A Special Considerations and Anesthesia Objectives

In contrast to direct laryngoscopes used by the anesthesiologists, which are designed only to identify the glottic opening, operating laryngoscopes can provide excellent and wide laryngeal exposure and allow diagnostic examination, biopsy, and operation on structures in the larynx and pharynx, with minimal distortion of the areas of surgical interest.^16,38 The handles of these laryngoscopes are integrated with the blades and have a wide proximal aperture that facilitates the passage of instruments during suspension laryngoscopy.^38,39 Many types of laryngoscopes exist (Fig. 38-4), each offering certain advantages for its intended application, such as the ability to better expose supraglottic, glottic, or subglottic areas.³⁸ Many laryngoscopes are multipurpose, and selection is frequently dictated by individual or institutional preference.³⁸

Figure 38-4 Commonly used operating laryngoscopes. The posterior apertures of the Kleinsasser (left), Dedo (center), and Holinger (right) operating laryngoscopes are shown. The bigger size and wider channel of the Kleinsasser and Dedo laryngoscopes allows passage of the surgical instruments and binocular microlaryngeal surgery. Notice the metal cannula inserted into the left side port of the Kleinsasser laryngoscope for supraglottic jet ventilation (JV). In the Dedo scope, the JV port is integrated with the lumen, and it can be used for smog evacuation during laser surgery. The Holinger laryngoscope is monocular but has greater maneuverability. It is widely used for diagnostic laryngoscopy and visualization of the anterior commissure. The left side channel of the Holinger laryngoscope is occupied by a light guide. Supraglottic JV through the Holinger laryngoscope requires insertion of a metal cannula inside its lumen (see Fig. 38-15).

With the use of these laryngoscopes, systematic endoscopy of the larynx and pharynx frequently proceeds in three stages, progressing from handheld examination to suspension laryngoscopy (for more detailed evaluation with the straight and angled telescopes) and then to microlaryngoscopy using the operating microscope for image magnification, biopsy, microsurgery, or laser surgery.³⁸ Suspension laryngoscopy (Fig. 38-5) frees the surgeon’s hands for precision bimanual surgery and facilitates maintenance of a stable plane of anesthesia.^38,40 The use of a video monitor by the surgeon permits the anesthesiologist to observe the surgical procedure and monitor the patient’s airway.

Figure 38-5 Types of suspension laryngoscopy. A, Gallows-type suspension device. B, Fulcrum-type suspension device (Storz apparatus). Notice the patients’ neck flexion and head extension, which are required for suspension laryngoscopy.

(A, From Rosen CA, Simpson CB, editors: Operative techniques in laryngology, Berlin, 2008, Springer-Verlag, p 68.)

The essential requirements for precision microlaryngeal surgery and optimal preservation of function include a clear and still surgical field, absence of patient movement, and allocation of sufficient time to carefully complete the procedure in an unhurried manner.^9,38,39,41 The patient’s airway must be protected from blood, debris, and irrigation fluid, and ventilation must be adequately controlled.^3,8,41 The anesthesiologist must safely share the patient’s airway with the surgeon, and must be prepared to skillfully and confidently switch from one ventilation technique to another during the case if needed or dictated by surgery.

In most surgical procedures, the patient’s airway is shared with the surgeon, and immediate access to the airway is difficult or impossible because the operating room (OR) table is turned 90 or 180 degrees away from the anesthesiologist. The ETT must be secured diligently to prevent accidental extubation under the surgical drapes or withdrawal of the ETT into the larynx, resulting in a sudden air leak or possible compression of the anterior branch of the recurrent laryngeal nerve by the ETT cuff.^42,43

Performance of conventional and operative direct laryngoscopy, supraglottic tissue distention, and laryngeal stimulation elicit intense cardiovascular responses, resulting in tachycardia, arterial and pulmonary hypertension, and arrhythmias.^44–46 Although these responses are usually short lived, myocardial ischemia and compromise of cerebral circulation may occur in high-risk patients, resulting in adverse outcomes.^47–49 Anesthetic technique should ensure a stable plane of anesthesia, nonstimulating emergence from anesthesia, a rapid return of consciousness, and protective airway reflexes, and it should facilitate quick discharge of patients, because most of these surgical procedures are done on an outpatient basis.^3,8

Special attention should be directed to adequately protecting the patient’s eyes and arms to prevent accidental injury or compression by heavy surgical instrumentation.⁹ When rigid endoscopy is planned, a tooth guard should be used routinely.³⁴ It may be prudent to warn the patients in advance of the potential for dental trauma, and any previous dental damage should be carefully documented.^34,43

Patients who are vocal performers or use the voice in some professional capacity present unique challenges.¹⁶ The anesthesiologist must frequently think outside the box and exercise different advanced airway management options to avert trauma to the patient’s vocal cords and cricoarytenoid joints.

B Airway Management for Microlaryngeal Surgery

1 Conventional and Advanced Airway Management

Patients presenting for diagnostic direct laryngoscopy and microlaryngeal surgery frequently have a difficult airway. The chosen approach to this airway depends on the pathology and the patient’s symptoms. In situations with critical airway compromise, an awake tracheostomy may be warranted from the outset, but it may prove to be technically challenging or impossible and may require general anesthesia. Even if an awake tracheostomy is chosen as a primary approach, full backup preparation for alternative airway management is necessary.

Video laryngoscopy reliably improves laryngeal exposure by at least one grade,^50–54 allows continuous observation of the entire intubation procedure by the entire team, and may therefore be a near-ideal technique for managing difficult airways in patients presenting for microlaryngeal surgery. Choosing the video laryngoscopic device depends on the operator’s preference and must consider the nature and location of the lesions. For example, it may be safer to navigate around tumors at the base of the tongue with the Pentax Airway Scope, whose blade engages under the epiglottis, unlike other devices that typically require the tip of the blade to be placed in the vallecula. Video laryngoscopes that use the steering technique (i.e., styleted ETT), such as the Glidescope video laryngoscope, offer better control of intubation and may facilitate ETT maneuvering around the intraoral masses.⁵⁵ Although the use of the Glidescope may be less traumatic compared with the Airtraq in patients presenting for microlaryngeal surgery,⁵⁶ in the largest published series of Glidescope-assisted intubations in more than 2000 patients with difficult airways,⁵⁷ the strongest predictor of the steering technique failure was altered neck anatomy with presence of a surgical scar, radiation changes, or a mass. These conditions are frequently encountered in patients presenting for diagnostic direct laryngoscopy and microlaryngeal surgery.

Although advanced airway management techniques can be highly successful when direct laryngoscopy fails, the patient’s unfavorable anatomy (Fig. 38-6) may not be modifiable for the surgical exposure, which requires the use of the largest operating laryngoscope and placement of the patient’s head in the Boyce-Jackson position using a combination of cervical flexion and atlantooccipital extension (see Fig. 38-5).^1,38,58,59 If suspension laryngoscopy fails or if the location of the lesion is not easily accessible, it can be performed, to the extent microlaryngeal surgery permits, with the help of the flexible fiberoptic bronchoscope (FFB) inserted through the laryngeal mask airway (LMA).^60–62 The intubating laryngeal mask airway (iLMA) offers certain advantages, such as a rigid, wide metal tube that can accommodate a large-diameter FFB,⁶¹ optimal alignment of the iLMA aperture with the glottic opening,⁶³ diminished hemodynamic responses compared with suspension laryngoscopy,⁶¹ and superior ventilation capabilities.^63–66

Figure 38-6 Anatomic features associated with a difficult airway exposure. Difficult laryngeal exposure during direct or suspension laryngoscopy may be encountered in patients with retrognathia; lingual hypertrophy or poor palatal visualization; trismus or reduced interincisor opening; short, thick neck; and limited neck extension.

(From In Rosen CA, Simpson CB, editors: Operative techniques in laryngology, Berlin, 2008, Springer-Verlag, p 56.)

The iLMA is associated with an outstanding success rate for blind endotracheal intubation in patients with difficult airways.^63,65 Unfortunately, the manufacturer-supplied iLMA ETTs are too big for most microlaryngoscopic surgery. An ETT with a smaller inner diameter (ID) (e.g., 5.0-mm ID microlaryngeal tracheal [MLT] tube) is typically required to maximize the surgical view (Fig. 38-7). Placement of MLT tubes through the iLMA can be achieved with the help of a small-diameter FFB; however, passage of the ETT through the laryngeal inlet into the trachea is blind. Blind advancement of the ETT may cause inadvertent laryngeal trauma and core out pedunculated supraglottic or glottic tumors, nodules, or cysts.^56,67 When the FFB route (with or without the use of a supralaryngeal airway device) is chosen for endotracheal intubation, it is advantageous to closely match the outer diameter (OD) of the scope with the ID of the ETT to minimize the risk of complications associated with blind ETT advancement. Use of optical stylets (e.g., Bonfils, Shikani, Clarus Video System) may also be beneficial in that regard, because the ETT will follow the trajectory of the stylet navigated under direct vision through the vocal cords. However, most of the available adult-size stylets require the use of an ETT with a minimum ID of 5.5 to 6.0 mm.

Figure 38-7 Microlaryngeal tracheal (MLT) tube. A standard endotracheal tube (ETT) with an inner diameter (ID) of 5.0 mm (top) is compared with a 5.0-mm ID MLT tube (center) and 8.0-mm ID ETT (bottom). A greater length and bigger cuff diameter of the MLT tube (equivalent to a standard 8.0-mm ID ETT) allows a sufficient depth of tracheal placement, a connection to the anesthesia circuit, and an adequate seal of the trachea.

The decision to proceed with an awake or asleep approach to an anticipated difficult airway should follow the American Society of Anesthesiologists (ASA) difficult airway algorithm,⁶⁸ with special attention directed to predictors of difficult mask ventilation, impossible mask ventilation, and their association with difficult intubation (see Chapter 8). The anesthesiologist also should review the pertinent preoperative findings identified on flexible fiberoptic laryngoscopy, chest radiography, CT, and MRI and should discuss these findings with the surgeon.

If an asleep approach to the difficult airway is chosen, several preformulated alternative airway management plans must be in place before induction of anesthesia. If the airway is marginal, the patient’s neck should be prepped, and the surgical team should be present on induction, ready to perform an emergent cricothyrotomy or tracheostomy, or to employ rescue techniques such as the use of the surgical anterior commissure scope or a rigid bronchoscope.^11,18,69,70 The anterior commissure scopes (e.g., Holinger, Ossoff-Pilling, Benjamin Slimline/Super-Slimline, Jackson) (Fig. 38-8; see Fig. 38-4) have great leverage capabilities, incorporate the recessed lighting and concurrent rigid microsuction, and can be very effective in handling poor laryngeal exposure or glottic obstruction.^1,13,38,69 The anterior flare at the distal oval end allows these scopes to be used as a conduit for orotracheal intubation when the bougie introducer or the ETT is passed directly down the lumen (Fig. 38-9).⁶⁹

Figure 38-8 Holinger anterior commissure laryngoscope. The pointed tip and the leverage capability of the laryngoscope facilitate visualization of at least part of the glottis. An anterior flare at the tip of the laryngoscope allows it to serve as a guide to endotracheal intubation.

