Presentation Authors: Scott Wiener*, Matt Mellema, Yuri Pishchalnikov, William Behnke-Parks, Daniel Laser, Marshall Stoller, San Francisco, CA
Introduction: Holmium:YAG lasers fragment urinary stones through both photothermal effects and generation of cavitation bubbles. Improved synthetic stone mass loss has been demonstrated for laser lithotripsy in the presence of stone targeting microbubbles. The present study hypothesizes that lipid-shell microbubbles with stone-binding properties also create smaller and more numerous stone fragments through enhancement of cavitation effects.
Methods: Synthetic hydroxyapatite (HA) discs [13 mm x 1.8 mm] were fragmented with a pulsed 100W Holmium:YAG laser (1000Î¼m fiber) along a circular path 9 mm in diameter over 60 seconds (Figure). This was performed with (n=10) and without (n=10) targeting microbubbles composed of a lipid-shell with calcium-binding moieties and perfluoroalkane gas. HA discs were weighed dry before and after a single lithotripsy session in which all fragments > 0.5mm were recovered using a sieve mesh. Fragments were digitally photographed on a standardized stage such that number, size, and volume of fragments could be calculated using ImageJ software. Comparisons were made with a 2-tailed Mann-Whitney U-test.
Results: The mean number of stone fragments was 4.6Â±1.6 for control vs 6.9Â±1.9 (p=0.02) for targeting microbubbles. The median fragment volume was 31 mm3 (IQR 21-67) for control and 26 mm3 (IQR 10-45) for targeting microbubbles (p=0.041). Mean stone mass loss was 3.9Â±3 mg for control vs. 11.3Â±5 mg for targeting microbubbles (p=0.045).
Conclusions: Targeting microbubbles fragment HA stones into smaller and more numerous fragments during in vitro Holmium:YAG laser lithotripsy in addition to causing increased mass loss. Stone targeting microbubbles, when used as an adjunct with Holmium laser lithotripsy, have the potential to reduce operative time, increase the number and decrease the size of stone fragments, and thereby result in higher stone-free rates and improved patient outcomes.
Source of Funding: Study funded by Applaud Medical