COSTS AND USEFULNESS: BURNING QUESTIONS IN CO2 LASER SURGERY

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Allan Boyd
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1 Vet Times The website for the veterinary profession COSTS AND USEFULNESS: BURNING QUESTIONS IN CO2 LASER SURGERY Author : Romain Pizzi Categories : Vets Date : October 12, 2009 Romain Pizzi provides an overview of the technical aspects of laser surgery, together with advantages and disadvantages, costs and useful applications AFTER agreeing to write an article on laser surgery, I had to stop for a second and decide on my position. It almost goes without saying that someone writing about an expensive piece of veterinary equipment is more likely to sing its praises. Not only because of the financial cost, but, in part, because it is one s professional judgement and decision to buy the equipment that one tends to end up defending. Hopefully, as I am in the fortunate position of having access to a new, top-of-therange CO2 laser that I did not have to buy, I can stand back a little and look at the benefits, and some possible disadvantages and alternatives, to purchasing or using a CO2 laser. Most of the veterinary articles and marketing literature that I have come across on CO2 lasers offer extensive technical details on what lasers are, and precisely how they work. Much as I would like to avoid such detail in this article, unless one has a modicum of understanding of the underlying physics at work, it is difficult to make an informed evaluation. Technical details The term laser stands for light amplification by stimulated emission of radiation. A laser is produced by using energy to excite the atoms of a lasing medium ; the energy can be heat, 1 / 12

2 electricity or light. When these atoms return to their normal, unexcited state they release the energy in the form of photons the stimulated emission part of the term laser. A lasing medium can be a crystal (such as ruby), a liquid, or a gas (such as CO2). The latter is the most commonly available lasing medium in veterinary practice. How it works In the early 1970s, a laser was used to remove a vocal cord mass in a dog, followed by reports of its use in equine laryngeal and upper respiratory tract procedures. Lasers are sometimes compared to using a magnifying lens to burn a piece of wood; however, laser light is a little more involved than just focused light. Laser light is monochromatic (all the same wavelength), determined by the lasing medium. This wavelength determines the behaviour of the different types of laser: The 10,600nm far infrared spectrum wavelength of a CO2 laser will be strongly absorbed by water and is, therefore, suited to cutting tissues, as cells have high water content. Diode lasers, with a wavelength between 635nm to 980nm in the near infrared spectrum, are better absorbed by pigments such as haemoglobin and, therefore, can coagulate larger blood vessels than a CO2 laser, but this results in more collateral thermal damage. Laser light is collimated (nondivergent) and coherent (parallel waves of photons move in phase with, and reinforce, each other). Laser output, described in terms of power and measured in watts, can be varied (for various thicknesses and water contents of different tissues and animal species), and can be emitted as a continuous, pulsed, or super-pulsed beam the latter consists of short, higherpower pulses. Laser light incises by causing cellular ablation due to vaporisation of intracellular water. The physiological response to photothermal laser incision is similar to a fine burn (not that different from a magnifying glass, after all). Wound edges may develop a small amount of char, and are surrounded by a zone of irreversible coagulative necrosis and a zone of reversible oedema and inflammation. When incising, the aim is to choose power settings, waveform, and focal distance that minimise this collateral thermal damage. Advantages There is no tissue contact, and, hence, no tissue drag when excising, but this does have the drawback of providing no tactile feedback. Incisions cause minimal trauma, using a focused beam with a small spot size. 2 / 12

