Anesthesia for Laser Surgery

Introduction:

The laser beam is a source of energy that can be aimed at a very high intensity and can vaporize tissues or photocoagulate, gradually replacing the surgeon's scalpel at the microscopic level. On the other hand, lasers can be dangerous because they can be invisible and misdirected or inflame anesthetic gasses or endotracheal tubes and damage normal tissues. The carbon dioxide laser or the neodymium-doped yttrium aluminum garnet (Nd: YAG) laser is frequently used in upper airway surgery. The wavelength of the carbon dioxide laser is 10.6 µm (micrometer), and it is strongly absorbed within 200 µm of any tissue traversed. As a result, it is widely used for the excision of laryngeal lesions, skin lesions, and so on because Nd: YAG lasers are predominantly absorbed by pigmented tissues.

As a result, it is no surprise that many practitioners prefer to use lasers to treat upper airway lesions. However, anesthetists must deal with the difficulties the obstructed upper airway faces while also taking measures to prevent laser beam hazards. Laryngeal cancer or papilloma excision, vocal cord nodule or cyst removal, post-corrosive or traumatic tracheal stenosis, obstructing tumor, vocal cord dysfunction, and other airway surgeries using lasers are among the most prevalent.

What Are the Hazards of Laser Surgery?

1. Hazards to Operating Room Personnel and Operating Team:

• Because the laser emits a high-intensity beam, it should be employed carefully. Specular reflection, such as that from a mirror surface, alters the beam direction without shifting the focal properties and can thus direct the full power of the beam in an unexpected direction.
• Matting the surfaces prevents deflection and lowers the energy density. The eye is the most vulnerable tissue to laser radiation damage. Carbon dioxide can damage the cornea, and the Nd: YAG laser can damage the retina.
• Personnel working in the operating room should wear safety glasses that fit snugly around the eyebrows and the forehead and have side shields that safeguard the lateral part of the eye.

• No skin shield is required to ensure that the laser beam is not reflected and that the energy density declines further than the focal point. However, for the safety of those accessing the operating room, an excellent noticeable sign should be placed on the outside of the entrance door.

2. Hazard to the Patient:

A. Fire Danger:

• Fire dangers arise when the laser beam collides with a combustible object, like an endotracheal tube. The likelihood of fire damage happening during laser surgery of the airway is determined by the material on which the laser beam is going to strike, the gas encompassing it, and the concentration of the laser beam.
• A well-focused laser beam can easily light the presence of 100 percent oxygen, regular rubber, and plastic endotracheal tubes. Nitrous oxide aids combustion. As a result, the usage of air with oxygen to completely eradicate fire hazards is recommended. Isoflurane, Sevoflurane, and other halogenated anesthetics do not encourage combustion and are not flammable.
• Although rubber and plastic tubes are incredibly harmful when used alone, they can be used by wrapping the tubes in aluminum foil to reduce risk. Arcing is the term used to describe the indirect burning of an endotracheal tube caused by burning tissue fragments inside the tube. There are numerous methods available today to minimize the risk of fire:

1. There is no tube in the airway.
2. Wrapping the exterior of the tube with different materials to safeguard it.
3. Make use of a noncombustible tube.

B. Damage to Normal Tissue: Normal tissue is destroyed when the laser beam is misdirected or reflected into exposed tissues. This may result in complications for the patient or the operating room staff. However, it can reduce tissue injury with an excellent surgical approach and an immobile target, which is the duty of the anesthetist. Water-soaked gauze pads, sponges, or swabs can protect the tissues adjacent to the operative field. After wrapping, the patient's eyes will be covered with moist eye pads. Surgical drapes cover the entire arm to shield the skin from the laser beam.

What Is Anesthesia for Laser Surgery of the Airway?

Because the airway is shared and a laser is used, anesthesia for laser surgery of the airway presents special challenges.

A. Preoperative Assessment:

• A thorough preoperative history and physical examination should be performed to assess the degree of present airway obstruction, ease of breathing, which may indicate adequate ventilation, and the existence of hoarseness, stridor, and hemoptysis.

• Patients typically present with coughing, hoarseness, odynophagia, dysphagia, pain from cartilage invasion, and other symptoms. In addition, glottic pedunculated tumors usually cause positional exacerbation of airway symptoms.

• Unexpected breathlessness with panic at night is a serious obstacle. In an airway emergency, anesthetists should plan the anesthesia technique according to the possible threat to the airway and be prepared with rescue measures such as tracheostomy.

• The surgeon could perform indirect laryngoscopy on the patients. Can generate computed tomography images in three dimensions to provide precise anatomical deviations.

• Cross-sectional imaging techniques deliver information on airway intrinsic obstruction. Preoperatively, the anesthesiologists and surgeons should discuss the procedure based on the findings.

B. Premedication:

• Premedication with an opiate, sedative, and anticholinergics seems to be safe in patients who do not have a compromised airway. Intravenous injections of 0.004 mg/kg (milligram per kilogram) Glycopyrrolate, 0.02 mg/kg Midazolam, 0.08 mg/kg Ondansetron, and 1 gm (gram) per kg Fentanyl.

• Dexmedetomidine 1 gm per kg injection is helpful in anticipated mild or suspected compromised airways, producing suitable sedation without respiratory depression. Therefore, no opiate or sedative premedication is given for a compromised airway.

