Exploring excimer laser plume dangers

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by Lisa B. Samalonis Contributing Editor

	The Mastel Clean Room System
	Mastel Clean Room System fixation ring

Although research on the subject in a variety of fields, including dermatology and gynecology, dates back to the mid-1980s, ophthalmic studies are sparse and show conflicting results. However, surgeons and their staffs aren't taking the warning signs lightly or waiting for definitive scientific clinical evidence. Those interviewed by EyeWorld said that while more clinical studies are needed, they are taking steps to reduce the laser plume and protect the entire operating room staff.

When a laser or electrosurgical unit is used during the surgical procedure, thermal destruction of tissue creates a smoke byproduct or plume. In ophthalmology, when the excimer laser strikes the cornea, a thin layer of corneal cells is released. These cells create a plume of tissue that scatters into the air seconds after the laser strikes. The plume consists of carbonized tissue, blood, and the gases benzene, toluene, and formaldehyde, and polycyclic aromatic hydrocarbons.

More plume smoke is being released into the air now as opposed to several years ago because newer small-spot lasers remove almost double the amount of tissue as the older lasers, said Richard Foulkes, MD, associate professor at the University of Illinois Eye and Ear Infirmary, Chicago. Hyperopic ablations release four times more tissue into the air than myopic ablations. "In creating what are the essential 'domes' ... the ablated area that is being treated is enormous. Therefore, the amount of tissue coming into the air is enormous," he said.

The surgeons' stories

Steven J. Dell, MD, clinical instructor of ophthalmology, Tulane University, New Orleans, said that it might take years to definitively determine if the laser plume is dangerous to the surgical staff. He has decided not to wait and is taking precautions, such as plume-filtering operating room masks and the Mastel Clean Room System, from Mastel, of Rapid City, S.D. (www.mastel.com). The system consists of a fixation ring coupled to a vacuum system with a series of high-performance filters. It employs a surgical handpiece that removes the smoke plume in four directions away from the stromal bed. Two other plume evacuation systems called the AirSafe VersaVac2 and MiniVac surgical smoke evacuators are sold by Stackhouse

(www.thermoresp.com/shi/). These evacuators are developed mainly for operating rooms with CO2 lasers and filter out very small particulate matter, including viruses.

Many surgeons are concerned that the laser plume may transport infectious diseases or viruses, such as HIV/AIDS or hepatitis. He pointed out that the dangers of breathing plume smoke from CO2 lasers are documented in dermatology literature. "The typical particle size in the plume of an excimer laser is 120 nm, which is in the general range of coal dust and several compounds in cigarette smoke. It is conceivable that the plume might also contain prions, and the consequences of breathing this material are unknown," said Dell, who is in practice in Austin, Texas.

Dell uses 0.1-µm plume-filtering face masks during excimer surgery. "To truly be effective however, the mask would need to be taped securely on all sides to the surgeon's face. This is simply not practical. Additionally, moisture from the surgeon's breath rapidly degrades the efficacy of the filter in the mask. These masks filter down only to 0.1 µm, which is equivalent to 100 nm. Many viruses, such as hepatitis A, echovirus, and enterovirus, are smaller than this. All prions are much smaller than this," he said.

Other surgeons, including John S. Jarstad, MD, medical director Evergreen Eye Center, Federal Way, Wash., believe they have gotten sick from the plume. Jarstad said that approximately 6 months after beginning excimer laser surgery in 1996, he developed his first case of obstructive airway disease, or asthma. He had never had asthma before and was a champion distance runner in high school.

Jarstad competed in 5-K and 10-K races without difficulty until asthma developed in early 1997. "I began using an inhaler with some relief, even though pulmonary function studies showed no significant disease," he said.

In December 2000, following 36 consecutive laser in-situ keratomileusis cases, Jarstad developed sudden shortness of breath with squeezing substernal chest pain and a pressure sensation, palpitations, and lightheadedness, along with a feeling of impending doom. When the symptoms would not fully subside 15 minutes after nitroglycerin and an aspirin, he went to the emergency department of his community hospital.

