Chapter 5. Anesthesia for Head & Neck Surgery

Head and neck surgery requires a cooperative relationship between surgeon and anesthesiologist. This is especially true in surgical procedures involving the airway. In fact, in most situations a common bond exists between otolaryngologist and anesthesiologist. In critical situations, where airway compromise is anticipated, it is the anesthesiologist and the otolaryngologist who have the best appreciation for the severity of the situation. In this chapter we will discuss briefly the pharmacology of some of more commonly used drugs in anesthesia. While a majority of these drugs are used by anesthetists in monitored conditions, these drugs may also be used in procedures requiring conscious sedation. It is hence of great importance for the physician or nurse involved on conscious sedation to be knowledgeable about the use and limitations of drugs used in conscious sedation.

This is followed by an overview of anesthesia equipment as pertains to the needs of the otolaryngologist. Quite often, surgery of the head and neck will involve the use of special equipment for endotracheal intubation. The otolaryngologist must have some knowledge of the available equipment for optimum operating conditions. This section is followed by a review of the difficult airway and suggested methods for control of the difficult airway. In the final section, an outline of the presurgical evaluation for patients with coexisting cardiovascular and pulmonary disease is presented, and anesthetic considerations for some common head and neck surgical procedures are presented. These procedures are discussed in greater detail in other parts of the text.

Analgesics, Sedatives & Hypnotics

Opioids

Opioids mediate analgesia through a complex interaction of opioid receptors in the supraspinal central nervous system (CNS). They produce reliable analgesia as well as provide some sedation and euphoria. There is no significant impairment of myocardial contractility, but sympathetically mediated vascular tone is reduced. Ventilation is depressed due to elevation of the carbon dioxide threshold for respiration. Opioids given at recommended doses do not reliably produce unconsciousness. They may, however, cause decreased bowel motility, biliary spasm, nausea, and pruritus. A brief review of some of the pharmacology of some of the more common opioids is presented below.

Morphine

Morphine is relatively hydrophilic and thus has a slower onset with a longer clinical effect. Only a small amount of administered morphine gains access to the CNS, but it accumulates rapidly in the kidneys, liver, and skeletal muscles. Profound vein vasodilatation may be induced due to the effects of histamine release and reduction of sympathetic nervous system tone.

Fentanyl

A synthetic opioid, fentanyl has similar effects, but is more lipid soluble and has more rapid onset and shorter duration of action. This reflects faster entrance into the CNS and prompt redistribution. Elevated doses may lead to progressive saturation in adipose tissues. When this occurs, plasma concentrations do not decline promptly. Thus, pharmacodynamic effects, including ventilatory depression, may be prolonged.

Remifentanil

Remifentanyl was recently introduced and has a much more rapid onset and offset than fentanyl. With an initial dose, anesthesia may be achieved in 30–60 seconds, and offset of the drug can occur within 5–10 minutes after the discontinuation of an infusion. Because remifentanil is metabolized in blood and skeletal muscle, it can be administered as a single dose or in infusion. Due to the potency of this opioid and since chest wall rigidity may occur, this drug should be administered by an anesthesiologist or an anesthetist.

Meperidine

Commonly known as Demerol, meperidine has one-tenth the potency of morphine and a shorter duration of action. In low doses it has been shown to decrease the shivering associated with rewarming after surgery and after amphotericin administration. Several metabolites are excreted by the kidney and may accumulate in the presence of renal disease. The major metabolite, normeperidine is a proconvulsant and may cause seizures in renal compromised patients.

Opioids may be given by intermittent intravenous (IV) or intramuscular (IM) routes. Plasma level peaks and valleys may lead to variations in desired analgesia or excessive side effects. Continuous infusions or patient-controlled analgesia with smaller, more frequent doses has been shown to lead to better analgesia, with fewer side effects and less total drug use. Fentanyl and morphine may also be administered by an intrathecal or epidural route. This allows placement of opioids in the vicinity of receptors in the spinal cord. A growing body of information supports the use of these routes in high-risk patients to provide superior analgesia, less sedation, and less decrement in pulmonary function.

Tolerance developed by induction of hepatic microsomal enzymes may occur over the course of days to weeks. The effects of narcotics may be reversed with a variety of antagonists (ie, naloxone). Acute reversal may be accompanied by agitation, pulmonary and systemic hypertension, and pulmonary edema.

Benzodiazepines

Benzodiapines produce anxiolysis and sedation by facilitation of the inhibitory actions of GABA on nerve conduction in the cerebral cortex. They may be used to produce sedation and amnesia, facilitate cooperation with care, attenuate alcohol withdrawal syndrome, treat seizures, and relieve muscle spasm.

Benzodiapines have no analgesic properties. They may cause transient decreases in blood pressure, due to decreased catecholamine levels and systemic vascular resistance, but with little effect on contractility. Respiratory depression is usually well tolerated in clinical doses, but may be accentuated in the elderly and those with COPD. Titration to a cooperative, oriented, and tranquil state (level 2 on Ramsey Scale) is the desired effect. Patients with a history of heavy alcohol or sedative use may require considerably more drug to achieve this response. Diazepam, midazolam, and lorazepam are three of the more commonly used benzodiapines.

Diazepam

Diazepam has a long clinical duration due to the long half life of several active metabolites. It is not water soluble and the parenteral suspension of propylene glycol is irritating when given intravenously or intramuscularly. Because diazepam requires microsomal nonconjugative pathways for degradation and elimination, it should not be used for patients with acute hepatitis.

Midazolam

Midazolam is the most commonly used benzodiazepine in the intensive care unit (ICU). It is water soluble, with short clinical duration, and few active metabolites. Midazolam offers a more rapid onset and a greater degree of amnesia, which makes it a good choice for brief procedures such as EGD and bronchoscopy.

