Anesthesia for ENT Surgery: Part 2 - 2nd Edition

Educational Objectives

Summary

Anesthesia for Ear, Nose, and Throat Surgery: Part 2

Vladimir Nekhendzy, MD, Clinical Associate Professor of Anesthesiology and Otolaryngology, Stanford University School of Medicine, Stanford, California

Diagnostic endoscopy: bronchoscopy and esophagoscopy typically performed as part of panendoscopy; other indications include therapeutic interventions (eg, removal of foreign bodies and dilation of stenotic areas); typically performed in outpatient setting; operating esophagoscopy commonly used for endoscopic resection of Zenker diverticulum

Rigid bronchoscopy: rigid bronchoscopy first in sequence — general anesthesia induced in standard manner and lungs hyperventilated through face mask with 100% oxygen; with onset of complete muscular relaxation, patient turned over to surgeon without securing airway; quick and gentle direct laryngoscopy (to apply topical laryngotracheal anesthesia prior to rigid bronchoscopy) used to blunt hemodynamic responses to subsequent surgical manipulation; consider risk for residual laryngeal anesthesia in short procedures; document no dental damage if direct laryngoscopy performed prior to rigid bronchoscopy; once rigid bronchoscope in trachea, begin jet ventilation or manual ventilation through anesthesia circuit, using Racine universal adapter connected to side arm of bronchoscope; rigid telescope and other instruments can be placed through central lumen of bronchoscope; total intravenous anesthesia (TIVA) provides most stable plane of anesthesia; in manual ventilation, high gas flows required because of variable leak around end of bronchoscope; close communication with surgeon essential to decrease manual inflating pressures when bronchoscope introduced into main stem bronchus and to ensure complete exhalation

Flexible bronchoscopy: can be performed with appropriately sized endotracheal tube, with small endotracheal tube with endotracheal tube cuff deflated, with laryngeal airway mask (LMA), or with special endoscopy masks; if performed through endotracheal tube, appropriate size (≥ 7.0 internal diameter) should be used; swivel bronchoscopy adapter should be used to allow concomitant ventilation; ventilation during bronchoscopy through endotracheal tube better controlled manually due to increased resistance to gas flow and high peak inspiratory pressures; gentle manual ventilation with small tidal volumes with fraction of inspired oxygen of 1 usually well tolerated over short course of procedure; greater efficacy of ventilation through endoscopy mask during flexible bronchoscopy than with LMA Classic or Unique, or intubating LMA; flexible esophagoscopy — can successfully follow same route; if Patil mask used, once endoscopy complete, begin appropriate ventilation for operative direct laryngoscopy and suspension microlaryngeal surgery; if no further surgery planned, patient can emerge from anesthesia, breathing spontaneously through Patil mask or laryngeal mask airway

Postoperative management: panendoscopy and microlaryngoscopic surgical procedures characterized by low postoperative pain scores, even when surgery prolonged; use of remifentanil infusion allows reduction of total dose of supplemental IV fentanyl to 1 to 2 μg/kg or may avoid fentanyl completely; in recovery room, intermittent IV boluses of fentanyl combined with oral analgesics usually sufficient for pain control; if increased pain noted postoperatively, possible surgical complications (eg, esophageal perforation); if acute opioid tolerance suspected, adequate doses of fentanyl and/or long-acting opioid analgesics; administer IV 5HT3 antagonists (eg, ondansetron)for routine antiemetic prophylaxis; use multimodal antiemetic prophylaxis for patients at high risk for postoperative nausea and vomiting

Emergence from anesthesia for microlaryngoscopic procedures: if tracheal intubation performed, smooth, nonstimulating emergence challenging; avoid or minimize patient reaction to endotracheal tube during extubation; straining, bucking, or coughing on endotracheal tube results in attempted forceful glottic closure (may provoke additional trauma to and even ulceration of mucosal surface of vocal cord, leading to wound formation); agitation, uncontrolled head movements, and postextubation laryngospasm exacerbate vocal cord further; subsequent vocal cord wound healing leads to remodeling of superficial layer of vocal cord lamina propria and epithelium, which may result in formation of vocal cord nodules, polyps, and cysts; strategies — extubating trachea to deep plane of anesthesia problematic because of increased risk for postextubation laryngospasm and increased need for airway support and protection; Bailey maneuver — insert LMA behind existing endotracheal tube with patient still anesthetized, remove endotracheal tube, and administer ventilator support through LMA until patient resumes spontaneous ventilation and awakens from anesthesia; pharmacologic approach — low dose remifentanil infusion to blunt tracheal responses and promote smooth extubation; remifentanil provides predictable, rapid recovery of consciousness and protective airway reflexes and blunts sympathetic responses associated with extubation