"After spending the next 24 hours in the cardiac intensive care unit and having negative enzymes and electrocardiogram, I underwent cardiac catheterization the following day. No coronary artery obstruction was identified and I was discharged without a definitive diagnosis, but possible coronary artery vasospasm," said Jarstad, who is also president, Washington Academy of Eye Physicians & Surgeons, Seattle.

In addition to his health problems, he said, his laser operator and circulating nurse have also complained of "bronchitis" following a day of LASIK cases.

Jarstad decided the situation warranted the installation of a Mastel Clean Room System. "Since installing this device, I noted an immediate decrease in respiratory symptoms in our surgical staff, better energy at the end of the day, and a clearer head. There is less coughing and fewer complaints of bronchitis," he said.

Jarstad believes his case is the first report of LASIK-related cardiopulmonary disease. "I am a 45-year-old ophthalmologist with no prior history of asthma or cardiovascular disease. I do have a family history of these diseases and have had borderline cholesterol treated successfully with Lipitor [Parke-Davis]," he added.

Questions about his case remain: Could a heavy bolus of inhaled LASIK plume particulate matter passing through the surgeon's mask and entering the lung alveoli cause severe shortness of breath and chest pressure mimicking asthma or angina? Could these particles then enter the circulation and create a vasospastic response in the coronary arteries in susceptible individuals? Is it possible for the sheer volume of small-diameter LASIK plume particles to accumulate in the pulmonary circulation to such an extent that it overwhelms the small vessels in the coronary circulation with a temporary blockage?

"Further studies are necessary to determine the effects of LASIK plume particulate matter in animals and humans to safeguard ophthalmologists, patients, and surgical staff," Jarstad said. "I would advise anyone with 'LASIK lung' or cardiac symptoms to evaluate a plume-evacuation system to prevent life-threatening cardiopulmonary complications."

Ronald A. Friedman, MD, in practice in Monterey, Calif., also believes that the laser plume from the excimer laser during refractive surgery poses potential harm to surgeons and their staff members. Last year, when his LASIK volume increased to 60 to 80 cases a year, he experienced several bouts with a bronchitis-like illness. Friedman said that he is unsure if the plume brought on his health problems.

"To guard against potential health hazards, a surgeon should make sure he has a laser clean-air type of device, as well as good room ventilation," he said.

After several weeks of using a plume evacuator, Friedman noticed improvement in his respiratory status and has not experienced a relapse.

In another case reported in 1998 in EyeWorld, Jerald L. Tennant, MD, a refractive surgeon from Texas, was forced to retire due to health problems he believes may have been caused by airborne corneal particles or viruses contained in the plume generated from the laser. Tennant, developed idiopathic thrombocytopenic purpura (ITP), a rare condition in non HIV-positive adults, in which the body's immune system produces antibodies that attack and destroy platelets. Another ophthalmologist, who prefers to remain anonymous, also developed ITP since beginning to use the excimer laser in 1990. "The incidence of ITP in the general public is rare," Tennant said. "To have two excimer laser surgeons develop ITP after the same amount of exposure is suspicious. That is why I have recommended that excimer surgeons follow their platelet count until the issue is resolved."

Plume presence

All the lasers generate surgical smoke that can be seen if the surgeon or technician looks for it, said Foulkes, who has been on the front line of plume elimination and worked with Mastel to develop its plume evacuator. "Although the evacuator doesn't get all of the plume particles, it gets most of them, including the bulbous gaseous plume," said Foulkes, who is in practice at the Future Vision Laser Center, Chicago.

Although Foulkes has never experienced a plume-related illness, he is aware of doctors who have. As a distance cyclist, he said, he is particularly concerned about guarding his pulmonary capacity. He is conducting a preliminary pulmonary study with several laser centers in the Chicago area that do not employ a smoke evacuator.

An added benefit of evacuator use, Foulkes said, is that it helps standardize the surgical process, resulting in a more-accurate laser performance and results. "Ablation profiles on eyes are more accurate with the evacuator. We want to standardize the process and have the same environment for the laser to do its job. We all are concerned about humidity and temperature, and we need to get worried about the plume," he said.