Lorazapam

Lorazepam is another frequently used long-acting benzodiazepine. There is no pain on injection and no active metabolites. This agent has become a popular choice for patients with liver disease because its metabolism is not dependent on microsomal enzymes.

Tolerance to benzodiapines develops as with prolonged alcohol and opiate use. Withdrawal may result in profound sympathetic autonomic response. Replacement of benzodiazepine plasma levels and transient autonomic control would be indicated for control of withdrawal symptoms.

Reversal of benzodiazepine-induced sedation has been reported with physostigmine and aminophylline. Flumazenil, a specific benzodiazepine receptor antagonist, provides consistent reversal of sedation within 2 minutes of IV administration. The duration of reversal is short; thus resedation is a possibility in cases of benzodiazepine overdose. Flumazenil has also been reported to transiently reverse the somnolence of hepatic encephalopathy. Therapy with this agent should be gradual, to avoid excitatory symptoms. Convulsions have been reported in seizure-prone and benzodiazepine-dependent patients.

Alpha2-Agonist

The α2-agonist Dexmedetomidine is a class of sedative drug that has been approved by the FDA for use as a sedative and analgesic in the operating room and in the ICU. Dexmedetomidine has similar pharmacologic actions as clonidine except that its affinity for the α2-receptor is 8 times greater, making Dexmedetomidine 5–10 times more potent than clonidine. In the past few years, the use of Dexmedetomidine for the management of sedation and analgesia in the perioperative setting has increased significantly. Dexmedetomidine also possesses several properties that may additionally benefit to postoperative patients who have an opioid tolerance or who are sensitive to opioid-induced respiratory depression. In spontaneously breathing volunteers, IV Dexmedetomidine caused marked sedation with only mild reductions in resting ventilation at higher doses. Head and neck surgeons will find this drug useful for conscious sedation cases, for augmented sleep studies, and for fiberoptic intubations and tracheostomy placement.

The drug does cause some cardiovascular instability, although this can be avoided when the drug is titrated carefully. Nevertheless, it should be appreciated that Dexmedetomidine does cause some moderate reductions in blood pressure and heart rate.

Anesthesia Induction Drugs

Barbiturates

Once a mainstay in sedation management, barbiturates now seem to have fallen out of favor, mainly due to availability of more titratable alternatives. They have numerous sites of action, but most likely promote the inhibitory effects of GABA on neuronal function. They have no analgesic effect and cause dose-related CNS, cardiac, and respiratory depression. Short-acting agents such as methohexital and thiopental are useful to produce unconsciousness for very short procedures such as cardioversions and intubations. Both agents can also be used for short-term procedures such as examination of the oropharynx in a noncooperative patient. As with most anesthetic induction drugs, patients should be adequately monitored (heart rate, blood pressure, electrocardiogram [ECG], and pulse oximetry), and supplemental oxygen should be given. Emergency endotracheal intubation equipment should be readily available together with emergency medications. Doses must be judicious due to the increased likelihood of respiratory and hemodynamic depression, especially in elderly patients.

Medium-acting (pentobarbital IV/PO) and long-acting (phenobarbital PO) agents have been used for violent agitation refractory to other agents, status epilepticus, andthe induction of barbiturate coma to treat increased intracranial pressure.

Propofol

Propofol is an ultra-short-acting IV anesthetic agent. Unconsciousness may be induced in less than 30 seconds followed by awakening in 4–8 minutes. It has potent sedative hypnotic activity, but unlike other agents, awakening is markedly rapid from even deep sedation with minimal residual sedative effects, and good antiemetic qualities. Hepatic metabolism is rapid, but rapid redistribution also plays a role in early awakening. It has no pharmacologic active metabolites. Propofol has been shown to decrease systemic blood pressure as a result of myocardial depression and vasodilatation. When used in low doses (10–50 mcg/kg/min) as a continuous infusion for sedation, these effects are minimal. It has no analgesic effects but has been shown to decrease narcotic requirements.

One of the disadvantages is that propofol is only slightly water soluble. It must be formulated in an oil/water emulsion of soybean oil, egg lecithin, and glycerol. This is similar to 10% Intralipid. Thus, this agent is contraindicated in patients with potential for allergic responses to the emulsion components. Pain is frequent on injection. This is often attenuated by pretreatment of the vein with a 20- to 40-mg lidocaine bolus prior to infusion. Blood chemistries should be assessed because prolonged use may result in hypertriglyceridemia.

Propofol should be treated with the same degree of caution as parenteral nutrition solutions. Multiple reports of bacterial contamination due to manipulations of the emulsion medium demonstrate that it supports rapid bacterial growth. Recent formulations of propofol have included bacteriostatic agents, such as EDTA or sulfites, which have made this issue less of a clinical concern. Nonetheless, clinical guidelines still limit handling opened vials to less than 24 hours and, when used as an infusion, advocate line changes at regular (usually 12-hour) intervals.

A soluble cousin of propofol marketed as Aquavan (fospropofol disodium) is currently awaiting FDA approval.The drug is described to have similar properties as propofol without the pain experienced during injection. The drug has been used for conscious sedation for colonoscopies with success in several phase III studies. Aquavan does have the respiratory depression function of propofol.

Ketamine

Ketamine is a phencyclidine derivative (similar to LSD) that produces a dossal, dissociative state that may be exploited as a sedative. Agitated patients may be given IM injection (3–5 mg/kg) or titration of 10-mg IV boluses in order to produce a cataleptic state in which the eyes remain open with a slow nystagmic gaze. Amnesia is present and analgesia is intense. Additional advantages include maintenance of airway reflexes, cardiovascular stimulation, and bronchial relaxation. Disadvantages include increased airway secretions, transient increases in intracranial pressure, and an association with unpleasant visual or auditory illusions. Addition of benzodiazepines may attenuate these untoward sensory effects. Examples of clinical utility include conscious sedation for burn wound dressing changes and facilitation of endotracheal intubation in the hypotensive patient.

