Influence of irrigation on incision and coagulation of 2.0-µm continuous-wave laser: an ex vivo study.

BACKGROUND: Several lasers are suitable for laparoscopic surgery but with remarkable smoke formation, which compromises surgical visibility and safety. Slow irrigation eliminates laser smoke efficiently, but gives rise to the concern of reducing the laser incision and coagulation efficiency. METHODS: Canine kidney specimens were manually cut with a 2-µm continuous-wave Thulium-YAG laser. Two laser powers (20 and 40 W) combined with 3 irrigation rates (0, 20, and 80 mL/min) were experimented. The depth of the cutting slot and the thickness of the coagulation layer were measured microscopically and compared statistically between different setting combinations using 2-way analysis of variance. RESULTS: The incision depth was decreased significantly at high (80 mL/min) but not low rate (20 mL/min). The thickness of the coagulation layer changed insignificantly with the irrigation rate. CONCLUSIONS: Slow irrigation had an acceptable influence on the incision and the coagulation ability of 2.0-µm continuous-wave laser and is suitable and efficient to address the smoke issue in laser laparoscopic surgery.

Ex vivo evaluation of femtosecond pulse laser incision of urinary tract tissue in a liquid environment: implications for endoscopic treatment of benign ureteral strictures.

BACKGROUND: The femtosecond (FS) pulse laser incises soft tissues with minimal peripheral damage and is a promising cutting tool for ureteroscopic endoureterotomy of benign ureteral strictures. OBJECTIVE: To evaluate the feasibility of applying the FS laser to ureteroscopic endoureterotomy. MATERIALS AND METHODS: A commercial Ti:Sapphire regenerative amplifier system (Coherent, RegA 9050, USA) was used in this study. Normal saline, 5% glucose solution, 4% mannitol solution, distilled water, and a 1% (v/v) suspension of whole blood with each of these solutions were tested for their attenuation rate (AR) of the FS laser's power. Bladder specimens from Sprague-Dawley (SD) rats were used as a surrogate model. The laser incised slots of 2 mm in length at bladder samples using three power grades (5×, 10×, and 20× the threshold power) combined with five effective pulse rates (40, 20, 10, 5, and 2.5 kHz), both in air and in normal saline. After samples were processed with standard hematoxylin-eosin staining procedures, the incision depth and collateral damage range were determined microscopically. RESULTS: The ARs of blood suspensions with each of the three isosmotic solutions were significantly higher than the other five solutions (P < 0.001). The FS laser's cutting depth and the collateral damage were increased with the laser power or power density but the collateral damages were less than 100 µm. Microbubble formation was detected in the liquid environments tested and influenced the effective laser power. CONCLUSIONS: Endoscopic application of the FS laser is feasible. Microbubble formation with the laser incision, however, may influence cutting effects. Proposed methods to address these issues include increasing the irrigation rate, using distilled water as irrigation or using gas insufflation instead of irrigation. It is necessary to evaluate these methods, as well as the long-term biologic response to laser incision, on living animal models in endoscopic settings before use on humans.