Figure 38-9 Airway rescue is achieved with a bougie introducer and a Holinger laryngoscope in a patient with difficult laryngeal exposure. The endotracheal tube (ETT) cannot be directly advanced down the narrow barrel of the Holinger laryngoscope due to impaired visualization during tube advancement. The bougie introducer is used first, followed by removal of the laryngoscope and railroading the ETT over the bougie into the patient’s trachea. The ETT can be directly advanced through the wider lumen of other laryngoscopes, such as the Lindholm or Dedo (see Fig. 38-14).

In experienced hands, rigid bronchoscopy may be used to rescue failed direct laryngoscopy and failed intubation and to manage a “cannot intubate, cannot ventilate” (CICV) situation.⁶⁸ It also serves as an indispensable tool for managing acute airway obstruction resulting from foreign bodies, hemoptysis, or tumors.⁷¹ After the bronchoscope is placed into the patient’s trachea by the surgeon, manual (Fig. 38-10) or JV can commence in a safe manner through the lumen of the bronchoscope. Subsequent airway exchange to the ETT can be performed using a bougie introducer (Fig. 38-11).^72,73 This exchange technique can also be conducted when the rigid bronchoscope is employed first as part of a panendoscopy procedure in patients with abnormal airway.

Figure 38-10 A rigid bronchoscope is connected to the anesthesia circuit by a Racine adapter (arrow). A flexible diaphragm of the Racine universal adapter (SunMed, Largo, FL) connects a side arm of a rigid bronchoscope to the anesthesia breathing circuit.

Figure 38-11 Airway exchange can be achieved with a rigid bronchoscope and a bougie introducer. A, The 9-F, 40-cm-long, rigid bronchoscope (CL Jackson Fiberoptic Bronchoscope, Pilling Inc., Fort Washington, PA); 15-F, 60-cm-long, multiple-use gum elastic bougie (GEB) (Eschmann Tracheal Tube Introducer, SIMS Portex Inc., Keene, NH); and 16-F, 41-cm-long, rounded, closed-tip suction catheter (Robi-Nel catheter, Kendall Dover, Mansfield, MA) are used to facilitate an airway exchange. The exchange technique involves several steps: deliberately passing the curved tip of the GEB (B) through the lumen of the bronchoscope into a bronchus (eliciting a distal hold up sign); stabilizing and extending a proximal straight tip of the GEB with a precut, distal, funnel-shaped end of the Robi-Nel suction catheter (C–E); safe removal of the bronchoscope over the extended GEB-catheter assembly (F); and removal of the catheter and railroading the endotracheal tube over the GEB into the patient’s trachea. Anchoring a round, atraumatic tip of the GEB in a large-caliber bronchus maintains a stable position of the intubation guide and prevents its distal end from accidentally springing backward out of the trachea during bronchoscope withdrawal. This approach is superior to the use of the airway exchange catheter (AEC), whose placement below the carina is not recommended because of the recognized risk of lung perforation by the straight tip of the device. Reliably maintaining proximal positioning of the AEC tip during the airway exchange is difficult, because the AEC centimeter markings mapping the distance to the carina will become embedded inside the bronchoscope during its withdrawal.

(A, B, and E, From Nekhendzy V, Simmonds PK: Rigid bronchoscope-assisted tracheal intubation: Yet another use of the gum elastic bougie. Anesth Analg 98:545–547, 2004.).

Patients with an advanced airway obstruction and inspiratory stridor at rest comprise some of the most feared and complicated cases for the anesthesiologist.³³ The incidence of difficult mask ventilation and impossible mask ventilation among patients with severe stridor and upper airway obstruction of more than 75% of the lumen reaches 40% and 6%, respectively,⁷⁴ compared with 1.4% and 0.15% for the general surgical population.^30,31,75 These patients frequently present for panendoscopy and microlaryngeal surgery on an emergent or semi-emergent basis, yet they require a systematic and thoughtful approach by the anesthesiologist and the surgeon.³⁸ The nature of the obstructing lesion (e.g., vascular, submucosal, pedunculated, inflammatory) and its location (e.g., supraglottic, glottic, subglottic, midtracheal, lower tracheal, and bronchial [mediastinal]) may require completely different intubation considerations and approaches.^{17,33,34,36,38,69,71}

In the context of laryngeal surgery, the optimal technique of airway management of the stridorous patient with an advanced proximal airway obstruction (i.e., supraglottic, glottic, and subglottic levels) remains a subject of controversy. An awake flexible fiberoptic intubation, inhalational induction, and intravenous induction with muscle relaxants^17,33,74,76 have been used successfully, but none should be considered fail-safe. Thorough preoperative discussion of the surgical pathology and formulation of closely coordinated airway management plan with the surgeon are essential for safe management of these patients.

Based on our experience and review of the pertinent literature,^{17,33,35,38,69,71,74,76–80} current recommendations for management of the critically obstructed airway can be outlined as follows:

1. For patients with severe stridor (e.g., symptoms exaggerated at night, hypoxemia-induced agitation or panic attacks, use of accessory muscles on inspiration, a large tumor, fixed hemilarynx, gross anatomic distortion, a larynx not visible on preoperative nasal endoscopy or flexible fiberoptic laryngoscopy), strongly consider tracheostomy under local anesthesia without sedation.

2. Patients with moderate stridor and a significant lesion seen on nasal endoscopy or flexible fiberoptic laryngoscopy, but who are considered possible to intubate, are best managed with an inhalational induction or an awake fiberoptic intubation. All airway instrumentation should proceed in a careful and gentle manner. Endotracheal intubation should be accomplished rapidly, with a small ETT. The number of attempts should not exceed two, because critical airway obstruction can quickly progress to complete as a result of manipulation of the airway.

3. If an inhalational induction is chosen, a sufficiently deep and stable plane of anesthesia is essential to avoid loss of the airway (e.g., avoidance of cough, laryngospasm). Endotracheal intubation should be performed under direct vision (e.g., direct laryngoscopy, video laryngoscopy, flexible fiberoptic bronchoscopy). Muscle relaxants should be avoided until after the intubation is completed to prevent sudden, complete airway obstruction, especially when the tumor is subglottic. The patient’s neck should be prepared, and the surgical team should be present and ready to attempt an airway rescue with an anterior commissure scope or a ventilating rigid bronchoscope or by emergent cricothyrotomy or tracheostomy.

4. If endotracheal intubation under direct vision (e.g., direct laryngoscopy, video laryngoscopy, flexible fiberoptic bronchoscopy) fails in an anesthetized or awake patient or is deemed problematic, tracheostomy should be performed expeditiously, with the patient breathing spontaneously.

5. An awake fiberoptic intubation should be used with caution, because sudden loss of the airway can be precipitated by one or more of the following factors:

• Bleeding from a friable tumor on impaction with the FFB or seeding parts of the broken tumor into the trachea

• “Cork in the bottle” effect, when the scope is introduced into the critically narrowed airway

• Inhibitory effect of local anesthetics on the tongue and upper airway musculature, laryngeal muscles, and function

• Central nervous system depressant effect of local anesthetics

• Local anesthetic-precipitated laryngospasm

• Patient’s apprehension and agitation during the procedure, resulting in hyperventilation and “sucking in” mobile, pedunculated tumors

6. Additional fallback strategies may include the following:

• Placement of a transtracheal jet ventilation (TTJV) catheter before induction of anesthesia in an attempt to provide apneic oxygenation or high-frequency TTJV (see “Intraoperative Ventilation Techniques and Strategies for Microlaryngeal Surgery”)

• High-frequency jet ventilation (HFJV) through the supralaryngeal airway device (e.g., LMA)

• JV approaches require caution, especially in the presence of subglottic lesions, to avoid air trapping and barotrauma

7. Patients with inspiratory obstruction due to bilateral vocal cord paralysis or fixation of cricoarytenoid joints typically do not present ventilation or intubation problems.

8. If tracheostomy is avoided, an extubation strategy must be decided on with the surgeon. Extubation should be performed over an airway exchange catheter (AEC), with the necessary reintubation equipment immediately available. Some patients should remain intubated until the airway inflammation and edema subside, and the patient’s airway is then reevaluated.

2 Intraoperative Ventilation Techniques and Strategies for Microlaryngeal Surgery

Surgery can be conducted in an awake patient, frequently under conscious sedation, or with the patient anesthetized (Box 38-1). The ventilation options under general anesthesia consist of “tube” (i.e., endotracheal intubation) and “tubeless” techniques, with the latter represented by the techniques of spontaneous ventilation, AIV, and JV.^{8,13,38,81,82}

Box 38-1 Ventilation Techniques and Strategies for Microlaryngoscopic Surgery

I. Awake airway surgery (conscious sedation)

II. Asleep airway surgery (general anesthesia)

II.1. Endotracheal intubation (cuffed microlaryngeal tracheal [MLT] tube)

II.2. Tubeless techniques

a. Spontaneous ventilation

Inhalational anesthesia (insufflation)

Total intravenous anesthesia

b. Apneic intermittent ventilation

c. Jet ventilation

Supraglottic

Subglottic

Low frequency

High frequency

Superimposed high frequency

a Awake Airway Surgery with Conscious Sedation

For selected patients, many laryngoscopic procedures can be safely and effectively performed in an office-based setting, including diagnostic endoscopy, laser surgery, panendoscopy for cancer screening and biopsies, and therapeutic vocal cord injections.^2–516 The key to success for office-based surgery remains adequate topical and regional anesthesia of the patient’s airway, which is usually performed by the surgeon and typically follows preparation of the patient for awake oral and nasal flexible fiberoptic intubation (see Chapter 19). Although highly motivated patients can undergo office-based laryngoscopic surgery strictly under local anesthesia, most desire sedation and amnesia.³

If presence of the anesthesiologist is requested, the main objectives are to monitor for possible local anesthetic toxicity (see Chapter 19), to supplement local anesthesia with a rapidly titratable and reversible state of sedation, and to treat acute hyperdynamic responses that can occur in up to 20% to 30% of patients, despite seemingly adequate topical anesthesia of the airway.^3,83 Judicious use of intravenous opioids or sedatives/hypnotics, or both, is paramount, because a loss of patient cooperation may result in intraoperative injury.^3,16,34 Sedation of the patients with obstructive sleep apnea and morbid obesity should be performed with extreme caution.^84,85

b Asleep Airway Surgery with General Anesthesia

General anesthesia for microlaryngeal surgery represents a unique example of some of the conflicting intraoperative goals that exist between the surgeon and the anesthesiologist with regard to the patient’s airway control and maintenance. For the surgeon, ideal operating conditions would be completely unobstructed surgical visualization, unimpeded surgical manipulation, and absence of movement in the surgical field. From the anesthesiologist’s perspective, the ideal anesthetic technique would allow adequate protection of the patient’s lower airway from aspiration and the use of stable, controlled mechanical ventilation with the ability to measure the concentration of anesthetic gases, peak inspiratory pressure (PIP), inspired oxygen concentration (FIO₂), and end-tidal carbon dioxide level (EtCO₂).⁸¹ In most cases, these objectives can be balanced by the use of a small MLT tube, maximizing the patient’s safety and the success of surgery.

