Nonionizing Radiation: Lasers

Laser is an acronym for light amplification by stimulated emission of radiation. Lasers produce infrared, visible, or ultraviolet light. Although the radiation from lasers is nonionizing, it is potentially unsafe both because of its intensity and because of the matter release from tissues during treatment.

Lasers are used in many surgical specialties, including ophthalmology, plastic surgery, gynecology, neurosurgery, urology, head and neck surgery, and gastrointestinal surgery. A surgical laser produces intense focused electromagnetic radiation to cut or destroy tissues. The radiation is usually infrared or visible light and is created in a "laser medium" that is stimulated by high-intensity energy to release photons of identical wavelength (coherent or monochromatic light) from a laser chamber. The material in the medium (e.g., carbon dioxide, argon) is responsible for the wavelength produced by the laser. Of those in common clinical use, carbon dioxide and neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers emit light in the far-infrared and near-infrared wavelengths, respectively; argon and tunable dye lasers produce visible light.^[22] The choice of laser used is based on the surgical goal.

Eye injuries are the greatest risk to personnel working near lasers. Strict standards for protection have been developed on the basis of current understanding but are subject to periodic revision as more experience is gained with these instruments. Either direct exposure or reflected radiation may cause eye damage. Injuries include burns to the cornea and retina, destruction of the macula or optic nerve, and cataract formation. Protective eyewear is designed to filter out the radiation produced by a specific type of laser while still permitting vision. For example, clear plastic lenses block the far-infrared (10.6-µm) radiation from carbon dioxide lasers but provide no protection against the near-infrared (1060-nm) radiation emitted by Nd:YAG lasers. The type of protection provided by a given filter is marked on the frame of the goggles and should be checked before use. Filters that are scratched or crazed should not be used. Because certain filters block portions of the visible spectrum, it is prudent to confirm preoperatively that patient monitors can be seen and interpreted correctly with goggles in place. Protective eyewear is recommended for all personnel because reflected radiation can be as hazardous as direct radiation and the intensity is not diminished significantly in the distances traveled in the average operating room.^[22]

Although the plume—the vapor and cellular debris produced during laser surgery—is commonly malodorous, until recently it was not considered to be other than unpleasant. Now, there is concern that the plume may present a significant risk. The median size of particles in plume samples obtained intraoperatively is 0.31 µm in diameter and ranges from 0.1 to 0.8 µm. Most surgical masks do not trap such small particles.^[23] Even after filtration of particles greater than 0.5 µm in diameter, exhaust smoke from tissues treated with a carbon dioxide laser causes pulmonary lesions in laboratory animals. If all particles larger than 0.1 µm are scavenged, no lung damage occurs, thus pointing out the importance of scrupulous removal of the plume.^[24] Under experimental conditions, viable bacteria have been recovered from the plume emanating from laser irradiation.^[25] Intact DNA from human papillomavirus (HPV) has been detected in the vapor from both laser-treated plantar warts and genital condylomata.^{[26] [27]} More frightening is that human immunodeficiency virus (HIV) proviral DNA has been found in laser smoke produced by vaporizing cultures of HIV-positive cells.

Although these experiments, which used tissue cultures, do not replicate the clinical situation, they stress the

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