By Noel Berger DVM, MS, DABLS For The Education Center
Originally Published In Veterinary Practice News, March 2018 – Download as a PDF
Three months prior to the surgery described here, a 10-year-old female spayed tortoiseshell cat was presented for a large swelling in the neck. Approximately 300 cc of clear, thin, amber fluid was aspirated, and a representative sample was sent to an outside diagnostic laboratory for fluid analysis, the results of which were unremarkable.
One month later, the owner re-presented the cat for the same problem; again, 300 cc of clear, thin, amber fluid was aspirated. Two weeks later the owner was concerned because the cat was snoring at rest and the swelling had returned with a vengeance. Preanesthetic bloodwork was normal with the remarkable exception of hypercalcemia (14.4 mg/dl, normal 7.8-11.3). Diagnostic imaging was considered, and the decision was made to surgically explore the neck area and better define the extent of the cystic structure (Figure 1).
Endotracheal intubation for general anesthesia was achieved with some difficulty due to the displacement of the larynx caused by the cervical cystic structure. A CO2 laser was utilized with a 0.4 mm diameter focal spot size to create a full-thickness, single-pass skin incision using 15 W SuperPulse (Figure 2). These parameters created a clean and dry incision with no bleeding, making possible the enhanced visualization of vital structures. There was minimal char or thermal necrosis of the incision. The sternohyoideus muscles were exposed, weakened, and stretched by the underlying cystic structure.
To explore the area deeper, the muscles would normally require a midline transection. In this case, the CO2 laser in continuous wave (CW) mode was utilized at 12 W using a 0.8-mm diameter focal spot size to divide the muscles on midline without causing any bleeding and without rupturing the cyst (Figure 2). Because the laser’s 10,600 nm wavelength is absorbed so efficiently by histologic water, there is shallow tissue penetration. I was confident before using the laser that most all of the laser energy would vaporize only the muscle tissue, and there would not be any residual energy transmitted to the underlying cystic structure (Figure 3).
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- Figure 1: The immediate preoperative image shows gross distortion of the underlying cervical tissues. The swelling was soft, fluctuant, and contained approximately 300 cc of clear, thin fluid. The cystic structure was localized to the left side.
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- Figure 2: Immediately after making a single-pass, full-thickness skin incision with a CO2 laser, the skin edges should be wiped witn a sterile saline soaked gauze to remove any char. Note the clean, dry, and smooth edges made by the laser incision.
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- Figure 3: The sternohyoideus muscle is divided on midline using CO2 laser at a lower power density than usea for the skin incision. This ensures maintaining the integrity of the underlying cyst, so the entire lesion can be removed intact.
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- Figure 4: Precise dissection is possible using short bursts of laser energy specifically targeted to ablate connective tissue and avoid damage to vital structures. On the left side of the body, the carotid artery, vagosympathetic trunk, recurrent laryngeal nerve, and thyroid lobe must be identified and protected. The cystic structure was adhered to the esophagus, and careful dissection was required to successfully separate the diseased tissue from normal structures.
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- Figure 5: A cotton-tipped applicator is demonstrating the intact esophagus following successful dissection of the cyst A 12 Fr. red rubber feeding tube is in place to identify the organ. At this point in the procedure, the remaining connective tissue was quickly divided to remove the cyst, intact, from the neck.
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- Figure 6: The intact parathyroid cyst (parathyroid carcinoma) is completely removed. Note the soft, tan, oval mass at the caudal pole of the structure. The pathologist made an accurate diagnosis of the lesion without indicating any evidence of coagulative necrosis.
Once the cyst was more carefully dissected out of the connective tissue, it became increasingly important to clearly identify the carotid artery. vagosympathetic trunk, recurrent laryngeal nerve, esophagus, trachea, and both lobes of the thyroid gland and their associated parathyroid glands (Figure 4). The dissection required meticulous identification of structures and their supporting connective tissues. Individual fibers of nonvital structures were easily vaporized using the CO2 laser in the CW mode at 8 W using a 0.4-mm focal spot size at a defocused distance from the tissue. This allowed me to carefully divide unnecessary tissue without causing damage to vital structures or the underlying cystic structure. Every moment was spent ensuring the patient’s safety, and maintaining the integrity of the cystic structure. Throughout the dissection there was no bleeding and visualization was pristine, thanks to the precision of the laser (Figure 5).
The left thyroid lobe was normal, and the right thyroid lobe and its associated parathyroid glands were normal as well. Having experience in performing thyroidectomy, I was enthusiastically impressed with the enhanced visualization, precision, and speed that I was able to complete the procedure, specifically with the use of a surgical CO2 laser. When the final attachments were released, the entire cystic structure, including its closely associated left caudal parathyroid gland, was submitted to an outside diagnostic laboratory for histopathologic evaluation, which unfortunately reported parathyroid carcinoma with a high mitotic index (Figure 6). The surgery site was closed with standard absorbable simple interrupted sutures. Upon anesthetic recovery the patient was given pain medication, prophylactic antibiotics, and calcitriol.
The following day the owner pleasantly reported that her cat was very comfortable, eating, grooming, and back to her normal self. The snoring had resolved and there was no swelling, pain, bleeding or discharge at the surgery site. We were all impressed and pleased with the performance of the CO2 surgical laser as an ideal tool for delicate and precise surgical procedures.
Dr. Berger is a graduate of Cornell University (1988, 1989) for both his DVM and MS in clinical sciences. He has been a certified diplomate of tire American Board of Laser Surgery in veterinary surgery since 2000, and he has written a textbook on the subject. He has lectured nationwide on laser physics and clinical applications for small animal veterinarians and is available for consultation and training at Quail Hollow Animal Hospital, Wesley Chapel, Fla.
This Education Center article was underwritten by Aesculight of Bothell. Wash., the manufacturer of the only American-made CO2 laser.
