Anesthesia for Laser Surgery

Introduction

• Laser is an acronym for light amplification by stimulated emission of radiation.
• Lasers are devices that emit a coherent beam of electromagnetic radiation at a specific wavelength. Unlike ordinary light, laser light is monochromatic (single wavelength), coherent (photons are in phase), and collimated (parallel with minimal divergence). These properties make it uniquely suitable for precise surgical applications.¹
• Laser energy is generated when electrons in an atom or molecule absorb external energy, move to a higher energy state, and then return to their ground state. As the electrons return, they release photons, which in turn stimulate the release of additional photons of the same wavelength. This process, known as stimulated emission, produces an amplified and highly organized beam of light.¹

All medical lasers share three core components:¹

• The energy source (pump) provides energy to excite the active medium. In medical systems, this is typically electrical or optical.
• The active medium determines the wavelength of the emitted light. The medium may consist of gases (e.g., CO₂, argon), solid crystals (e.g., neodymium-doped yttrium aluminum garnet [Nd:YAG]), semiconductors (e.g., diode lasers), or liquid dye solutions.
• The resonant chamber is a cavity with mirrors that amplify light. One mirror is fully reflective, while the other is partially reflective, allowing a portion of the amplified photons to exit as the laser beam.

Once generated, the laser beam can be delivered to tissues in several ways:¹

• Line-of-sight systems direct the beam via mirrors or micromanipulators, often attached to a surgical microscope (e.g., CO₂ laser in microlaryngoscopy).
• Fiberoptic systems use flexible fibers that allow delivery into confined or remote anatomical regions (e.g., Nd:YAG, KTP, and fiber-delivered CO₂ lasers).

When laser light reaches tissue, it can be absorbed, scattered, reflected, or transmitted.

The interaction between the wavelength and the tissue chromophore governs clinical effects:

• Water is the primary chromophore for mid-infrared lasers (e.g., CO₂, erbium-doped yttrium aluminum garnet [Er:YAG]).
• Hemoglobin strongly absorbs visible green and yellow light (e.g., Potassium titanyl phosphate [KTP], pulsed dye).
• Melanin absorbs across shorter visible and near-infrared wavelengths (e.g., diode, alexandrite).

These interactions can produce photothermal (coagulation, vaporization), photoablative (tissue disruption), or photochemical (photosensitizer-mediated) effects, depending on the laser parameters.¹

Types of Medical Lasers¹

• CO₂ (10,600 nm): This laser is strongly absorbed by water, allowing for precise tissue vaporization and ablation. It is commonly used in ENT, airway, and dermatologic procedures. Although it has traditionally required line-of-sight delivery, newer systems allow fiber-delivered applications.
• Er:YAG (2,940 nm): This laser also has high water absorption, making it well-suited for ablative dermatologic and dental procedures.
• Nd:YAG (1,064 nm) / KTP (532 nm): These lasers are absorbed by hemoglobin, which makes them effective for coagulation and hemostasis. They are widely used in ENT and urologic surgery.
• Argon (488–514 nm), diode (various near-infrared wavelengths), pulsed dye (585–595 nm), and Q-switched lasers: These modalities are primarily used in dermatology and ophthalmology for targeting vascular and pigmented lesions due to selective absorption by hemoglobin and melanin.
• Excimer (193 nm): This ultraviolet laser produces photoablation and is primarily used in ophthalmology for corneal refractive procedures.

Delivery systems: Lasers may be delivered using line-of-sight micromanipulators, such as with CO₂ lasers in micro-laryngoscopy, or through flexible fiberoptic systems, as with Nd:YAG, KTP, and newer fiber-delivered CO₂ lasers.

Indications

Medical lasers are used across multiple specialties.¹

• ENT/airway: Vocal cord lesions, papillomas, subglottic stenosis.
• Pulmonology: Tracheobronchial tumor debulking.
• Dermatology: Vascular malformations, pigmented lesions, scar revision, cosmetic resurfacing.
• Ophthalmology: Corneal refractive procedures (LASIK procedure), retinal photocoagulation.
• Urology/gynecology: Prostate vaporization, endometriosis.
• Gastroenterology: Photocoagulation of gastrointestinal vascular lesions, tumor palliation.
• Neurosurgery: Tumor resection, epilepsy surgery (select cases).

Complications

Laser hazards extend beyond surgical fires and include:

• Surgical fires are a major risk in airway cases involving lasers. For more detailed information, see the OpenAnesthesia summary on Surgical Fires. Ignition of PVC endotracheal tubes by CO₂ and Nd:YAG lasers not only poses a fire hazard but also releases toxic byproducts such as hydrochloric acid and dioxins, which can cause further airway injury and systemic toxicity.
• Other airway complications, such as thermal injury, edema, granulation, and stenosis, may occur.
• The eyes and skin are most susceptible to damage by laser radiation.¹
• Ocular injuries may occur from direct exposure of the eye to the laser or a reflection of the laser beam. They can cause permanent blindness. Therefore, all operating room (OR) personnel should wear wavelength-matched protective goggles, designed to block the specific wavelength(s) emitted by the laser in use. Additionally, the patient’s eyes should be taped shut and covered with a moistened gauze pad.
• The most commonly affected eye structures are the cornea (water-rich) and the retina (pigment-rich). Argon lasers can pass through the cornea and lens without causing damage, but cause damage to the retina. In contrast, CO₂ lasers only injure the cornea. Nd:YAG lasers injure the cornea, posterior chamber, and retina.
• Skin injuries, such as burns, may occur from stray beams or drape ignition.
• Laser plume exposure to particulates, viral DNA, and carcinogens necessitates the evacuation of smoke. All OR personnel should wear individually fitted respiratory filter masks when a significant laser plume is expected.
• Equipment hazards such as misaligned beams or reflective instruments can cause unintended burns.^2-5

Anesthetic Considerations

Global Safety Measures

• A team time-out should be performed for laser type, wavelength, protective eyewear, and safety protocols.
• The lowest feasible FiO₂ should be used, and nitrous oxide should be avoided.
• Wet sponges, non-reflective instruments, and active smoke evacuation should be employed.
• Wavelength-specific eye protection should be provided for all staff and the patient.
• Warning signs should be placed outside the operating rooms to alert staff about the use of medical lasers.

Airway Laser Surgery (e.g., larynx/trachea)

• As mentioned earlier, the lowest feasible FiO₂ should be used, and nitrous oxide should be avoided.
• Laser-resistant ETTs are often used in airway laser surgery to reduce the risk of airway fires. Several different types of laser-resistant ETTs are available.
• Metal tubes (e.g., stainless steel, Xomed, Sheridan) are highly resistant but can conduct heat.
• Wrapped tubes (silicone tubes wrapped with metallic foil) provide protection but risk peeling. This technique is obsolete and not recommended.
• Specialty tubes (e.g., Mallinckrodt LaserFlex, Rusch) are designed to withstand specific laser types and often feature double cuffs.
• Inflate the ETT cuff with saline tinted with methylene blue to make the cuff rupture more obvious.
• Saline-soaked pledgets may be placed in or near the airway to minimize the risk of airway fires.
• A source of water (e.g., a water-filled 60 mL syringe) should be immediately available.
• Tubeless ventilation strategies include intermittent apnea, jet ventilation (barotrauma risk), or supraglottic devices in selected cases.^2,6

Other Perioperative Points

• Standard monitoring with attention to shared airway dynamics; deep, immobile conditions (Total intravenous anesthesia or inhalational) to suppress airway reflexes.
• Consider steroids/epinephrine pledgets for airway edema per surgeon preference, plan for postoperative observation and voice rest.