Background and Objectives
Clinicians have yet to reach a consensus on whether blood aspiration tests are reliable when administering filler injections. Better understanding of the characteristics and patterns of blood aspiration tests for filler injections is important in reducing false negative results. In this study, we sought to outline the characteristics of blood aspiration tests for different types of fillers with different gauges of needles and cannulas.
Materials and Methods
Four biphasic hyaluronic acid fillers and ten monophasic hyaluronic acid fillers of four brands and two collagen stimulators were tested. Aspiration tests were performed with needles and cannulas of different gauges . The time before blood was seen in the needle hub and the vacuum space patterns generated were analyzed.
Results
Different aspiration patterns were observed with different fillers, depending on the viscosity of the product and the sizes of the needle and cannula used.
Conclusion
When factors influencing aspiration are considered, including the characteristics of fillers and the size of injection tools, aspiration tests with proper maneuver can be helpful to increase injection safety.

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Keywords: Fillers, Aspiration, Complications, Prevention