Chapter 37: Anesthesia for Otolaryngology–Head & Neck Surgery

Cooperation and communication between surgeon and anesthesia provider are critical elements of all surgery within or adjacent to the airway. Establishing, maintaining, and protecting an airway in the face of abnormal anatomy and simultaneous surgical intervention are demanding tasks. An understanding of airway anatomy (see Chapter 19) and an appreciation of common otorhinolaryngologic and maxillofacial procedures are invaluable in handling these anesthetic challenges.

Endoscopy includes laryngoscopy (diagnostic and operative) and microlaryngoscopy (laryngoscopy aided by an operating microscope) for conditions including vocal cord cysts and polyps and upper airway papillomatosis and malignancy, esophagoscopy, and bronchoscopy (discussed in Chapter 25). Endoscopic procedures may be accompanied by laser surgery.

Preoperative Considerations

Patients presenting for endoscopic surgery are often being evaluated for voice disorders (often presenting as hoarseness), stridor, or hemoptysis. Possible diagnoses include foreign body aspiration, trauma to the aerodigestive tract, papillomas, tracheal stenosis, tumors, or vocal cord dysfunction. Thus, a preoperative medical history and physical examination, with particular attention to potential airway problems, must precede any decisions regarding the anesthetic plan. In some patients, flow–volume loop (see Chapter 6), radiographic, computed tomography, ultrasound, or magnetic resonance imaging studies may be available for review. Many patients will have undergone preoperative indirect laryngoscopy or fiberoptic nasopharyngoscopy, and the information gained from these procedures may be of critical importance.

Important initial questions that must be answered are whether adequate positive-pressure ventilation via face or laryngeal mask is feasible, and whether the patient can be intubated using conventional direct or video laryngoscopy. If the answer to either question is “no,” the patient’s airway should be secured prior to induction using an alternative technique such as fiberoptic bronchoscope or tracheostomy under local anesthesia (see Case Discussion, Chapter 19). However, even the initial securing of an airway with tracheostomy does not prevent intraoperative airway obstruction due to surgical manipulation, a foreign body, or hemorrhage.

Sedative premedication should be avoided in a patient with threatening upper airway obstruction. Glycopyrrolate (0.2–0.3 mg) works more effectively and persistently when given intramuscularly rather than intravenously 1 h before surgery and may prove helpful by minimizing secretions, thereby facilitating airway visualization.

Intraoperative Management

The anesthetic goals for laryngeal endoscopy include an immobile surgical field and adequate masseter muscle relaxation for introduction of the suspension laryngoscope (typically profound muscle paralysis will be sought), adequate oxygenation and ventilation, and cardiovascular stability despite rapidly varying levels of surgical stimulation.

A. Muscle Relaxation

Intraoperative muscle relaxation can be achieved by intermittent boluses or infusion of intermediate-duration nondepolarizing neuromuscular blocking agents (NMBs) (eg, rocuronium, vecuronium, cisatracurium), or with a succinylcholine infusion. Rapid recovery is important, as endoscopy is often an outpatient procedure. Given that profound muscle relaxation is often needed until the very end of the operative procedure, endoscopy remains one of the few remaining indications for succinylcholine infusions. Use of sugammadex (Bridion) to reverse profound degrees of rocuronium or vecuronium neuromuscular blockade is an alternative approach.

B. Oxygenation & Ventilation

Several methods have successfully been used to provide oxygenation and ventilation during endoscopy, while simultaneously minimizing interference with the operative procedure. Most commonly, the patient is intubated with a small-diameter endotracheal tube through which conventional positive-pressure ventilation is administered. Standard endotracheal tubes of smaller diameters, however, are designed for pediatric patients, and therefore are too short for the adult trachea and have a low-volume cuff that will exert increased pressure against the tracheal mucosa. A 4.0-, 5.0-, or 6.0-mm specialized microlaryngeal endotracheal tube (Mallinckrodt MLT) is the same length as an adult tube, has a disproportionately large high-volume low-pressure cuff, and is stiffer and less prone to compression than is a conventional endotracheal tube of the same diameter. The advantages of intubation in endoscopy include protection against aspiration and the ability to administer inhalational anesthetics and to continuously monitor end-tidal CO₂.

