Utility of Preinjection Aspiration for Hyaluronic Fillers: A Novel In Vivo Human Evaluation

Background: Hyaluronic acid (HA) fillers have increased in popularity. While complications are rare, practitioners should focus on their prevention. Preinjection aspiration remains controversial as an effective safety checkpoint. Objectives: Our study investigated the utility of preinjection aspiration as a safety checkpoint for HA fillers through comparison of physiochemical and rheological properties in a novel in vivo human model. Methods: An in vivo human model consisted of a cannula inserted into a peripheral vein. Preinjection aspiration was evaluated using syringes of 10 commonly used HA fillers. The time required to visualize a flash was recorded. Results: Using a multivariable regression model, needle gauge, HA concentration, elastic modulus (G′), viscous modulus (G″), and complex modulus (G*) had significant relationships with time to flash, whereas pullback volume did not. However, when comparing pullback volume using a more appropriate paired analysis, 0.5 cc pullback volume had a significantly decreased time to flash than 0.2 cc. Conclusions: Preinjection aspiration for HA fillers has utility as a safety checkpoint. The times to visualize flashback decreased when using a human peripheral vein model compared to a previous in vitro model, suggesting that there may be real-time clinical utility of preinjection aspiration. Waiting times to visualize flashback may be affected by physiochemical and rheological properties. Additional studies would help to validate our results.