Endotracheal Intubation with Microlaryngeal Tracheal Tubes

The use of a small (5.0-mm ID) MLT tube with positive-pressure ventilation remains the standard for airway management in most nonlaser microlaryngeal surgery, and it is associated with minimal or no intraoperative complications.^86,87 (For anesthetic management of the laser airway surgery see Chapter 40.) Adequate gas exchange can be maintained through small-ID ETTs in most adult patients,^88,89 unless the duration of surgery approaches 2 hours (which happens rarely).⁸⁸ Even then, despite a consistent trend toward progressive hypercapnia and respiratory acidosis, the pH and EtCO₂ values remain within physiologic range.⁸⁹

With most glottic pathology originating in the anterior two thirds of the larynx,⁹⁰ consistent positioning of a small MLT tube between the arytenoid cartilages in the posterior part of the glottis leaves most of the surgical field unobstructed to the surgical view and manipulations.^{4,13,16,38,91} Even with many posterior glottic disorders, it may be possible for the surgeon to gently displace the MLT tube anteriorly with the microsurgical cupped forceps or to perform the surgery using the specially designed posterior glottic laryngoscopes.^90,92

However, if the posterior glottis is occupied by a significant surgical pathology (e.g., posterior glottic or subglottic stenosis, transglottic tumor) (Fig. 38-12), use of alternative, tubeless ventilation techniques becomes necessary.³⁸ Because of the surgeon’s preference, tubeless ventilation can also be requested as a primary ventilation mode from the outset of the procedure.

Figure 38-12 A right vocal process granuloma is located in the posterior glottis. The location and the nature of the pathology preclude the use of the microlaryngeal tracheal (MLT) tube and require the use of jet ventilation.

(Courtesy of Edward Damrose, MD, Stanford University Medical Center, Stanford, CA.)

Tubeless Techniques

Spontaneous Ventilation

Spontaneous ventilation is rarely used in adult microlaryngeal surgery,^93–95 but it is commonly employed in the pediatric patient population, for whom it offers the additional ability to evaluate dynamic airway function and the level of obstruction (see “Anesthesia for Pediatric Airway Endoscopy and Microlaryngeal Surgery”). Anesthetic gases can be delivered (insufflated) through a nasal trumpet connected through an ETT adapter to the anesthesia circuit,^96–99 an ETT positioned in the nasopharynx,^82,100,101 a metal cannula, a side port of the rigid bronchoscope or operating laryngoscope (Fig. 38-13; see Fig. 38-10),³⁸ or a catheter placed through the vocal cords into the patient’s trachea.^9,102,103 Scavenging of anesthetic gases can be facilitated with an open suction tube at the corner of the patient’s mouth.

Figure 38-13 A child in suspension laryngoscopy using the spontaneous ventilation (insufflation) technique. Notice the precut endotracheal tube connecting the anesthesia circuit to a metal cannula inserted into a side port of the suspension laryngoscope.

(Courtesy of Peter Koltai, MD, Stanford University Medical Center, Stanford, CA.)

Although this technique offers free access to the larynx, it does not provide a still surgical field for precision surgery, it affords no protection of the lower airway, and it contaminates the OR environment.^34,87,103 Deep planes of anesthesia are usually required to blunt the laryngeal responses and to prevent patient movement, which tends to provoke cardiovascular instability and ventilatory compromise (i.e., hypoxemia, hypercarbia, and short periods of apnea).^8,39,104 With careful technique, inhalational agents can be substituted for total intravenous anesthesia (TIVA).^82,96,105 However, control of the patient’s movement and a stable plane of anesthesia frequently remains problematic.¹⁰⁴ Monitoring an adequate hypnotic state (e.g., processed electroencephalographic activity) may be advisable for these patients.

The protagonists of spontaneous ventilation technique may wish to routinely supplement general anesthesia with topical or local anesthesia of the airway (usually done by the surgeon after deployment of suspension laryngoscopy), which facilitates maintenance of a more stable and lighter plane of anesthesia, promotes hemodynamic and respiratory stability, and decreases the incidence of intraoperative laryngospasm.^{39,82,96,103,105,106}

Apneic Intermittent Ventilation

AIV remains a relatively popular technique for microlaryngeal surgical procedures of short duration in some surgical centers.⁸⁷ Compared with spontaneous ventilation, it affords more stable and controlled anesthetic conditions, as well as full muscle relaxation. After induction of anesthesia, the patient’s lungs are ventilated by a face mask or an LMA, which is followed by a period of apnea to allow deployment of a suspension laryngoscope by the surgeon. The patient’s trachea is subsequently intubated by the surgeon with a small-diameter, preferably uncuffed ETT that is placed through the lumen of the laryngoscope,⁸⁷ and the patient’s lungs are hyperventilated with an FIO₂ of 1.0 (Fig. 38-14). The ETT is then removed to provide a fully unobstructed and still surgical view of the larynx. The ETT is withdrawn and reinserted as frequently as necessary to maintain an oxygen saturation by pulse oximetry (SpO₂) of 90% or greater and EtCO₂ between 40 and 60 mm Hg,^18,87,107 allowing periods of apnea up to 5 to 10 minutes in healthy adult patients.^87,108 Apneic oxygenation through the hypopharyngeal catheter, preceded by an adequate period (10 minutes) of preoxygenation and denitrogenation of the patient’s lungs, can be tried in anesthetized and paralyzed patients.¹⁰⁸

Figure 38-14 Apneic, intermittent ventilation during microlaryngeal surgery. The endotracheal tube is intermittently placed through the lumen of a suspension (Lindholm) laryngoscope by the surgeon and connected to the anesthesia breathing circuit for positive-pressure ventilation.

TIVA is typically used for maintenance. Monitoring the hypnotic state of anesthesia is advisable during AIV, because the incidence of awareness and recall may reach 4% (30 times higher than in the general surgical population), especially when the inhalational agents are used to supplement intravenous anesthesia.^109,110

The disadvantages of AIV include slowing the pace of surgery, disruption of the surgical field, possible trauma to the vocal cords and lower airway due to repeated endotracheal intubation, and a propensity for laryngospasm.⁸⁷ In a study of more than 350 patients,⁸⁷ the incidence of intraoperative laryngospasm with AIV was 1.4%. The AIV may not be suitable for patients with significant lung or cardiovascular disease,¹⁰⁷ and it leaves the patient’s lower airway unprotected to aspiration.¹⁸

Appropriate and successful phonomicrosurgery can rarely be performed using AIV, because the apnea periods are too short to permit unhurried precision surgery.^1,111 This technique may be better reserved for short, uncomplicated cases.

Jet Ventilation

Supraglottic JV (i.e., jet nozzle above the glottic opening) for microlaryngeal surgery can be performed through the side port of a suspension operating laryngoscope, with the jet cannula attached to the lumen of the laryngoscope (Fig. 38-15; see Fig. 38-4)^1,24,59,112 or through a specialized jet laryngoscope.^113,114

Figure 38-15 A Dedo operating laryngoscope with the integrated side port (top) can be used for supraglottic jet ventilation, and different jetting metal cannulas (bottom) can be inserted through the side ports of the operating laryngoscopes or directly through their lumen (see Fig. 38-4).

Subglottic JV (i.e., jet nozzle below the glottic opening) is established by bypassing the larynx from above (i.e., translaryngeal or transglottal approach) or below (i.e., percutaneous approach) through the CTM or the upper TTJV rings.^74,86,87,111 Transglottal JV typically employs specialized, laser-safe, small-diameter, orally placed, double-lumen catheters (Fig. 38-16),^{24,81,115,116} in which the large port is used for jetting and the smaller lumen for monitoring the distal airway pressure and respiratory gases. Long, single-lumen catheters (typically 1.5- to 3-mm ID), some of which are laser resistant, may be used and can be placed through the oral or nasal route^{24,34,87,102,117–119}; however, they lack concurrent monitoring capability. Alternatively, a small-diameter, movable, metal jet cannula can be passed through the glottis by the surgeon after the suspension laryngoscope is in position (Fig. 38-17).^87,120 For transglottal JV, midtracheal placement of the catheter or cannula is usually preferred. TTJV is typically administered through a long catheter or Ravussin-type cannula (Fig. 38-18).^74,86,121 For TTJV catheter or cannula placement, the use of an FFB or a rigid bronchoscope may be advocated to monitor the procedure^87,111,122 and to minimize the risk of unnoticed posterior tracheal wall laceration, which may lead to submucosal gas injection and barotrauma.^87,111 Use of a rigid bronchoscope with the bevel turned posteriorly may be especially efficacious, because the posterior tracheal wall is protected by the bronchoscope from the needle entry.⁸⁷ For transglottal JV and TTJV, endoscopic control also allows adjustment of the position of the distal end of the catheter or cannula to optimize HFJV.^24,86,87,122

Figure 38-16 The Hunsaker Mon-Jet Ventilation Tube (Medtronic Xomed Inc., Jacksonville, FL) (A) and a double-lumen catheter (LaserJet, Acutronic medical systems AG, Hirzel, Switzerland) (B) are laser-resistant, come with the metal stylet to facilitate tracheal placement, and have a large port that is used for jet ventilation (JV) and a smaller port that is used for monitoring the distal airway pressure and respiratory gases. The green, basket-shaped distal end of the Hunsaker Mon-Jet tube (A) facilitates self-centering of the tube within the trachea, preventing the catheter “whip” that may lead to submucosal gas injection and possible occlusion of the distal end of the jet tube by tracheal mucosa. C, The small-diameter Hunsaker Mon-Jet tube is placed through the glottis to facilitate a clear surgical view and surgical access. D, The Hunsaker Mon-Jet tube is taped in place during JV, with the monitoring port connected to the ventilator through a three-way stopcock. The jet ventilator tubing is suspended to prevent kinking, and an oral airway is inserted to facilitate full egress of air during JV.

(B, Courtesy of Acutronic medical systems AG, Hirzel, Switzerland; C and D, from Davies JM, Hillel AD, Maronian NC, et al: The Hunsaker Mon-Jet tube with jet ventilation is effective for microlaryngeal surgery. Can J Anaesth 56:284–290, 2009.).

