Transoral CO 2 Laser Microsurgery for Cancer of the Larynx

Introduction

Transoral CO ₂ laser microsurgery is a well-established treatment for cancer of the larynx, particularly for T ₁ or T ₂ glottic cancer. Alternative treatment options include radiation therapy or hemilaryngectomy for glottic cancer and supraglottic or supracricoid laryngectomy for supraglottic cancers. The advantages of using CO ₂ laser with an operating microscope include microsurgical precision, excellent intraoperative detail, and a dry surgical field. Swallowing and speech outcomes exceed that of external surgical approaches and radiation therapy. Other advantages include patient convenience, savings both on direct and hidden patient costs, reserving radiation as potential therapy for recurrence or for second primaries, and that patients who recur are more likely to have larynx preservation.

Surgeons must familiarize themselves with the laser machine, its settings and delivery system, and its tissue effects before attempting to use it clinically and should hone their skills on animal tissue and then small tumors. They must also understand the safety aspects relating to CO ₂ laser surgery.

Key Operative Learning Points

• Surgeons without prior experience using a laser should start with simpler cases (e.g., smaller cancers of the aryepiglottic fold, supraglottis, or medial wall of the piriform fossa).

• Spot size, focus, power, and mode (super pulse [SP]/pulsed/continuous) are important to achieve the desired effects and may be altered during an operation for different tissues or to achieve coagulation, cutting, or vaporization effects.

• Check the alignment of the aiming beam with the laser beam.

• Avoid past-pointing, as this may cause laser fires. Be aware of reflection of the laser beam off of instruments and scopes, and ensure that the backstop is correctly positioned to protect the endotracheal tube.

• Apply constant traction to tissues to define dissection planes and facilitate dissection.

• Maintain a relatively slow, smooth hand-speed.

• Use Ligaclips, not diathermy, for large vessels to avoid postoperative bleeding.

• Minimize tissue injury by employing super pulse (SP) as opposed to continuous mode.

• One may have to resect structures (e.g., suprahyoid epiglottis) to improve access.

• Debulking the cancer allows one to create space within which to move tissues around.

• Distinguish the cancer from normal tissue by transecting it and checking pliability (cancer tissue is rigid) and colors of tissues (cancer chars and is brown/black when transected) ( Fig. 11.1 ).

  

• Bread slice ( Fig. 11.2 ; see also Fig. 11.1 ) the cancer to determine its depth and to ensure an adequate deep resection margin.

  

• Do not lose orientation of specimens; pin specimens to cork that is placed in formaldehyde and make a detailed drawing for the pathologist and in the patient’s notes of the precise location of resected specimens.

• What constitutes an adequate resection margin is controversial and might determine whether to return a patient to the operating room for an additional resection, whether to advise close surveillance, or whether to recommend adjuvant radiation therapy. Factors include tumor site, size, function (voice and swallowing), patient fitness, extent of the initial resection (e.g., onto cartilage or carotid), not knowing precisely where the positive or close margin is located, and reliability of follow-up.

• Pathologists are reticent to do frozen sections on very small resections (e.g., T ₁ glottic cancer).

• A surgeon’s impression of the adequacy of a resection as seen through the microscope is important; one may adopt a watchful waiting approach even when the cancer is reported to be “present at the margin” with the knowledge that cells are denatured and killed at the margin by the laser.

• Follow laser safety procedures ( Table 11.1 ).

  TABLE 11.1

  Laser Safety Precautions and Management of Laser Fires

  With permission from Apfelbaum JL, Caplan RA, Barker SJ, et al: Practice advisory for the prevention and management of operating room fires: an updated report by the American Society of Anesthesiologists Task Force on Operating Room Fires. Anesthesiology 118(2):271-290, 2013.

  Safety Precautions (Surgical)—Develop a Check LIST Which Includes

  Place laser warning signs outside the operating room. Cover windows and securely close doors while the laser is “on” or in “standby” mode. Personnel and patients must use eye protection specific for CO 2 laser; it should also be available at entrances to the room; standard prescription eyeglasses are sufficient for CO 2 laser; side-guards are recommended. Tape the patient’s eyes shut and cover them with moist pads. Do not use alcohol or flammable cleaning prep solutions in the operating room. Use flame retardant materials and drapes. Keep an open container filled with water or saline immediately available to douse a laser fire. Place moistened swabs/sponges adjacent to the path of the laser beam to protect surrounding tissues and structures. Minimize the possibility of a “blow-torch effect” by carefully protecting endotracheal tubes with wet cloth or neuro patties. The locking key to laser machine should be accessible only to persons trained in the use of laser; it should not be stored in or on the laser machine but kept in secure location; some lasers have electronic keypads. Keep the laser turned off or in “standby” mode unless in use. Instruments should have brushed, beaded, or sand-blasted surfaces to prevent reflection of the laser beam.

  Safety Precautions (Anesthetic)

  “Nonflammable” endotracheal tubes may be used. (All tubes are flammable.) Fill the cuff of the endotracheal tube with saline colored with methylene blue. Maintain inspired oxygen (FiO 2 ) as low as clinically feasible (<30% FiO 2 ). Wait a few minutes for the oxygen concentration in the airways to drop before approving activation of the laser. Avoid nitrous oxide if possible.

  Laser Airway Fire

  Turn off laser at emergency switch. Turn off all anesthetic gases. Remove swabs and flammable materials from the airway. Immediately remove the endotracheal tube. Pour saline into the airway.

Preoperative Period

Preoperative assessment is directed at the patient’s general fitness for surgery, counseling about risk factors, the ability to cope with a degree of aspiration (supraglottic cancer resections), and to determine whether the cancer is amenable to endoscopic laser resection.

Operative Period