Inhaled Anesthetics

In the operating room, general anesthesia is commonly maintained with inhaled anesthetics. These agents also provide some analgesia, amnesia, and muscle relaxation. In pediatric cases where there is no IV access, anesthesia may be induced by inhalation. All of the inhaled anesthetics with the exception of nitrous oxide are bronchodilators and may be useful in patients with reactive airways. Most inhaled agents will reduced blood pressure due to direct cardiac depression (eg, halothane), or by vasodilation (eg, isoflurane, sevoflurane, or desflurane). The rapidity of induction of anesthesia as well as emergence from anesthesia is based on the lipid solubility characteristics of the inhaled anesthetic. Hence, the more insoluble the anesthetic agent, the faster the induction of anesthesia. Also, the agents with high lipid solubility prolong the emergence from anesthesia.

Nitrous Oxide

Nitrous oxide produces general anesthesia through interaction with the cellular membranes of the CNS. It is the only nonorganic inhaled anesthetic in clinical use. Although it is nonvolatile, it does support combustion, and caution should be taken in the event of airway fires. Uptake and elimination of nitrous oxide are relatively rapid compared with other inhaled anesthetics, primarily as a result of its low blood-gas partition coefficient. Elimination of nitrous oxide is via exhalation. It produces analgesia, amnesia (with a concentration greater than 60%), mild myocardial depression, and mild sympathetic nervous system stimulation. It does not significantly affect heart rate or blood pressure. Nitrous oxide is a mild respiratory depressant, although less than the volatile anesthetics.

Isoflurane

Until recently isoflurane was the most commonly used inhaled anesthetic in the United States of America. Isoflurane is noted for its minimal cardiac depression. Like other volatile, isoflurane causes respiratory depression with a fall in minute ventilation. The ventilatory response to hypoxia and hypercapnia are diminished. Another characteristic in common with other volatile anesthetics is the ability of isoflurane to cause bronchodilation. This effect occurs despite its ability to cause airway irritation.

Isoflurane increases skeletal muscle blood flow, decreases systemic vascular resistance, and lowers arterial blood pressure. High concentrations of isoflurane may increase cerebral blood flow (CBF) and intracranial pressure. These effects are effectively reduced by hyperventilation. At even higher concentrations isoflurane reduces cerebral metabolic oxygen requirements and provides cerebral protection. Isoflurane decreases renal blood flow, glomerular filtration rate, and urinary output.

Desflurane

The structure of desflurane is very similar to isoflurane except for substitution of a fluorine atom for a chlorine atom. This makes desflurane highly insoluble. Its low solubility in blood and body tissues causes a very rapid wash-in and washout of anesthetics. Wake-up times are approximately half as long as those observed following isoflurane administration. Desflurane has cardiovascular and cerebral effects similar to those of isoflurane.

Sevoflurane

Sevoflurane has begun to replace halothane as a primary inhaled anesthetic agent used in the induction of anesthesia where an IV induction cannot be performed. It is used primarily in pediatrics where IV access is not available and induction has to be achieved by other means. Nonpungency and rapid increase in alveolar anesthetic concentration make it an excellent choice for smooth and rapid inhalation induction of anesthesia. Sevoflurane's solubility in blood is slightly greater than that of desflurane. Sevoflurane mildly depresses myocardial contractility. Systemic vascular resistance and arterial blood pressure decline slightly less than with isoflurane or desflurane. As with isoflurane and desflurane, sevoflurane causes slight increases in CBF and intracranial pressure at normocarbia. Sevoflurane is reported to have potential for nephrotoxicity and hence should be used with a gas flow of greater than 2 L.

Halothane

Halothane is a halogenated alkane that is used primarily for induction of anesthesia in patients where an IV induction is not possible. Halothane's nonpungent and sweet-smelling odor makes it especially suitable for this purpose. Halothane causes a dose-depression reduction in arterial pressure by myocardial depression. It also causes respiratory depression. Halothane has been associated with a drug-induced hepatitis known as halothane hepatitis. This condition is extremely rare (1 in 35,000) and has an increased incidence in patients exposed to multiple halothane anesthetics within short intervals, in middle-aged obese women, and in patients with a genetic predisposition to halothane hepatitis.

Antiemetics

Droperidol

Droperidol has greater antiemetic and sedative effects, but may also produce respiratory depression. If administered alone, dysphoria can happen; at clinical doses it is used in combination with a narcotic or benzodiazepine for sedation. More recently, the FDA has discouraged the use of droperidol in an unmonitored setting.

Ondansetron and Dolasetron

Ondansetron and dolasetron are selective antagonists of serotonin 5-HT3 receptors with little or no effect on dopamine receptors. Unlike droperidol they do not cause sedation, extrapyramidal signs, or alteration of the GI motility and lower esophageal sphincter tone. 5-HT3 receptors are found in the chemoreceptor trigger zone of the area postrema, in the nucleus tractus solitarius, and also along the gastrointestinal tract. The most common reported side effect is headache. Dolasetron can prolong the QT interval.

Newer Antiemetics

In the last few years, two new medications have been approved for the treatment of nausea and vomiting. Palonosetron, a 5-HT3 antagonist, has been shown to be effective in delayed emesis and has been shown to be superior to other the 5-HT3 antagonists ondansetron and dolasetron. In most studies, however, the efficacy has been best when the 5-HT3 antagonist was given with 20 mg of Dexamethasone. Another new antiemetic is aprepitant, an NK1 receptor antagonist. The scientific basis of aprepitant is based on its antagonism of substance P, a pro-emetic, which exerts its biological effect (emesis), by binding to the tachykinin neurokinin NK1 receptor. Aprepitant antagonizes this binding. The antiemetic effects of Aprepitant had added efficacy when given with Dexamethasone.