Laser surgery of upper airway

Lasers: CO₂ laser widely used for vocal cord laser surgery; neodymium:yttrium aluminum garnet laser usually used for airway tumor debulking because of ability to coagulate deeper lesions; neodymium:yttrium aluminum garnet laser can be used through suction channel of fiberoptic video bronchoscope; CO₂ laser must be aimed directly at targeted tissue; wave lengths of both lasers lie outside visible spectrum; separate lower-energy visible beam used for aiming; patient must be motionless, eyes protected with tape and moistened gauze, and operating room personnel must wear protective goggles

Conduct of anesthetic: closely follows microlaryngeal surgery; total IV anesthesia most commonly used; airway management — may use specialized catheters; diameter of tubes usually small (5 mm internal diameter) to allow better surgical exposure; laser flex tube or laser shield endotracheal tube (Hunsaker or laser jet); airway fire — specialized tubes do not provide 100% protection from lasers and airway fire; prevention and management should follow American Society of Anesthesiologists Practice Advisory (2013); awareness of and avoidance of fire triad (oxider, fuel, and ignition source) of primary importance; collaboration of team essential to prevent; have predetermined management plan in place; fire drills must be instituted; specific precautions include specialized laser endotracheal tubes and lowest possible fraction of inspired oxygen (<30% strongly preferred); oxygen should be diluted with air, nitrogen, or helium; avoid nitrous oxide; use colored methylene blue-tinged normal saline in cuff of endotracheal tube to immediately alert surgeon of laser hit, signifying airway may be left unprotected; endotracheal tube must be placed sufficiently deep into trachea for cuff to be out of surgical site as much as possible; management — stop procedure immediately; call for help; anesthesiologist should stop flow of oxygen and other gases immediately; at same time, surgeon pulls endotracheal tube from airway, extinguishes fire, then patient turned over to anesthesiologist for subsequent airway management; severe laryngeal, tracheal, and upper airway burn injury requires reintubation and ventilatory support; lower airway must be evaluated by rigid bronchoscopy or flexible fiberoptic bronchoscopy; debris inside lower airway (if present) must be removed; many patients present subsequently with severe complications (eg, laryngeal stenosis) and may require long-term tracheostomy

Traumatized airway

Management of patients with maxillofacial trauma and laryngotracheal injuries: follow general guidelines for managing patient with trauma; maxillofacial and laryngotracheal trauma may quickly lead to upper airway obstruction or patients may present with frank upper airway obstruction due to direct trauma or associated traumatic brain injury with resulting loss of protective airway reflexes; upper airway anatomy may be significantly distorted following injury, hence very low threshold for instituting surgical airway; associated cervical spine injury — may contribute to difficulty in airway management; ≤8% of patients have associated C-spine injuries and present in C collar; should presume C-spine injury present until ruled out on clinical grounds or radiographically

Instituting surgical airway: if anesthesiologist confronts patient in emergency department, observe patient before securing airway by tracheal intubation; deciding whether to institute surgical airway in otherwise stable patient, consider 3 factors: immediate failure to maintain oxygenation or ventilation, immediate failure to protect airway, and anticipated clinical course for patient with regard to maintenance of oxygenation, ventilation, and airway protection; predicted deterioration determines decision to intubate while airway relatively stable

Assessment: examine sites of laryngotracheal injury or disruption (eg, subcutaneous emphysema, crepitus, poor or absent neck anatomic landmarks, neck pain, neck swelling, neck bruising, hoarseness, stridor, or dysphagia)

Intubation: if disruption suspected, intubate patient conventionally; advance endotracheal tube deep inside airway, intentionally causing main stem intubation; avoids severe barotrauma and total disruption of partially compromised airway; nasal intubation — should not be attempted in severe midface trauma or fractures of skull base (to avoid possible breach of cranial wall)

Techniques for nonsurgical airway: in general, ventilation should take precedence over immediate intubation in patients with trauma and with traumatized airway in particular; surgeon must be ready to perform emergency surgical cricothyrotomy or tracheostomy; supraglottic airways, Combitube, laryngeal tube can be tried as first rescue attempt in patient with upper airway trauma (especially if hypoxemia present); if advanced techniques of airway management contemplated or attempted, several considerations: fiberoptic bronchoscope — use limited because blood and secretions, poor patient cooperation, patient agitation, intoxication, and lack of time; video laryngoscopy — valuable alternative to direct laryngoscopy, much more robust in handling blood and secretions; high-volume suction should be present; effective due to significant reduction in C-spine movement; channel laryngoscopes — more effective in reducing C-spine movement compared with steering techniques; studies show Pentax airway scope most effective in preventing C-spine movement at all levels followed by Airtraq then GlideScope; intubating LMA — used successfully in many reports to manage airway; anatomically shaped, delivering LMA opening close to laryngeal inlet; high success rate of rescue ventilation in difficult airway situations; light-guided intubation — avoid or attempt with extreme caution if intraoral trauma present; retrograde intubation — viable technique, but requires time (median intubation time 2.5-3.0 minutes)