In some cases (eg, those involving the posterior commissure or vocal cords), intubation with an endotracheal tube may interfere with the surgeon’s visualization or performance of the procedure. A simple alternative is insufflation of high flows of oxygen through a small catheter placed in the trachea. Although oxygenation may be maintained in patients with good lung function, ventilation will be inadequate for longer procedures unless the patient is allowed to breathe spontaneously.

Another option is the intermittent apnea technique, in which positive-pressure ventilation with oxygen by face mask or endotracheal tube is alternated with periods of apnea, during which the surgical procedure is performed. The duration of apnea, usually 2 to 3 min, is determined by how well the patient maintains oxygen saturation, as measured by pulse oximetry. Risks of this technique include hypoventilation with hypercarbia, failure to reestablish the airway, and pulmonary aspiration.

Another attractive alternative approach involves manual jet ventilation via laryngoscope side port. During inspiration (1–2 s), a high-pressure (30–50 psi) jet of oxygen is directed through the glottic opening and entrains a mixture of oxygen and room air into the lungs (Venturi effect). Expiration (4–6 s duration) is passive. Chest wall motion must be monitored and sufficient exhalation time allowed in order to avoid air trapping and barotrauma. This technique requires total intravenous anesthesia. A variation of this technique is high-frequency jet ventilation, which utilizes a small cannula or tube in the trachea, through which gas is injected 80 to 300 times per minute (see Chapter 58). Capnography will not provide an accurate estimate of end-tidal CO₂ during jet ventilation due to constant and sizable dilution of alveolar gases.

C. Cardiovascular Stability

Blood pressure and heart rate often fluctuate markedly during endoscopic procedures for two reasons. First, some of the patients undergoing these procedures are elderly and have a long history of heavy tobacco and alcohol use that predisposes them to cardiovascular disease. In addition, the endoscopic procedure is, in essence, a series of physiologically stressful laryngoscopies and interventions, separated by varying periods of minimal surgical stimulation. Attempting to maintain a constant level of anesthesia invariably results in alternating intervals of hypertension and hypotension. Providing a modest baseline level of anesthesia allows supplementation with short-acting anesthetics (eg, propofol, remifentanil) or sympathetic antagonists (eg, esmolol), or both, as needed during periods of increased stimulation. Alternatively, some anesthesia providers utilize regional nerve block of the glossopharyngeal nerve and superior laryngeal nerve to help minimize intraoperative swings in blood pressure (see Case Discussion, Chapter 19).

Laser Precautions

Laser light differs from ordinary light in three ways: It is monochromatic (possesses one wavelength), coherent (oscillates in the same phase), and collimated (exists as a narrow parallel beam). These characteristics offer the surgeon excellent precision and hemostasis with minimal postoperative edema or pain. Unfortunately, lasers introduce several major hazards into the operating room environment.

The uses and side effects of a laser vary with its wavelength, which is determined by the medium in which the laser beam is generated. For example, a CO₂ laser produces a long wavelength (10,600 nm), whereas yttrium–aluminum–garnet (YAG) lasers produce a shorter wavelength (1064 or 1320 nm). As the wavelength increases, absorption by water increases, and tissue penetration decreases. Thus, the effects of the CO₂ laser are much more localized and superficial than are those of the YAG laser.

General laser precautions include suction evacuation of toxic fumes (laser plume) from tissue vaporization because they have the potential to transmit microbial diseases. When a significant laser plume is generated, individually fitted respiratory filter masks compliant with U.S. Occupational Safety and Health Administration (OSHA) standards should be worn by all operating room personnel. In addition, during laser procedures, all operating room personnel should wear laser eye protection and the patient’s eyes should be taped shut. Operating room windows should be covered and appropriately placed signage should be used to alert those entering the room that a laser device is in use.

The greatest risk during laser airway surgery is an airway fire. This risk can be moderated by minimizing the fraction of inspired oxygen (FiO₂ <30% if tolerated by the patient) and can be eliminated when there is no combustible material (eg, flammable endotracheal tube, catheter, or dry cotton pledget) in the airway. If an endotracheal tube is used, it must be relatively resistant to laser ignition (Table 37–1). These tubes not only resist laser beam strikes, but they also possess double cuffs that should be inflated with saline instead of air in order to better absorb thermal energy and reduce the risk of ignition. If the proximal cuff is struck by the laser and the saline escapes, the distal cuff will continue to seal the airway. Alternatively, endotracheal tubes can be wrapped with a variety of metallic tapes; however, this is a suboptimal practice and should be avoided whenever use of a specialized, commercially available, flexible, stainless steel, laser-resistant endotracheal tube is possible (Table 37–2).

