Aspiration Revisited: Prospective Evaluation of a Physiologically Pressurized Model With Animal Correlation and Broader Applicability to Filler Complications.

Background: Aspiration testing before filler injection is controversial. Some believe that aspiration can help prevent inadvertent intravascular injection, whereas others cite false-negative results and question its value given that the needle position always changes somewhat during injection procedures.

Objectives: The authors sought to test the relation of false-negative results to the viscosity of the material within the needle lumen and determine whether a less viscous material within the needle lumen could decrease the incidence of false-negative results.

Methods: In vitro aspiration tests were performed utilizing 30-G and 27-G needle gauges, 2 cross-linked hyaluronic acid fillers, normal saline bags pressurized at 140 and 10 mmHg to mimic human arterial and venous pressures, and 3 needle lumen conditions (normal saline, air, and filler). Testing was repeated 3 times under each study condition (72 tests in total). For in vivo correlation, aspiration tests were performed on femoral arteries and central auricular veins in 3 rabbits (4-5 aspirations per site, 48 tests in total).

Results: In vitro and in vivo testing utilizing 30-G needles containing filler both showed false-negative results on aspiration testing. In vitro and in vivo testing utilizing needles containing saline or air showed positive findings.

Conclusions: False-negative results from aspiration testing may be reduced by pre-filling the needle lumen with saline rather than a filler. The pressurized system may help overcome challenges of animal models with intravascular pressures significantly different from those of humans. The adaptability of this system to mimic various vessel pressures may facilitate physiologically relevant studies of vascular complications.