The anatomic structures of the head and neck and their relationships are complex (Figure 38-1). The sensory and motor supply of the upper airway originates from cranial nerves and includes the trigeminal, glossopharyngeal, facial, and vagus nerves. Understanding the sensory supply is required to provide sufficient local and regional anesthesia. Likewise, motor function evaluated during and after surgical procedures may indicate trauma or damage to muscles. A thorough knowledge of which nerves control muscle function is essential to preventing such trauma.

FIGURE 38-1 Anatomy of nasal cavity, oral cavity, nasopharynx, oropharynx, and hypopharynx. (From RD Miller, et al. Miller’s Anesthesia. 7th ed. Philadelphia: Churchill Livingstone; 2010:2358.)

The relationships of the oropharynx, nasopharynx, nasal chambers, sinuses, esophagus, and lower airway structures such as the larynx, cricoid, thyroid, and vocal cords provide a basis for directing and providing care for the patient receiving ENT surgery. The nose is a major anatomic structure that is responsible for warming, filtering, and providing humidity to the air taken in during inspiration. The structures of the nose include the external nose, the nasal cavity, and frontal, maxillary, and ethmoid sinuses. The nares or nostrils are separated by the septum. The lateral margins of the nares are cartilaginous structures and extend posteriorly over the hard palate, leading to a confluence at the soft palate, oropharynx, and base of the tongue. The oropharynx rests superior to the epiglottis, vocal cords, larynx, and trachea.

The external nose is composed largely of cartilage supported primarily by soft connective tissue and delicate mucous membranes, as is the nasal septum. The nasal cavities are hollow structures formed by a floor, roof, lateral wall, and the septum. The lateral aspects of the nasal cavities contain concha, or turbinates. The turbinates are highly vascular and are divided into three separate compartments: the superior, middle, and inferior. The turbinates greatly increase the surface area of the nasal cavities, aiding in filtration and humidification of inspired gases.

The extensive vascular supply of the turbinates may lead to severe bleeding if the nasal airway or nasoendotracheal tube is not inserted along the superior margin of the hard palate. Congestion of the mucosal veins in the turbinates of the nose causes swelling of these tissues, reducing the size of the nasal cavity (most notably, the paranasal sinuses) and thus creating the feeling of “congestion” during respiration. Inadvertent palatine submucosal insertion of the nasoendotracheal tube can lead to severe bleeding or infection in the perioperative period if entry of the tube is forced or tissues are engorged. These paired sinuses include the sphenoid, ethmoid, frontal, and maxillary sinuses. They not only serve as resonators for the voice but also filter, humidify, and warm the air during inspiration. These hollow structures are formed of low-density bone and are lined with a thin layer of mucous membranes, reducing the weight of the skull but making these bones more susceptible to fractures and cerebral spinal fluid leak secondary to facial trauma.1–3

The pharynx is composed of the terminal end of the nasopharynx, the oropharynx, and laryngopharynx or hypopharynx extending to the sixth cervical vertebra. The medulla inhibits respiration with swallowing; the pharynx then serves as a muscular tube that constricts, allowing the passage of food. The pharynx allows the smooth passage of air and functions as a modulator for the voice. The nasopharynx is continuous with the internal nasal cavities and extends to the soft palate. The nasopharynx communicates with the oropharynx and forms the posterior aspect of the throat. Major structures of the oropharynx include the base of the tongue, soft palate, uvula, and lymphatic structures (tonsils). The tonsils are the most sensitive areas of the oropharynx. Beginning with the anterior margin and progressing bilaterally and posteriorly, the oropharynx is defined by the soft palate, base of the tongue, uvula, palatine tonsils, and adenoids, forming Waldeyer’s ring.1–3

Hypertrophy of the palatine and adenoid tonsils (exaggerated many times by chronic infection) and of the soft palate and uvula can pose serious airway compromise, particularly in young children. The generous blood supply to the tonsils from branches of the external carotid, maxillary, and facial arteries and their close proximity to the facial and internal arteries are matters of concern regarding potential bleeding during “routine and simple” tonsillectomy. The laryngopharynx includes the epiglottis, which provides protection for the vocal cords, and is the region shared by the esophageal orifice and larynx.