Figure 38-17 Subglottic high-frequency jet ventilation (JV) through a movable metal jet nozzle. Transglottal JV is provided through the metal jet nozzle (Brock & Mechelsen A/S, Birkerod, Denmark) and is secured on the suspension laryngoscope for the operation for vocal cord carcinoma.

Figure 38-18 Devices for transtracheal jet ventilation (TTJV). A, The 7.5-cm long, 2-mm inner diameter TTJV catheter (Cook Medical Inc., Bloomington, IN) is mounted on a 14-gauge (G) needle. The catheter is wire reinforced to prevent kinking. B, Different sizes of the Ravussin-type cricothyrotomy catheter (VBM Medizintechnik GmbH, Sulz, Germany) for TTJV. The 13-gauge, 1.3-mm outer diameter catheter with the fixation flange and foam Velcro neck tape is most frequently used in adults.

(Courtesy of Acutronic Medical Systems, GmbH, Salzburg, Austria.)

Compared with endotracheal intubation, supraglottic and subglottic JV techniques have distinct advantages of providing the surgeon with an enlarged, clear or minimally impeded, and undistorted view of the endolarynx, facilitating surgical access and eliminating flammable material (i.e., ETT) from the patient’s airway during laser surgery.^24,115 Although supraglottic and subglottic ventilation techniques can use low-frequency jet ventilation (LFJV), HFJV, or superimposed high-frequency jet ventilation (SHFJV) modes,^{34,86,111,123–125} the use of these modes in clinical practice is usually more restrictive (Table 38-1).

TABLE 38-1 Preferred Use of Jet Ventilation Techniques for Microlaryngeal Surgery

The use of manual supraglottic LFJV (i.e., Venturi jet ventilation) at a rate of less than 60 breaths/min continues to predominate in clinical practice,¹¹¹ probably because of the low cost and easy accessibility of manual JV devices (Fig. 38-19) (a manual mode also can be preset on commercially available jet ventilators, where available).^{59,111,126,127} Although an overall incidence of complications with manual supraglottic LFJV may be low (0.42%),¹²⁰ a survey of 229 U.K. centers revealed that it was responsible for most major complications (e.g., significant hypoxemia, barotrauma, unplanned admission to the intensive care unit) and for all deaths, especially when applied subglottically.¹¹¹ This suggests that LFJV should be reserved for uncomplicated, elective procedures of short duration and that it may not be regarded as a standard of practice for microlaryngeal surgery.²⁴ For increased safety, LFJV should be started with a low driving pressure (≤10 psi), which is gradually increased until visible chest excursions are observed, and adequate oxygen saturation is maintained.^24,59,111

Figure 38-19 A simple Sanders-type injector (AA Jet Ventilator, Anesthesia Associates, San Marcos, CA) (left) and a manual jet ventilator (QuickJet, Rusch-Teleflex Medical, Durham, NC) (right) are used for manual (Venturi) low-frequency jet ventilation. Both devices contain a pressure hose (1), an adjustable pressure-regulating valve (2), a manual lever for delivering the pressurized gas (3), an easily readable pressure gauge (4), and noncompliant jet ventilation tubing (5). QuickJet allows presetting a desired level of driving pressure, indicated by the colored scale on the pressure gauge.

The subglottic HFJV mode (respiratory rate of 100 to 300 breaths/min; tidal volumes [V_T] of 1 to 3 mL/kg), delivered through specialized automated jet ventilators, is typically used.^24,34 Compared with supraglottic LFJV, in which intermittent apnea is frequently required due to significant vocal cord movement, subglottic HFJV significantly reduces laryngeal motion and affords a quiet surgical field without the need for interrupting ventilation.¹²⁵ If vocal cord movement becomes a problem, HFJV driving pressure can be decreased, and the respiratory frequency can be increased to provide a smoother gas flow, or the ventilator can be turned off during particularly delicate parts of the procedure.^24,125

Despite very small V_T values, CO₂ elimination during subglottic HFJV is facilitated by the upstream turbulent convective flow of CO₂ along the decreasing gradient from the alveoli to the conducting airways.³⁴ The alveolar-arterial CO₂ gradient in patients with normal lung function is largely maintained within normal range.^34,128 Monitoring EtCO₂ during HFJV can be accomplished by briefly switching to LFJV mode on the ventilator to get a reliable signal or by using transcutaneous Pco₂ monitoring.²⁴ Administration of subglottic HFJV also results in a higher inspired O₂ concentration, because entrainment of air is reduced deep inside the airway.^24,86 Improved oxygenation is further enhanced by generation of continuous positive end-expiratory pressure in small airways (auto-PEEP), leading to alveolar recruitment and increased functional residual capacity (FRC).^24,34,119 Nevertheless, patients with severely restricted lung compliance, mismatch or shunting, and reduced FRC (e.g., morbid obesity) remain at increased risk for hypoxemia.⁸⁶

In contrast to supraglottic LFJV, with which contamination of the lower airway due to air entrainment is possible,^34,81 a continuous, upward-directed flow of gas during subglottic HFJV creates a positive-pressure build-up, preventing blood and surgical debris from being directed down an unprotected airway.^111,119,129 However, increased airway pressure creates concern about air trapping and barotrauma, mandating maintenance of adequate gas outflow at all times.¹³⁰

Before the suspension laryngoscope is secured, with the patient anesthetized and a subglottic JV catheter or cannula in place, strategies for minimizing the risk of barotrauma on initiation of subglottic HFJV may include starting ventilation with low driving pressures (<15 to 30 psi), allowing sufficient exhalation time by avoiding high-frequency ventilation (i.e., starting with LFJV first), and maintaining the patient’s airway patency with the assistance of an oral airway or providing a jaw lift, if needed.^{74,86,87,125,131} Alternatively, initiation of the subglottic HFJV can be held off until the suspension laryngoscope is deployed, and ventilation is supported conventionally through a face mask or the LMA. It may be prudent to confirm absence of the subglottic catheter or cannula obstruction by the EtCO₂ return and to check the catheter or cannula position endoscopically before subglottic HFJV commences.^86,125

On emergence from anesthesia, small V_T values and low peak and mean airway pressures associated with subglottic HFJV enable the patient to breathe spontaneously, facilitating a transition to adequate spontaneous ventilation.^{24,34,86,132,133} This transition can be further assisted at the end of surgery by increasing the frequency of ventilation to 300 breaths/min, increasing FIO₂ to 1.0, and setting a ventilator driving pressure at about 10 psi (0.8 bar), which enables almost continuous flow of O₂ and apneic oxygenation, as well as a rise in the carbon dioxide (CO₂) level.²⁴ If the conversion to spontaneous ventilation through a small subglottic catheter proves difficult, the patient’s airway can be supported through a face mask, LMA, or ETT, as required; these conventional bridge airway strategies equally apply to transitioning from supraglottic JV. If obstructive airway lesions exist, subglottic HFJV must be used with extreme caution. If upper airway obstruction is greater than 50%, the position of the jet nozzle should be proximal to the site of the obstruction to prevent barotrauma, or the obstruction must be bypassed by a rigid bronchoscope first.^24,79

Total outflow obstruction with resultant barotrauma during subglottic HFJV can be quickly precipitated by surgical instrumentation, glottic edema, laryngospasm, or closure of the vocal cords due to inadequate depth of anesthesia or inadequate muscle relaxation.^81,86,130 Modern automated jet ventilators (e.g., Monsoon III Universal Jet Ventilator [Acutronic Medical Systems AG, Hirzel, Switzerland], Twin Stream [Carl Rainer GmbH, Vienna, Austria]) incorporate multiple safety features, including automatic ventilator shutdown, if the user-preset pressure limits are exceeded.^24,74 This design has enabled some experienced providers to successfully use high-frequency TTJV in patients with massive supraglottic lesions and severe airway compromise,⁷⁴ for which the use of supraglottic or subglottic JV was not possible or surgically feasible. The presence of a second anesthesiologist to facilitate monitoring and maintenance of an upper airway was required and deemed an important safety factor in preventing intraoperative pressure-related complications in all cases.⁷⁴ Although no major complications were observed in this series of 50 patients,⁷⁴ the incidence of minor complications reached 20%, a more than threefold increase compared with the instances when high-frequency TTJV has been used in patients with less severe airway compromise.⁸⁷ Study results hold some promise that a simple,^134,135 portable expiratory ventilation assistance (EVA) device may be able to facilitate egress of gas through the jet catheter during TTJV, thereby increasing the safety of this technique; however EVA suitability for microlaryngeal surgery remains to be established.

Compared with the transglottal approach, high-frequency TTJV is associated with a significantly higher combined major and minor (e.g., transient hypoxemia) complication rate (see “Intraoperative Complications”),^86,87 and it represents an independent risk factor for complications during JV for microlaryngeal surgery.⁸⁷ Modern automated JV may not be able to remediate all possible causes of barotrauma associated with high-frequency TTJV; complications may be related to the TTJV catheter insertion problems, laryngospasm, and high-pressure episodes (e.g., coughing, active expiration) during the recovery period.^80,86 Notwithstanding the attractive features of high-frequency TTJV, such as a motionless surgical field and a particularly easy transition to spontaneous respiration,⁸⁶ it may be advisable to reserve the elective use of this technique (especially in cases of severe supraglottic airway obstruction) for the most complicated patients⁷⁴ and to designate operators with significant clinical experience and expertise.^74,80,86,111

SHFJV, which combines high-frequency and low-frequency ventilation modes, has been used effectively in surgical treatment of high-grade laryngeal and tracheal stenosis, even with a remaining glottic opening as small as 2 to 3 mm.¹³⁶ SHFJV is delivered supraglottically through a specialized jet laryngoscope, which incorporates welded low-frequency and high-frequency jet nozzles (Fig. 38-20).^113,136,137 As the streams (LFJV of 12 to 20 breaths/min; HFJV of 100 to 900 breaths/min) get simultaneously directed from the ventilator toward the center of the distal end of the jet laryngoscope, LFJV entrains air (Fig. 38-21) and produces cyclic changes in V_T (similar to supraglottic LFJV), facilitating maintenance of PaCO₂ at near-normal limits and allowing HFJV to be adjusted as needed.^136,137 HFJV builds up a continuous PEEP and promotes alveolar recruitment, maintaining PaCO₂ even in the presence of the low FIO₂ required for laser surgery.^136–139 Safety of SHFJV is enhanced by an integrated port for continuous pressure (PIP and PEEP) and gas (FIO₂ and EtCO₂) monitoring at the end of the jet laryngoscope (see Fig. 38-21)¹³⁷ and of an automatic pressure-triggered ventilator shutdown feature, similar to an isolated HFJV mode.

