Holmium: YAG lithotripsy: optimal power settings.

PURPOSE: We tested the hypothesis that holmium:YAG laser lithotripsy speed is best maximized by using low pulse energy at high pulse frequency. MATERIALS AND METHODS: To demonstrate that optical fiber damage increases with pulse energy and irradiation, the 365-microm optical fiber irradiated calcium hydrogen phosphate dihydrate (CHPD), calcium oxalate monohydrate (COM), cystine, magnesium ammonium phosphate hexahydrate (MAPH), and uric acid calculi at pulse energies of 0.5 to 2.0 J. Optical energy output was measured with an energy detector after 10 J to 200 J of total energy. To demonstrate that lithotripsy efficiency varies with power, fragmentation was measured at constant power settings at total energies of 200 J and 1 kJ with the 365-microm optical fiber. Fragmentation was measured for the 272-microm optical fiber at pulse energies of 0.5 J to 1.5 J at 10 Hz. To demonstrate that low pulse energy produces smaller fragments than high pulse energy, fragment size was characterized for COM and uric acid calculi after 0.25 kJ of irradiation using the 272-microm to 940-microm optical fibers at 0.5 J to 1.5 J. RESULTS: Damage to the 365-microm optical fiber was greatest for irradiation of CHPD, followed by MAPH, and COM (P<0.001). There was no significant optical fiber damage after cystine and uric acid lithotripsy. For the 365-microm optical fiber and CHPD, fragmentation after 200 J was greatest for pulse energies < or =1.0 J (P< 0.001). For other compositions, fragmentation was not statistically different among the power settings for constant irradiation. No significant difference was noted in fragmentation for any composition at different pulse energies (1.0 v. 2.0 J) for 1-kJ irradiation. However, for all compositions, the calculated lithotripsy speed was greatest at high power settings (P<0.001). For the 272-microm optical fiber, CHPD fragmentation was greatest for the 1.0-J pulse energy. The mean fragment size and relative quantity of fragments > or =2 mm both increased as pulse energy increased. CONCLUSIONS: Optical fiber degradation varies with stone composition, irradiation, and pulse energy. Holmium:YAG lithotripsy speed is maximized with higher power (either increased pulse energy or higher pulse frequency). Because low pulse energy may be safer and yields smaller fragments than high pulse energy, holmium:YAG lithotripsy speed is best increased by using pulse energies < or =1.0 J at a high repetition rate.

Holmium:YAG lithotripsy of uric acid calculi.

PURPOSE: Holmium:YAG lithotripsy of uric acid calculi produces cyanide. We review our experience with holmium:YAG lithotripsy of uric acid calculi to determine if there is any clinical evidence of cyanide toxicity. MATERIALS AND METHODS: A retrospective analysis of all of our cases of holmium:YAG lithotripsy of uric acid calculi was done. Anesthetic and postoperative data were reviewed. RESULTS: A total of 18 patients with uric acid calculi were treated with holmium:YAG lithotripsy by ureteroscopy (5), retrograde nephroscopy (2), percutaneous nephrolithotomy (5) or cystolithotripsy (6). No patient had increased end-tidal carbon dioxide, changes in electrocardiogram or significant decrease in postoperative serum bicarbonate. An 84-year-old woman had decreased diastolic pressure of 30 mm. Hg while under general anesthesia. No cyanide related neurological, cardiac or respiratory complications were noted. CONCLUSIONS: There were no obvious cyanide related complications from holmium:YAG lithotripsy of uric acid calculi. These data suggest no significant cyanide toxicity from holmium:YAG lithotripsy of uric acid calculi in typical clinical settings. Animal studies are warranted to characterize the risk.