The complexity of the neuromuscular system, which controls the epiglottis, allows the isolation of the trachea from the esophagus during swallowing. Any interruption of this coordinated neuromuscular function of the epiglottis or of any other protective reflexes can provide a dangerous opportunity for the entrance of food or liquid into the larynx and lower airway. As food is squeezed posteriorly, an automatic swallowing reflex is initiated. The larynx is pulled superiorly, allowing the epiglottis to cover and protect the opening of the larynx.¹ The epiglottis does not operate as a movable lidlike structure that falls to close the larynx during swallowing, as is often claimed. Passage of food into the trachea can occur if the muscles and protective elevation of the larynx become rigid or are changed due to nerve interruption. A series of reflex and involuntary processes mediated by the superior laryngeal, recurrent laryngeal, and glossopharyngeal nerves coordinates and regulates glottic closure during swallowing.^1–3

The larynx is a rigid organ composed of three paired and three unpaired cartilages (arytenoid, corniculate, and cuneiform and thyroid, cricoid, and epiglottis, respectively) and is supported by the hyoid bone. This hollow structure forms a reservoir distal to Waldeyer’s ring and provides the connection of the oropharynx to the trachea (Figure 38-2). The primary functions of the larynx are vocalization and articulation; secondarily, it provides protection of the airway and allows respiration.¹ In the adult, the area of the vocal cords, or rima glottis, is the narrowest portion of the larynx. In children, the cricoid ring is the narrowest portion of the airway until approximately 10 years of age. Cuffed tubes are then generally recommended for those older than 8 to 10 years of age to allow for a better seal of the airway, prevent subglottic edema, and reduce the incidence of postoperative airway compromise.⁴

FIGURE 38-2 Laryngeal cartilages. Some softer tissues of the larynx and surrounding structures have been removed to make it possible to see the cartilages of the larynx. Note the position of the nearby thyroid gland. A, Anterior view. B, Posterior view. (From Patton KT, Thibodeau GA. Anatomy & Physiology. 8th ed. St. Louis: Mosby; 2013:804.)

Specific nervous structures of the head and neck are worthy of note because of their superficial location or proximity to operative sites. Surgeons may use audible or visual nerve-locating devices to find these nerves and their appropriate branches. To accurately locate these nerves, neuromuscular blocking agents may be avoided during the maintenance of certain general anesthetics.

The facial nerve (VII) has six major branches: four anterior (temporal, zygomatic, buccal, and mandibular), one inferior (cervical), and one posterior (posterior auricular) branch. The facial nerve located at the tragus of the ear is the motor and sensory supply to the muscles for facial expressions. The zygomatic branch leaves the skull via the stylomastoid foramen and advances anteriorly over the maxilla. The corda tympani branch of the facial nerve conveys taste from the anterior two thirds of the tongue, and the more superficial tri-branched facial nerve controls facial expression. The trigeminal nerve begins at the gasserian ganglion and divides into three branches; they are the ophthalmic (the first division, V₁), maxillary (the second division, V₂), and mandibular (the third division, V₃). All three divisions provide sensory and motor innervation to the nose, sinuses, palate, and tongue. They aid in the motor control of the face and in mastication.1–3

The glossopharyngeal nerve provides motor and sensory innervation for the base of the tongue and nasopharynx and oropharynx. The glossopharyngeal nerve is responsible for eliciting the gag reflex during instrumentation of the posterior pharynx and vallecula.

The superior laryngeal and recurrent laryngeal nerves are both branches of the vagus (X). The superior laryngeal nerve descends to the hyoid bone and then branches into the internal laryngeal nerve, which passes through the thyrohyoid membrane, and the exterior laryngeal nerve, which descends over the lateral thyroid cartilage to the distal trachea. The recurrent laryngeal nerve ascends from the vagus up the distal trachea, passing through the cricothyroid ligament into the proximal trachea and vocal cords. The recurrent laryngeal nerve lies between the trachea and esophagus and supplies sensory innervation to the trachea and vocal cords. This branch of the vagus nerve also affects vocal cord closure and sensory function up to the inferior aspect of the epiglottis. Stimulation of the epiglottis with the tip of a straight laryngoscope, blades, suction catheters, and placement of an endotracheal tube in the trachea can produce a vagal response.³ The paired and unpaired cartilages of the larynx are listed in Table 38-1. Nerve supply to the larynx is given in Table 38-2. The intrinsic muscles of the larynx, their nerve supply, and function are listed in Table 38-3. The extrinsic muscles of the larynx, their nerve supply, and function are listed in Table 38-4.^1–5

