Laser Surgery of the Airway

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Laser Surgery of the Airway

• Airway Issues, Anesthesia Choices and Ventilation

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Disclosures/Conflicts

• Vanderbilt Anesthesia Department
• Board of Trustees, MTSA
• Clinical Consultant, Organon-Schering Plough

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Airway Surgery Issues

• Stimulation of surgery
• Difficult intubation
• Airway competition
• Potential loss of airway
• Positioning
• Emergence timing issues

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Difficult Airway Presentations

• Anatomic
• Narrowing of airway
• Vocal cord dysfunction
• Trauma
• History of difficult intubation
• Low threshold for FOI

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Anesthesia Requirements

• Light premedication with antisialagogue
• Adequate intraop and postop analgesia
• Quiet surgical field/paralysis
• Smooth emergence
• Anesthetic choices range from local to inhalation
  to TIVA

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FiO2 Management

• Maintain 100 FiO2, affording longer periods of
  apnea
• For laser, use lowest FiO2, maintaining adequate
  oxygen saturation
• Dilute oxygen with air
• May use heliox (lower FiO2, improved
  flow/resistance)

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Airway Management

• Airway is shared continuously between the surgeon
  and the anesthetist
• Small cuffed tube (effective in 95)
• Laser ET tube
• Intermittent apnea (1-5 minutes)
• Jet ventilation

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Introduction to Lasers

• CO2 is the most widely used laser (longer
  wavelength, less tissue penetration)
• Absorbed by water contained in blood and tissues
• Invisible beam offers unobstructed view of the
  lesion
• Several applications with potential for rare
  severe complications

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Laser Media Wavelengths

• Medium Wavelength Application
• (nm)
• CO2 10,600 General, cutting
• Nd-YAG 2,930 Coag, fiberoptics
• Ruby 694 Tattoos, nevi
• Organic dye 632 Phototherapy
• KTP-YAG 532 General, pig. lesion
• Argon 514 Vascular, pig. lesion
• Xenon fluoride 351 Cornea, angioplasty
• Krypton fluoride 248 Cornea, angioplasty

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Laser Applications for ENT

• Laryngeal or vocal cord papillomas
• Laryngeal webs
• Redundant subglottic tissues
• Debulking of tumors

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Advantages of Laser

• Precise lesion targeting
• Minimal bleeding
• Minimal edema/tissue reaction
• Preservation of surrounding structures and normal
  tissues
• Rapid healing/less postop pain

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Hazards of Laser

• Eyes are vulnerable to misdirected beam
• Fire hazard (up to 0.4)
• Damage by reflection of light by tube,
  instruments
• Laser smoke may damage lungs
• Hypoxic mixture of inhaled gases
• Vaporization of cancers may aerosolize
  carcinogens (plume, fine particles)

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Laser Plume

• Viral DNA has been detected in plume from
  condylomas and warts but not from laryngeal
  papillomas
• CO2 lasers produce the most smoke and NdYAG
  produces the least
• Ordinary masks filter down to 3 micrometers so
  that special filter masks are required along with
  vacuum of field

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Other Precautions for Laser Surgery

• Eye goggles for OR staff (laser specific)
• Warning sign outside OR
• Wet towels for eyes of patient
• Special ET tube vs. apneic ventilation vs. jet
  ventilation

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Heliox

• Combustion is more vigorous when excess oxidizer
  is used (e.g., oxygen)
• Index of flammability is reduced only by 2 when
  helium is substituted for air
• Helium lowers density and allows use of smaller
  ET tube without turbulence and high flow
  resistance

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Endotracheal Tubes for Laser Surgery

• Standard is 5.0 cuffed tube coming from left side
  of mouth
• Saline-soaked gauze pads to limit risk of
  ignition
• 60 ml bulb syringe with saline should be
  immediately available
• Used with preexisting lung disease, long case

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Laser Endotracheal Tubes

• Standard polyvinyl chloride tubes (PVC) are
  flammable and can ignite, vaporize
• Wrapped tubes still have a vulnerable cuff
• Fill cuff with sterile saline and methylene blue
  for easy detection and fire dousing

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Advantages and Disadvantages of ET Tube Types
Type of tube Advantages Disadvantages
PVC Inexpensive, nonreflective Low melting point, combustible
Red rubber Puncture resistant, nonreflective Highly combustible
Silicone rubber Nonreflective Combustible, turns to toxic ash
Metal Combustion resistant Reflects laser, flammable cuff, cumbersome
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Airway-Fire Protocol

• Stop ventilation, remove endotracheal tube,
  submerge in water
• Turn off O2 and disconnect circuit
• Ventilate with face mask
• Assess airway damage with bronchoscopy
• Consider bronchial lavage and steroids

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Apneic Ventilation

• Usually used for infants, small children and
  short cases
• Advantage is absence of ET tube
• Anesthetized deep vs. muscle relaxant
• Between laser applications the patients lungs are
  ventilated either by mask, jet or ETT ventilation
• Debris may enter airway

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Jet Ventilation

• Main advantage is clear operating field for
  surgeon and laser safety
• Operating laryngoscope is fitted with a side port
  
• Oxygen is delivered under pressure through a
  reducing valve (20-30 torr) via a metal catheter

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Jet Ventilation

• 100 oxygen is used, rise and fall of chest as
  monitor
• Surgeon will usually direct ventilations
• TIVA necessary as vaporizers are bypassed

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Complications of Jet Ventilation

• Barotrauma (SQ emphysema, pneumothorax)
• Gastric distention
• Ball-valve distention from tumor
• Blown debris down unprotected trachea
• Dessicated vocal cord with long procedure
• Hypoxia/hypercarbia

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Total Intravenous Anesthesia (TIVA)

• Useful when inhalation agent is unavailable or
  undesirable (jet vent, evoked potentials)
• 100-300 mcg/kg/minute propofol
• 0.1-0.5 mcg/kg/minute remifentanil
• Remifentanil 0.1 mg/10 ml propofol
• BIS used to monitor state of anesthetic

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Jet Ventilation with TIVA

• Standard induction with propofol, sevoflurane
  maintenance
• Turn off sevoflurane, start propofol infusion _at_
  200 mcg/kg/minute with syringe pump
• Maintain infusion while ventilating patient as
  per surgeon request, maintain BIS _at_ 40-60
• At completion of procedure, turn propofol off and
  ventilate by mask until awake

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Laser Airway Surgery with ETT

• Check helium tanks (max. 1600 psig)
• Set up and test jet ventilation (adjust to 20-30
  torr)
• 5.0 laser ETT from core, 10 cc NS from blue cart,
  tape _at_ 20 cm (unmarked)
• Narrow stylet for tube

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Emergence Issues

• Rodeo emergence
• Must be able to maintain airway and deal with
  spasm/pain
• Reversal must be complete, and easy-on, easy-off
  agents a necessity

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Key Points

• Airway issues include sharing and difficult
  intubation
• Choice of anesthesia must be individualized after
  communication with surgeon
• Emergence dependent upon control of analgesia and
  ability to protect airway