KTP laser safety by Dr. Sunil Verma
Transcription
KTP laser safety by Dr. Sunil Verma
Otolaryngology http://oto.sagepub.com/ -- Head and Neck Surgery Evaluating the Effects of a 532-nm Fiber-Based KTP Laser on Transoral Laser Surgery Supplies Carolyn A. Coughlan and Sunil P. Verma Otolaryngology -- Head and Neck Surgery 2013 149: 739 originally published online 20 September 2013 DOI: 10.1177/0194599813505423 The online version of this article can be found at: http://oto.sagepub.com/content/149/5/739 Published by: http://www.sagepublications.com On behalf of: American Academy of Otolaryngology- Head and Neck Surgery Additional services and information for Otolaryngology -- Head and Neck Surgery can be found at: Email Alerts: http://oto.sagepub.com/cgi/alerts Subscriptions: http://oto.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav >> Version of Record - Nov 4, 2013 OnlineFirst Version of Record - Sep 20, 2013 What is This? Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013 Original Research—Laryngology and Neurolaryngology Evaluating the Effects of a 532-nm Fiber-Based KTP Laser on Transoral Laser Surgery Supplies Otolaryngology– Head and Neck Surgery 149(5) 739–744 Ó American Academy of Otolaryngology—Head and Neck Surgery Foundation 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0194599813505423 http://otojournal.org Carolyn A. Coughlan, MD1, and Sunil P. Verma, MD1 Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. Abstract Objective. The KTP laser has become commonplace in transoral head and neck surgery. The interactions of this laser with commonly used supplies in transoral surgery have not been formally examined. This study evaluates the effects of the KTP laser on surgical supplies. Study Design. Experimental study. Setting. The study was conducted in an empty operating room at a university-affiliated medical center. Methods. An Aura XP 532-nm KTP laser with a 600-nm fiber was used in pulsed and continuous modes. The beam was focused at the shaft and balloon of 3 ‘‘laser-safe’’ endotracheal tubes (ETTs), a polyvinyl chloride (PVC) ETT, and a Codman surgical patty. Time to penetrate was recorded. Results. The KTP laser beam was unable to penetrate any of the laser-resistant ETTs. It did react with the black number markings on the PVC ETT by producing sparks but was unable to penetrate the shaft of the ETT. The KTP laser was nonreactive with all ETT cuffs except in 1 of 3 trials with the outer balloon cuff of a Rusch Lasertubus ETT when the laser was used in a continuous mode. The KTP laser caused the production of a flame upon contact with the blue radiopaque strip of the surgical patty, even when the patty was wet. Conclusion. This study demonstrates that a number of safe ETT options may be used during transoral laser microsurgery with a KTP laser. In addition, Codman surgical patties are shown to be a significant fire risk in KTP laser surgery. 1 Keywords transoral laser surgery, KTP laser, laser safety Received May 22, 2013; revised August 1, 2013; accepted August 27, 2013. T tissue within the pharynx, larynx, and trachea. Unfortunately, it was soon realized that the risks of using lasers could be devastating and deadly, particularly in the case of an airway fire. For an airway fire to occur, all 3 components of the ‘‘fire triad’’ must be present: an oxidizer, an ignition source, and fuel. In transoral laser surgery, the oxidizer can include oxygen and anesthetic gases, the laser itself supplies the ignition source, and fuels include endotracheal tubes (ETTs) and sponges in the airway. Airway fires are a more distinct risk during surgeries of the oral cavity and larynx due to the proximity of these 3 components. To avoid this feared complication, laser-resistant ETTs and special ventilation techniques have been developed.1-4 Materials such as Codman surgical patties (#80-1407; Codman & Shurtleff, Raynham, Massachusetts) are commonly used to protect a specialized laser-safe endotracheal tube and the larynx and subglottis from aberrant laser energy beam during transoral laser surgery. In addition, new protocols have been initiated to raise awareness of laser and fire safety during the mandatory timeout at the start of every procedure.5,6 Although these laser-resistant tubes have assisted in the prevention of airway fires, they do add considerable cost to the patient in comparison to standard polyvinyl chloride (PVC) ETTs. The safety of the carbon dioxide laser has been extensively studied in the literature ever since it was first introduced into practice in 1972.7 Multiple case reports of airway fires have been detailed.8-14 In addition, controlled studies have been performed to test the safety of lasers on ETTs in head and neck surgery.7,15-22 Since the advent of the carbon dioxide laser, many alternative lasers have been developed, each intended for a specific target.23 The KTP laser was developed in the 1980s from the Nd:YAG laser and preferentially targets oxyhemoglobin.24 The KTP laser he introduction of lasers revolutionized otolaryngology–head and neck surgery by allowing the surgeon to use energy to precisely cut and coagulate University Voice and Swallowing Center, Department of Otolaryngology– Head and Neck Surgery, University of California, Irvine School of