Although specialized, laser-resistant endotracheal tubes may be used, it must be emphasized that no endotracheal tube or currently available endotracheal tube protection device is reliably laser-proof. Therefore, whenever laser airway surgery is being performed with an endotracheal tube in place, the following precautions should be observed:

• Inspired oxygen concentration should be as low as possible by utilizing air in the inspired gas mixture (many patients tolerate an FiO₂ of 21%).

• Nitrous oxide supports combustion and must be avoided.

• The endotracheal tube cuffs should be filled with saline. Some practitioners add methylene blue to the saline to make cuff rupture more obvious. A well-sealed, cuffed endotracheal tube will minimize oxygen concentration in the pharynx.

• Laser intensity and duration should be limited as much as possible.

• Saline-saturated pledgets, although potentially flammable, should be placed in the airway to limit risk of endotracheal tube ignition and damage to adjacent tissue.

• A source of water (eg, water-filled 60-mL syringe and basin) should be immediately available in case of fire.

These precautions limit, but do not eliminate, the risk of an airway fire; anesthesia providers must proactively address the hazard of fire whenever laser or electrocautery is utilized near the airway (Table 37–3).

If an airway fire should occur, all air/oxygen should immediately be turned off at the anesthesia gas machine, and burning combustible material (eg, an endotracheal tube) should be removed from the airway. The fire can be extinguished with saline, and the patient’s airway should be examined to be certain that all foreign body fragments have been removed.

Common nasal and sinus surgeries include polypectomy, endoscopic sinus surgery, maxillary sinusotomy (Caldwell–Luc procedure), rhinoplasty, and septoplasty.

Preoperative Considerations

Patients undergoing nasal or sinus surgery may have a considerable degree of preoperative nasal obstruction caused by polyps, a deviated septum, or mucosal congestion from infection. This may make face mask ventilation difficult, particularly if combined with other causes of difficult ventilation (eg, obesity, maxillofacial deformities).

Nasal polyps are often associated with allergic disorders, such as asthma. Patients who also have a history of allergic reactions to aspirin should not be given any nonsteroidal antiinflammatory drugs (including ketorolac) for postoperative analgesia. Nasal polyps are a common feature of cystic fibrosis.

Because of the rich vascular supply of the nasal mucosa, the preoperative interview should concentrate on questions concerning medication use (eg, aspirin, clopidogrel) and any history of bleeding problems.

Intraoperative Management

Many nasal procedures can be satisfactorily performed under local anesthesia with sedation. The anterior ethmoidal nerve and sphenopalatine nerves (see Figure 19–3) provide sensory innervation to the nasal septum and lateral walls. Both can be blocked by packing the nose with gauze or cotton-tipped applicators soaked with local anesthetic. The topical anesthetic should be allowed to remain in place at least 10 min before instrumentation is attempted. Supplementation with submucosal injections of local anesthetic is often required. Use of an epinephrine-containing or cocaine solution will shrink the nasal mucosa and potentially decrease intraoperative blood loss. Intranasal cocaine (maximum dose, 3 mg/kg) is rapidly absorbed, reaching peak levels in 30 min, and may be associated with cardiovascular side effects (see Chapter 16).

General anesthesia is often preferred for nasal surgery because of the discomfort and incomplete block that may accompany topical anesthesia. Special considerations during and shortly following induction include using an oral airway during face mask ventilation to mitigate the effects of nasal obstruction, intubating with a reinforced or preformed Mallinckrodt oral RAE (Ring–Adair–Elwyn) endotracheal tube (Figure 36–1), and tucking the patient’s padded arms, with protection of the fingers, to the side. Because of the proximity of the surgical field, it is important to tape the patient’s eyes closed to avoid a corneal abrasion. One exception to this occurs during dissection in endoscopic sinus surgery, when the surgeon may wish to periodically check for eye movement because of the close proximity of the sinuses and orbit (Figure 37–1); nonetheless, the eyes should remain protected until the surgeon is ready to observe them. NMBs are often utilized because of potential neurological or ophthalmic injury that may occur if the patient moves during sinus instrumentation.