Figure 38-20 Jet laryngoscope for superimposed high-frequency jet ventilation. The jet laryngoscope (Carl Reiner GmbH, Vienna, Austria) incorporates a port for jet ventilation (1) with two welded jet nozzles for high-frequency and low-frequency ventilation and a port for pressure and gas monitoring (2).

(Courtesy of Carl Reiner GmbH, Vienna, Austria.)

Figure 38-21 Technical diagram of the jet laryngoscope and superimposed high-frequency jet ventilation. High-frequency and low-frequency jet ventilation are simultaneously delivered to the patient from the ventilator through the high-frequency (1) and low-frequency (2) jet nozzles connected to the ventilator input tubing (3). The gas flow to the patient is augmented by air entrainment (blue circles). The pressure monitoring system (4) and jet laryngoscope handle (5) are indicated.

(Modified image courtesy of Carl Reiner GmbH, Vienna, Austria.)

To achieve adequate SHFJV, it appears to be sufficient to generate a PIP of 15 to 30 cm H₂O, as measured at the end of the jet laryngoscope, which closely correlates with the PIP at the glottic and tracheal levels (i.e., no further increase in pressure occurs in the distal airway).^136,138 The PEEP values may not exceed 2.5 to 5 cm H₂O.^137,138 As a result, no adverse hemodynamic effects and barotrauma were observed in more than 1500 adult and pediatric patients who had undergone supraglottic SHFJV for laryngotracheal surgery, and endotracheal intubation was required in only 3 patients (0.2%), with concomitant significant restrictive or obstructive pulmonary disease.¹³⁶ Due to the HFJV component, vocal cord movement is greatly attenuated during SHFJV; if a perfectly still surgical field is requested by the surgeon, HFJV can be further increased, LFJV decreased or stopped, or a short period of full apnea instituted.^24,136,137

SHFJV is a completely tubeless, laser-safe, open breathing system that allows a fully unobstructed surgical field (Fig. 38-22). It enables an easy switch between different JV modes and parameters, and it offers greater versatility and ventilation capabilities over the single-frequency JV techniques, especially in patients with preexisting compromised gas exchange. However, its effective use requires optimal laryngoscope alignment and adjustability in relation to the glottic opening.

Figure 38-22 Superimposed high-frequency jet ventilation allows a completely unobstructed surgical view through the jet laryngoscope. Notice the ventilator input tubing (green, left) and the pressure or gas monitoring system (red and yellow, right) connected to the jet laryngoscope.

(Courtesy of Lise Nørrekjær, MD, Department of Anaesthesia, Køge Sygehus, Køge, Denmark.)

Despite the increased safety profile of SHFJV, clinical monitoring of the patient to prevent barotrauma should remain the standard of care for all JV techniques (Fig. 38-23).^86,87 Close cooperation between the surgeon and the anesthesiologist is essential; if the operating laryngoscope moves or is removed and obstructs the airway without a warning to the anesthesia team, major barotrauma may result.¹⁶ Ensuring an adequate level of anesthesia, analgesia, and muscle relaxation; painstaking attention to maintaining unobstructed exhalation; and close monitoring of vital signs and chest excursions are essential for the patient’s safety.^59,86,87,138 The main advantages and disadvantages of the ventilation techniques used for microlaryngeal surgery are compared in Table 38-2.

Figure 38-23 Challenges of intraoperative jet ventilation (JV). A, Manual, supraglottic low-frequency JV using QuickJet, connected (red arrow) to the suspension laryngoscope. The position and attentiveness of the anesthesiologist are required for multitasking and the challenging situations that exist. The anesthesiologist’s attention (white arrows) must be simultaneously directed at maintaining close communication with the surgeon, observing the chest excursions, looking at the epigastric area for possible gastric distention, controlling driving pressure of the jet ventilator, maintaining adequate neuromuscular blockade (evaluated in this case at the ulnar nerve), ensuring a stable level of anesthesia delivered intravenously through the programmable infusion pumps, and observing the patient’s vital signs. B, Automated, subglottic high-frequency JV in an 11-month-old child with recurrent respiratory papillomatosis. The JV is accomplished transglottally through a movable metal jet nozzle that is closely controlled by the anesthesiologist. Notice a different operating room setup compared with that in A and presence of two anesthesiologists, which increases the patient’s safety.

TABLE 38-2 Advantages and Disadvantages of Ventilation Techniques Used for Microlaryngeal Surgery

Technique	Advantages	Disadvantages
Awake airway surgery	Avoidance of general anesthesia Unobstructed surgical field and free surgical access to the larynx Increased patient cooperation Ability to evaluate dynamic airway function Ability to monitor voice quality throughout the surgery Possible improvement in surgical outcomes Convenience for the surgeon and the patient Cost savings

Success depends on adequate topical and regional anesthesia of the airway

Local anesthetic–induced side effects

Lack of powered magnification

Lack of precision afforded by a still surgical field

May require conscious sedation

Loss of patient cooperation may result in injury

Limited ability to handle major intraoperative complications, such as bleeding and edema

Limited amount of tissue biopsied or excised

May not be suitable for patients with significant PD or CVD or for young pediatric patients

Endotracheal intubation (microlaryngeal tracheal tube)

Adequate surgical field and surgical access to the larynx in most cases

Still surgical field

Adequate airway protection

Control of patient immobility and vocal cord movement with adequate NMB

Stable and controlled ventilation technique

Ability to continuously and reliably monitor FIO₂, EtCO₂, PIP, and anesthetic gases

Suitable for prolonged procedures

Largely unsuitable for surgery of the posterior glottic pathology (e.g., posterior glottic or subglottic stenosis, transglottic tumor)

Unsuitable for laser if the need arises

May not be used according to the surgeon’s preference

Spontaneous ventilation (insufflation and total intravenous anesthesia)

Unobstructed surgical field and free surgical access to the larynx

Ability to evaluate dynamic airway function and obstruction

Suitable for laser surgery

Unprotected lower airway

Precision surgery difficult or impossible in the moving surgical field

Contamination of operating room environment with anesthetic gases, if insufflation technique is used

Difficulty controlling adequate depth of anesthesia and absence of patient movement

Inability to continuously and reliably monitor FIO₂, EtCO₂, and anesthetic gases

May not be suitable for patients with significant PD or CVD or for very young pediatric patients

Best reserved for short, uncomplicated cases

1 Premedication and Monitoring

The main anesthesia objectives and special considerations for microlaryngeal surgery are discussed in “Special Considerations and Anesthesia Objectives.” Premedication can frequently be omitted. Administration of an antisialogogue (e.g., 0.2 mg of glycopyrrolate given intravenously) may be desired by the surgeon to facilitate the surgical field, especially in patients with copious secretions,^3,10 but it does not constitute the standard of care.⁴³ Mucosal intake of drying agents may result in increased vocal cord viscosity and impaired vibration, markedly changing the patient’s voice postoperatively and contributing to postoperative dysphonia.¹⁴⁰ Steroids (e.g., 8 to 12 mg of dexamethasone given intravenously) are frequently used to prevent or minimize excessive postoperative swelling,^16,34 although controlled studies documenting this beneficial effect appear to be lacking.³⁴

Standard OR monitors are used. Invasive arterial blood pressure monitoring is rarely indicated, and its use should be dictated by the patient’s medical history, physical examination results, and special considerations such as prolonged JV or intraoperative problems (see “Jet Ventilation Problems”), for which intermittent sampling of arterial blood gases may become necessary. Monitoring the degree of neuromuscular blockade (NMB) with a conventional nerve stimulator should constitute the standard of care during panendoscopy and microlaryngeal surgery (see “Neuromuscular Blockade”).

2 Anesthesia Induction and Maintenance

Conventional and advanced airway management is discussed in “Conventional and Advanced Airway Management.” In most patients, standard intravenous induction can be safely performed. Difficulty in maintaining the airway during inhalational induction in patients with large, pedunculated tumors, granulomas and cysts should be anticipated, even if preoperative symptoms of airway obstruction are mild,³⁸ and early application of continuous positive airway pressure (CPAP) can help to stent the airway open. Another useful strategy involves preparing the patient’s nares with a mixture of a vasoconstrictor and a topical anesthetic before induction, which will allow early passage of a nasal airway if the airway obstructs.^17,33

Sevoflurane is most commonly used for inhalational induction in adult and pediatric patients.^34,141 The minimum alveolar concentration (MAC) of sevoflurane required to provide adequate endotracheal intubating (EI) conditions in 50% of unpremedicated adult patients (MAC_EI50) is 4.5% (95% confidence interval [CI], 3.9% to 5.2%), and the 95% effective dose (ED₉₅) for endotracheal intubation is 8%.¹⁴² Although the ED₉₅ time for achieving this target concentration in patients with normal airway is approximately 7 minutes,¹⁴³ up to 20 minutes may be required in patients with partial airway obstruction due to preexisting increase in minute ventilation and mismatch.^17,34 This time can be shortened with the addition of small intravenous doses of midazolam or fentanyl,^141,144 although at the expense of an increased risk of apnea and loss of the airway.

If the patient’s airway is reassuring, TIVA with propofol and an opioid is most commonly used during induction and maintenance of anesthesia for panendoscopy and microlaryngeal surgery.^{34,74,86,87,111} TIVA offers many practical advantages, such as delivering a stable, consistent level of anesthesia in cases of JV and other settings in which the delivery of inhalational anesthetics is compromised. TIVA facilitates maintenance of induced hypotension, resulting in improved surgical visibility; ensures rapid return of protective airway reflexes; promotes rapid awakening and early postanesthesia recovery; and decreases the incidence of postoperative nausea and vomiting.^70,145–150 A propofol-based anesthetic results in profound depression of pharyngeal and laryngeal musculature and reflexes, and it effectively blocks the catecholamine release and hyperdynamic cardiovascular responses.^{145,151–153} Full synergistic effect of propofol with rapidly acting opioids (e.g., remifentanil, alfentanil) allows rapid titration of anesthetic to the desired clinical effect.^154–156

Remifentanil and alfentanil are widely used because of their favorable pharmacokinetic profile. Remifentanil is superior to fentanyl and alfentanil in promoting intraoperative hemodynamic stability, improving respiratory and general recovery, and facilitating patients’ discharge after outpatient surgery.^157–162 The recommended induction doses are an intravenous bolus of 0.5 to 2 µg/kg of remifentanil and intravenous bolus dose of 1 to 2 mg/kg of propofol, followed by continuous maintenance infusions of 0.1 to 0.5 µg/kg/min of remifentanil and 80 to 180 µg/kg/min of propofol.^{48,156–158,160,163} For alfentanil, an intravenous bolus of 20 to 30 µg/kg is commonly used for induction, followed by a continuous maintenance infusion of 0.25 to 1 µg/kg/min.^{159,160,164,165}