Medicine, Irvine, California, USA This article was presented as a poster at the 2012 AAO-HNSF Annual Meeting & OTO EXPO; September 29 to October 3, 2013; Vancouver, British Columbia, Canada. Corresponding Author: Sunil P. Verma, MD, University Voice and Swallowing Center, Department of Otolaryngology–Head and Neck Surgery, University of California, Irvine School of Medicine, 62 Corporate Park, Ste 115, Irvine, CA 92606, USA. Email: verma@uci.edu Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013 740 Otolaryngology–Head and Neck Surgery 149(5) is especially useful in laryngeal surgeries as it is fiber based and able to be angled and targeted precisely toward the intended tissue.25-28 To date, 1 study has been performed evaluating the safety of the KTP laser on reinforced laryngeal mask airways (LMAs).23 Multiple studies have been performed to evaluate the effect of patties as a safety buffer to protect the airway and ETT during carbon dioxide laser surgery, but the interaction of patties and ETTs with the KTP laser has not been assessed.7,15,29 To our knowledge, there has been no investigation of the interaction of the KTP laser with commonly used transoral laser surgery supplies. In this study, we evaluated the safety of the KTP laser in transoral laser surgery by testing the time to perforation of various ETTs after exposure to a KTP laser. We also tested the time to perforation of surgical patties after exposure to a KTP laser to gauge the safety of current practices in transoral laser surgery. Methods Laser Source An Aura XP 532-nm KTP laser (American Medical Systems, Minnetonka, Minnesota) with a 600-nm fiber was used in pulsed and continuous modes in an empty operating room at the University of California, Irvine Medical Center. In the pulsed mode, the laser was set at 35 watts with a 15-ms pulse width and 5 pulses/s. In continuous mode, the laser was set at 8 watts. The laser beam was focused a distance of 0.5 cm from the shaft and balloon of 4 ‘‘laser-safe’’ ETTs, a PVC ETT, and surgical patties. The laser was applied for a maximum of 90 seconds before the trial was discontinued. Target: Endotracheal Tubes, Endotracheal Tube Cuffs, and Surgical Patties Four laser-safe endotracheal tubes were tested: (1) a Xomed Laser-Shield II silicone elastomer tube with an outer aluminum strip covered by a polytetrafluoroethylene sheet (7060300; Medtronic, Jacksonville, Florida); (2) a Mallinckrodt Laser Oral/Nasal Tracheal Tube made of stainless steel (86398; Coviden, Mansfield, Massachusetts); (3) a Rusch Lasertubus with an off-white rubber tube, corrugated copper foil, and outer absorbent sponge (102004060; Teleflex, Research Triangle Park, North Carolina); and (4) a Hudson RCI Sheridan Laser-Trach with a red rubber tube surrounded by copper foil and an absorbent sponge (5-20612; Teleflex).30 A ‘‘standard’’ Mallinckrodt Hi-Lo PVC ETT (86448; Coviden) was also tested. All tubes were 6.0 in size. These tubes were placed on wet towels throughout the experiment. The handheld KTP laser was held steady at a distance of 0.5 cm from the target at an angle of incidence of 90 degrees. A white note card was placed behind the target or within the ETT and the time to penetration of the card was measured by a stopwatch and determined by visual examination. All ETTs were evaluated in 3 separate trials, and the results were averaged for the final result. Two laser-safe endotracheal tube cuffs and a standard PVC ETT cuff were tested in 3 trials each. Standard Figure 1. Xomed Laser-Shield II, Rusch Lasertubus, and polyvinyl chloride endotracheal tubes filled with 10 mL of saline. instructions for use of the endotracheal tube cuffs were followed for all laser-safe ETTs. The Xomed and Rusch endotracheal tube cuffs were filled with 10 mL of saline (Figure 1). The cuffs of the Mallinckrodt and Sheridan ETTs were not tested due to insufficient supplies for thorough testing. The PVC ETT cuff was tested while filled with either air or saline. The time taken for the laser beam to penetrate through the ETT cuff was recorded in seconds, and the mean of 3 trials was recorded. In addition, the interaction and time to perforation between the laser and ½ 3 3-inch Codman surgical patties was examined. These patties were tested in 2 conditions: dry and soaked in normal saline for 15 seconds. The white cottonoid portion and blue radiopaque blue strip of the patty were independently exposed to the laser in both wet and dry conditions in 3 trials each (Figure 2). Results Endotracheal Tube Shafts None of the ETT shafts were perforated by the KTP laser in continuous or pulsed mode, including the PVC ETT. The laser was able to perforate the outer absorbent layer of the Sheridan Laser-Trach, Xomed Laser-Shield II, and Rusch Lasertubus instantaneously (Figure 3). The KTP laser was unable to perforate the metallic layer of these tubes. The KTP laser in pulsed and continuous mode did not react with the clear, unmarked portion of the PVC ETT and was unable to perforate the ETT in this area after 90 seconds of uninterrupted contact with the laser. The beam did react with the black number markings on the PVC ETT by producing a spark. The beam was unable to perforate the ETT at this location after 90 seconds of direct contact with the beam despite the presence of an initial spark. In summary, the PVC ETT was resistant to perforation by the KTP laser in all trials, but the laser did react to the black markings on the ETT by producing an instantaneous spark. Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013 Coughlan and Verma 741 Discussion Figure 2. The Codman surgical patty with a white absorbent sponge and blue radiopaque strip, used for easy localization with xray. Figure 3. Perforation of the outer sponge layer of the Sheridan Laser-Trach tube after exposure to a 532-nm fiber-based KTP laser, revealing the copper metal sheet underneath. Endotracheal Tube Cuffs The KTP laser was nonreactive with all ETT cuffs except the Rusch Lasertubus ETT cuff. In 2 of 3 trials of the Rusch Lasertubus cuff, no damage was noted. However, in 1 of the 3 trials, the outer cuff was perforated at 29 seconds. The second, inner cuff stayed intact for all 90 seconds. The laser was unable to penetrate the Xomed cuff as well as the PVC ETT cuff when filled with either saline or air. Surgical Patties Results of the trials with Codman surgical patties are summarized in Table 1. The laser reacted differently with the white absorbent portion of the patty as compared with the blue radiopaque strip. Minor sparking was visualized when the pulsed beam first made contact with the blue strip (Figure 4). Airway fire has long been a concern with the use of lasers in head and neck surgery.5,6,8-14 In fact, attention to fire safety has been emphasized by the Food and Drug Administration and the Joint Commission.5,31 As a result of these efforts, the assessment of fire risk is now a standard portion of the surgical ‘‘timeout’’ procedure prior to the initiation of surgery.5 The Aura KTP laser was introduced to laryngologic surgery in 2003 and is commonly used at many medical centers. As a fiber-based laser, it can be aimed toward specific targets at a very close distance and is often used near the endotracheal tube. Despite the frequency with which fiberbased KTP lasers are used, this is the first investigation of the effects of the 532-nm pulsed and continuous KTP laser on ETTs, ETT cuffs, and surgical patties. In this study, the bodies of all ETTs were found to be resistant to the laser beam. Only the black markings on the shaft of the PVC ETT and the absorbent sponges on the surface of the Xomed Laser-Shield II, Rusch Lasertubus, and Sheridan Laser-Trach tubes were found to react with the laser. The absorbent outer layer is important to create a dull surface on the laser-safe endotracheal tube that does not reflect the beam toward an unintended target.30 If the beam is in contact with this absorbent surface for a prolonged period, however, it can penetrate this layer and hit the underlying metallic, reflective surface. This metallic surface is important to protect the endotracheal tube from penetration but can lead to tissue injury by reflecting the beam toward unintended targets. The findings in this study are consistent with the results of a study by Pandit et al23 in which a KTP laser reacted with solely the black markings of a laryngeal mask airway, causing an instant flare that produced a ‘‘crater filled with silica ash.’’ The laser was ultimately unable to penetrate the LMA tube. These findings are in agreement with our own: although a spark was ignited, the tube was not penetrated. The ETT cuffs appear to be similarly resistant to the KTP laser. Typical laser-safe ETT cuffs are reinforced and are saline-filled rather than air-filled for improved protection.30,32,33 In this study, the KTP laser was resistant to all ETT cuffs, including the PVC cuff filled with air. The lone exception was 1 trial with the Rusch Lasertubus outer cuff. This tube has both an inner and outer saline-filled cuff. In this trial, the inner cuff remained intact. These findings are different from the results of studies evaluating the safety of ETTs and the CO2 laser, which show almost instantaneous perforation of ETT cuffs with application of the CO2 laser beam.14 Given these findings, it is possible that the use of a standard PVC ETT without any black markings could be equally efficacious as the laser-resistant tubes at the power levels typically used in clinical practice. Surgical patties are commonly used in practice as another safety measure to protect the tissues surrounding the target area as well as the cuff of the endotracheal tube from unintended injury. The effects of the carbon dioxide laser on these Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013 742 Otolaryngology–Head and Neck Surgery 149(5) Table 1. Interactions between portions of a Codman surgical patty and the 532-nm KTP laser. KTP Continuous Mode Dry White sponge Blue strip KTP Pulsed Mode Wet Perforated in 15 seconds Spark, then perforated in 3 seconds Dry Wet Unable to perforate Unable to perforate Unable to perforate Flame, then unable to perforate Spark, then perforated in 4.8 seconds Spark, then unable to perforate All results are reported as the mean of 3 trials. Figure 4. Perforation of a dry surgical patty after the laser was aimed at the blue strip after a mean time of 4.8 seconds. patties have been evaluated, but the interaction with a KTP laser has not.7 Results from this study demonstrate that the various portions of the patty interact