TABLE 38-1

Paired and Unpaired Cartilages of the Larynx

Paired	Unpaired
Arytenoid	Thyroid
Corniculate	Cricoid
Cuneiform	Epiglottis

TABLE 38-2

Nerve Supply of the Larynx

TABLE 38-3

Intrinsic Muscles of the Larynx

Muscle	Innervation	Function
Cricothyroid	Superior laryngeal nerve	Tension and elongates vocal cords
Thyroarytenoid	Recurrent laryngeal nerve	Relaxes vocal cords
Vocalis	Recurrent laryngeal nerve	Relaxes vocal cords
Posterior cricoarytenoid	Recurrent laryngeal nerve	Abducts vocal cords
Lateral cricoarytenoid	Recurrent laryngeal nerve	Adducts vocal cords
Transverse arytenoid	Recurrent laryngeal nerve	Adducts vocal cords
Aryepiglottic	Recurrent laryngeal nerve	Closes glottis
Oblique arytenoid	Recurrent laryngeal nerve	Closes glottis; approximates folds

TABLE 38-4

Extrinsic Muscles of the Larynx

Muscle	Innervation	Function
Sternohyoid	Cervical plexus; C1, C2, C3	Draws hyoid bone inferiorly
Sternothyroid	Cervical plexus; C1, C2, C3	Draws thyroid cartilage caudad
Thyrohyoid	Cervical plexus; hypoglossal nerve; C1 and C2	Pulls hyoid bone inferiorly
Thyroepiglottic	Recurrent laryngeal nerve	Inversion of aryepiglottic fold
Stylopharyngeus	Glossopharyngeal	Folds thyroid cartilage
Inferior pharyngeal constrictor	Pharyngeal plexus; vagus	Aids swallowing

Preparation and Considerations for Ear, Nose, and Throat Procedures

The Shared Airway and Considerations for Positioning

Operative procedures involving the airway, mouth, or bony structures of the face involve a true sharing of the airway between the surgeon and the anesthetist. Therefore, proper preparation requires planning and communication between the surgeon, surgical personnel, and the anesthetist prior to the surgical procedure. Sharing the airway with the surgeon also requires preparing and planning the use of the appropriate equipment. For example, during laryngoscopy the endotracheal tube may have to be smaller in diameter and moved to one side of the oropharynx to allow the surgeon to work around the tube and to facilitate the surgery. Many times the head of the table is rotated 90 to 180 degrees away from the anesthetist, resulting in a vulnerable airway to which the anesthetist may have little or no access. Of particular concern are the maintenance of adequate ventilation and patency of the anesthesia circuit and endotracheal tube. Extubation, disconnects, and leaks must be prevented. Adequacy of ventilation is constantly assessed by observing chest movement, auscultation, pulse oximetry, end-tidal CO₂, and blood gas analysis. A sudden loss of breath sounds, rising inspiratory pressures, or a reduction in end-tidal CO₂, particularly in the presence of a sharp reduction in inspiratory effort, may be due to a deflation of the endotracheal tube cuff, obstruction of the endotracheal tube, dislodgment of the endotracheal tube, a disconnection of the anesthesia circuit, or severing of the endotracheal tube during surgical dissection.⁵ When coupled with vigilance, the precordial or esophageal stethoscopes are simple devices that should not be overlooked; these devices, in addition to more sophisticated mechanical devices, help the anesthetist maintain assessment of the airway.