C. Anesthesia Goals: Anesthesia objectives encompass profound muscle paralysis to provide relaxation of the masseter muscle for scope introduction, an immobile surgical field, sufficient oxygenation, ventilation, and stability of the cardiovascular system during the surgical stimulation period. Profound relaxation is necessary until the surgery is completed, and rapid recovery is critical.

D. Monitoring: A multipara monitoring device is needed to measure heart rate, rhythm, saturation, end-tidal carbon dioxide, temperature, and respiration.

E. Induction of Anesthesia:

• Standard intravenous or inhalation induction methods can be employed without airway obstruction. However, an experienced anesthetist and surgeon must plan the procedure to safeguard the airway in a patient with an altered airway based on a prior nasendoscopy. A backup plan should be in place if plan A fails.

• To that end, one should keep various airway devices on hand. Various laryngoscopes, airways, bougies, endotracheal tubes, and bronchoscopes (fiberoptic bronchoscopy or endoscopy devices, both direct and video, are kept in the operating room. Video laryngoscopes, a cricothyrotomy set, a surgical mini-tracheostomy set, and a standard tracheostomy set are included.

What Are the Anesthesia Techniques?

As previously stated, we can avoid fire hazards by employing one of the following approaches: no tube, noncombustible tube, or protecting the external surface from a conventional tube.

A. No Tube with Spontaneous or Controlled Ventilation:

• The larynx could either be blocked or anesthetized with topical anesthesia, and the patient is induced with standard drugs such as Thiopentone or Propofol, as well as Fentanyl and Midazolam.

• Anesthesia is preserved using nasal catheters and a nitrous oxide-oxygen mixture containing a noninflammable drug such as Isoflurane or Sevoflurane. The other approach is administering a relaxant while retaining depth with Propofol and ventilating the patient with a jet.

• Moreover, one must be fully conscious of the side effects of jet ventilation: pneumothorax, pneumomediastinum, stomach inflation, aspiration of resected material, and mucosal surface dehydration. The surgeon and anesthetist conversely distribute the airway in this approach.

• The advantage of this technique is that the surgeon can operate in the larynx without being hindered by an endotracheal tube.

• The disadvantage of the spontaneous ventilation procedure is that the patient does not consistently retain a sufficient depth of anesthesia.

B. Protecting External Surface of Conventional Tube:

• A red rubber or a vinyl plastic cuffed tube of one or two sizes smaller than the correct size for the patient is used in this method. If a cuffed tube is unavailable, we could use an uncuffed tube for children.

• The cuff is filled with saline rather than air. The tubes are well covered in a spiral fashion with aluminum or copper adhesive tape. The tube surrounding should begin near the cuff and end in the uvula.

• The covering is designed so that each spiral covers two-thirds of the previous spiral, eliminating the possibility of an uncovered area in the tube around the surgical field. However, with using foils, there are a few potential complications.

C. Laser Fire:

• If a fire occurs, immediately detach the tube from the gas source because most tubes do not burn in the air. Smoke inhalation of the smoke or direct thermal burns can cause massive lung and tracheal damage.

• A chest X-ray and bronchoscopy are conducted to determine the injury's degree. In addition, steroids, inhaled gasses, humidification, tracheostomy, and continuous postoperative ventilation may be required.

• Tracheal stenosis is a late side effect that can take place. The laser beam can perforate the cuff, resulting in a leak and insufficient ventilation. As a result, saline-soaked gauze pieces must be placed between the vocal cords and the cuff.

• The foil can become loose and tear off, resulting in foil aspiration. It is also possible for the tube to kink. Patil et al. recommends wrapping the tube in moistened muslin cloth.

• The water or saline in the muslin cloth prevents laser energy from being ignited and dissipated.

The disadvantage of this technique is that the muslin cloth must be moistened frequently with an epidural catheter or by the surgeon to prevent the dry muslin from catching fire.

D. Noncombustible Tube: Many tubes are partially noncombustible and can be used in laser airway surgery.

• Bivona Foam Cuff Tube: This tube features an aluminum and silicone rubber spiral, a silicone covering, and a self-inflating foam sponge cuff. The inner surface of this tube is non-flammable. Apart from laser penetration, the cuff generally keeps a seal.

• Disadvantages include flammable external surface, which is flammable, and cuff. In addition, if the cuff or inflation tube is broken, deflating it may be difficult and time-consuming.

• Laser Flex: This has an airtight stainless steel corrugated spiral, a murphy eye tip, and double cuffs. For pediatric usage, an uncuffed version is also available. This product is designed for carbon dioxide or potassium titanyl phosphate lasers.

• Benefits: Noninflammable metal parts. The tube retains its shape during intubation. The proximal tracheal cuff protects the distal tracheal cuff.

• Disadvantages: The metal may reflect the laser and cause damage to nontargeted tissues.

Conclusion:

Anesthesia for laser airway surgery presents unique difficulties for anesthetists. Preoperatively and all through the procedure, anesthetists and surgeons should communicate effectively. Anesthetists should have an anesthesia plan ready and be prepared if an alteration in the plan is required at the induction time. Anesthetists should understand the basic principles and applications of lasers. In the case of a sudden complication, such as a laser fire, anesthetists should be able to quickly recognize and interrupt the flow of oxygen or nitrous oxide, as opposed to an anesthetist's reflex to provide 100 percent oxygen in times of disaster.