Neuromuscular Blockers

Neuromuscular blocking agents are used in most cases for endotracheal intubation and in the operating room when patient movement is detrimental to the surgical procedure. The most prominent side effect of giving neuromuscular blockers is that they cause paralysis of the muscles of respiration. Hence, ventilation of the patient is in the hands of the anesthesiologist and can be achieved with a mask or with a secured endotracheal tube.

Most muscle relaxants induce paralysis by blocking acetylcholine receptors at the neuromuscular junction of skeletal muscle. They have no intrinsic sedative or analgesic properties and must be used in concert with other medications. At a minimum, these agents should be used in conjunction with an anxiolysis agent. Inadequate sedation and hypnosis during use of neuromuscular blockers can produce unpleasant recall by patients with long-term side effects. Neuromuscular blockers can be classified as depolarizing neuromuscular blockers, such as succinylcholine, which bind to the acetylcholine receptor and produces a “persistent” depolarization of the neuromuscular junction. Muscle relaxation is achieved because propagation of action potentials is prevented by the area of inexcitability that occurs around the acetylcholine receptors. The second type of neuromuscular blockers is termed nondepolarizing neuromuscular blockers, which directly bind the acetylcholine receptor and prevent the binding of acetylcholine. All drugs described belong to the nondepolarizing neuromuscular blocker group (Table 5–1).

Vecuronium is a popular relaxant due to its short clinical duration (30–60 minutes) and lack of hemodynamic side effects. It may be given as a bolus or continuous infusion. It is metabolized by the liver and excreted by the kidney.

Cisatracurium undergoes degradation in plasma at physiologic pH and temperature by organ-independent Hofmann elimination. Metabolism and elimination appear to be independent of renal or liver failure. It does not affect heart rate or blood pressure, nor does it produce autonomic effects.

Pancuronium has a longer duration of action (60–90 minutes) and is eliminated primarily by renal mechanisms. The major limiting factor to its use is tachycardia, especially after bolus administration, resulting from a vagolytic effect.

Rocuronium has an onset of action similar to but slightly longer than succinylcholine, making it suitable for rapid-sequence inductions, but at the cost of a much longer duration of action. This intermediate duration of action is comparable to Vecuronium. It undergoes no metabolism and is eliminated primarily by the liver and slightly by the kidneys, so its duration of action is modestly prolonged by severe hepatic failure and pregnancy.

NSAIDs—Ketorolac

Ketorolac is a recently released potent parenteral nonsteroidal analgesic without opioid-related side effects such as respiratory depression. IM doses of 60 mg are reported to be equivalent to 10 mg morphine for up to 3 hours. Clinical dosing is every 8 hours, and it appears to be most effective in situations where swelling contributes to pain (ie, dental, gynecologic, and orthopedic surgery). There is minimal impact on ventilation, hemodynamics, and bowel motility. Disadvantages include a limited analgesia effect beyond recommended doses and impaired platelet function. Substantial gastrointestinal mucosal breakdown may occur with use over periods as short as one week.

Anticholinergics

Anticholinergic agents are sometimes used to produce sedation and amnesia. They also have an antisialogue effect and prevent reflex bradycardia. Atropine and scopolamine are tertiary amines that cross the lipid barrier protecting the CNS. Scopolamine has 10 times the potency of atropine in terms of centrally induced sedation and amnesia. Because scopolamine produces tachycardia as its major hemodynamic side effect, it is a popular choice as an urgent amnestic for the hemodynamically unstable or hypovolemic patient (ie, trauma victim).

Undesirable side effects include toxic delirium (known as central cholinergic syndrome), tachycardia, relaxation of lower esophageal sphincter tone (with associated potential for regurgitation), mydriasis, and potential elevation of temperature via suppression of sweat gland function.

The basic equipment for airway management used by the anesthesiologist should be familiar to the otolaryngologist. This includes laryngoscope blades, endotracheal tubes, and breathing circuits.

Laryngoscope Blades

In general laryngoscope blades may be classified as either straight or curved. With proper head positioning, both types of blades provide a direct pathway to the vocal cords for tracheal intubation. There are several designs of laryngoscope blades, and these are shown in Figure 5–1. Some blades like the Bainton blade may be used in special situations where redundant tissue or airway edema is present and the vocal cords are not easily visible.

Endotracheal Tubes

Otolaryngologists often require specialized endotracheal tubes depending on the procedure performed (Figure 5–2). The standard endotracheal tube is made of polyvinyl chloride and is disposable. Endotracheal tubes can also be made from clear silicon material. Reusable rubber tubes are also available. These tubes have to be cleaned and autoclaved prior to reuse. Endotracheal tubes come in various sizes and may be cuffed or uncuffed. Uncuffed endotracheal tubes are used in neonates, infants, and children usually up to the age of 12 years. A suggestion of tube size in children is shown in Table 5–2. The tracheal end is usually beveled and may contain a Murphy eye. Endotracheal tube cuffs may be of either the high-volume variety or the low-volume variety. Both types of cuffs may cause tracheal necrosis with long-term intubation. Endotracheal tubes have gradations usually in centimeters to allow for the clinician to keep track of correct position of the tube and prevent endobronchial migration or extubation. It should be noted that for common procedures of the larynx, use of a small-diameter endotracheal tube allows for better exposure. The recommended size is 5.0-mm ID for women and 5.5-mm ID for men.

For a variety of head and neck procedures, specially designed endotracheal tubes may be required. The otolaryngologist should be familiar with these tubes. These tubes are designed to provide optimal exposure for the surgeon working in the oral and nasal cavities. Their anatomical design prevents kinking of the tubes during surgery.

