Airway for Laser Surgery

Medical lasers are used in procedures in various specialties, including otolaryngology, ophthalmology, dermatology, plastic surgery, and dental surgeries, as well as in intraabdominal, cardiothoracic, neurologic, gynecologic, and urologic procedures. Lasers provide a source of focused, coherent light capable of transmitting intense energy to a precise location. Each laser type acts upon a specific chromophore that preferentially absorbs the laser light resulting in heat and eventually in the destruction and cauterization of the tissue. Importantly, lasers can ignite flammable materials present in the operating field, such as endotracheal tubes, sponges, and catheters. Such foreign materials may themselves absorb the laser energy and ignite, or a spark can be created from the laser cauterization that then spreads to the combustible foreign material. Lasers also pose a risk of eye injury (both to the patient and operating room personnel), laser plume, electrical tripping, and release of chemical contaminants. Using a laser in upper aerodigestive surgery introduces a source of ignition that is especially dangerous when supplemental oxygen is added to the inspiratory gas mixture. This dilemma is constantly discussed, and multiple techniques have been developed to provide ventilation to an anesthetized patient while keeping the surgical field maximally accessible and minimizing laser-related hazards. The common ventilatory strategies include conventional endotracheal intubation, jet ventilation, intermittent apnea technique, and spontaneous breathing. Multiple methods and numerous "laser-resistant" endotracheal tubes (ETT) were designed to protect the operating field from the hazards of medical lasers. The American Society of Anesthesiologists now recommends these as the default endotracheal airway during laser surgery of the respiratory tract. The cuff is the most vulnerable part of the ETT. During intubation, once the tube passes through the vocal cords, the balloon at its distal end (cuff) is inflated with air (or saline) to occlude the trachea external to the tube and thus directs all the gas flows from the ETT exclusively to the trachea, and vice versa. A dye such as methylene blue is typically instilled into the cuff for such cases, so there is an obvious visual alert if the balloon is inadvertently popped. If the cuff is damaged by a laser (or other instruments or the patient's dentition), it becomes compromised and can no longer seal the trachea. This leads to a gas mixture rich in oxygen that can escape to the upper airway and surgical field. A fire may be ignited during this event or subsequent use of the laser. The ETT and other materials potentially present in the field, such as gauze and surgical drapes, are the most common fuels for an airway fire.