Uterine surface temperature changes caused by endometrial treatment with the Nd:YAG laser

The report of a bowel injury's occurring during Nd:YAG laser ablation of the endometrium without associated uterine perforation has raised the question of the safety of the procedure. The fibers used during the initial study on temperatures caused by Nd:YAG laser treatment of uterine tissue were placed directly in contact with the tissue. The results may not be applicable to a noncontact technique. Three patients underwent measurement of surface temperature of the uterus during ablation with the Nd:YAG laser using a noncontact technique. The temperatures were within acceptable ranges in two of the patients but reached potentially dangerous levels in the third. In vitro measurements of temperatures in uterine tissue obtained from fresh hysterectomy specimens were made using fine thermocouples. The temperature rise at 10 mm was greater per joule of delivered energy at 55 W than at 95. The temperature rise varied inversely with the tissue depth when the laser was applied in a continuous fashion with a noncontact technique. When the laser was applied continuously, the temperature rise at a depth of 8 mm was significantly greater than at 10 mm. Precise knowledge of the thickness of the uterine wall may be the limiting factor in determining the safety of the procedure.