Three of the more commonly used endotracheal tubes for head and neck procedures are the RAE tracheal tubes, the armored tracheal tubes, and the laser resistant tracheal tubes. RAE tubes, named after the inventors of the tube (Ring, Adair, and Elwyn), have a preformed shape to fit the mouth or nose. The tubes are available in a variety of pediatric and adult sizes and may be cuffed or uncuffed. Nasal RAE tubes are commonly used in surgery of the oral cavity as they do not obstruct the surgical field. Oral RAE tubes are commonly used for surgeries of the oral cavity, particularly those involving the tonsils. A drawback to RAE tubes is that their shape may cause them to cause an endobronchial intubation, particularly in patients with short necks.

Armored tracheal tubes are commonly used in surgery of the head and neck. The primary advantage of using these tubes is that they can withstand the constant moving of the head without kinking. Laser resistant tracheal tubes are used in laser surgery, as in the treatment of vocal cord papillomas. Regular endotracheal tubes can be converted to laser resistant tubes by wrapping the ends with aluminum foil.

A high percentage of cases involving the head and neck involve patients with “difficult airways.” A patient with a difficult airway is one who may pose a challenge for both manual ventilation and placement of an endotracheal tube. Patients with difficult airways should be identified prior to surgery, more specifically prior to the induction of general anesthesia, particularly with use of neuromuscular blockade. Preoperative evaluation by the otolaryngologist either by direct vision of the airway or by other diagnostic tools such as a CT scan and an MRI may provide invaluable information to the anesthesiologist, particularly if a difficult airway is involved.

Identification of Patients with Potentially Difficult‐to-Manage Airways

With the improvement in record keeping and patient–physician communications, patient history should provide important information with regards to the patient's airway and potential problems for securing the airway in the operating room. Knowledge of prior history of difficult intubation, prior surgery of the head and neck, immobility of cervical vertebrae, and radiation therapy to the airway should be basic alert items for a potential difficult airway. Other alert items should include dysphagia, trauma to the head and neck, and hoarseness or stridor (see Table 5–3).

Physical Exam of Airway

Examination of the Head and Neck

In most cases involving head and neck surgery, a detailed preoperative assessment of the airway may be performed by the otolaryngologist. This is extremely helpful in determining which patients are going to be challenged for tracheal intubation. The preoperative exam should thus include:

• a detailed frontal and a profile view to assess mandibular size and mobility;
• examination and assessment of mental-alveolar process and mental-hyoid bone or mental-thyroid cartilage distance;
• assessment of neck rotation and flexion-extension mobility;
• examination of the neck for evidence of masses, tracheal deviation, size of tracheal and cricoid cartilage, and tissue plasticity.

In patients classified as morbidly obese, a neck circumference greater than 50 cm may be used as a predictor of increased difficulty of endotracheal intubation.

Recognition of certain breathing pattern and phonation may also provide with important clues about airway patency and potential difficulty with endotracheal intubation.

In addition an intraoral examination should be performed as part of the preoperative assessment. This would include an assessment of tongue size, protrusive occlusion, and degree of overbite, (see Table 5–4). Recognition of a potentially difficult airway can be done by examining the oral cavity and assessing the structures that can be seen with a wide open mouth. The classification of these views, shown in Figure 5–3, is called the Mallampati classification. At the bottom of the figure are shown graded laryngoscopic views.

The American Society of Anesthesiologists has provided stepwise guidelines for dealing with patients who present with problematic intubation of the trachea (Figure 5–4).

Awake Intubations

Preparation of the Patient

In patients with anticipated difficult airways or patients who are unable to open their mouths or have cervical spine precautions, an awake intubation is often necessary. This can be done by anesthetizing the oropharynx with a local anesthetic. The use of 2% lidocaine sprayed in the mouth and throat may cause the loss of a gag reflex and allow for awake laryngoscopy (see below). In other situations tracheal intubation either via the oral or via nasal route should be done awake using a fiberoptic scope. In this latter situation, facilitation of fiberoptic intubation may require blockade of specific nerves.

• In the mouth, sensation to the anterior aspect of the tongue is innovated by the lingual nerve. In contrast, the posterior third of the tongue and the oropharynx are innovated by pharyngeal braches of the glossopharyngeal nerve and by the vagus nerve. These nerves can be easily anesthetized by spraying the oral cavity with local anesthetic and asking the patient to gargle and swallow the spray medication. Alternatively, these nerves are easily blocked by bilateral injection of 2 mL of local anesthetic into the base of the palatoglossal arch with a 25-gauge spinal needle. The inferior aspect of the larynx to the level of the vocal cords is innervated by the superior laryngeal nerve, a branch of the vagus nerve. This nerve can be blocked by placement of local anesthetic-soaked gauze in the pyriform sinuses. Also this nerve may be blocked externally by locating the hyoid bone and injecting 3 mL of 2% lidocaine 1 cm below each greater cornu, where the internal branch of the superior laryngeal nerves penetrates the thyrohyoid membrane.
• The recurrent laryngeal nerve innervates the mucosa below the cords. This nerve may be blocked by transtracheal injection of local anesthetic. A transtracheal block is performed by identifying and penetrating the cricothyroid membrane while the neck is extended. After confirmation of an intratracheal position by aspiration of air, 4 mL of 4% lidocaine is injected into the trachea at the end of expiration. A deep inhalation and cough immediately following injection distributes the anesthetic throughout the trachea.

Use of local anesthetic to block the above nerves may facilitate awake intubation of the trachea by depressing the protective cough reflex and the swallowing reflex. Special precaution should be taken with those patients at high risk for aspiration. In some patients the use of anesthesia may be limited to the nasal passages with either a blind-nasal intubation being used or a fiberoptic nasal intubation. Using local anesthetics in the nares will allow patients who are high risk for aspiration to protect their airway.

