Photothermal laser lithotripsy of uric acid calculi: clinical assessment of the effects of cyanide production

The mechanism of holmium:YAG lithotripsy is photothermal. Holmium:YAG lithotripsy of uric acid calculi produces cyanide, which is a known, thermal decomposition produce of uric acid. we review our experience with holmium:YAG lithotripsy of uric acid to determine if there is any clinical evidence of cyanide toxicity. A retrospective analysis of all of our cases of holmium:YAG lithotripsy of uric acid calculi was done. Anesthetic and postoperative data were reviewed. A total of 18 patients with uric acid calculi were tread with holmium:YAG lithotripsy by urethroscopy (5), retrograde nephroscopy (2), percutaneous nephrolithotomy (5) or cystolithotripsy (6). Total holmium:YAG irradiation ranged from 1.2 to 331 kJ. No patient had evidence of increased end-tidal carbon dioxide, change sin 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 neurologic, cardiac or respiratory complications were noted. These data suggest no significant cyanide toxicity from holmium:YAG lithotripsy or uric acid calculi in typical clinical settings. More specific studies in animals are warranted to characterize the risk.