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Case Presentation: Micro Laryngeal Surgery (MLS)

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I. DEMOGRAPHIC DETAILS

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II. CHIEF COMPLAINTS

1. Hoarseness of voice - 4 months duration (progressive)
2. Throat discomfort / foreign body sensation - 2 months
3. Mild dysphagia to solids - 3 weeks
4. No significant breathing difficulty at rest

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III. HISTORY OF PRESENTING ILLNESS

• He also noticed throat discomfort and a foreign body sensation for 2 months, without true odynophagia.
• Mild difficulty swallowing solids developed over the past 3 weeks.
• Denies hemoptysis, otalgia (referred), or significant dyspnea at rest. No episodes of sudden worsening (which would suggest a pedunculated polyp causing airway intermittent obstruction).
• Possible precipitating factors: prolonged vocal overuse as a teacher, history of voice misuse and shouting in classroom settings.
• No prior treatment sought; voice therapy not yet tried.

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IV. FAMILY HISTORY

• No family history of head and neck malignancies
• No familial laryngeal papillomatosis (rules out recurrent respiratory papillomatosis in family members)
• Father - hypertension (controlled); Mother - alive and well
• No family history of bleeding disorders or anesthetic complications

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V. PERSONAL HISTORY

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VI. GENERAL PHYSICAL EXAMINATION

• Patient is conscious, cooperative, and well-oriented (to time, place, and person)
• Well-nourished, moderately built
• No pallor, icterus, cyanosis, clubbing, lymphadenopathy, or edema

• Mouth opening: >3 finger breadths (adequate)
• Mallampati Class: II
• Thyromental distance: 6.5 cm (adequate)
• Neck mobility: Full range of motion; no restriction
• Jaw protrusion: Normal
• Dentition: Upper incisors intact; no loose teeth
• No stridor at rest; no use of accessory muscles of respiration
• Indirect laryngoscopy / flexible nasopharyngoscopy: Left vocal fold - pedunculated polyp at mid-membranous region; preserved mucosal wave on stroboscopy

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VII. LOCAL EXAMINATION

ENT Examination

• Bilateral auricles normal; no tragal tenderness
• External auditory canals clear
• Tympanic membranes intact bilaterally
• No hearing loss noted

• External nose normal; no deformity
• Nasal septum - midline
• Inferior turbinates - mildly hypertrophied
• No polyps, no discharge

• Oral cavity - no ulcers, tongue normal
• Oropharynx - mild post-nasal drip
• Tonsils - Grade I bilaterally
• Uvula - midline; soft palate moves symmetrically

• No cervical lymphadenopathy
• Thyroid - not palpable; no tracheal deviation
• Carotid pulses equal bilaterally

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VIII. INVESTIGATIONS

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IX. DIAGNOSIS

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X. ANESTHESIA MANAGEMENT FOR MICRO LARYNGEAL SURGERY (MLS)

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A. Pre-anesthetic Evaluation

1. Airway history - detailed assessment is the cornerstone. The key questions are:
   • Is positive-pressure ventilation via face mask or LMA feasible?
   • Can the patient be intubated using conventional direct or video laryngoscopy?
   • Is there any degree of airway obstruction?
2. Review of preoperative imaging - CT neck and flexible nasopharyngoscopy findings reviewed.
3. Premedication:
   • Sedative premedication is AVOIDED in patients with potential airway obstruction or stridor.
   • Glycopyrrolate 0.2 mg IM given 1 hour before surgery - dries secretions and improves airway visualization. IM route is preferred over IV for more sustained antisialagogue effect.
   • Ranitidine (H2 blocker) may be added to reduce gastric acid risk.

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B. Anesthetic Goals for MLS (the "4 Pillars")

1. Immobile surgical field - absolutely no movement during delicate vocal fold microsurgery
2. Adequate masseter muscle relaxation - for introduction of the rigid suspension laryngoscope
3. Profound muscle paralysis - ideally maintained until the very end of the procedure
4. Adequate oxygenation and ventilation - despite a shared airway
5. Cardiovascular stability - despite rapidly varying stimulation levels

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C. Induction

• Preoxygenation: 100% O2 for 3 minutes via tight-fitting mask
• Induction agents:
  • Propofol 1.5-2 mg/kg IV - smooth induction, antiemetic properties, rapid recovery
  • Remifentanil - short-acting opioid; ideal as MLS is brief with intense stimulation followed by minimal pain
• Muscle relaxant for intubation:
  • Succinylcholine 1.5 mg/kg IV for rapid-sequence (if needed) OR
  • Rocuronium 0.6-1.2 mg/kg IV (reversed with sugammadex at end)

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D. Airway Management Options

