In the August, 2000 issue of"Accuvet LaserPoints," Dr. Gary Norsworthy presented an article about "Tough Tumors to Remove." He related a case of sebaceous gland adenocarcinoma in the ear canal of a cat and how he would do a lateral ear canal resection to access the tumor to laser it.
I would like to expand on this topic of the use of the AccuVet NovaPulse laser in treating ear diseases.
I have been using the laser through the MedRx Video Vetscope (MedRx Inc. Seminole, FL) to vaporize tumors in the ear canal without having to do a lateral ear canal resection. I also do laser myringotomy in my otisis media cases. The Vetscope probe is a specially designed tapered Video Otoscope which contains a lens pack that provides a crystal clear image of the ear canal. The Vetscope probe is mounted to a miniature camera connected to a video monitor and provides a highly magnified image of the structures in the ear canal. There is a straight 2mm working channel built into the probe that allows rigid instrument, endoscopic forceps and catheters to be passed through the Vetscope.
I use a 180mm x 0.8 mm laser tip that will go right through the Vetscope. The laser tip is placed into the Vetscope so that the beveled tip is just in view on the video monitor. When I remove ear tumors, I set the NovaPulse laser to the P10 program and 3-4 watts. I want to melt the tumor without casein any charring.
The P10 program provides a 100 millisecond laser pulse and then an 800 millisecond pause so that I can move the Vetscope/Laser combination to the adjacent area before the next pulse. In this manner I can get very precise destruction of the tumor.
Another advantage of the P10 program is that after the short laser pulse, there is a puff of air to clear the smoke. So the evacuator is not needed. If there is concern about possibly hitting the tympanic membrane, a small saline soaked cotton tipped applicator can be placed into the ear canal behind the tumor.
The other procedure that I do is laser myringotomy. With the Vetscope, I can get a good examination of the eardrum. I often see otitis media with exudate behind the ear drum. If the eardrum is intact it needs to be punctured to drain the exudate and to flush out the bulla. If there is a painful bulging eardrum, the increased fluid pressure can be relieved by puncturing the eardrum.
To perform the laser myringotomy, I use the same P10 program, but I use 6-8 watts for only 3-5 pulses without moving the laser's position. The goal is to melt a small hole in the eardrum so that I can insert a 3 1/2 Fr. Tomcat catheter through it. The location for the hole is at the 5:00 or 7:00 position at the periphery of the eardrum away from the malleous bone. Puncturing the eardrum in that location preserves vital structures necessary to allow the eardrum to heal after the procedure.
The combination of the MedRx Video Vetscope and the Accuvet NovaPulse is an unbeatable combination for simplifying two very difficult procedures
The laser is placed in a defocused mode. The lesions are vaporized layer by layer with the resulting carbonization being wiped away frequently to allow for visualization of the lased area for further lasing. Once the desired depth is reached, the eschar or carbonization is left to help keep small blood vessels sealed.
A focused cutting mode is is used much as a scalpel to perform a virtually bloodless gingivectomy to remove hyperplastic areas. Human dental patients experienced less pain on the side of the laser surgery compared to contralateral lesions removed with the scapel.
Saline moistened sponges are placed over exposed facial areas to protect the patient from in adverting aiming of the laser beam. Safety glasses are worn by the operator and assistant(s). An evacuator is used to remove the laser smoke plume from the surgical area to protect the operators.
For excisions, a superficial incision away from the tumor is made with a focused beam, An edge of wound is lifted with an instrument from the base of the mass and with traction the laser is applied to the underside of the margin vaporizing the attached tissue.
The operator has the option of applying the laser to either focused or defocused in a continuous or pulsed mode, and at varying wattage (or power) settings. A lesion operated at continuous power is exposed to more energy which allows the biopsy to be completed faster. The lesions lased using the pulsed mode are exposed to less energy and less tissue destruction, but take longer to excise or ablate.
Hard tissues (bone, tooth structure)- osseous tissue has less water content than oral mucosa, therefore carbon dioxide laser light is not readily absorbed by bone (will only remove three or four cell layers) thus making it ineffective for cutting bone and potentially harmful for a vital tooth.
In procurement of free gingivial grafts and preparation of recipient sites. Since the laser seals off the blood vessels for up to three days, using a laser could jeopardize the initial vascularization of the free gingival grafts.
In soft tissue pocketing where there is a minimal band of attached keratinized gingiva. If a gingivectomy/gingivoplasty is to be performed, there may not be enough attached gingiva to result in success.