Controlled temperature tissue fusion: Ho:YAG laser welding of rat intestine in Vivo, part two

Background and Objective: Temperature feedback control (TFC) during laser-assisted tissue welding was implemented to eliminate exponential increases in the rate of denaturation associated with rapidly increasing temperatures. This study was undertaken to investigate and compare the weld strengths and healing responses of laser welded enterotomies with and with- out TFC using a cw Ho:YAG laser and to examine the effects of wavelength on weld strength and histology. The Ho:YAG experimental results were compared with a similar study using cw argon ion laser irradiation. Study Design/Materials and Methods: An automated system was developed for temperature feedback controlled laser irradiation. An experimental device incorporating co-aligned laser delivery and temperature detection was used to perform cw Ho:YAG laser-welded enterotomies (with and without TFC). The weld strength and histology of laser welded and control sutured enterotomies were compared in an in vivo rat model (Ho:YAG, n = 42; argon, n = 41). Animals were sacrificed at 1, 3, 7, and 21 days postoperatively and the anastomotic site was removed for bursting/leaking pressure measurements and histological examination. Results: Argon and Ho:YAG laser-welds with and without TFC and the control sutured anastomoses healed comparably, although wound abscesses were more prevalent in the Ho:YAG group leading to delay in mucosal healing. Laser-welded anastomoses without TFC were associated with more spontaneous ruptures and leaks (argon: 4/6 ruptures; Ho:YAG: 1/4 leak, 2/4 ruptures, and 1/3 stenosis) during the survival period than those with TFC (argon: 1/3 leak; Ho:YAG: 1/5 rupture). Bursting pressures of the Ho:YAG welds were weaker at 1 week than the argon welds, but by 3 weeks, laser welds and suture anastomoses were equally strong. Conclusion: From the spontaneous failure rates encountered, it is believed that TFC improves the quality and stability of laser-assisted enterotomy closures in surviving animals. However, TFC does not provide a satisfactory method to identify completion of a weld.