Assessment of the airway prior to induction is critical in most ENT patients. Although the induction of anesthesia and securing of the airway are performed in the usual manner (with the anesthetist at the head of the table), the management of the airway can become questionable and difficult while at a distance. Obtaining a thorough history and performing an extensive evaluation of the airway for the ENT patient is crucial. A good examination of the airway will (1) allow for a careful and deliberate approach to airway management, (2) aid in evaluating the need for additional equipment and assistance, and (3) include alternative approaches for the difficult airway if the initial plan proves not to be successful. Once the induction is complete and the airway established, the anesthetist must be prepared to provide adequate ventilation, deliver necessary anesthetic and adjunct agents, place invasive lines, and safely monitor the patient while remaining at a distance and isolated from the airway.

Orchestrating how the patient is turned so that the patient’s head is away from the anesthetist demands clear planning. The endotracheal tube should be secured with tape or suture to prevent removal. The invasive line tubing, intravenous access lines, monitoring devices, and breathing circuit require added length to extend to the patient without creating tension at the site before induction. The patient’s entire head is frequently draped and prepped into the surgical field, limiting access to the endotracheal tube and breathing circuit connections (Figure 38-3).

FIGURE 38-3 Illustration of secured airway for a patient undergoing face, neck, or maxillofacial surgical procedures. Note that the tube is positioned to prevent pressure on the lip, nose, or forehead and secured with tape to prevent movement during surgery. The connection is covered by sterile surgical drapes and allows only limited access during the surgical procedure.

When repositioning of the head is necessary, communication between the surgeon and anesthetist is important to reduce the possibility of extubation, position change, or occlusion of the endotracheal tube. Signs of air leaks around the endotracheal tube (e.g., bubbling, the sound of air escaping, or the smell of anesthetic agent from the patient’s mouth) may well be more sensitive indicators than mechanical airway monitors. Occlusion of the endotracheal tube is best prevented but can be determined by good auscultation, watching chest wall motion, and monitoring inspiratory pressures and morphology of CO₂ waveforms. The surgeon must communicate any changes in the surgical field, such as changing the position of a suspended or fixed laryngoscope, dark blood, manipulation of carotid bodies, or the need for a change in the patient’s head position.⁶ Increased inspiratory pressures or a rapid loss of inspiratory pressure, decreased oxygen saturation, changes in end-tidal CO₂ measurements, or diminished breath sounds should, in turn, be communicated to the surgeon so that inspection of the airway and anesthesia circuit may be undertaken. If unable to arrive at a cause, undraping the patient may become necessary for a thorough examination of tube placement and connections or to find a leak in the anesthesia circuit that could compromise patient ventilation.

Procedures of the head and neck typically require access to all planes of the head by several members of the surgical team.⁷ Because a number of problems can be encountered with the intubated patient during the surgical procedure, the surgeon may elect to perform a tracheostomy, then place and suture a flexible endotracheal tube in a fixed position during the procedure. A heightened state of vigilance must be maintained for occlusions from mucous plugs or blood, disconnects, endotracheal tube fires, and other problems that may arise during the anesthetic. During some ENT procedures, the surgical team also may need access to the chest and abdomen for securing grafts for the esophagus or oral cavity. Often this requires the anesthetist to take residence at either the side of the patient or at the foot of the operating table (Figure 38-4). Providing a smooth transition with protection of the established airway and prevention of hypoxia are the primary concerns during movement of an operating table with an anesthetized patient.

FIGURE 38-4 Position of the anesthetist for surgery of the head and neck. Left, The anesthetist is positioned at the side of the table and using a standard circle circuit. Right, The anesthetist is positioned at the foot of the bed and using a coaxial (Bain) circuit. ESU, Electrosurgical unit. (From Phillips N. Berry & Kohn’s Operating Room Technique. 12th ed. St Louis: Mosby; 2013:873.)

The anesthesia circuit and other monitors should be temporarily and briefly disconnected before the bed is turned. This will prevent undue tension on the circuit and other lines that could lead to traumatic extubation or loss of access. Ventilation of the patient with 100% oxygen and adequate tidal volumes for 3 to 5 minutes before disconnection will denitrogenate the functional residual volume and provide an extra reservoir of oxygen during the turn, preventing even a short period of hypoxia. However, if a volatile agent is the primary source of anesthesia, the addition of intravenous anesthesia during this preoxygenation is necessary to maintain an adequate level of anesthesia and/or amnesia during this period. A saturation of 100% is a reasonable goal before the disconnection and table movement.

