Laser lithotripsy and cyanide

Background and Purpose: Holmium:YAG lithotripsy of uric acid calculi produc es cyanide. The laser and stone parameters required to produce cyanide are poorly defined. In this study, we tested the hypotheses that cyanide produc tion: (1) varies with holmium:YAG power settings; (2) varies among holmium: YAG, pulsed-dye, and alexandrite lasers; and (3) occurs during holmium:YAG lithotripsy of all purine calculi. Materials and Methods: Holmium:YAG lithotripsy of uric acid calculi was don e using various optical fiber diameters (272-940 mu m) and pulse energies ( 0.5-1.5 J) for constant irradiation (0.25 kJ). Fragmentation and cyanide we re quantified. Cyanide values were divided by fragmentation values, and fra gment sizes were characterized. To test the second hypothesis, uric acid ca lculi were irradiated with Ho:YAG, pulsed-dye, and alexandrite lasers. Frag mentation and cyanide were measured, and cyanide per fragmentation was calc ulated. Fragment sizes were characterized. Finally, Ho:YAG lithotripsy (0.2 5 kJ) of purine and nonpurine calculi was done, and cyanide production was measured. Results: Fragmentation increased as pulse energy increased for the 550- and 940-mu m optical fibers (P < 0.05). Cyanide increased as pulse energy incr eased for all optical fibers (P < 0.002). Cyanide per fragmentation increas ed as pulse energy increased for the 272-mu m optical fiber (P = 0.03). Fra gment size increased as pulse energy increased for the 272-mu m, 550-mu m, and 940-mu m optical fibers (P < 0.001). The mean cyanide production from 0 .25 kJ of optical energy was Ho:YAG laser 106 mu g, pulsed-dye 55 mu m, and alexandrite 1 mu g (P < 0.001). The mean cyanide normalized for fragmentat ion (mu g/mg) was 1.18, 0.85, and 0.02, respectively (P < 0.001). The mean fragment size was 0.6, 1.1, and 1.9 mm, respectively (P < 0.001). After 0.2 5 kJ, the mean amount of cyanide produced was monosodium urate stones 85 mu g, uric acid 78 mu g, xanthine 17 mu g, ammonium acid urate 16 mu g, calci um phosphate 8 mu g, cystine 7 mu g, and struvite 4 mu g (P < 0.001). Conclusions: Cyanide production varies with Ho:YAG pulse energy. To minimiz e cyanide and fragment size, Ho:YAG lasertripsy is best done at a pulse ene rgy less than or equal to 1.0 J. Cyanide production from laser lithotripsy of uric acid calculi varies among Ho:YAG, pulsed-dye, and alexandrite laser s and is related to pulse duration. Cyanide is produced by Ho:YAG lasertrip sy of all purine calculi.