differently with the KTP laser energy. The white absorbent sponge is slow to interact with the laser, especially when saturated with saline. The radiopaque blue strip, however, quickly reacted with laser energy with an instantaneous flame in all trials, even when wet. This blue strip can present a serious fire hazard in laser surgery. Unfortunately, the strip is necessary as it is the sole portion of the patty that is radiopaque, an important safety measure. It would be interesting to investigate whether a different color or material of radiopaque ribbon would react differently with a KTP laser. The importance of keeping patties wet is also highlighted by the results of this study since the wet patty was unable to be perforated in 90 seconds of continuous laser energy. The surgeon should be vigilant about constantly moistening patties as they can become dry from suction, from passage of air, and during the course of a normal surgery. The results of these trials question whether the patty is necessary in the course of KTP laser surgery to protect the ETT. The blue radiopaque strip produced a spark in both the dry and wet conditions, creating a high risk for an airway fire. Although patties may have value in protecting unintended tissue targets from aberrant laser energy, the risk of an airway fire outweighs the benefit of protecting the tissues. As the cost of health care continues to rise, it is important to continually reevaluate the effectiveness of expensive treatments and materials in comparison to more costconscious options. In the case of transoral laser surgery, the cost of laser-resistant ETTs can be up to 100 times the cost of the standard PVC ETT. At our institution, the PVC ETT costs approximately $1.50 for a size 6.0. By comparison, the Xomed Laser-Shield II 6.0 costs roughly $150. A PVC ETT could potentially be minimally reengineered for KTP laser surgery and in the process confer a great cost savings compared with existing laser-safe endotracheal tubes. Further study must be performed before these results can be implemented into clinical practice. Before widespread changes are initiated, variables such as the power settings as well as the distance between the laser and the target should be examined. Initially, we planned to vary the distance of the laser from the target. However, when the ETT showed no reactivity at a close distance in continuous mode, the trials were limited to this one, close distance, which most commonly approximated clinical practice. Similarly, power settings that are often used were chosen for this study. Variations in the angle of incidence between the laser and targets may be investigated in future studies as well. Ahmed et al7 demonstrated that a carbon dioxide laser was able to perforate an endotracheal tube in less than 1 seconds when aimed at 90 degrees to the ETT, while the time increased to 42 seconds when the beam was aimed at a 45degree angle. Given these results, this study was limited to 90-degree beams of incidence to test the most powerful setting. When the laser was unable to perforate the tube at this incidence, we refrained from further trials at a more indirect angle. Finally, it is important to evaluate the effect of blood on these supplies. Sosis et al34 evaluated the effect of blood on laser-resistant ETTs and found increased flammability in some trials with the Mallinckrodt Laser-Flex tube and also copper- and aluminum-wrapped PVC tubes. Given the KTP laser’s affinity for oxyhemoglobin, investigating the effect of blood on the ETT, ETT cuff, and surgical patty is absolutely necessary for future study. Conclusions The fiber-based 532-nm KTP laser may be used safely with a number of laser-safe ETTs. The black number markings Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013 Coughlan and Verma 743 on a standard PVC ETT are the only areas that were noted to interact with the laser in this study. Care should be taken with use of surgical patties, as a fire may occur if they are not maintained in a moist condition or if the laser beam is aimed toward the blue radiopaque strip. Acknowledgments We thank Universal Health Systems for donating all laser supplies. Also, we thank Medtronic, Inc and Teleflex, Inc, which donated multiple ETTs for evaluation in this study. Author Contributions Carolyn A. Coughlan, acquisition of data, drafting of the manuscript, analysis and interpretation of data, critical revision of the manuscript, and final approval; Sunil P. Verma, study concept and design, acquisition of data, analysis and interpretation of data, critical revision of the manuscript, final approval, study supervision, and administrative, technical, and material support. Disclosures Competing interests: Sunil P. Verma is an educational/consulting liaison for Acclarent. Sponsorships: None. Funding source: None. References 1. Jaquet YM, Monnier P, Van Melle G, et al. 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Sosis MB, Dillon FX. Saline-filled cuffs help prevent laserinduced polyvinylchloride endotracheal tube fires. Anaesth Analg. 1991;72:187-189. 34. Sosis MB, Pritikin JB, Caldarelli DD. The effect of blood on laser-resistant ETT combustion. Laryngoscope. 1994;104:829831. Downloaded from oto.sagepub.com at UNIV CALIFORNIA IRVINE on December 21, 2013