The degree of table movement should be discussed with the surgeon before any interruption in the anesthesia or the breathing circuit takes place. Turning of the operating table should be a well-organized procedure, understood by all members of the surgical team, and one that takes the minimum amount of time. After relocking the bed, reconnection of the anesthesia circuit must be immediate to reestablish oxygenation and/or anesthesia. Reevaluation and assessment of the tube placement, breath sounds, chest expansion, oxygen saturation, anesthetic level, line and intravenous access, and end-tidal CO₂ should be performed before prepping and draping is begun and throughout the case. Once adequate ventilation is established, the use of an “artificial nose” or airway humidifier will help in preserving heat and moisture during long periods of anesthesia.

Attention to simple practical points may prevent airway mishaps. At least one large-bore intravenous line, as well as arterial and central venous pressure lines, should be started on the nonoperative side, if possible on the side of the patient that will be nearest to the anesthetist during the procedure. This will prevent obstruction of flow due to the surgical procedure, afford easier access for drug administration and blood sampling, facilitate the manipulation or maintenance of lines during surgery, and allow the surgeon easy access to the operative field. If such lines must be placed on extremities opposite the anesthetist, adequate extensions should be placed before a change in position of the table to reduce the chance of lines being removed, infiltrated, or disconnected during movement. The calf of the leg may be used for noninvasive blood pressure measurements to prevent dampening of intravenous fluid flows in the upper extremities. Care must be taken to ensure that the measurement of the blood pressure takes into account variations in table changes from the horizontal position to prevent hypotension to vital organs. Monitoring of neuromuscular relaxation may be performed at locations other than the adductor pollicis. Stimulation of the tibial nerve produces flexion of the big toe and is similar to that of the adductor pollicis.⁸ Because ENT procedures may take more than 2 hours and can require significant fluid administration, monitoring urinary output with a Foley catheter may be included in the plan.

Specialized Equipment for Ear, Nose, and Throat Procedures

Endotracheal Tubes Designed for ENT Surgery

A number of endotracheal tubes are available for securing an airway. Standard endotracheal tubes equipped with flexible or straight connectors are acceptable for many ENT procedures. The diameter and length of the endotracheal tube (ETT) will affect ventilation and seal of the airway. Using a small-diameter ETT in a large adult airway will not only lead to less ventilation through increased resistance but also will allow only a small portion of the cuff to contact the trachea. Using specialized tubes with small diameters allows more even distribution of the cuff over the trachea during inflation. Several of these specially designed ETTs have found wide acceptance in ENT anesthesia. A variety of designs are used to limit encroachment of the ETT into the surgical field, prevent kinking of the ETT when severe angles are necessary, prevent fires in the airway during laser therapy, and provide maximal patient ventilation and safety.⁹

A number of ETTs have been introduced for use in ENT anesthesia. The purpose for the evolution of these various types of ETT cuffs was to reduce cuff pressure on the tracheal wall and allow for improved tracheal perfusion, reduced tracheal injury, and more convenient airway access. Preformed right-angled ETTs, in cuffed and noncuffed types, are available for either oral or nasal intubation of adults or children. Oral Ring, Adair, and RAE tubes (named after inventors Ring, Adair, and Elwyn) are an excellent choice for cleft palate repair, tonsillectomy, uvulopalatopharyngoplasty, and procedures of the eye or upper face. Nasal RAE tubes are particularly well suited to maxillofacial surgery that does not allow for oral intubation. The nasal RAE can be used for cosmetic procedures of the face, surgical procedures of the oral cavity and mandible, or to correct malocclusion. However, although the preformed bend in the RAE tube prevents the ETT from kinking in many instances, it may be too distal or proximal for an individual patient’s airways. This then allows the tip of the ETT to rest well below or above the carina. A careful check of the breath sounds and inspiratory pressures is imperative after intubation with the RAE to ensure proper positioning. Nasal intubation and placement of a nasogastric tube in the unconscious patient with facial trauma is best avoided to prevent possible penetration of the brain.10,11

