San Diego, CA USA (UroToday.com) In performing laser lithotripsy, previous models of these devices have only offered two modes: short pulse and long pulse. More recent models however, offer various ranges, from ultra-short-pulses (150 µm) to short (300 µm) to medium (600 µm) to long pulses (800 µm). Dr. Kronenberg describes the pulses like a cup of water being poured over a sand castle.
Shorter pulses would be analogous to quickly dropping the water, which would demolish the sand, while longer pulses would be like a steady stream being poured, allowing the sand castle to retain its structure.
In this non-funded study, Dr. Kronenberg and colleages evaluated the different pulse modes against two artificial stones, Plaster of Paris and Begostone. Using the novel lithotripter, StoneLight 30 from AMS with AMS’s SurFlex 273-µm core laser fibers, the authors tested the various pulses at 30-second intervals. They found that each of the different pulse lengths yielded statistically significant differences in ablation volumes (p<0.00001). Ablation volumes were inversely proportional to the wavelengths, i.e. shorter pulses yielded greater ablation volumes and vice versa. When comparing the ultra-short pulse to the long pulse, the energy deliver of the ultra-short pulse was 5.3 times faster. Dr. Kronenberg describes this as being similar to the amount of air mass distributed on a windy day. With 50 mph winds, with the air mass spread over 5 minutes, no significant change would occur. However, if the same air mass was blown in 1 minute, streets would be destroyed.
In conclusion, the authors explained that although shorter pulses led to bigger ablation volumes, the drawback was increased retropulsion on larger or entrapped stones, while only smaller calculi are affected and also chasing of the stone. That is, short pulses will yield fragments of stone, while longer pulses we more prone to dusting. Lastly, he added that lithotripter settings should be adjusted on a case by case basis.
Presented By: Peter Kronenberg, MD
Written By: Victor Huynh, CCRP, Department of Urology, University of California, Irvine at the 2016 AUA Annual Meeting - May 6 - 10, 2016 – San Diego, California, USA