Nd:YAG laser in urogenital surgery of the dog and cat

Abstract

It was hypothesized that the fiber-guided Nd:YAG laser with its incisional and hemostatic action, could be useful for meticulous tissue dissection in a subcapsular partial prostatectomy in dogs, and in laparoscopic surgery of dogs and cats. Prior to clinical use, its action was investigated in vitro. Spatial distribution of Nd:YAG laser-induced temperature distribution was investigated in a polyacrylamide gel using a dynamic color schlieren technique, comparing contact and free beam laser exposure. Short-term (up to 20s), laser-induced, thermal damage was investigated in ex vivo canine prostate tissue. Tissue temperature was measured using thermocouple probes. Prediction of thermal damage using Arrhenius theory was discussed and compared to the in vitro damage threshold, determined by histological evaluation. Contact mode laser application caused vaporization of tissue. Mean extend of tissue damage underneath the vaporization crater floor was 4 mm coagulation necrosis. The tissue damage results were comparable to the schlieren temperature distributions, indicating that the schlieren technique can be used to model laser-tissue interaction. The laser was used in subcapsular partial prostatectomy in 4 mongrel dogs and in 8 dogs with prostate carcinoma (PCA). The urethra and dorsal capsule were spared and urinary continence was maintained postoperatively. It was concluded that laser assisted subcapsular partial prostatectomy is a potential palliative treatment for PCA in dogs and that the Nd:YAG laser is capable of precise prostate tissue dissection with acceptable thermal damage margins, comparable to the in vitro study. The Nd:YAG laser was compared to bipolar electrocoagulation (BEC) forceps in laparoscopic ovariectomy (lapOVE) in dogs and cats. The Remorgida forceps, combining BEC and sharp incision in one instrument, was compared to laser surgery in lapOVE in dogs. Laparoscopic laser ovariectomy was useful but did not have a significant advantage over BEC-OVE. The main reason for this is that blood vessels of >2 mm in diameter can not be properly coagulated with the laser, and BEC forceps were still needed to prevent mesovarial hemorrhage. The Remorgida forceps reduced surgical time, was not associated with an increased complication rate, produced less fume, and was used as a stand-alone device in ovariectomy. Under certain circumstances (pedicles containing much adipose tissue) the laser performed better than Remorgida. Laser surgery took more time (~2 min) than bipolar electrosurgery in lapOVE. Obesity significantly increased surgery duration in dogs, but not in cats because of the small amount of adipose tissue in the ovarian ligament of cats. No major difficulties or complications were encountered during or after surgery. In cats, low-pressure pneumoperitoneum, easy manipulation of the ovaries and a minimal amount of fat in the ovarian ligament facilitated excellent surgical access and outcome. The main conclusion is that the Nd:YAG laser is useful for precise open and laparoscopic soft tissue surgery, with minimal accompanying thermal tissue damage and adequate hemostasis, except for blood vessels of >2 mm in diameter which are best coagulated using bipolar forceps.