Anode, armored, reinforced, and Kant Kink tubes all have an embedded coiled wire or plastic coil strand to produce a tube with greater flexibility and memory. Armored tubes for oral or nasal intubation resist kinking and retain their original integrity. They are useful when acute neck flexion or severe angles of the ETT are required, as in procedures involving the base of the skull or posterior aspect of the neck. However, several reports suggest that even the edentulous patient can on occasion occlude a reinforced ETT.¹² Several varieties of metal-impregnated tubes are available for use with laser surgery; these are designed to reduce the occurrence of an airway fire (Figures 38-5 and 38-6). The cuff of the laser tube is usually filled with saline to dampen or prevent the ignition. In addition, it is recommended that the cuff be filled with dyed saline so that a cuff perforation is readily apparent. Wrapping a standard ETT with reflective tape is not an adequate alternative to these commercially prepared tubes because the wrapped standard ETT will dry and lead to greater flammablility.¹³

FIGURE 38-5 Endotracheal tubes for laser surgery of the airway.

FIGURE 38-6 The Laser Flex endotracheal tube comes with a double cuff or no cuff. The double cuff is typically filled with normal saline. (Courtesy of Mallinckrodt Inc.)

Although not classified as an endotracheal tube, the laryngeal mask airway (LMA) and intubating laryngeal mask airway may be used to facilitate intubations as well as control the airway. The LMA does not produce tracheal stimulation, which can be a considerable advantage in ENT procedures. The incidence of coughing on emergence is lower with the LMA than with the endotracheal tube. Another advantage of the LMA is the ability to insert the device without the use of neuromuscular blocking agents or for airway rescue situations. Although LMA is contraindicated in some patients with laryngeal pathology, it is often the airway of choice when dealing with patients with pharyngeal pathology. Indications for LMA use in ENT surgery include a conduit for surgical access to the glottis and trachea, an aid to neurologic monitoring to avoid relaxant use, and as a means to isolate the glottis from bleeding from pharyngeal sources.¹⁴

Special Considerations for Ear, Nose, and Throat Procedures

Pharmacologic Considerations

The use of local anesthetics is particularly prevalent during nasal and sinus surgery. The most commonly used local anesthetics for ENT surgery include the amide-based drugs. Many procedures are performed using topical and local anesthesia as the sole agent, in combination or supplemented with monitored anesthesia care, intravenous sedation, or general anesthesia. Table 38-5 gives some topical local anesthetics commonly used in ENT surgery. Determination of doses of local anesthetics administered by injection and topically must be carefully calculated because more than one agent in various combinations are commonly used.

TABLE 38-5

Topical Anesthetic Drugs

Additional information regarding local anesthetics for injection and topical use can be found in Tables 10-7, 10-8, and 10-9.

Vasoactive Drugs

The duration of action of a local anesthetic is proportional to the time the drug is in contact with nerve fibers. For this reason, epinephrine in varying concentrations (1:200,000 or 5 mcg/mL; 1:100,000 or 10 mcg/mL; and 1:50,000 or 20 mcg/mL) may be added to local anesthetic solutions to produce vasoconstriction. Vasoconstriction limits systemic absorption and maintains a higher drug concentration in the vicinity of the nerve fibers to be anesthetized, thus extending the effects of the local anesthetic. Addition of epinephrine to a local anesthetic prolongs the duration of blockade and decreases systemic absorption and plasma concentrations, thus decreasing toxicity.¹⁵

It is estimated that in the United States, topical cocaine (4% to 10% solution) anesthesia is used in more than 50% of ENT procedures performed annually—specifically rhinolaryngology procedures.¹⁶ Cocaine is a naturally occurring ester of benzoic acid that is hydrolyzed by plasma cholinesterase. Applied topically, it is an excellent local anesthetic and vasoconstrictor. The duration of action is approximately 45 minutes.¹⁵ Cocaine produces vasoconstriction by blocking catecholamine reuptake into the adrenergic nerve ending, resulting in vasoconstriction and shrinking of the mucosa. Epinephrine is also injected for ENT procedures and is usually injected shortly after the application of cocaine. This combination of cocaine and epinephrine sets the stage for a significant interaction. Because cocaine that is absorbed into the plasma can block the uptake of epinephrine systemically, a toxic effect of epinephrine can result from the injection. This interaction can result in severe headaches, hypertension, tachycardia, and dysrhythmias.¹⁷