Techniques to minimize intraoperative blood loss include topical vasoconstriction with cocaine or an epinephrine-containing local anesthetic, maintaining a slightly head-up position, and providing a mild degree of controlled hypotension. A posterior pharyngeal pack is often placed to limit the risk of aspiration of blood. Despite these precautions, the anesthesiologist must be prepared for major blood loss, particularly during the resection of vascular tumors (eg, juvenile nasopharyngeal angiofibroma).

Coughing or straining during emergence from anesthesia and extubation should be avoided, as these events will increase venous pressure and increase postoperative bleeding. However, relatively deep extubation strategies that are commonly and appropriately utilized to accomplish this goal also may increase the risk of aspiration.

Surgery for cancer of the head and neck includes laryngectomy, glossectomy, pharyngectomy, parotidectomy, hemimandibulectomy, and radical neck dissection. An endoscopic examination following induction of anesthesia often precedes these surgical procedures. Timing of a tracheostomy, if planned, depends upon the patient’s preoperative airway compromise. Some procedures may include extensive reconstructive surgery, such as the transplantation of a free microvascular muscle flap, with long surgical time duration.

Preoperative Considerations

The typical patient presenting for head and neck cancer surgery is older and often has had many years of heavy tobacco and alcohol use. Common coexisting medical conditions include chronic obstructive pulmonary disease, coronary artery disease, hypertension, diabetes, alcoholism, and malnutrition. These patients often greatly benefit from an enhanced recovery after surgery program that includes preoperative nutritional repletion over the course of days and hydration with a carbohydrate–protein drink during the 24 h prior to surgery

Airway management may be complicated by abnormal airway anatomy, an obstructing lesion, or by preoperative radiation therapy that has fibrosed, immobilized, and distorted the patient’s airway structures. If there is concern regarding potential airway problems, intravenous induction may be avoided in favor of awake direct or fiberoptic laryngoscopy (cooperative patient) or direct or fiberoptic intubation following an inhalational induction, maintaining spontaneous ventilation (uncooperative patient). Elective tracheostomy under local anesthesia prior to induction of general anesthesia is often a prudent option. In any case, the appropriate equipment and qualified personnel required for emergent tracheostomy must be immediately available.

Intraoperative Management

A. Monitoring

Because many of these procedures are lengthy and associated with substantial blood loss, and because of the prevalence of coexisting cardiopulmonary disease, arterial cannulation may be utilized for blood pressure monitoring and frequent laboratory analyses. If central venous access is deemed necessary, the surgeon should be consulted to ascertain that planned internal jugular or subclavian venous access will not interfere with the intended surgical procedures; antecubital or femoral veins are reasonable alternatives. Arterial lines and intravenous cannulas should not be placed in the operative arm if a radial forearm flap is planned. A minimum of two large-bore intravenous lines and a urinary catheter (preferably with temperature-monitoring capability) should be placed. A forced-air warming blanket should be used to help maintain normal body temperature. Intraoperative hypothermia and consequent vasoconstriction can be detrimental to perfusion of a microvascular free flap.

Intraoperative nerve monitoring is increasingly utilized by surgeons in anterior neck operations to help preserve the superior laryngeal, recurrent laryngeal, and vagus nerves (Figure 37–2), and the anesthesia provider may be asked to place a specialized nerve integrity monitor endotracheal tube (Medtronic Xomed NIM endotracheal tube) to facilitate this process (Figure 37–3).

B. Tracheostomy

Head and neck cancer surgery often includes tracheostomy. Immediately prior to surgical entry into the trachea, the endotracheal tube and hypopharynx should be thoroughly suctioned to limit the risk of aspiration of blood and secretions. If electrocautery is used during the surgical dissection, the FiO₂ should be lowered to 30% or less, if possible, in order to minimize the risk of fire as the trachea is surgically entered. In any case, the easiest way to minimize airway fire risk in this circumstance is for the surgeon not to use the cautery to enter the trachea. After dissection down to the trachea, the tracheal tube cuff is deflated to avoid perforation by the scalpel. When the tracheal wall is transected, the endotracheal tube is withdrawn so that its tip is immediately cephalad to the incision. Ventilation during this period is difficult because of the large leak through the tracheal incision. A sterile, cuffed tracheostomy tube is placed in the trachea, the cuff is inflated, and the tube is connected to a sterile breathing circuit. As soon as correct position is confirmed by capnography and bilateral chest auscultation, the original endotracheal tube is removed. An increase in peak inspiratory pressure immediately after tracheostomy usually indicates a malpositioned endotracheal tube, bronchospasm, debris or secretions in the trachea, or, rarely, pneumothorax.

