Learning Objectives:After participating in this continuing professional development activity, the provider should be better able to:

1. Identify risk factors for surgical smoke exposure.

2. Describe adverse symptoms and clinical conditions that may arise from surgical smoke exposure.

3. Develop protective measures to mitigate the risk of surgical smoke exposure.

As long as electrocautery methods have been in the arsenal of health care providers, surgical smoke has been a source of uncertainty and potential concern. Surgical smoke is the gaseous byproduct of the electrocautery of blood, tissue, pathogens, chemicals, dyes, and any other elements the surgeon may encounter when operating. Without proper personal protection equipment and evacuation techniques, surgical smoke not only poses a cumbersome visual obstruction of the surgical field-it also can aerosolize infectious agents and carcinogenic particles.

Cervical cancer is the second leading cause of cancer death in women between the ages of 20 and 39 years. Each year in the United States, 14,000 new cases of invasive cervical cancer are identified, and 4300 cancer-related deaths occur. Human papillomavirus (HPV) is intrinsically implicated in cervical neoplasia, and it can be detected in 99.7% of cervical cancers.1 Surgical management of cervical cancer and HPV includes electrocautery and laser CO₂ procedures, events that create surgical smoke. More broadly, approximately 90% of all endoscopic and surgical procedures will produce surgical smoke, and 500,000 health care workers will encounter surgical smoke each year.2 This article focuses on the transmissibility of HPV via thermal destruction of infected tissue and necessary precautions to prevent this.

Surgical Smoke: What Is It?

Surgical smoke is generated from energy transfer to tissue, which heats up cells to their boiling point. This perforates the cell membranes and vaporizes the water and organic matter within. The tools that can achieve this include monopolar and bipolar electrocautery, ultrasonic scalpels, surgical drills, and lasers. The particles released into the air can be ultra-fine and can be odorous and respirable.3 One study documented the contents of the surgical smoke, and its potential to carry viral particles, carcinogens, mutagens, and bacteria. Surgical smoke is 95% vaporized water and 5% cellular particulate matter. The matter can be from sources such as blood, tissue, chemicals, dyes, and infectious pathogens.4

Surgical smoke plumes can harbor volatile organic compounds in concentrations exceeding permissible safe exposure; over 80 different organic compounds have been identified in samples of surgical smoke. Extended exposure to laser-produced surgical smoke in the operating room (OR) is linked to inflammatory interstitial pneumonia and can increase the risk of chronic pulmonary diseases like asthma. Laser surgery-related smoke plumes can harbor dangerous chemicals such as benzene, formaldehyde, acrolein, styrene, toluene, acetaldehyde, acrylonitrile, and polyaromatic hydrocarbons-all potential carcinogens as classified by the International Agency for Research on Cancer.5

However, the carcinogenic effects and the risk of developing cancer are not well established in humans. Gates et al5 sought to identify a link between extended exposures to smoke in OR nurses and new diagnoses of lung cancer. In this study, 86747 OR nurses were asked for their duration of OR experience and subsequently followed up for new diagnoses of lung cancer. Adjusting for age, smoking history, secondhand smoke exposure, dietary habits, and carcinogen exposures, the incidence rate of lung cancer between different exposure groups and controls was assessed. Surprisingly, OR employment was not associated with increased rates of lung cancer, and nurses in the highest exposure category (>=15 years) had the lowest incidence.5

That is not to say that surgical smoke is benign. Due to its gaseous nature, smoke permeates deep into the human respiratory system. Particle size influences the final destination within the respiratory tract of the operator: larger p^[infinity]articles (5 [mu]m) tend to land on the walls of the nasopharynx and the trachea whereas smaller particles (2 [mu]m) can land in the bronchioles and alveoli.6,7 Up to 77% of aerosolized particulate matter is less than 1.1 [mu]m, which means particulate matter can cause inflammatory changes at the alveolar level. Once inhaled, health care providers often experience symptoms including mucosal irritation of the eyes, nose, and throat, headaches, coughing, nasal congestion, and asthma-like symptoms.8 As for viral particles, the persistence of HPV DNA in surgical smoke has been controversial; however, it has been identified in surgical smoke, and its transmissibility is possible.