Anticholinergics

Anticholinergics were used liberally in the early days of anesthesia, predominantly because of the excessive secretions caused by older volatile inhalation agents. With the advent of newer anesthetic agents, excessive secretions are not an issue and the need for anticholinergics has diminished. The antisialagogue effects, however, may still be useful in certain intraoral procedures that require a drier operative field. Glycopyrrolate may be a better choice than atropine because it produces less tachycardia in comparison to atropine. Glycopyrrolate does not readily cross the blood-brain barrier and thus lacks sedative effects.

Corticosteroids

Glucocorticoids may be administered preoperatively and intraoperatively to decrease laryngeal edema formation, reduce nausea and vomiting, and prolong the analgesic effects of local anesthetics. They should be administered as early as possible in the perioperative period so as to reach their peak effect prior to initiating surgery. The use of steroids may reduce the nausea and vomiting experienced after surgery. Dexamethasone was also reported to prolong the analgesic effects of local anesthetics.¹⁸ It has been postulated that prostaglandins, histamine, and other mediators increase the permeability of local vessels, changing nociception at the site of trauma and leading to the sensation of pain. Steroids inhibit the production of prostaglandins and therefore reduce pain. Although the use of steroids may be beneficial, they can also create sufficient immunosuppression to mask inflammation or infection.

Postoperative Nausea and Vomiting

All patients are at risk for postoperative nausea and vomiting (PONV). ENT procedures, particularly of the middle ear, are associated with a high incidence of PONV.¹⁹ Patients experiencing PONV are uncomfortable after surgery, their discharge may be delayed from the postanesthesia care unit (PACU), or they may have an unscheduled hospital admission. The accumulation of blood in the posterior oropharynx, which may drain into the stomach or be swallowed during the postoperative period, can lead to PONV. This frequently occurs during throat procedures such as tonsillectomy. Packing the back of the throat with surgical packs during the procedure can prevent some drainage into the stomach. Care must be taken that the patient is awake, all surgical packs are removed, and suctioning of the airway precedes the extubation process, producing a clear airway and ensuring the control of protective airway reflexes. A multimodal approach is advocated to attenuate PONV in ENT patients.^20,21

Special Anesthetic Techniques Associated with ENT Procedures

Deliberate Controlled Hypotension

Extensive dissection is required for many head and neck tumors, with operative times extending to 12 or more hours. Considerable fluid replacement, blood loss, electrolyte imbalances, and cardiovascular and respiratory changes may occur during surgery. The surgeon may request deliberate controlled hypotension to reduce blood loss. Patients must be individually evaluated prior to controlled hypotension to determine a safe mean pressure. The effects of common intravenous controlled hypotensive techniques are compared in Table 38-6.^22,23 The practice of controlled hypotension focuses on reducing the mean arterial pressure to some predetermined level related to the limits of cerebral and systemic autoregulation. The mean pressure is not usually allowed to fall below 60 mmHg, maintaining cerebral and renal autoregulation, as well as adequate coronary artery blood flow. Patients with chronic hypertension may require a higher mean pressure to maintain adequate perfusion.²³ Regardless of the technique or medication chosen, it is imperative that urine output, mean arterial blood pressure, cerebral and cardiac perfusion pressure, and arterial blood gases be closely monitored and maintained. When using hypotensive anesthesia, an arterial line is required. Hypotensive techniques are also used with endoscopic sinus surgery. It has been noted that better operating conditions are achieved when moderate hypotension is produced with a vasoconstrictor such as a beta blocker than when vasodilating agents are used.²⁴