C. Maintenance of Anesthesia

The surgeon may request the omission of NMBs during neck dissection, thyroidectomy, or parotidectomy to allow nerve identification (eg, spinal accessory, facial nerves) by direct nerve stimulation and thereby facilitate their preservation. If a nerve integrity monitor endotracheal tube is utilized, succinylcholine (or propofol with no relaxant) may be used to facilitate intubation. Moderate controlled hypotension may be helpful in limiting blood loss; however, cerebral perfusion may be compromised with moderate hypotension when a tumor invades the carotid artery or jugular vein (the latter may increase cerebral venous pressure). If head-up tilt is utilized, it is important that the arterial blood pressure transducer be zeroed at the level of the brain (external auditory meatus) in order to most accurately determine cerebral perfusion pressure. In addition, head-up tilt increases the risk of venous air embolism.

Following reanastomosis of a microvascular free flap, blood pressure should be maintained at the patient’s baseline level. The use of vasoconstrictive agents (eg, phenylephrine) should be minimized because of potential decrease in flap perfusion due to vasoconstriction. Similarly, the use of vasodilators (eg, sodium nitroprusside or hydralazine) should be avoided in order to minimize any decrease in graft perfusion pressure.

D. Transfusion

Transfusion decisions must balance the patient’s immediate surgical risks with the possibility of an increased cancer recurrence rate resulting from transfusion-induced immune suppression. Rheological factors make a relatively low hematocrit (eg, 27–30%) desirable when microvascular free flaps are performed. Excessive diuresis should be avoided during microvascular free-flap surgery in order to optimize graft perfusion in the postoperative period.

E. Cardiovascular Instability

Manipulation of the carotid sinus and stellate ganglion during radical neck dissection has been associated with wide swings in blood pressure, bradycardia, arrhythmias, sinus arrest, and prolonged QT intervals. Infiltration of the carotid sheath with local anesthetic will usually moderate these problems. Bilateral neck dissection may result in postoperative hypertension and loss of hypoxic drive due to denervation of the carotid sinuses and carotid bodies.

Postoperative Management

The principal postoperative complications associated with head and neck cancer surgery include hypocalcemia secondary to acute hypoparathyroidism, and threats to airway integrity secondary to hemorrhage, hematoma formation, and bilateral vocal cord palsy with stridor resulting from bilateral recurrent laryngeal nerve injury (see Chapter 35). Postoperative hypoparathyroidism is a common condition, resulting from injury to the parathyroid glands or their blood supply during thyroidectomy or neck dissection, or from unintentional or intentional removal of all four parathyroid glands. It may be either symptomatic or asymptomatic, and occurs transiently in up to 49% of thyroidectomy patients, and is permanent in up to 33% of thyroidectomy patients. Symptoms and signs depend upon the rate of onset and severity of hypocalcemia. Clinical signs of acute, severe hypocalcemia include laryngospasm, bronchospasm, QT prolongation-related arrhythmias, and congestive heart failure. Neurological symptoms and signs range from circumoral paresthesias, distal extremity numbness, and carpopedal spasm to confusion, delirium, and seizure activity. Symptomatic hypocalcemia is a medical emergency and should be treated with intravenous calcium salts, whereas asymptomatic hypocalcemia may be treated with oral calcium preparations (see Chapter 49).

Maxillofacial reconstruction is often required to correct the effects of trauma (eg, fractures of the mandible or maxilla) or developmental malformations, or for radical cancer surgeries (eg, maxillectomy or mandibulectomy). Orthognathic procedures (eg, LeFort osteotomies, mandibular osteotomies) for skeletal malocclusion share many of the same surgical and anesthetic techniques.