Laryngeal trauma: low threshold for surgical airway because tracheal intubation can be extremely difficult; if attempted, use gentle technique and small-diameter endotracheal tube to minimize risk for further injury and complete loss of airway; limit number of intubating attempts to 2 and expeditiously proceed with surgical airway

Maxillofacial trauma: often associated with severe bleeding; increased risk for aspiration because of blood, broken teeth, and soft tissue debris; classification of fractures — Le Fort level I fracture horizontal fracture that involves inferior nasal aperture, separating maxillary alveolar from midfacial skeleton; typically occurs as result of direct force applied to low or mid face; Le Fort II fracture may result from blow to lower or mid maxilla and involves inferior orbital rim; Le Fort II fractures usually pyramidal-shaped nasal maxillary fractures that can break from upper craniofacial skeleton; Le Fort III fractures more rare and usually result from blunt force to nasal bridge or upper maxilla; fractures may also result in separation of facial skeleton from skull base; associated airway implications — Le Fort I type fractures rarely cause airway compromise; same true of Le Fort II, unless significant hemorrhage present; patients with Le Fort III can have significantly compromised airway due to posterior displacement of entire central face and dissociated displacement of oronasopharynx, which collapses on upper airway; mandibular fractures — special concern when they occur bilaterally, as flailed mandible may quickly lead to acute upper airway obstruction by unsupported intraoral tissues; may be associated with vascular injuries to internal carotid and inferior alveolar artery

Superior laryngeal nerve block: useful adjunct during awake airway management

Sensory innervation of upper airway: when performing superior laryngeal nerve block, internal laryngeal nerves blocked posterior to penetration of thyrohyoid membrane, where they enter closed compartment filled with fatty tissue; limited anteriorly by thyrohyoid membrane and posteriorly by epiglottis and pharyngeal mucosa; internal laryngeal nerves lie freely on both sides

Approaches: external — patient positioned supine, head extended; hyoid bone identified by palpation (hyoid bone easily moveable because it does not articulate with any other bone); clean skin with alcohol; introduce small 25- to 27-g needle attached to syringe filled with 2 mL 1.5% to 2.0% lidocaine parallel to floor, aiming to contact cornu of hyoid bone; after contacting cornu, needle walked cortal and slightly medial until it slips off hyoid and pierces through thyrohyoid membrane; puncture of superior laryngeal artery extremely rare; after careful aspiration to detect air or blood, inject 2 mL 1.5% to 2.0% lidocaine and repeat procedure on opposite side; when combined with topical application of local anesthetic to nose and mouth and transtracheal block performed through puncture of cricothyroid membrane, complete anesthesia of upper airway achieved; if difficulty locating hyoid bone, block technique could be altered by identifying superior cornu of thyroid cartilage first, then walking needle cephalad of structure; internal approach — performed by applying local anesthetic to piriform fossa, where internal branch of superior laryngeal nerve lies submucosally and blockade possible; administer topical anesthetic to oropharynx; patient asked to protrude tongue, which is grasped gently and pulled forward; with dominant hand, anesthesiologist introduces curved forceps and places sponge soaked in 4% lidocaine into piriform sinus on right and left; wait approximately 5 minute for internal branch to be adequately anesthetized

Safety: superior laryngeal nerve block usually safe and effective with little risk for complications

Other considerations: in patient with full stomach requiring awake intubation, perform superior laryngeal nerve blocks with caution, as block may contribute to abrupt decrease in laryngeal proprioception and lead to airway obstruction; contraindications — inflammation, significant anatomic distortion, masses, and trajectory of block; complications — bradycardia and hypertension may be observed due to manipulation around vagal nerve; treat complications expeditiously

Questions and answers

The first immediate action on part of anesthesiologist during airway fire: disconnecting patient from anesthesia circuit

Strategies not feasible for promoting smooth extubation of patients after microlaryngeal surgery: deep extubation; IV administration of lidocaine

Readings

Disclosures

Acknowledgements

CME/CE INFO

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