Compared with conventional weight-based manual infusions, target-controlled infusions allow easier and more rapid titration of analgesia to the individual patient’s responses, avoiding overshoot, improving the time course of the drug effect, and facilitating perioperative hemodynamic control.^166–168 Targeting propofol concentrations of 3 to 3.5 µg/mL and remifentanil concentrations of 2 to 5 ng/mL should be sufficient for most otherwise young (18 to 65 years old) and healthy (ASA physical class I or II) patients during the maintenance stage of anesthesia if adequate NMB is maintained.^{166,169–171}

Severe bradycardic response to remifentanil should be treated promptly: activation of afferent parasympathetic fibers during direct and suspension laryngoscopy and endotracheal intubation or instrumentation may result in severe cardiac arrhythmias and asystole.^172,173 Pediatric patients and adults with high vagal tone may be at highest risk for these grave complications,¹⁷² and pretreatment with anticholinergic agents may prevent or attenuate vagus-mediated cardiac arrhythmias. Treatment of reflex bradycardia and asystole during direct or suspension laryngoscopy must include immediate cessation of the offending stimulus, prompt administration of anticholinergics (e.g., atropine), and cardiopulmonary resuscitation, if necessary; infusion of isoproterenol or cardiac pacing may be required.¹⁷²

Sevoflurane can be effectively combined with remifentanil and alfentanil for microlaryngeal surgery, producing good operating conditions, cardiovascular stability, and rapid emergence from anesthesia.¹⁶² Compared with other inhalational anesthetics, sevoflurane may be preferred for outpatient microlaryngeal surgery. It improves the quality of postoperative patient recovery and shortens the discharge time, is associated with a reduced incidence of coughing compared with desflurane,¹⁷⁴ and produces less somnolence and postoperative nausea and vomiting compared with isoflurane.¹⁷⁵ Compared with TIVA, sevoflurane decreases salivary gland excretion, potentially promoting better visibility for the surgeon,¹⁷⁶ although clinical significance of this effect is unknown.

3 Neuromuscular Blockade

Maintenance of adequate NMB for microlaryngeal surgery is recommended,^{1,34,38,86,111} but this advice is not universally followed.^111,177 Lack of appreciation for the benefits of adequate muscle relaxation constitutes a significant area for improvement in anesthesia care in general¹⁷⁷ and microlaryngeal surgery in particular.

Full muscle relaxation facilitates smooth endotracheal intubation, which should be accomplished in patients presenting for microlaryngeal surgery without the use of an ETT stylet when possible.¹ Maintenance of adequate NMB can prevent disastrous consequences of sudden patient movement, such as bucking or coughing while in suspension or during bronchoscopy or esophagoscopy,⁴³ and it can facilitate respiratory compliance during JV.³⁴ For some short surgical interventions, for which adequate muscle relaxation is only transiently required, combined administration of 2 µg/kg of remifentanil, 2 mg/kg of propofol, 1.5 mg/kg of lidocaine, and only one half of an intubating dose of rocuronium (0.3 mg/kg) can be administered, producing intubating conditions similar to intravenous administration of 1.5 mg/kg of succinylcholine.¹⁷⁸ For very short diagnostic procedures, for which muscle relaxants can be completely avoided, a bolus dose of 3 to 4 µg/kg of remifentanil (or intravenous bolus of 40 to 60 µg/kg of alfentanil), administered over 90 seconds and followed by an intravenous bolus of 2 to 2.5 mg/kg of propofol should provide excellent conditions for endotracheal intubation^179–181 or a quick “surgical look.”

For most adult microlaryngeal surgical and panendoscopy procedures, maintenance of a high degree of NMB is strongly preferred and is most commonly achieved by administration of intermittent intravenous bolus doses of intermediate-acting, non-depolarizing neuromuscular blockers or succinylcholine infusion.⁸⁶ In the absence of contraindications to succinylcholine, the choice may be largely influenced by the duration of the procedure, the anesthesiologist’s preference, and special surgical requirements. If rapid or intermittent return of spontaneous ventilation is required intraoperatively, an intravenous bolus of succinylcholine followed by an infusion may be preferred.³⁴ A succinylcholine infusion at a rate of 0.1 mg/kg/min (95% CI, 0.06 to 0.14 mg/kg/min) provides 100% twitch depression to the train-of-four (TOF) stimulation of the ulnar nerve (adductor pollicis muscle) and can be easily titrated to effect due to its linear kinetics.¹⁸² The infusion should be started after the intubating dose of succinylcholine has dissipated and a twitch response has reappeared.^182,183 For practical purposes, it should be titrated to a barely visible single twitch during TOF stimulation of the ulnar nerve, which corresponds to 95% to 98% of twitch depression.¹⁸² The observed increased succinylcholine requirements (i.e., tachyphylaxis) should alert the anesthesiologist to a rapidly developing transition from phase 1 to phase 2 NMB.^183,184 Similar phenomena are observed in children.¹⁸⁵

In the absence of a phase 2 block, succinylcholine infusions may avoid postoperative residual curarization (PORC). The incidence of PORC with the use of the intermediate-acting, non-depolarizing muscle relaxants reaches 20% to 30% in the general surgical population.^186,187 PORC is associated with delayed discharge from the recovery room, even in the absence of respiratory compromise.¹⁸⁶ The use of mivacurium, despite its short duration of action, is associated with an almost 10% incidence of residual block, unless its action is pharmacologically reversed.¹⁸⁸ This highlights the need for vigilant intraoperative monitoring of NMB and routine reversal of NMB after microlaryngeal surgery to ensure adequate TOF recovery to a level of more than 0.9.^189–192 Even small degrees of residual paralysis (TOF of 0.7 to 0.9) are associated with impaired pharyngeal function and increased risk of aspiration, significant attenuation of the hypoxic ventilatory response, unpleasant symptoms of muscle weakness, and weakness of the laryngeal and upper airway muscles, which may contribute to the possibility of acute upper airway obstruction postoperatively (see “Postoperative Complications”).¹⁹²

During microlaryngeal surgery, access to the patient’s arms is frequently difficult or impossible, and the anesthesiologist is faced with an alternative choice of monitoring NMB at the temporal branch of the facial nerve (i.e., orbicularis oculi muscle) or posterior tibial nerve (i.e., flexor hallucis brevis muscle). Monitoring TOF at the orbicularis oculi correlates best with NMB at the laryngeal adductor muscles, which are responsible for vocal cord movement and glottic closure¹⁹³ and may constitute the surgeon’s preference.⁴³ For adequate orbicularis oculi monitoring, the following guidelines should be followed^194,195:

The onset of and the recovery from non-depolarizing NMB at the larynx and orbicularis oculi are similar and faster than at the ulnar nerve.^{191,193–196} Significantly quicker recovery of NMB is observed in adults at the flexor hallucis brevis muscle (i.e., great toe) compared with the hand muscles.¹⁹¹ Assessment of the residual block at the end of the surgery must still be guided by a twitch recovery at the ulnar nerve, because the adductor pollicis muscle recovers last.^191,194,196

The anesthesiologist must maintain constant communication with the surgeon to match the maintenance of adequate NMB with the duration of surgery. If additional muscle relaxation is requested at the end of the procedure to abolish vocal cord movement, administration of non-depolarizing muscle relaxants should be avoided, and deepening the level of anesthesia and/or administration of additional analgesia (e.g., intravenous bolus of remifentanil) should be performed instead.⁴³ Pharmacologic reversal of non-depolarizing NMB should be routinely done at the end of microlaryngeal surgery.

Sugammadex, a selective relaxant binding drug, can antagonize any level of NMB, including the profound blockade induced by rocuronium, adding flexibility to the use of non-depolarizing relaxants.¹⁹⁷ The recommended dose is 2 to 16 mg/kg, depending on the level of the block.^188,197 Profound NMB induced by rocuronium can be reversed in less than 3 minutes.¹⁹⁸ Sugammadex, however, has no affinity for atracurium, cisatracurium, or succinylcholine; is not widely available; and is very expensive.¹⁹⁷

4 Conventional and Operative Direct Laryngoscopy

The intense sympathoadrenal response observed during direct laryngoscopy and endotracheal intubation (see “Special Considerations and Anesthesia Objectives”) may be further accentuated by continuous deployment of the suspension laryngoscope and intralaryngeal or intratracheal surgical manipulations, resulting in a 10% to 17% incidence of transient intraoperative myocardial ischemia.¹⁹⁹ The administration of 1.5 to 2 mg/kg of esmolol by intravenous bolus, followed by continuous intravenous infusion at a rate of 100 to 300 µg/kg/min, may be particularly effective in promoting hemodynamic stability and preventing intraoperative myocardial ischemia.^200–202 Potentiation of the action of opioids and anesthetic agents by esmolol further results in decreased postoperative opioid analgesic requirements,^203–206 facilitates emergence from anesthesia, and shortens a discharge time after outpatient surgical procedures.^207–210

5 Jet Ventilation Problems^24,34

6 Bronchoscopy and Esophagoscopy

Diagnostic and therapeutic forms of endoscopy (i.e., bronchoscopy and esophagoscopy) are typically performed as part of the panendoscopy procedure. The use of operating flexible and rigid bronchoscopy in central and distal airway surgery, including tracheal and endobronchial stent placement, is beyond the scope of this discussion, and JV is most commonly employed for these surgical procedures. Operating esophagoscopy is commonly used for endoscopic resection of Zenker’s diverticulum.

If rigid bronchoscopy is planned first, general anesthesia is induced in a standard manner, and the patient’s lungs are hyperventilated through the face mask with an FIO₂ of 1.0. With the onset of complete muscle relaxation, the patient is immediately turned over to the surgeon without securing an airway.⁴³ Quick and gentle direct laryngoscopy for the purpose of applying topical laryngotracheal anesthesia (3 to 4 mL of 4% lidocaine) before rigid bronchoscopy can be tried to help blunt hemodynamic responses to subsequent surgical manipulation; however, the risk of residual laryngeal anesthesia should be kept in mind if the procedure is short.²¹²

After the rigid bronchoscope is introduced into the patient’s trachea, JV can be instituted, or ventilation can commence manually through the OR anesthesia circuit by using the Racine universal adapter connected to the side arm of the bronchoscope (see Fig. 38-10). A rigid telescope and many accessory instruments such as forceps, suction catheters, laser fibers, or silicone stent delivery systems can be placed by the surgeon through the central lumen of the bronchoscope.²¹³ Although balanced inhalational anesthesia has been used successfully in this setting,³⁴ TIVA can provide a more stable plane of anesthesia. With manual ventilation, high gas flows are usually required because of the variable leak around the end of the bronchoscope. Close communication with the surgeon is essential for decreasing the manual inflating pressures when the bronchoscope is introduced into a main stem bronchus and to ensure complete exhalation.⁴³

After rigid bronchoscopy is completed, if endotracheal intubation is planned, a resumption of adequate mask or LMA ventilation with an FIO₂ of 1.0 is advisable before direct laryngoscopy. If necessary, the airway can be exchanged with the ETT through the in situ rigid bronchoscope (see Fig. 38-11).^72,73

If endotracheal intubation is chosen, a small-diameter (e.g., 6.0 mm ID), wire-reinforced ETT may be preferred for rigid esophagoscopy to avoid possible compression of the ETT lumen; however, if suspension laryngoscopy with endotracheal intubation is planned next, a 5.0 mm ID MLT tube should be used instead. The ETT should be moved over to the left side of the patient’s mouth to facilitate introduction of the surgical instruments and securely taped to the lower jaw, facilitating full opening of the patient’s mouth by the surgeon.⁴³

Intraoperative flexible fiberoptic bronchoscopy can be performed by the surgeon through an appropriately sized ETT, alongside the small ETT with its cuff deflated; through the LMA; or through Patil-Syracuse endoscopy mask (Ambu Inc., Glen Burnie, MD) (Fig. 38-24). If flexible fiberoptic bronchoscopy is performed through the ETT (7.5 to 8.0 mm ID) using a swivel bronchoscopy adapter, ventilation is better controlled manually because of increased resistance to the gas flow and high PIP. Gentle, manual ventilation with small tidal volumes and an FIO₂ of 1.0 is usually well tolerated by the patient over the short course of the procedure. The efficacy of ventilation through the Patil-Syracuse mask during flexible fiberoptic bronchoscopy is greater than through the Classic LMA or iLMA,²¹⁴ and the Patil-Syracuse mask can be used to facilitate flexible esophagoscopy.