Other Helpful Tools for the Patient with a Difficult Airway

In cases where a difficult airway was not anticipated and patients may be already medicated with anesthetic induction drugs and neuromuscular blockers and cannot be awoken, a patient airway and ventilation is essential. If manual ventilation with a mask is adequate, then this is less of a life-threatening situation, and the patient may be ventilated until he or she wakes up and can be intubated by an alternative technique. In cases where manual ventilation is difficult, even with use of oral or nasal airways, then aggressive intervention including a surgical airway may become imperative. The introduction of the laryngeal mask airway (LMA) and fast-track LMA has added to the available options when conventional methods of tracheal intubation with a laryngoscope are unsuccessful and respiratory compromise is imminent. The LMA was designed in 1981 and is a compromise between the face mask and the tracheal tube. It is used extensively throughout the world and has been included in the American Society of Anesthesiologist algorithm for the difficult airway. It requires no direct visualization of the cords. The one setback of this device is that it does not prevent aspiration. Hence in patients with high aspiration risk, a small endotracheal tube can be placed under fiberoptic guidance. More recently two new laryngeal masks have been introduced: the fast-track LMA and the ProSeal LMA. The fast-track LMA can be used as a regular LMA. Its main advantage is that it allows the placement of endotracheal tubes without direct laryngoscopy (see Figure 5–5). The ProSeal LMA is very similar to the LMA, but with an extra-lumen for suction of stomach and intestinal contents. It should be emphasized that all three types of LMA do not protect against aspiration of gastrointestinal contents if the patients vomits.

The esophageal-tracheal combitube is another device that can be used in emergency situations. The combitube is a hybrid of the traditional endotracheal tube and the old esophageal obturator airway. This device can prevent aspiration because of the presence of a tracheal cuff (see Figure 5–6).

The Glidescope

The GlideScope® (Saturn Biomedical Systems Inc., Burnaby, British Columbia, Canada) is a new video laryngoscope that can be a useful alternative to the conventional fiberoptic scope for placement of an endotracheal tube in the trachea when confronted with a difficult airway. The GlideScope has a high-resolution digital camera incorporated in the blade, which displays a view of the vocal cords on a monitor. The blade is fashioned after the Macintosh blade with a 60° curvature to match the anatomical alignment. The blade is made of a soft plastic material and has a thickness of 18 mm. The blade also has an embedded antifogging mechanism. The GlideScope can be used with minimal treatment of the oropharynx with local anesthetic and is useful for not only endotracheal intubation but also as a diagnostic tool. Currently, there are several other video laryngoscopes on the market that improve our ability to deal with the difficult airway.

Patients who are scheduled for surgery should have a preoperative evaluation by the surgeon and the anesthesiology, especially if general anesthesia is to be administered. These patients should have some baseline laboratory assessment that should include at a complete blood count. In patients with coexisting disease, an evaluation of other function is necessary. Patients over the age of 50 years should also have an ECG as should patients with heart disease. A preoperative pulmonary function assessment in patients with pulmonary disease is also warranted. These tests may determine postoperative care requirements and assess if preoperative treatment may reduce the perioperative risks. In this section a review of the current functional tests for cardiac and pulmonary function is presented. While in a high percentage of cases a cardiac or pulmonary consultant will be involved with the assessment of the patients, it is important for the otolaryngologist to understand some of the functional tests that will be ordered.

Assessment of Patient with Cardiac Disease

Patients over the age of 50 years and patients with cardiac disease should have an ECG prior to surgery. The preoperative ECG can provide important information on the status of the patient's cardiac and coronary circulation. Patients with abnormal Q waves seen on their ECG suggest a past myocardial infarction. These patients may be at increased risk of a perioperative cardiac event and may need further preoperative assessment. In fact about 30% of infarctions are silent and only detected on routine ECG, most notably in patients with diabetes or hypertension. In addition to the ECG, history taking can provide important information with regards to the patient's cardiac status. Assessing the patient's functional status by knowing the patient's exercise tolerance may determine the need for a cardiac evaluation. The information from cardiovascular testing may allow for optimization of preoperative medications, provide information on perioperative monitoring, or determine the need for coronary revascularization. There are several tests for assessing functional status (Table 5–5). These include the following:

24-Hour Ambulatory ECG

This ECG requires the placement of a Holter monitor, which records a continuous 12-lead ECG for 24 hours. This will detect arrhythmias and ischemic changes during a 24-hour period. This test will often require further testing, particularly if ischemic changes are noted.

Exercise Stress Test

Essentially, in an exercise ECG stress test where a patient is asked to exercise with the ECG, heart rate and blood pressure monitored. The presence of ECG signs of myocardial ischemia and/or the patient complaints of chest pain or dyspnea, and clinical signs of left ventricular dysfunction, are considered positive. Even more important is a decrease in blood pressure in response to exercise. This may be associated with global ventricular dysfunction. Syncope during the test also signifies decreased cardiac output. A positive exercise ECG stress test should alert the anesthesiologist that the patient is at risk for ischemia, within a wide range of heart rates, which may occur during surgery. These patients may require further workup and optimization of medical management.

Thallium Exercise Test

The sensitivity and specificity of the noninvasive stress test can be increased by nuclear imaging techniques. Thallium-201 (Tl-201) is a radioactive compound that mimics potassium uptake by viable myocardial cells. The sensitivity of exercise Tl-201 imaging depends upon the imaging technique. Qualitative visual Tl-201 imaging has an average sensitivity of 84% and specificity of 87% for detecting coronary artery disease (CAD), although these numbers are improved with better imaging techniques. The drawback is that patients have to remain stationary for imaging to avoid artifact. Thallium defects are reported as normal, fixed, and/or reversible. Other measures of importance, particularly during stress Tl-201 imaging, are size of defect, lung uptake, and left ventricular cavity size. A large lung uptake of isotope has been associated with myocardial ischemia that produces left ventricular dysfunction that may result in pulmonary edema. The presence of a distended left ventricular cavity on the immediate post-stress image is another marker of severe CAD, presumably as a result of myocardial ischemia.