Preoperative Considerations

Patients undergoing maxillofacial reconstruction or orthognathic surgical procedures often pose airway challenges. Particular attention should be focused on jaw opening, mask fit, neck mobility, micrognathia, retrognathia, maxillary protrusion (overbite), macroglossia, dental pathology, nasal patency, and the existence of any intraoral lesions or debris. If there are any anticipated signs of problems with mask ventilation or endotracheal intubation, the airway should be secured prior to induction of general anesthesia. This may involve fiberoptic nasal intubation, fiberoptic oral intubation, or tracheostomy with local anesthesia facilitated with cautious sedation. Nasal intubation with a straight tube with a flexible angle connector (Figure 37–4A) or a preformed nasal RAE (Figure 37–4B) tube is usually preferred in dental and oral surgery. The endotracheal tube can then be directed cephalad over the patient’s forehead. With any nasal intubation, care should be taken to prevent the endotracheal tube from putting pressure on the tissues of the nasal opening, as this situation may result in local tissue pressure necrosis in the setting of a lengthy surgical procedure. Nasal intubation should be considered with caution in LeFort II and III fractures because of the possibility of a coexisting basilar skull fracture (Figure 37–5).

Intraoperative Management

Maxillofacial reconstructive and orthognathic surgeries can be lengthy and involve substantial blood loss. An oropharyngeal (“throat”) pack is often placed to minimize the amount of blood and other debris reaching the larynx and trachea, and one must remember to remove the pack at the end of surgery before the jaws are wired shut! Strategies to minimize bleeding include a slight head-up position, controlled hypotension, and local infiltration with epinephrine solutions. Because the patient’s arms are typically tucked at the side, two intravenous lines may be established prior to surgery. An arterial line may be placed. As previously noted, if head-up tilt is utilized, it is important that the arterial blood pressure transducer be zeroed at the level of the brain (external auditory meatus) in order to most accurately determine cerebral perfusion pressure. In addition, the anesthesia provider must be alert to the increased risk of venous air embolism in the setting of head-up tilt.

Because of proximity of the airway to the surgical field, positioning of surgical team personnel, and positioning of the patient’s head often 90° or 180° away from the anesthesia provider, there is an increased risk of critical intraoperative airway problems, such as endotracheal tube kinking, disconnection, or perforation by a surgical instrument. Monitoring of end-tidal CO₂, peak inspiratory pressures, and breath sounds via an esophageal stethoscope assume greater importance in such cases. If the operative procedure is near the airway, the use of electrocautery or laser increases the risk of fire. At the end of surgery, the oropharyngeal pack must be removed and the pharynx suctioned. If there is risk of postoperative tissue edema involving structures that could potentially obstruct the airway (eg, tongue, pharynx), the patient should be closely observed and perhaps kept intubated. In such uncertain situations, extubation may be performed over an endotracheal tube exchanger (eg, Cook Airway Exchange Catheter with Rapi-Fit Adapter, Cook Medical), which can facilitate reintubation and provide oxygenation in the setting of immediate postextubation respiratory obstruction. In addition, the operating team should be prepared for emergent tracheotomy or cricothyrotomy. Otherwise, extubation can be attempted once the patient is fully awake and there are no signs of continued bleeding. Patients with intermaxillary fixation (eg, maxillomandibular wiring) must have suction and appropriate wire cutting tools continuously at the bedside in case of vomiting or other airway emergencies. Extubating a patient whose jaws are wired shut and whose oropharyngeal pack has not been removed can lead to life-threatening airway obstruction. “Has the throat pack been removed?” should be asked before intermaxillary fixation is initiated and again before removing the endotracheal tube.

Frequently performed ear surgeries include stapedectomy or stapedotomy, tympanoplasty, and mastoidectomy. Myringotomy with insertion of tympanostomy tubes is the most common pediatric surgical procedure and is discussed in Chapter 42.

Intraoperative Management

A. Nitrous Oxide

Nitrous oxide is not often used in anesthesia for ear surgery. Because nitrous oxide is more soluble than nitrogen in blood, it diffuses into air-containing cavities more rapidly than nitrogen (the major component of air) can be absorbed by the bloodstream (see Chapter 8). Normally, changes in middle ear pressures caused by nitrous oxide are well tolerated as a result of passive venting through the eustachian tube. However, patients with a history of chronic ear problems such as otitis media or sinusitis often suffer from obstructed eustachian tubes and may, on rare occasion, experience hearing loss or tympanic membrane rupture from administration of nitrous oxide anesthesia.