3 Lasers have been shown to sterilise the incised wound edges more effectively than any disinfectant skin scrubs. CO2 lasers seal smaller blood vessels (less than 1.0mm in size), and, histologically, have been demonstrated to seal incised nerves, leading to claims of reduced postoperative pain in comparison to scalpel incision. Human studies have demonstrated conflicting results as to whether this is the case. Disadvantages Some of the main disadvantages include the following: CO2 lasers cannot be used in a fluid medium. There are few terminal attachments, making their endoscopic use difficult or impractical. Over-penetration can occur (damage to underlying viscera when incising the linea alba unless using a burnished scalpel guide). Health and safety considerations need to be addressed. Lasers can cause retinal damage and shielded goggles are needed for all personnel in theatre, as well as clear signage. Like electrocautery and radiosurgery, lasers generate smoke, which can contain viable infectious microorganisms, as well as cytotoxic particles, and a smoke evacuator is needed. Research A search of the published literature on the veterinary use of CO2 lasers revealed a surprising dearth of even fairly basic research. One would hope that evidence-based medicine would lead the way for marketing of CO2 lasers. A quick PubMed search in early September 2009, using veterinary carbon dioxide laser as a search term, found fewer than 50 publications. This is far from complete, but is still useful as a rough barometer of the quantity and quality of published studies. The majority consisted of either single case reports, or small case series where the laser had been used and found to be effective. Only eight publications dealt with the all-important comparison of laser versus other modalities (scalpel, electrosurgery, radiosurgery) and any comparison of histological damage, postoperative pain and healing. Hernandez-Divers et al (2008, 2009) compared CO2 laser and radiosurgery incisions in birds and 3 / 12

4 reptiles and concluded that, while both had the advantage of being bloodless in comparison to sharp (scalpel) incisions, radiosurgery was significantly less traumatic on histology. Rizzo et al (2004) found that diode lasers were more traumatic and resulted in greater histological artefact than CO2 lasers in canine skin biopsies. Silverman et al (2007) found that, while all heat-generating devices had adverse effects on the histological suitability of biopsies, radiosurgery was less traumatic and resulted in less artefact than CO2 lasers. It must be remembered, of course, that radiosurgery is by no means the same as the less expensive electrosurgery units of lower frequency most commonly encountered in veterinary practices (we won t even mention the occasional thermal cautery unit still knocking around, which is little more than trying to use a soldering iron to perform surgery). However, even a highend veterinary radiosurgery unit is markedly less expensive than most veterinary CO2 lasers on the market. A comparative study (2007) on laser versus scalpel onychectomy in cats found that cats appeared less painful in the laser, compared to scalpel, group for the first 48 hours. In contrast, a previous study by Mison et al (2002) found no clinical significance between scalpel and laser onychectomy. What is it with Americans and cats nails anyway?. As regards skin healing, Mison et al (2003) found that the use of CO2 laser, in comparison to orthodox surgery, had adverse effects on healing to the degree that this was clinically more likely to result in skin flap complications, such as dehiscence. While Davidson et al (2001) found there was no significant clinical advantage to performing soft palate resection with CO2 laser versus scalpel, they did note the operating time was shorter, at just over five minutes, compared to 12 minutes. As regards postoperative pain, the human literature is hardly more supportive. Despite the histological evidence of laser incisions sealing severed nerves, Rombaux et al (2003) and Troell et al (2000) both found that postoperative pain and discomfort was greater for laser soft palate resections in comparison with radiosurgery, and more patients needed opiod analgesia in the postoperative period. So far, all this is hardly outstanding justification for a 20,000 equipment purchase. Practical notes Now, while none of us chose our profession for the financial rewards, any equipment purchase does need to be considered in the hard light of day. 4 / 12

5 Will it cover its costs and maintenance in a reasonable time, while also making one s life easier, or help to generate extra income? What other equipment could this outlay be spent on? Does that equipment fill these criteria better? To cover the costs of a standard CO2 surgical laser over a four-year period, it would need to generate an additional 100 a week. While this does not sound like a great deal, this has to come from a value-added, optional increase in prices for procedures already being performed. Having a CO2 laser does not, in itself, generate new procedures. Despite being marketed for use in procedures such as elongated soft palate resections, it is likely surgeons using it for this purpose will already be confident in performing soft palate surgery without a laser. Buying a laser unit is not going to generate new cases, and will not magically allow a veterinary surgeon to confidently and competently start performing soft palate resections. In comparison, a simple endoscope stack and a single flexible endoscope generates new procedures; a separate set of charges and one or two endoscopic examinations a month will pay for the equipment in less than four years. It also has the advantage of allowing a gradual increase in equipment piecemeal (adding an additional scope and accessories) over time, or branching into laparoscopy. It is unlikely that making all the bread-and-butter, first opinion neutering more expensive is good competitive business practice. Therefore, this is very much an opt-in, relying on the miscellany of lumps, bumps, and other soft tissue procedures for many cases. On the upside, it is amazing how many clients are keen on the concept of the surgical laser when, in comparison, many owners fail to appreciate the benefits of, for example, laparoscopy. Useful aspects So what aspects of the surgical laser do I find useful? I particularly like using the CO2 laser for incising snake and lizard skin, as it is rapid and bloodless, with no annoying tissue drag on the scales due to its non-contact nature. Concerns about the small zones of incision edge oedema are largely immaterial, as using an inverting suture pattern (such as horizontal mattress sutures) means healing occurs at the base of the sutures, not at the skin edges. The histological evidence of incised nerves being sealed by laser incision may mean that the everted skin edges are less likely to be irritated or painful postoperatively although, of course, this 5 / 12

