the while aspirating. Once the desired location of filler injection is reached, the syringe is exchanged for the syringe containing filler, securely grabbing the hub of the needle and taking care to not dislodge the needle tip. Prior to this, we remove 0.1mL of filler to allow for space inside the syringe for aspiration. We again aspirate and inject retrograde as a stack or bolus. SANIT is especially useful for fat or CaHA, since the G’ is much higher than HA and thus reflux of blood into the syringe is exceedingly unlikely to occur.
Results/Complications:
The technique has been used by the author (PSP) safely for the past 2 years with no adverse events; the increase in cost is negligible (only the cost of 2mL of normal saline and a 3mL syringe). Twenty-five patients undergoing HA or CaHA injection to the nose, temporal, glabellar or malar regions (total of 73 syringes) were treated with this technique. There was one case of a positive SANIT test in the temporal region, despite pre-procedure marking of visible veins and superficial temporal artery course; the needle was withdrawn, compression applied for 15 minutes, and subsequent saline aspiration test and HA injection were performed 2 days later. This technique is suited for bolus or stacked injection in danger zones, while it is not practical for the tear trough or other regions where tiny volumes of filler are to be used, or when a fanning or microbolus technique is needed.
Conclusion:
While the risk of intravascular filler injection is low, consequences can be disastrous. All practitioners performing facial fillers should be aware that there is no true safe zone for filler injection and must have necessary safety supplies, including hyaluronidase, and protocols in place. We believe that adding the SANIT technique can help further mitigate risk with no significant untoward effects and could be considered as an additional safety step by facial filler injectors. Further studies are needed to evaluate the reproducibility and safety of the technique is ongoing.