Option 1: Small-diameter Endotracheal Tube

• A microlaryngoscopy tube (MLT) - 5.0 mm cuffed; long and narrow
• Passed atraumatically, kept away from the surgical field
• Advantages: secure airway, continuous capnography, protects against aspiration, inhalational agent delivery
• Used for most routine vocal fold polyps not involving the posterior commissure

Option 2: Manual Jet Ventilation (Sanders Injector)

• Used when the ETT interferes with visualization (posterior commissure lesions, bilateral lesions)
• High-pressure jet (30-50 psi) directed through the laryngoscope side port into the glottis
• Entrains room air via the Venturi effect (inspiration 1-2 s; expiration 4-6 s passive)
• Requires TIVA (total intravenous anesthesia) - no inhalational agent delivery possible
• Chest wall motion must be continuously observed to prevent air trapping and barotrauma

Option 3: High-Frequency Jet Ventilation (HFJV)

• Small cannula in trachea, gas injected 80-300 times/minute
• Used in combination with TIVA for complex cases (e.g., stenosis, bilateral lesions)
• Capnography unreliable during jet ventilation (dilution of alveolar gases)

Option 4: Intermittent Apnea Technique

• Alternating positive-pressure ventilation with apnea windows (2-3 min)
• Duration guided by SpO2 on pulse oximetry
• Risk: hypoventilation, hypercarbia, failure to reestablish airway

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E. Maintenance of Anesthesia - TIVA Protocol (Preferred for MLS)

• TIVA is mandatory when jet ventilation is used (no circuit for volatile agent delivery)
• Provides stable hemodynamics with quickly titratable depth
• Rapid offset of remifentanil allows fast emergence

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F. Neuromuscular Blockade

• Profound NMB (TOF count 0) is required until the very end of the procedure to prevent sudden vocal fold movement during microsurgery
• This is one of the few remaining indications where deep NMB must be maintained until procedure completion
• Reversal: Sugammadex 2-4 mg/kg for rocuronium/vecuronium reversal at end; has largely replaced succinylcholine infusions

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G. Cardiovascular Management

• The procedure is a series of physiologically stressful laryngoscopies interspersed with minimal stimulation intervals
• Many patients have cardiovascular risk factors (smoking, age)

• Short-acting propofol boluses or increased infusion
• Remifentanil boluses 0.5-1 mcg/kg
• Esmolol 0.5-1 mg/kg for hypertensive/tachycardic responses
• Regional blocks (glossopharyngeal + superior laryngeal nerve block) can attenuate responses in selected cases

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H. Laser Safety Precautions (If CO2 Laser MLS)

• Laser-safe ETT (metal-wrapped, laser-resistant) is mandatory if ETT is in situ
• FiO2 kept ≤ 30% - avoid oxygen-enriched environment; N2 or helium used as diluent
• Saline-moistened eye pads secured over both eyes (corneal protection)
• Saline-moistened swabs around the surgical field
• Laser plume evacuator in use continuously (toxic fumes)
• All personnel wear laser-appropriate eye protection specific to the wavelength used
• Airway fire protocol must be immediately available (remove tube, stop O2, submerge tube in water, reintubate, bronchoscopy)

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I. Positioning

• Supine, neck gently extended (Boyce-Jackson position / "sniffing position")
• Shoulder roll placed to optimize laryngeal axis
• Eyes taped closed and protected with saline-moistened pads
• Arms tucked to sides, padded

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J. Monitoring

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K. Emergence and Recovery

• Residual NMB fully reversed with sugammadex before extubation
• Extubate awake with adequate respiration, head-lift, and cough reflex confirmed
• Dexamethasone 8 mg IV given at induction - reduces post-operative edema
• Post-op monitoring in recovery room for:
  • Laryngeal edema (stridor)
  • SpO2 and respiratory effort
  • Nausea/vomiting (PONV - common with opiate/propofol)
• Voice rest advised for 48-72 hours post-surgery

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L. Complications to Anticipate

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XI. POST-OPERATIVE PLAN

• ICU/HDU monitoring for 4-6 hours
• Humidified oxygen via face mask
• Dexamethasone 8 mg IV Q8H for 24 hours
• Nebulization with budesonide
• IV fluids; soft diet after 4 hours
• Voice rest - strict for 48-72 hours
• Follow-up flexible laryngoscopy at 2 weeks
• Voice therapy (speech-language pathology) referral post-healing

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• Morgan & Mikhail's Clinical Anesthesiology, 7th ed. - Chapter 37: ENT Procedures (Endoscopy, Microlaryngoscopy, Jet Ventilation, Laser Precautions)
• KJ Lee's Essential Otolaryngology - Vocal Fold Polyp, Cysts, Microlaryngoscopy
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery - Suspension Microlaryngoscopy, TIVA with HFJV
• Cummings Otolaryngology Head and Neck Surgery - Microlaryngoscopy under GA