Blood Aspiration Test for Cosmetic Fillers to Prevent Accidental Intravascular Injection in the Face
The author first conducted an ink aspiration test in vitro with needles recommended by manufacturers of cosmetic fillers. The author tested 17 products (3 primed syringes of each product with each syringe containing 0.1 mL of filler). The author then conducted an in vitro needle gauge test after the initial ink aspiration test: (1) fillers that had a negative ink aspiration test were retested with larger-gauge needles and (2) fillers that had a positive ink aspiration test were retested with smaller-gauge needles to determine whether a smaller needle could be used safely. According to the heading of the table reporting the results of this second test (Table 2), it seems that blood is used instead of ink. However, the text mentions nothing about this, implying that ink is used also for the second test.
To evaluate the reliability of the ink aspiration test, the author randomly selected 5 fillers that had a positive reflux test with ink for an aspiration test in rabbit ear vessels. However, according to the table identifying the “randomly” selected products (Table 1), 1 hyaluronic acid (HA) product and 1 calcium hydroxyapatite product had initial negative reflux tests with ink, making this section unclear. Furthermore, the author reported, “In the aspiration test with rabbit ear vessel in vivo, all 3 hyaluronic acids, 1 PLLA, and 1 calcium hydroxyapatite filler were positive and showed equal results regarding the time of reflux and positivity.” Based on the author's results, one could conclude that regardless of ink test results, the 3 “randomly” selected HA products and the other 2 non-HA fillers perform well in vivo. In other words, the ink test cannot be used to predict the outcome of aspiration in vivo.
Another limitation is that the author assumed that the ink solution would behave similarly to blood during aspiration. To help support the author's hypothesis, why was the ink reflux test not repeated with blood in vitro and then in vivo using the same 17 products? Other factors that were not controlled (or addressed) in the author's study that could confound aspiration results include the type of technique used to withdraw blood (speed of plunger retraction) and force of suction.2 Therefore, it is difficult to draw valid conclusions from these data suggesting that fillers with positive and negative ink reflux tests would behave similarly in blood in vivo.
In summary, the reliability of the ink aspiration test and the conclusions drawn by the author were not supported by this study. Other studies should evaluate the influence of identified confounders on blood aspiration with fillers before clinical importance of ink aspiration data can be determined.