Thallium Imaging in Patients WHO Cannot Exercise

The use of pharmacologic agents to induce cardiac stress in patients who cannot exercise can also detect CAD. These agents can be divided into two categories: those that result in coronary artery vasodilatation, such as dipyridamole and adenosine, and those that increase myocardial oxygen demand, such as dobutamine and isoproterenol. Coronary artery vasodilators are useful for defining myocardium at risk by causing differential flows in normal coronary arteries compared with those with a stenosis. The use of dolbutamine is an alternative method of increasing myocardial oxygen demand without exercise. The goal is to increase heart rate and blood pressure.

Echocardiography

The use of echocardiography for preoperative cardiac evaluation has increased in the last few years. Left ventricular function, pulmonary vascular pressures, and valvular competence can be evaluated. In most cases, a transthoracic approach has been used. Transesophageal echocardiography may provide better measurement of valvular abnormalities and left ventricular function. Echocardiography can also be performed with exercise, and in patients unable to exercise, dolbutamine has been used to mimic the stress effects of exercise.

Coronary Angiography

Coronary angiography has been called the gold standard for defining coronary anatomy. In addition, angiography also can assess valvular function and hemodynamic indices, including ventricular pressure and gradients across valves. In most cases, angiography is performed after a positive stress test to determine if coronary revascularization will improve cardiac function and reduce perioperative cardiac morbidity after noncardiac surgery. One major difference between stress tests described previously and coronary angiography is that the latter provides the clinician with anatomic, not functional, information. It is also an expensive test with potential complications.

Patient with Drug-Eluting Stents (DES)

In the last several years, percutaneous vascular interventions have replaced open surgical procedures (coronary artery bypass graft [CABG]) in a number of situations. One such situation is percutaneous placement of DES for coronary revascularization in patients with CAD. DES, unlike their counterparts, the bare metal stents (BMS), are coated with slow-release chemicals that prevent thrombus formation with the help of antiplatelet drugs such as clopidogrel. As the number of patients with DES who present for head and neck surgery increases, it is imperative that surgeons and anesthesiologists be aware of guidelines for stopping antiplatelet medications. The current recommendation for patients with DES is that elective surgery should be postponed if the duration between stent placement and noncardiac surgery is less than 6 months. For semi-emergent procedures, both aspirin and clopidogrel should be continued during surgery unless clearly contraindicated by the nature of the surgery. If the risk of bleeding is high, then modification of antiplatelet medications should be considered on a case-by-case basis.

Patients with Pacemakers and Aicds

With the advances in pacemaker technology, the placement of pacemakers in patients with both cardiac conduction defects and arrhythmias has dramatically increased. Hence some basic knowledge of pacemakers must be known. In addition to patients with pacemakers, some patients who present for surgery may have automated implantable cardioverter defibrillators (AICDs). Both groups of patients benefit from a careful preoperative evaluation and device interrogation by a cardiologist specializing in electrophysiology. It is important to know the type of the device; in the case of the pacemaker, the configuration should be known and then also the reaction of either device to “inhibition” by placing a magnet over the implanted device. Most of the problems encountered with pacemakers and AICD devices are due to electrocautey. Several measures can be made to avoid potential adverse effects. These include the use of bipolar cautery. If unipolar cautery is needed, then the grounding pad should be placed away from the pacemaker and close to the operative site. It is recommended that electrocautery not be used at a distance less than 15 cm from the pacemaker or AICD device; if this is unavoidable, then use of cautery with short bursts and long pauses will reduce adverse events. The pacemaker may be programmed to an asynchronous mode by a magnet or by a programmer. The magnet will place the pacemaker in a backup-pacing mode. Reprogramming of the device should be instituted after the surgery.

Patients with Drug-Eluting Stents

In the last few years, percutaneous coronary intervention by placement of coronary stents has surpassed CABG for revascularization due to CAD. This is due primarily to the introduction of DES. In the past, patients with multi-vessel CAD requiring revascularization would often undergo CABG surgery instead of stent placement because of concerns regarding re-stenosis with BMS. Nevertheless, patients with DES merit special consideration if they are scheduled for surgery. Because of the risk of thrombus formation during the period of re-endothelialization of the stent, antiplatelet drugs are given particularly in the first 6 months to prevent thrombus formation. Aspirin and clopidogrel are the two most common drugs used. In most patients with DES, antiplatelet drugs should be used in the first 6 months, and stopping these medications puts patients at risk for thrombus formation in the stents. Hence, in patients with a DES, a preoperative cardiology consultation is essential. Elective surgery should be postponed if the duration between DES placement and noncardiac surgery is less than 6 months. For semi-emergent procedures, both aspirin and clopidogrel should be continued during surgery unless clearly contraindicated by the nature of the surgery. If the risk of bleeding is high, then modification of antiplatelet medications should be considered on a case-by-case basis.

Preoperative Pulmonary Evaluation

Patients scheduled for head and neck surgery may present with coexisting pulmonary diseases. For patients with acute pulmonary disease scheduled for elective surgery, the surgery may be postponed until the pulmonary disease resolves. Postoperative pulmonary complications include atelectasis, pneumonia, respiratory failure, and exacerbation of chronic pulmonary disease. Patients with chronic pulmonary disease may merit from a preoperative pulmonary workup that includes an arterial blood gas, chest X-ray, and pulmonary function tests. The presence of pulmonary disease may increase perioperative morbidity and mortality. Preoperative pulmonary function tests measure the severity of lung disease, measure the efficacy of bronchodilator therapy to improve the pulmonary function, and can predict the need for the patient for postoperative mechanical ventilation.

