CO₂ laser en bloc resection of equine dermal tumor mass

By Ruth Garvenell, RVN, For The Education Center
Originally Published In Veterinary Practice News, June 2017 – Download as a PDF

Zara, a 26-year-old mare, presented for an ulcerated dermal mass (presumed to be a sarcoid) on her left hind fetlock (Figure 1). Prior to 2014, a small, reoccurring wound was present for approximately nine years. In 2014, it developed into a 2-centimeter firm, pink lump, and within a year, it slowly increased to about the size of a golf ball. In October 2016, the tumor suddenly became ulcerated, and in November, the owner opted for surgical removal.

Anesthesia

The patient was premedicated with phenylbutazone (anti- inflammatory), penicillin (antibiotic) and acepromazine (sedative/tranquillizer). General anesthesia was induced with romifidine, ketamine and diazepam, and maintained with isoflurane in oxygen via an endotracheal tube.

Laser Equipment and Settings

A 40-watt surgical CO₂ laser with a flexible hollow waveguide (Aesculight by LightScalpel LLC, Bothell, Wash.) and a tipless adjustable handpiece (Figures 3-A through 3-E) were used.

For the resection, the laser was used at 20 watts in SuperPulse mode with a focal spot size of 0.4 millimeters. For tumor bed ablation, the same settings were utilized with the focal spot size increased to 1.4 millimeters to achieve better hemostasis.

Procedure Preparation

The patient was positioned in right lateral recumbency. A large clip and routine skin preparation around the distal metacarpus and the left hind fetlock were performed (Figures 2-A, 2-B). An indelible marker was used to plan 1.5- to 2-centimeter margins for surgical excision (Figure 2-C).

A sterile skin preparation was performed, followed by a standard sterile scrub and gloving.

Drapes were applied and secured with towel clamps.

Laser Procedure

Using the CO₂ laser, the mass was circumscribed (Figure 3-A). After the initial incision, traction tension was applied via forceps to ensure faster, more efficient resection (Figures 3-B, 3-C, 3-D). The mass was undermined sharply (Figures 3-C, 3-D).

Post-resection, the focal laser spot size was increased to 1.4 millimeters, and the exposed subcutaneous surface was ablated lightly to remove any possible remaining tumor cells and to control minor bleeding (Figure 3-E).

The large wound was left unsutured to heal by secondary intention (Figure 3-F). Hydrogel was placed within the surgical site, and a single layer bandage was applied.

The excised specimen (Figure 4) was submitted for histopathology. The histopathologic appearance of the mass was somewhat unusual and of an adnexal tumor, and it was most consistent with a diagnosis of an apocrine ductular adenoma.

Post-operative Care Instructions

The mare was maintained on box rest for two to three days with in-hand grazing. Phenylbutazone and potentiated sulphonamides (antimicrobials) were administered twice daily for five days. Daily bandage changes were performed initially. Following re-examination, the bandage was changed every other day for a further 14 days, with the addition of an anti-bacterial ointment (flamazime) being applied at every change. Figures 5-A through 5-D show the healing progression of the wound. Eleven and a half weeks after the surgery, the surgical defect almost completely re-epithelialized.

Some of the Benefits of CO₂ Laser Surgery

Nursing benefits:

• Better time efficiency compared to conventional surgery. Reduced blood loss reduces the time required for the clean-up of the operating theatre. freeing up the nurse.
• Reduced anesthetic time and less risk of myopathy compared to the alternative (diode) laser used in the practice. The CO₂ laser procedure is approximately 20 to 30 minutes quicker, depending on the amount of tissue that needs to be removed.
• Faster recovery (to stand) immediately post-op due to reduced anesthesia time.