During tympanoplasty, the middle ear is open to the atmosphere, and there is no pressure buildup. However, once the surgeon has placed a tympanic membrane graft, the middle ear becomes a closed space, and if nitrous oxide is allowed to diffuse into any gas remaining in this space, middle ear pressure will rise and the graft may be displaced. Conversely, discontinuing nitrous oxide after graft placement will create a negative middle ear pressure that could also cause graft dislodgment. Therefore, nitrous oxide is either entirely avoided during tympanoplasty or discontinued prior to graft placement. Obviously, the exact amount of time required to wash out the nitrous oxide depends on many factors, including alveolar ventilation and fresh gas flows (see Chapter 8), but 15 to 30 min is usually recommended.

B. Hemostasis

As with any form of microsurgery, even tiny amounts of blood can obscure the operating field. Techniques to minimize blood loss during ear surgery include mild (15°) head elevation, infiltration or topical application of epinephrine (1:50,000–1:200,000), and moderate controlled hypotension. Because coughing on the endotracheal tube during emergence (particularly during neck movement associated with head bandaging) will increase venous pressure and may cause bleeding and increased middle ear pressure, deep extubation is often utilized.

C. Facial Nerve Identification

Preservation of the facial nerve is an important consideration during some ear procedures, such as resection of a glomus tumor or acoustic neuroma. During such cases, intraoperative paralysis with NMBs will make identification of the facial nerve by direct nerve stimulation impossible. Thus, intraoperative paralysis should not be employed unless requested by the surgeon.

D. Postoperative Vertigo, Nausea, & Vomiting

Because the inner ear is intimately involved with the sense of balance, ear surgery may cause postoperative dizziness (vertigo) and postoperative nausea and vomiting (PONV). Induction and maintenance with propofol have been shown to decrease PONV in patients undergoing middle ear surgery. Prophylaxis with decadron prior to induction, and a 5-HT₃ blocker prior to emergence, should be considered. Patients undergoing ear surgery should be carefully assessed for vertigo postoperatively, and their ambulation closely monitored, in order to minimize the risk of falling.

Oral Surgical Procedures

Most minor oral surgical procedures are performed in a clinic or office setting utilizing local anesthesia, augmented with varying degrees of sedation. If intravenous sedation is employed, or if the procedure is complex, a qualified anesthesia provider should be present. A qualified anesthesia provider must be present to administer deep sedation or general anesthesia if either is utilized. Typically, a bite block and an oropharyngeal throat pack protect the airway. For light to moderate levels of sedation, the oropharyngeal pack prevents irrigating fluids and dental debris from entering the airway. Deep sedation and general anesthesia require an increased level of airway management by a qualified anesthesia provider. Regardless of whether deep sedation or general anesthesia is inadvertent or intended, appropriate equipment, supplies, and medications must be immediately available to help ensure that any anticipated or unexpected anesthesia-related problem occurring in an office or clinic environment can be safely addressed with the same standard of care that is required in the hospital or ambulatory surgery center setting.

Minor oral surgical procedures, such as dental extractions, typically last no longer than 1 h. Nerve block or local anesthetic infiltration is typically utilized. In adults, most oral surgeons use 2% lidocaine with 1:100,000 epinephrine or 0.5% bupivacaine with 1:200,000 epinephrine in quantities no greater than 12 mL and 8 mL, respectively. Articaine is commonly used in Europe. The anesthesia provider must be informed by the surgeon of the local anesthetic used and its concentration and volume injected so that the allowed dosage based on patient weight is not exceeded. Pediatric patients are particularly at risk of local anesthesia toxicity due to excess local anesthetic dose administration or accidental intravascular injection.

Intravenous sedation during oral surgical procedures greatly increases the patient’s comfort and facilitates surgery. Small doses of fentanyl and midazolam are usually adequate for adults prior to injection of the local anesthetic. The sedation can be further augmented by additional small dosages of fentanyl, midazolam, or propofol. Incremental doses of propofol, 20 to 30 mg for adults, are often used if the surgeon requires a brief episode of deep sedation or general anesthesia.

These techniques require a high level of cooperation and participation by both the surgeon and anesthesia provider. If there is the possibility of increased risk due to preexisting medical conditions, less than ideal airway, or extent of contemplated surgical procedure, it is safer to perform the procedure in a hospital or ambulatory surgery center setting with general endotracheal anesthesia.