Surgical Smoke as a Vector for HPV Transmission

Health care workers who perform procedures to remove lesions associated with HPV will inevitably come into contact with the virus; however, it was thought that the probability of transmission via surgical smoke was minuscule. Ilmarinen et al9 concluded that HPV in the OR could spread through direct contact, having demonstrated that HPV could be detected on protective surgical gloves, but not on surgical masks or the mucosal surfaces of surgical staff. Samples from patients with urethral warts and laryngeal papillomas were analyzed before surgery via polymerase chain reaction (PCR) to identify the HPV genotypes. Samples collected from OR staff's gloves and surgical masks, and oral swabs of the OR staff, were analyzed by PCR before and after surgery. After surgery, HPV DNA was detected on 70% of gloves used in the OR, and the HPV types on the gloves were consistent with the types analyzed from the patients. However, no trace of HPV DNA was discovered on the surgical masks or the oral mucosa of the OR staff members.9

Weyandt et al10 studied whether HPV DNA could be detected in other parts of the OR because it was thought that surgical smoke can disperse throughout the room. Petri dishes were left 1 and 2 m away from the operating area, but no HPV DNA was identified in them. The nasolabial folds and the glasses of the OR staff were swabbed, also revealing no HPV DNA. Bellina et al11 collected CO₂ laser plumes and analyzed them for viable cells and HPV using labeled glucose and nucleotides. The plume material underwent DNA, RNA, and cytologic metabolic studies, all indicating that the vaporized biomatter was biologically inert and incapable of causing infection. These studies concluded that HPV could not be significantly dispersed throughout the operating theater via surgical smoke, and that if HPV were to contaminate a surface, it would be through direct contact via the gloves of OR personnel. Lastly, HPV viral particles and other microbes were deemed not viable in the surgical smoke and therefore could not cause infection.

However, the results of other studies contradicted the finding that surgical smoke is devoid of harbor harmful viral particles. In 1998, Garden et al12 demonstrated that, in a controlled setting with lasers delivering energy to bovine papillomavirus (BPV) lesions, the smoke specimen contained intact BPV virions in plumes emitted by multiple varying energy settings. They also demonstrated similar results with human tissue (plantar verrucae) undergoing carbon dioxide laser treatment. Of the 7 patients treated, the surgical smoke from 2 patients showed intact HPV virus. Despite the small sample size and the inconsistent findings among all patients, this experiment successfully points toward the possibility of HPV DNA being released into surgical smoke by laser elements.12 Sood et al13 demonstrated the possibility that loop electrosurgical excision procedures (LEEPs), which use electrocautery, could introduce HPV DNA into the surgical smoke. Using a filter attached to the suction evacuation device, the contents of the surgical smoke could be collected later for analysis. Of 49 patients who were studied, 39 were HPV positive, and 18 filters showed evidence of HPV DNA. Those who were initially HPV negative showed no HPV in their filters. The HPV types found in the filters were consistent with those of the patient, thus demonstrating that surgical smoke from LEEP can carry HPV DNA from patients.13 Garden then went on in 2002 to show that BPV DNA collected from CO₂ laser plumes could be used to inoculate previously healthy tissue (bovine calfskin) and produce tumors that yielded the same HPV type as those found in the original smoke specimen.14 This was the first experiment to demonstrate the transmissibility of papillomavirus disease through viral particles suspended in laser plumes.

Furthermore, in 2015-2016, Zhou et al15 performed a test collecting tissue samples, smoke samples, and nasal swabs before and after LEEP for cervical intraepithelial neoplasia. In 134 patients, they found HPV in 94.8% of patients, 29.9% of smoke samples, and in 1.5% of gynecologic surgeon nasal swabs. The genotypes of the HPV DNA found in the samples were consistent with the genotypes found in the patients. Although the surgeons subsequently tested negative for HPV at 3- and 6-month follow-ups, the study demonstrated the risk of transmission to OR staff.15 This study shares parallels to the study designed by Ilmarinen et al,9 indicating that methods and data may not be consistent enough for accurate reproducibility. Although the surgeons mentioned in the previous study did not permanently acquire an HPV infection, there are documented cases.