Safety first

Marguerite B. McDonald? MD? clinical professor of ophthalmology at Tulane University and director of the Southern Vision Institute, New Orleans, said that the potential danger of the laser plume was so worrisome that she also purchased a clean-room system with a vacuum that evacuates both the low-hanging fog of plume that hovers just over the entire ablative corneal surface, and the high-speed ejected plume, which requires a different evacuation system.

"It's a sophisticated system, which has eliminated the odor, and has a high-speed photography that has [been] shown to get nearly all of the plume out of the faces of the medical staff," she said.

Although expensive - the system runs $35,000 at list price ($15,000 extra for a LASIK cart) - McDonald believes it is worth it. She is concerned about the danger from the plume, not only because of infectious agents, but because of bronchitis. "Most ophthalmologists know a LASIK surgeon with laser lungs," she said, adding that many surgeons have asthma and experience the loss of their voices.

"My staff is very concerned about it; they know LASIK technicians with chronic coughs," she added.

But the scientific jury is still out on the reality of transmission of infectious diseases via the smoke plume. Terrence P. O'Brien, MD, director of ocular infectious diseases and refractive eye surgery at the Wilmer Eye Institute, Johns Hopkins University, Baltimore, said that he and his colleagues compulsively collected the plume from autopsy eyes of individuals who were HIV-positive. He said that while they we were able to demonstrate the presence of the viral DNA, they were not able to prove the presence of infectious particles or agents.

In another study, Peter J. McDonnell, MD, chairman of the Department of Ophthalmology, University of California-Irvine, and colleagues concluded that aerosolization of infectious virus could exist with photoablation using a large-diameter excimer laser beam. However, the experimental design of the study did not prove that spread of infectious virus is likely to occur in the clinical setting.

In the study, published in the American Journal of Ophthalmology (March 1997), the researchers set out to determine the potential for aerosolization of infectious virus present within the tear film during excimer laser photoablation of the cornea. They took cell monolayers infected with herpes simplex virus or adenovirus, simulating virus-infected corneas, and ablated them with the 193-nm excimer laser. Adjacent dishes containing noninfected cell monolayers were subsequently assayed for viral infection. As a result, viral spread to sentinel dishes occurred with both herpes simplex and adenovirus, the researchers noted. The titer of virus present in the infected cell monolayers influenced the likelihood of spread to adjacent dishes. The presence of a vacuum-aspiration system appeared to influence the direction of virus spread, with dishes located in the direction of the vacuum most likely to contain virus.

They recommended that appropriate measures be taken to reduce the possibility of the spread of virus from the patient to the surgeon, other medical staff, or other patients (see sidebar).

Operating room personnel

The Association of periOperative Registered Nurses (AORN) has been campaigning for formal guidelines regarding the potential dangers of surgical smoke. The association's book of 2001 Standards, Recommended Practices, and Guidelines, lists guidelines for electrosurgery and exposure to the surgical smoke plume culled from a variety of sources.

Candace Romig, director of government affairs, said that while AORN has worked with Occupational Safety and Health Administration to develop formal guidelines on electrosurgical smoke, the agency's current position is that insufficient scientific data exist to warrant formal guidelines. OSHA recommended AORN consult with the National Institute for Occupational Safety and Health (NIOSH).

"We have been meeting with NIOSH," Romig said. "We have also gotten approval to look at secondary data from the Harvard Nurse's Study. We are working on trying to raise money so we can have the Harvard researchers look at speciality nurses in the operating room ... to see if we can find anything that will satisfy OSHA."

Contact Information
Dell: 512-327-7000, fax 512-327-5200
Foulkes: 708-499-6811, fax 630-920-8533
Friedman: 831-375-2486, fax 831-375-0128
Jarstad: 253-952-2010, fax 253-661-7383
McDonald: 504-896-1250, fax 504-896-1251
O'Brien: 410-955-1671, fax 410-614-0682
Romig: 303-755-6304 x263, fax 303-338-4838
Tennant: 817-540-5619, fax 817-267-5276