TABLE 38-6

Common Intravenous Agents for Hypotensive Techniques

Drug and Dosage	Advantages	Disadvantages
Sodium nitroprusside Variable age- and anesthetic-dependent effects Young adults: 1-5 mcg/kg/min Children: 6-8 mcg/kg/min	Potent; reliable; rapid onset and recovery; cardiac output well preserved	Reflex tachycardia; rebound hypertension; pulmonary shunting; cyanide toxicity possible
Esmolol 200 mcg/kg/min to achieve 15% reduction of mean arterial pressure	Particularly useful to control tachycardia	Potential for significant cardiac depression
Nitroglycerin Adults: 125-500 mcg/kg/min Children: 10 mcg/kg/min	Preserves myocardial blood flow; reduces preload; preserves tissue oxygenation	Increases intracranial pressure; highly variable dosage requirements
Nicardipine 5 mcg/kg/min	Ca⁺⁺ channel blocker Preserves cerebral blood flow
Remifentanil with propofol Remifentanil: 1 mcg/kg IV then continuous infusion 0.25-0.5 mcg/kg/min Propofol: 2.5 mg/kg IV then infusion of 50-100 mcg/kg/min	Remifentanil reduces middle ear blood flow, creating a dry surgical field for tympanoplasty Propofol may help reduce PONV	No analgesic effect once remifentanil infusion discontinued

PONV, Postoperative nausea and vomiting.

Modified from DeGoute CS. Controlled hypotension: a guide to drug choice. Drugs. 2007; 67(7):1053-1076.

Select Techniques Commonly Used in Ent Procedures

Laser Surgery

Anesthesia and laser surgery is also discussed in Chapter 43; however, some specific issues concerning lasers are relevant to ENT surgery. Laser technology has been used in medicine for more than 30 years. The two most common lasers used in ENT surgery are the CO₂ and Nd:YAG (neodymium-doped yttrium aluminum garnet); recently the argon laser has become a popular choice as well.²⁵ Laser light is different from standard light. Whereas standard light has a variety of wavelengths, lasers have only one wavelength (monochromatic). Laser light oscillates in the same phase, or all the photons are moving in the same direction (coherent), and its beam is parallel (collimated). The wavelength of the Nd:YAG laser beam is shorter as it passes through the garnet than that of the CO₂ laser. The shorter wavelength allows less absorption by water and therefore less tissue penetration. For example, the shorter wavelength of the Nd:YAG allows the laser light to pass through the cornea, whereas the longer wavelength of the CO₂ laser would burn the cornea. Laser light emits a small amount of radiation and can be infrared, visible, and ultraviolet in the spectrum. Lasers enable very precise excision, produce minimal edema and bleeding, and are favored by surgeons for resection of tumors and other obstructions of the airway. For operations in and around the larynx, the CO₂ laser is frequently used because of its shallow depth of burn and extreme precision.¹³ The CO₂ laser produces a beam with a relatively long wavelength that is absorbed almost entirely by the surface of these tissues, vaporizing cellular water. Intermittent bursts of the CO₂ laser produce intense, precisely directed energy that results in a clean cut through the target tissue with a minimal amount of penetration of surrounding tissue. A low-energy helium-neon laser is commonly used to aim or direct CO₂ laser beams.

The holmium:yttrium-aluminum-garnet (Ho:YAG) laser is a fairly new laser. The Ho:YAG laser has a pulsed infrared output with a wavelength of 2.1 mm. The laser has excellent absorption in water-rich tissues, and in otolaryngology, it has been used for nasal surgeries and for tonsillectomies.

Laser light beams are primarily used for their thermal effect and can be used to cut, coagulate, or vaporize tissues. The exact tissue interaction of a laser is dependent on several variables, including the types of tissues being irradiated, the wavelength of the emitted beam, and the power of the beam.

The majority of surgical fires occur during head and neck surgery. This is due to the presence of oxygen and the extensive use of lasers. The use of laser technology mandates taking measures to ensure the safety of the patient and operating room personnel (Box 38-2). Specific concerns include eye protection with appropriate colored glasses, avoidance of the dispersion of noxious fumes, and fire prevention. Stray or reflected beams of the Nd:YAG laser are capable of traversing the eye to the retina; therefore, green-lensed eye protection for all personnel is mandatory during use of the Nd:YAG laser. All persons in the operating room must wear goggles specifically designed to absorb Nd:YAG laser beams. The required protective eyewear for CO₂ lasers can be any clear glass or plastic that surrounds the face. Orange-red eye protection is required for the potassium-titanyl phosphate (KTP) laser, and orange glasses are required for the argon laser.

BOX 38-2 General Safety Protocol for Surgical Lasers