Case Reports of HPV Transmission via Surgical Smoke

Based on the studies described previously, HPV DNA can be identified in smoke from both CO₂ lasers and LEEP electrocautery, and can cause HPV-associated disease in animals. However, there are very few reports of transmission causing long-term sequelae in humans. In 2013, Rioux et al16 published a case describing a 53-year-old gynecologic surgeon who presented to an otolaryngologist with several months of a right tonsillar lesion, a right neck mass, and general fatigue. Imaging revealed a 2.2-cm soft tissue lesion in the right tonsil. Biopsy confirmed squamous cell carcinoma with moderate to poor differentiation and HPV type 16. The patient had no significant risk factors for HPV infection: he had never smoked; he had consumed alcohol socially; and he was in a long-term monogamous relationship with his wife who tested HPV negative. His only major risk factor was occupational exposure to HPV as a gynecologic surgeon. He had been working for 20 years performing LEEP and CO₂ laser ablations for over 3000 patients for cervical and vulvar lesions related to HPV. Most of these procedures were done in an office setting without adequate ventilation and without a surgical mask. Rioux et al16 also reported another patient, a 63-year-old gynecologist, who initially presented to an otolaryngologist for a foreign-body sensation in his throat. He was found to have squamous cell carcinoma at the base of his tongue that was positive for HPV 16. He had never smoked and had consumed alcohol occasionally. Unfortunately, the report does not comment on the HPV status of his previous partners. However, it is important to note that he had been performing LEEP and CO₂ laser ablations for 30 years. For 15 of those years, he was doing laser ablations in an office setting without adequate ventilation.16 Another 44-year-old surgeon with no other risk factors or potential exposures was treating anogenital condylomas with CO₂ lasers. He was found to have laryngeal papillomatosis from HPV types 6 and 11.17 A 28-year-old OR nurse who routinely assisted with laser and electrocautery treatments for anogenital condylomas also developed laryngeal papillomatosis. A virologic institute reviewed her case and ruled that it was due to occupational exposure.18 Although there is no epidemiologic or statistical power in these case reports, they demonstrate the feasibility of this route of transfer, and they warrant further study on a broader scale. They provide a proof of concept that HPV can remain viable long enough in surgical smoke to cause an infection that can lead to malignancy. Questions remain regarding the length and degree of exposure required to pose a significant risk, and whether other risk factors may have been present in the surgeons who may have not been assessed.

Measures to Reduce Exposure

Two of the cases reported mentioned lack of adequate ventilation during the procedure, and for 1 of the surgeons, lack of a surgical mask during the procedure. These are potentially significant, yet modifiable risk factors for occupational HPV exposure. There may be progress in recent years to use personal protective equipment; in a 2016 survey conducted by the Centers for Disease Control and Prevention, 90% of those who perform laser surgeries wear surgical masks and 98% of those who perform electrosurgery wear surgical masks. However, even a surgical mask does not maximize protection against surgical smoke due to its inability to create a seal against the skin. Furthermore, according to studies comparing surgical mask filtration under standardized airflow, the collection efficiency of common surgical masks can range from less than 10% to 90%.19 More adequate and reliably consistent respiratory protection can be achieved with properly fit-tested N95 respirators. Universally known, the N95 respirator has been an effective tool for health care providers across the globe. They can be essential in the OR setting as well, providing adequate filtration of up to 95% of particles as small as 0.3 [mu]m.19 Given its fit advantage and stringent filtration performance standards, the N95 respirator provides more robust protection than common surgical masks. Even so, surgical masks or N95 respirators, with their inherent limitations, are especially crucial in environments where ventilation and smoke extraction is not readily available.