Figure 38-24 A, The reusable, clear-view Patil-Syracuse mask (Ambu Inc., Glen Burnie, MD) has a soft, blue, flexible diaphragm that facilitates passage of flexible endoscopes and endotracheal tubes. A black cap seals off the diaphragm and allows positive-pressure ventilation (PPV) through the anesthesia circuit when endoscopy is not in use. B, Flexible fiberoptic bronchoscopy is performed through the Patil-Syracuse mask. Placement and manipulation of the flexible fiberoptic bronchoscope by the surgeon is aided by a concomitant use of a pink Williams oral airway intubator, which facilitates central positioning and maneuvering of the fiberoptic bronchoscope. Maintenance of a good seal through the flexible diaphragm allows adequate PPV by the anesthesiologist.

After endoscopy through the Patil-Syracuse mask is completed, an appropriate ventilation strategy can be instituted for the performance of operative direct laryngoscopy and suspension microlaryngeal surgery. If no further surgery is planned, the patient can be allowed to emerge from anesthesia, breathing spontaneously through the Patil-Syracuse mask or the LMA.

7 Emergence from General Anesthesia

Although highly stimulating intraoperatively, panendoscopy and microlaryngoscopic surgical procedures are typically characterized by low postoperative pain scores, even when the operation is prolonged.⁴³ Use of remifentanil infusions frequently allows reduction of the total dose of supplemental intravenous fentanyl to 1 to 2 µg/kg or avoidance of intraoperative use of fentanyl completely. In the recovery room, intermittent intravenous bolus doses of fentanyl in combination with oral analgesics are usually sufficient for pain control.⁴³ Remifentanil-induced hyperalgesia has not been an issue in our experience, possibly because of the short duration of most cases and the relatively low infusion rates that are typically required intraoperatively (0.1 to 0.3 µg/kg/min). If increased pain occurs postoperatively, it should raise an alert about possible surgical complications, such as esophageal perforation (see “Intraoperative and Immediately Postoperative Complications”).

Antiemetic prophylaxis should be routine,⁴³ and it is most commonly achieved by intravenous administration of a serotonin 5HT₃ receptor antagonist (e.g., ondansetron). Multimodal antiemetic prophylaxis should be employed for patients at high risk for postoperative nausea and vomiting.

If endotracheal intubation was performed, smooth, nonstimulating emergence from anesthesia constitutes one of the most challenging tasks.^1,43 Patient’s straining, bucking, or coughing with the ETT in situ results in an attempted forceful glottic closure, which may provoke additional trauma to and ulceration of the mucosal surface of the vocal cords, leading to wound formation.^140,215,216 Emergence phenomena such as a patient’s agitation and uncontrolled head movements and post-extubation laryngospasm may exacerbate the surgically compromised vocal cords further.¹⁴⁰ Subsequent vocal cord wound healing leads to remodeling of the superficial layer of the vocal cord lamina propria and the epithelium, which may result in formation of vocal cord nodules, polyps, and cysts.²¹⁵

Three strategies can facilitate smooth tracheal extubation. First, the patient’s trachea can be extubated at a deep plane of anesthesia, and the airway supported by a mask until the patient resumes spontaneous ventilation and emerges from anesthesia. Although this may be a viable approach, it is time and labor consuming, carries an increased risk of post-extubation laryngospasm, and leaves the patient’s airway unprotected. It should be undertaken only if airway management on induction was uncomplicated. The second approach (i.e., Bailey maneuver), with the patient still anesthetized, involves insertion of a supralaryngeal airway (usually an LMA) behind the existing ETT, removal of the ETT, and administration of the supraglottic ventilatory support until the patient resumes spontaneous ventilation and awakens from anesthesia.²¹⁷ With the third, pharmacologic approach, the anesthesiologist relies on a low-dose remifentanil infusion to blunt the tracheal responses and to promote smooth extubation and awakening at the end of surgery.

Remifentanil is ideally suited for the control of tracheal extubation, because the return of consciousness and the cough reflex occur almost simultaneously.¹⁷ Although the optimal dose of remifentanil required to blunt tracheal responses to extubation remains to be determined, current data indicate that a remifentanil infusion of 0.05 to 0.06 µg/kg/min (target concentration of 1.5 ng/mL) during emergence is likely sufficient; it reliably and effectively suppresses the cough reflex in awake intubated patients while promoting hemodynamic stability.^218,219

A Intraoperative Complications

Panendoscopy and microlaryngeal surgery remain very safe procedures. The mortality rate is exceedingly low (0.02% to 0.6%).^221,223 In a large, single-institution, retrospective review of 1093 endoscopic laryngeal surgery cases, Jaquet and colleagues⁸⁷ reported no intraoperative deaths, an incidence of major complications of 0.37% (all related to barotrauma during subglottic JV), and no major complications for 281 pediatric patients between the ages of less than 1 year and 16 years.

Loss of the airway on induction, requiring emergent cricothyrotomy or tracheostomy, can be sudden, especially in patients with critical airway obstruction. Proper preparation of the OR team is the key to promptly and efficiently dealing with intraoperative airway emergencies.³⁸ An overall incidence of major barotrauma complications (e.g., cervicomediastinal emphysema, pneumothorax, tension pneumothorax) is small (0.2% to 0.5%),^87,111,120 and these complications are most frequently observed during TTJV (1.1%).⁸⁷ Intraoperative bronchial or transbronchial biopsy represents an independent risk factor for intraoperative pneumothorax (about 10%).²²¹ These patients also carry a higher risk of developing pulmonary edema after transbronchial biopsy.²²¹ Although the overall incidence of cardiovascular compromise may reach 20% to 50%,^2,83,142 major cardiac and cerebrovascular complications are rarely observed (0% to 2.2%).^{86,87,111,221} Massive bleeding is rare and may be encountered in patients while coring out friable vascular tumors or during inadvertent perforation of the tracheal or bronchial wall with the laser or rigid bronchoscope.^71,213 Ensuing respiratory failure with an inability to wean the patient from the ventilator has been described.⁷¹ The rigid bronchoscope should be used by experienced operators, because improper technique frequently results in dental or oropharyngeal trauma.²¹³ Particular care must be exercised when introducing a rigid bronchoscope into the airway of patients considered at high risk for cervical spine (C-spine) dislocation during neck extension (e.g., elderly, patients with rheumatoid arthritis, those with congenital C-spine abnormalities).⁷¹ Prospective trials identify the incidence of dental trauma after suspension laryngoscopy at 0% to 6.5%,^40,224 depending on the operator’s experience, methodology of the study, dental injury criteria, preexisting dentition status of the patient, and suspension technique used.⁴⁰

Esophageal perforation is a rare event if flexible esophagoscopy is used.² A significantly higher complication rate (2.6%) was reported for rigid esophagoscopy, in which case patients with a history of head and neck cancer present a particular risk.²²⁰ Pulmonary aspiration remains a particular concern when the patient’s airway is left unprotected (e.g., JV), especially in patients at increased risk for aspiration of gastric contents. Intraoperative airway soiling may occur from aspiration of blood, secretions, surgical debris, or tumor cell contamination of the lower airway.³⁸

Minor intraoperative anesthesia-related complications happen infrequently (2.6%).⁸⁷ The incidence of minor intraoperative laryngospasm during microlaryngeal surgery has been reported by Jaquet and colleagues as 3.1%⁸⁷; it was exclusively related to the use of AIV and was associated with a light plane of anesthesia. In contrast, prospectively recorded, surgery-related minor complications are common (37.5% to 73%).^40,222 Minor surgical complications, such as sore throat, mucosal injury (e.g., cuts, edema, hematoma), and cranial nerve dysfunction (e.g., lingual, glossopharyngeal, hypoglossal), are most commonly observed.^1,40,221,222 The latter are likely caused by direct pressure or stretch injury associated with laryngoscopy or suspension of the laryngoscope,⁴⁰ and they are related to the size of the operating laryngoscope used and the duration of suspension.^1,40 Presenting symptoms in the recovery room may include dysesthesia and taste alteration, swallowing problems, and deviation of the tip of the tongue.^40,222

B Postoperative Complications

The risk of postoperative airway compromise is significantly greater among the patients who underwent diagnostic laryngoscopy and panendoscopy than those in the general surgical population.²²⁵ The residual effects of anesthetics, analgesics, and inadequately reversed NMB may further contribute to the development of hypoventilation, atelectases, and poor mobilization of secretions in the early postoperative period.³⁴ Airway surgery invariably produces a certain degree of traumatic edema, which may precipitate acute airway obstruction postoperatively in an already compromised airway.¹³ Development of airway obstruction should be suspected if the patient has symptoms such as dyspnea, respiratory distress, and particularly inspiratory stridor.³⁴ Aggressive early treatment with humidified oxygen and nebulized racemic epinephrine constitutes the first reasonable therapeutic intervention.^13,34 Postoperative laryngospasm may precede or accompany airway obstruction^226,227 and quickly lead to development of acute negative-pressure pulmonary edema.^34,226 Although the incidence of these complications in the general surgical population is small (0.3% and 0.09%, respectively),^226,228 negative-pressure pulmonary edema is preceded by laryngospasm in more than 50% of cases.²²⁷ Treatment is supportive and consists of reestablishment of airway patency, O₂ supplementation, ventilatory support (i.e., CPAP or endotracheal intubation with positive-pressure ventilation and PEEP), management of fluid shifts, and maintenance of normal intravascular volume.^34,226–228 Postoperative hemoptysis is usually associated with interventional bronchoscopy, for which the incidence may reach as high as 41%.²²¹ It is common for the suspension laryngoscopy to aggravate preexisting temporomandibular joint disease, and these patients should be advised accordingly before surgery.¹