6 has not been demonstrated in clinical studies. I have found the laser to be useful in managing pododermatitis in old, obese rats, which has also been demonstrated to reduce the incidence of post-surgical neuroma formation (useful, but hardly financial justification for the purchase of a unit). Summary When considering purchase, it is best, perhaps, to simply regard a veterinary CO2 unit as a very nice, relatively atraumatic scalpel albeit an expensive one. References Davidson E B et al (2001). Evaluation of carbon dioxide laser and conventional incisional techniques for resection of soft palates in brachycephalic dogs, J Am Vet Med Assoc 219 (6): Hernández-Divers S J et al (2009). Comparison of CO2 laser and 4MHz radiosurgery for making incisions in the skin and muscles of green iguanas (Iguana iguana), The Veterinary Record 164(1): Hernández-Divers S J et al (2008). Comparison between CO2 laser and 4MHz radiosurgery for incising skin in white carneau pigeons (Columba livia), J Avian Med Surg 22(2): Mison M B et al (2002). Use of carbon dioxide laser for onychectomy in cats, J Am Vet Med Assoc 221(5): Mison M B et al (2003).Comparison of the effects of the CO2 surgical laser and conventional surgical techniques on healing and wound tensile strength of skin flaps in the dog, Vet Surg 32(2): Rizzo L et al (2004). Histologic comparison of skin biopsy specimens collected by use of carbon dioxide or 810nm diode lasers from dogs, J Am Vet Med Assoc 225(10): 1,562-1,566. Robinson D A et al (2007). Evaluation of short-term limb function following unilateral carbon dioxide laser or scalpel onychectomy in cats, J Am Vet Med Assoc 230(3): Rombaux P et al (2003). Postoperative pain and side effects after uvulopalatopharyngoplasty, laserassisted uvulopalatoplasty, and radiofrequency tissue volume reduction in primary snoring, Laryngoscope 113(12): 2,169-2,173. Silverman E B et al (2007). Histologic comparison of canine skin biopsies collected using monopolar electrosurgery, CO2 laser, radiowave radiosurgery, skin biopsy punch, and scalpel, Vet Surg 36(1): Troell R J et al (2000). Comparison of postoperative pain between laser-assisted uvulopalatoplasty, uvulopalatopharyngoplasty, and radiofrequency volumetric tissue reduction of the palate, Head Neck Surg 122(3): / 12

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8 Above: the rigid arm of a CO2 laser unit can be unwieldy at times. 8 / 12

9 Inset: health and safety precautions require clear signage of theatres where lasers are used. 9 / 12

10 Right: despite other disadvantages, the author finds the CO2 laser ideal for rapid atraumatic and relatively blood-free incision of reptile skin. 10 / 12

11 Far right: using a CO2 laser to excise a rabbit facial abscess. A disadvantage is the lack of tactile feedback, and care is needed to avoid inadvertently incising the abscess wall. In this photo, the power setting is too high, resulting in wound-edge char. 11 / 12

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Introduction. Sara M. Burns, DVM

Introduction. Sara M. Burns, DVM Comparison of the Carbon Dioxide Laser and the Radiofrequency Unit for Feline Onychectomies This study compared the collateral tissue damage and incisional bridging with granulation tissue via histopathological