Although masks serve as a protective measure against aerosolized particles, decreasing the particle density in the air can further reduce the risk of exposure. When possible, smoke extraction systems should be in place and used. Adequate smoke evacuation can prevent smoke from obscuring the surgical field and will minimize odor. Local exhaust ventilation (LEV) is preferred to general ventilation (GV); LEV systems attempt to capture and evacuate smoke at the source of emission whereas GV provides a general flow of air in and out of the room. Therefore, GV potentially introduces smoke to other areas of the room, as smoke migrates to the exhaust egress point, exposing OR staff not adjacent to the surgical field.20 LEV systems include room suction systems that use wall connections to an in-line filter and suction canister; these systems can filter about 2 to 5 ft³/min. Given the lack of substantial suction power, this evacuation method is better suited for shorter procedures that generate lower volumes of smoke. Smoke evacuators have on-board vacuum pump powered suction and triple filtration systems that can filter 35 to 50 ft³/min for cases that can produce large volumes of smoke. These portable units are usually fitted with a prefilter for larger matter followed by ultra-low particulate air (ULPA) filters that can trap particulate matter as small as 0.12 [mu]m with an efficiency rate of 99.9999%. Beyond the ULPA filter is a charcoal filter meant to capture toxins and carcinogens in surgical smoke.20 Unfortunately, these machines are reportedly cumbersome to use practically and are often overlooked due to their inconvenience when it comes to increased noise levels and difficulty accommodating its place in the surgical suite. However, if routinely used and maintained, portable smoke evacuation units can reliably remove harmful substances from surgical smoke and protect OR staff. Lastly, there are central smoke evacuation systems, often found in higher volume ORs in the inpatient setting.

There are various types of smoke capture devices connected to the portable suction unit: a traditional wand suction device, electrosurgery unit (ESU) with pencil suction, and cell foam technology. The most important factor for adequate smoke capture is the distance of the intake nozzle from the point of smoke emission. A suction wand with an inner diameter of 22 mm connected to a smoke evacuation device generating 25 ft³/min of suction captures only 53% of smoke when held at 7.5 cm from the source of emission compared with capturing 99% of smoke when held at 2.5 cm.20 Some systems have adopted ESU pencils that place the suction intake nozzle 2 cm from the point of smoke emission as part of the exterior housing of the cautery device; this has been shown to provide adequate smoke evacuation. These devices only turn on when the cautery is active, limiting the noise disturbance of traditional suction. Further, they do not require an additional surgical team member to operate them. Cell foam suction technology relies on an adhesive suction device that features a layer of open cell foam in a flat housing that is placed adjacent to the surgical field. The edge closest to the surgical field is open, and suction is maintained throughout the procedure via tubing connected to the portable suction evacuation device. Approximately 99.5% suction efficiency is achieved passively and without further obstruction of the surgical field that a traditional wand would cause.21

Unfortunately, LEV does not seem to be used as widely as one would hope. In one study by Steege et al,8 in a survey of 4500 electrosurgeries, only 14% of respondents reported using LEV; of 1392 laser surgeries, only 47% used LEV. The most frequently reported reasons for forgoing LEV in both electrosurgery and laser surgery were "not part of protocol," "exposure was minimal," "general room ventilation was sufficient," and "not provided by employer."8 Furthermore, smoke evacuation is often overlooked due to lack of awareness of the recommendations to remove smoke, distraction due to noise, inconvenience due to space limitations in the OR, and adjusting current protocols to acknowledge and recommend smoke evacuation.

Conclusion

The transmissibility of HPV via surgical smoke has long been a controversial topic, and multiple studies have sought a definitive answer. Unfortunately, studies have been inconsistent in demonstrating feasibility, and have reproduced results with varying degrees of success. Data to date have shown that HPV DNA can indeed be carried by surgical smoke and that it can be reintroduced to host tissue and cause disease.12-14 This phenomenon was done in a controlled experimental study, but case reports have also described occupational HPV exposure causing squamous cell carcinoma of the tongue and tonsil. Although these cases are few, and the incidence and prevalence are currently impossible to calculate, the evidence leans heavily in favor of HPV being transmissible in surgical smoke.16-18 Unfortunately, by the surgeons' accounts in these cases, they did not take measures to prevent exposure to the surgical smoke; masks and ventilation were not employed.

The best measure to reduce exposure and reduce transmission is to minimize contact with surgical smoke. Surgical smoke evacuation devices should be used as often as possible, and OR staff should use masks, preferably N95s, to provide maximum protection from aerosolized pathogens.19,22 Ensuring the consistent use of preventive measures is also important, as many surgeons will find proper smoke evacuation cumbersome and respirator masks distracting.8 Therefore, it is important that employers are aware of the risks of exposure to surgical smoke, and that OR staff advocate for institutional protocols that mandate smoke evacuation. Future well-designed studies that might conclusively answer the questions of transmissibility and morbidity would be most welcome. Until such studies are available, we should conclude that surgical smoke is not benign, and in the face of such concerns, surgeons should implement protective measures consistently to mitigate any potential risk.

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