Patient benefits:

• Efficient hemostasis. CO₂ laser efficiently coagulates small blood and lymphatic vasculature as it cuts. This helps to maintain bloodless surgical field and results in less post-operative edema. Excellent intraoperative visibility compared to conventional surgery allows for better margins to be obtained.
• Less post-operative pain and discomfort. Studies show that compared to scalpel surgery, CO₂ laser procedures result in less pain and better function immediately post-op.^[1-3]
• Reduced risk of post-operative infection or recurrence. The CO₂ laser surgery is performed photothermally (i.e., in a noncontact mode, with only the focused beam of light touching the tissue). As a result, the risk of infection is minimized, and intraoperative contamination of the wound by tumor cells and the likelihood of recurrence are reduced.^[4,5]
• Better healing. A number of studies compared scalpel and CO₂ laser skin incisions. They concluded that laser wounds healed slightly slower but with less keloid and scar tissue formation than scalpel wounds.^[6-11]

Other benefits:

• Possibility of avoiding general anesthesia. CO₂ laser excision of equine cutaneous tumors can be performed easily in many patients standing (under heavy sedation), which leaves the operating theater free for other surgeries. Note: In this particular case, the proximity of the tumor to the floor made it easier for the horse to be in lateral recumbency, with the leg raised to ensure a thorough job was done. Moreover, the tumor was located on the horse’s hind leg, and it was much safer for the surgeon to operate under general anesthesia, as this eliminated the risk of being kicked. The proximity of the tumor to fetlock joint required careful dissection to avoid damage to the joint capsule and collateral ligament—this is safer when done under general anesthesia.
• Financial efficiency for the owners. Horses often go home the day of the surgery, which saves owners money on livery and transport. This makes our clients very happy.

Conclusion

Considering the numerous advantages of the CO₂ laser, such as benefits for veterinary personnel and patients, as well as its efficiency and predictable outcomes, the laser is a better alternative to conventional surgery for equine cutaneous tumor removal.

Ruth Gravenell, RVN, is a qualified equine veterinary nurse working at Bell Equine Veterinary Clinic in Kent, U.K. She trained at the Open College of Equine Studies while working full time at Bell Equine Veterinary Clinic and completed a Level 3 diploma in equine veterinary nursing in 2014. She has a special interest in surgery and patient care.

References

1. Haytac M, Ozcelik O. “Evaluation of patient perceptions after frenectomy operations: a comparison of carbon dioxide laser and scalpel techniques.” J Periodontol. 77(11):1815-1819, 2006.
2. Niccoli-Filho W, Neves ACC, Penna LAP, Seraidarian PI, Riva R. “Removal of epulis fissuratum associated to vestibuloplasty with carbon dioxide laser.” Lasers in Medical Science. 14(3):203-206, 1999.
3. López-Jornet P, Camacho-Alonso A. “Comparison of pain and swelling after removal of oral leukoplakia with CO₂ laser and cold knife: A randomized clinical trial.” Med Oral Patol Oral Cir Bucal. 18(1):e38–e44, 2013.
4. Berger N, Eeg PH. “Veterinary laser surgery: a practical guide.” Iowa: Blackwell Publishing, 2006.
5. Holt TL, Mann FA. “Soft tissue application of lasers.” Vet Clin Small Anim. 32:569-99, 2002.
6. Luomanen M, Lehto V-P, Meurman JH. “Myofibroblasts in healing laser wounds of rat tongue mucosa.” Arch Oral Biol. 33:17-23, 1988.
7. Hendrick DA, Meyers A. “Wound healing after laser surgery.” Otolaryngol Clin North Am. 56:969-986, 1995.
8. Zeinoun T, Nammour S, Dourov N, et al. “Myofibroblasts in healing laser excision wounds.” Lasers Surg Med. 28:74-79, 2001.
9. Grbavac RA, Veeck EB, Bernard JP, et al. “Effects of laser therapy in CO₂ laser wounds in rats.” Photomed Laser Surg. 24(3):389-396, 2006.
10. Tambuwala A, Sangle A, Khan A, Sayed A. “Excision of oral leukoplakia by CO₂ lasers versus traditional scalpel: A comparative study.” J Maxillofac Oral Surg. 13(3):320-327, 2014.
11. Carreira LM, Azevedo P. “Comparison of the influence of CO₂ laser and scalpel skin incisions on the surgical wound healing process.” ARC J of Anesthesiol. 1(3):1-8, 2016.

This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO₂ laser.