A General Considerations

The general principles of adult airway endoscopy can be applied to infants and children, although important anatomic, physiologic, and pathologic differences in the airway exist (see Chapter 36). Some of the most common indications for flexible and rigid airway endoscopy in pediatric patients and neonates are listed in Table 38-4. Usually, examination of the entire airway, including the nasopharynx, larynx, the subglottic region, and the remaining tracheobronchial tree is indicated, because abnormalities at more than one site are found in 10% to 20% of patients.^229–231

TABLE 38-4 Indications for Flexible and Rigid Airway Endoscopy in Pediatric Patients

1 Special Considerations and Anesthesia Objectives

Some of the most commonly used general purpose (diagnostic or intubating) operating laryngoscopes are the Storz and Parsons laryngoscopes (Storz, Tuttlingen, Germany), which are available in different sizes.²⁴⁵ The Parsons laryngoscope (Fig. 38-25) can also be used for bronchoscopy, and after suspension, for some types of microlaryngeal surgery.²⁴⁵ The Benjamin-Lindholm laryngoscope (Storz) provides a more panoramic view of the larynx and facilitates access for microlaryngeal surgery.²⁴⁶ The Parsons and Benjamin-Lindholm laryngoscopes allow continuous insufflation of O₂ or anesthetic gases through a channel on the left side of the device (see Fig. 38-13). The pediatric rigid bronchoscopes manufactured by Storz are used almost universally.²²⁹ The OD of the bronchoscope typically is larger than an ETT with the same ID, and careful attention to choosing a bronchoscope with the appropriate OD is important to avoid damage to laryngeal structures.²⁴⁷

Figure 38-25 The flange of the pediatric Parsons operating laryngoscope (Storz, Tuttlingen, Germany) is open on the right side, allowing the passage of a rigid bronchoscope, if desired.

The anesthesia objectives in pediatric patients are similar to those in adults (see “Special Considerations and Anesthesia Objectives”). Because of the shared airway, communication between the surgeon and the anesthesiologist before and during the procedure is critical, and it is probably the most important factor in avoiding complications.²⁴⁸

2 Intraoperative Ventilation Techniques and Strategies

Pediatric patients undergoing upper airway endoscopy and microlaryngeal surgery frequently present with difficult airway problems. Alternative techniques for pediatric difficult airway management are addressed in Chapter 36. The approach to ventilation of the pediatric patient usually follows the one used for adults (see “Intraoperative Ventilation Techniques and Strategies for Microlaryngeal Surgery”).

3 General Anesthesia Management for Pediatric Airway Endoscopy and Microlaryngeal Surgery

4 Complications of Pediatric Airway Endoscopy

Major and minor complications of pediatric airway endoscopy largely replicate those observed in adult patients (see “Intraoperative and Immediately Postoperative Complications”).^249,267,283 No major complications were recorded with different intraoperative ventilatory techniques in more than 280 pediatric patients.⁸⁷ Intraoperatively, adverse airway events are most likely to occur with an inadequate depth of anesthesia.²⁶⁷ Interventions that seem to decrease complications are careful and effective topicalization of the airway, close observation of the child for any movement or response to initial stimulation, and immediate withdrawal of the laryngoscope or bronchoscope with patient response until an adequate depth of anesthesia is reestablished.²⁶⁷ In two large series of pediatric patients undergoing rigid bronchoscopy, the complication rate was 2% to 3%.^232,284 Stridor due to airway edema is the most commonly seen complication in the immediate postoperative period, and it should be treated with nebulized racemic epinephrine.

5 Recurrent Respiratory Papillomatosis

Recurrent respiratory papillomatosis (RRP) (Fig. 38-26) is the most common benign neoplasm of the respiratory tract in children, and it is characterized by the proliferation of exophytic squamous papillomas within the respiratory tract.^285–287 Because of the recurrent nature of the disease, most children return frequently for treatment. The average enrollee in the National Registry for Juvenile-Onset Recurrent Respiratory Papillomatosis underwent a mean of 5.1 operations annually.²⁸⁸ Repeated surgical treatment may lead to laryngeal web formation and irreversible damage to the vocal cords.^287,288

Figure 38-26 Recurrent respiratory papillomatosis.

(Courtesy of Alan Cheng, MD, Stanford University Medical Center, Stanford, CA.)

The most common symptoms of RRP are related to laryngeal obstruction and include hoarseness, abnormal cry or voice change, and stridor.^187,289 The larynx and glottis are affected in almost all cases, followed by supraglottic involvement and subglottic involvement. Distal spread to the trachea, bronchi, and lungs has been reported.^286,287 Pulmonary lesions can cause bronchiectasis, pneumonia, and declining pulmonary status.²⁸⁶

Anesthesia and airway management for patients with RRP can employ tubeless spontaneous ventilation,²⁹⁰ AIV, and JV^247,267,291; the advantages and disadvantages of each technique have been discussed (see “Intraoperative Ventilation Techniques and Strategies for Microlaryngeal Surgery”). A 2002 survey of members of the American Society of Pediatric Otolaryngology showed a preference for spontaneous ventilation or AIV (63.5%), followed by JV (24.3%) and laser-safe ETTs (9.6%),²⁸⁵ although a theoretical risk of carrying the human papillomavirus (HPV) particles into the distal airways with AIV or JV exists.^267,291 A higher incidence of apnea and laryngospasm may be observed during spontaneous ventilation in RRP patients under TIVA compared with positive-pressure ventilation through an ETT.²⁹²

Current surgical preference for debulking RRP lesions appears to favor the use of the microdebrider over the CO₂ laser,^285,286 because it shortens the operating time, eliminates the risk of a laser fire, and is associated with decreased postoperative pain.²⁹³ With microdebrider surgery, the ETT can be used for the entire procedure, although it limits the surgeon’s access to the posterior glottis.

1 Foreign Body Aspiration

Foreign body aspiration in the airway is most common in children 1 to 3 years old^289,294 and is a leading cause of accidental death in children younger than 5 years.²⁹⁵ Food products (especially nuts and seeds) are the most commonly aspirated airway foreign bodies (77% to 86%).²⁹⁶ Nuts with oils on the surface can be particularly problematic because they may stimulate a significant inflammatory response.²⁹⁷

Foreign body aspiration is suspected when a child has an acute choking event or severe coughing with respiratory distress, but in many instances, the diagnosis is delayed.^297–299 Foreign bodies in children with a delayed diagnosis may be more difficult to extract,³⁰⁰ and these children are also at higher risk for complications.^300,301 Symptoms and signs associated with bronchial aspiration include coughing, wheezing, dyspnea, and decreased breath sounds on the affected side, whereas coughing, stridor, dyspnea, and cyanosis are more common with laryngeal or tracheal foreign bodies.³⁰²

Most airway foreign bodies lodge in the bronchial tree (85% to 91%), preferentially on the right side, with the remainder catching in the larynx or trachea^233,296 (Fig. 38-27). A foreign body in the bronchus can cause a ball-valve obstruction with hyperinflation of the distal lung, and if the obstruction is complete, the distal lung collapses.²²⁹

Figure 38-27 Airway foreign bodies. A, Laryngeal foreign body. B, Foreign body (peanut) in the left main stem bronchus. C, Foreign body (tip of a pen) in the right main stem bronchus.

(A-C, Courtesy of Peter Koltai, MD, Stanford University Medical Center, Stanford, CA.)

Preoperative assessment should consider the likely position of the foreign body, the extent of airway compromise, and the urgency of the procedure. Physical examination may reveal diminished breath sounds and rhonchi on the affected side. A chest radiograph should be obtained just before surgery to confirm that the coin, for example, has not already passed into the stomach. Because many objects are radiolucent, the chest radiograph should also be reviewed for evidence of secondary changes, such as distal air trapping, infiltrates, or atelectasis.

The treatment of choice for airway foreign bodies is prompt endoscopic removal under conditions of maximal safety and minimal trauma.^297,301 Following preoperative fasting guidelines is recommended if the procedure is not an emergency.²⁹⁹ An intravenous catheter should be inserted in most cases. In an emergency situation or with a distressed infant, establishing intravenous access immediately after inhalation induction is acceptable.²⁹⁹ As with most pediatric endoscopy cases, glycopyrrolate should be administered to decrease secretions, and intravenous dexamethasone is recommended to minimize postoperative airway edema.²⁴⁷

Before induction of anesthesia, the possibility of complete airway obstruction should be anticipated. Distal airway foreign bodies are more difficult to remove, whereas proximal foreign bodies are more likely to obstruct the airway.²⁹⁹ A backup plan should include emergency rigid bronchoscopy, deliberate advancement of the foreign body into a main stem bronchus, tracheotomy, and thoracotomy in selected cases.

Induction and maintenance of anesthesia are similar to anesthesia described earlier for direct laryngoscopy and rigid bronchoscopy. The choice between maintaining spontaneous respiration and controlling ventilation remains controversial, with both techniques producing equally good results.^289,299,303 For airway foreign bodies, pediatric anesthesiologists seem to prefer maintenance of spontaneous ventilation,³⁰⁴ because positive pressure can force the foreign body deeper into the smaller airways.^299,303 For the esophageal foreign bodies, controlled ventilation with an ETT is the preferred technique.³⁰⁴

When the airway foreign body is too large to withdraw through the lumen of the bronchoscope, the bronchoscope, forceps, and foreign body are removed as a single unit.^289,294 If the foreign body is dropped in the proximal airway and cannot be immediately retrieved, it should be pushed distally into the bronchus. If the foreign body is pushed into the contralateral bronchus, there is a potential for complete obstruction from edema in the original bronchus.³⁰⁵ The FFB can be preferentially used when the foreign body is lodged far into the periphery of the lung.²⁹⁷

Esophageal foreign bodies (usually coins) are considered less serious than airway foreign bodies, and most pass through the gastrointestinal tract harmlessly.^306–308 For asymptomatic esophageal coins, an observation period of 8 to 16 hours is considered appropriate³⁰⁹; batteries and magnets are exceptions and should be removed expeditiously.^310,311 Esophageal foreign bodies most commonly lodge at the level of the cricopharyngeal muscle,²⁹⁴ and foreign body impaction is most frequently associated with vomiting, gagging, odynophagia, dysphagia, poor feeding, and excessive salivation.³⁰⁸ A large esophageal foreign body may cause symptoms of airway obstruction by compression or irritation of the upper airway, necessitating emergent intervention.³⁰¹

2 Complications of Endoscopy for Foreign Body Removal