In general, disease of the pulmonary system may be classified as obstructive or restrictive.

Obstructive Pulmonary Diseases

Obstructive pulmonary disease includes asthma, emphysema, chronic bronchitis, bronchiectasis, and bronchiolitis. These disorders are characterized by an increase in expiratory airflow resistance that results in an increase in the work of breathing. The most typical finding noted on pulmonary function tests is that both forced expiratory volume in 1 second (FEV1) and the FEV1/FVC (forced vital capacity) ratio are less than 70% of the predicted values. The expiratory airflow resistance results in air trapping. In addition, the residual volume (RV) and the total lung capacity (TLC) are increased. Wheezing is a common clinical finding and represents turbulent airflow. In mild obstructive disease, wheezing may be absent but can be elicited by prolonged exhalation.

Restrictive Pulmonary Diseases

Restrictive lung diseases may be acute or chronic intrinsic disorders that include pulmonary edema, ARDS, infectious pneumonia, or the interstitials lung diseases. Restrictive pulmonary disease may also represent extrinsic disorders involving the pleura, chest wall, diaphragm, or neuromuscular function.

The hallmark of this group of disorders is decreased lung compliance that increases the work of breathing due to a characteristic rapid-shallow breathing pattern. Lung volumes are typically reduced as well as the FEV1 and the FVC. There is a normal FEV1/FVC ratio. The expiratory flow rates are unchanged.

Management of Patients with Chronic Anticoagulation

As noted above, some patients who present for elective surgery often require chronic anticoagulation for conditions such as venous thromboembolism, mechanical valve implants, or chronic atrial fibrillation. The management of these patients requires careful consideration. Common medications used include vitamin K antagonists such as Coumadin and antiplatelet agents such as aspirin and clopidogrel. For patients undergoing a major surgical or invasive procedure, if the intent is to eliminate any effect of antithrombotic therapy, it should be stopped at a time before the procedure. Coumadin (warfarin) should be stopped approximately 5 days if the patient's INR is maintained between 2 and 3, with the goal of bringing the INR to 1.5 prior to surgery. If the INR persists between 1.8 or higher, then the option of administering a small dose (1 mg, subcutaneously) of vitamin K is an option for antagonism of anticoagulation. If the INR is maintained at greater than 3.0, then Coumadin should be stopped 10 days prior to surgery. In patients in whom there is concern for thrombus formation if the vitamin K antagonist is stopped, then “bridging therapy” with lower molecular weight Heparin given via subcutaneous means or unfractionated heparin given intravenously, can be used as bridging therapy.

In patients receiving an antiplatelet drug, clopidogrel, medication should be stopped 7–10 days prior to surgery. In patients who are receiving antiplatelet drugs alone, bridging anticoagulation is not typically administered.

Ear, nose, and throat surgery often requires special anesthetic considerations and equipment. These concerns are important to both the surgeon and the anesthesiologist. In this section, concerns that merit attention are outlined in brief. A more detailed description of the procedures can be found elsewhere in the text.

Surgery of the Oral Cavity and Airway

Tonsillectomy and Adenoidectomy

Preoperative Considerations

• Most patients are usually young and healthy.
• A few may present with symptoms of obstructive sleep apnea (OSA). Patients with OSA are often obese, with potentially difficult airway. They may have a short, thick neck, large tongues, and redundant pharyngeal tissue, so they may require an awake tracheal intubation. Sedative premedication may be avoided in children with OSA, intermittent obstruction, or very large tonsils.
• Patients may present with upper respiratory tract infections (URI). Surgery for these patients should be postponed until resolution of the URI (usually 7–14 days). These patients may develop laryngospasm with airway manipulation. This is an undesirable complication with potential for significant morbidity and even mortality.

Intraoperative Considerations

• Tracheal intubation in some patients may be significantly difficult; hence the presence of an otolaryngologist may be helpful at the time of intubation.
• The use of an oral RAE tube for tracheal intubation may optimize visualization of the surgical field.
• In younger children in whom an uncuffed tracheal tube is used, in order to avoid inhalation blood from the pharynx area, the supraglottic area may be packed with petroleum gauze tube provided an appropriate leak around the endotracheal tube is obtained.
• Patients should be extubated awake when protective airway reflexes have returned. In patients with reactive airway disease, including asthma, deep extubation of the patients may be warranted to prevent airway reactivity, including bronchospasm and laryngospasm.
• The use of LMAs for tonsillectomies has been increased in the last few years. With a well-trained team, adenotonsillectomy on children can be carried out safely in an office-based setting with LMA and a short postoperative stay.

Postoperative Complications

• Retention of throat pack.
• Pulmonary edema. Acute airway obstruction such as laryngospasm can lead to pulmonary edema. This occurs as the patient breathes against a closed glottis, creating a negative intrathoracic pressure. This pressure is transmitted to the interstitial tissue, increasing the hydrostatic pressure gradient and enhancing fluid out of the pulmonary circulation into the alveoli.
• Hemorrhage from bleeding tonsil. Often re-intubations may be difficult. Care should be taken not to over-sedate the patient who may aspirate large quantities of blood. If bleeding is not controlled, then the patients should be returned to the operating room for exploration and surgical hemostasis.
• In the last few years, the performance of tonsillectomies in morbidly obese patients has come under much scrutiny due to postoperative respiratory complications due to opioid use for analgesia. It is clear that morbidly obese patients and patients with OSA merit special consideration and may not be ideal candidates for same-day surgery.

Laser Surgery of the Airway

Laser surgery for lesions in the airway provides precision in targeting lesions, minimal bleeding and edema, as well as preservation of surrounding structures and rapid healing. The carbon dioxide laser has particular applications in the treatment of laryngeal or vocal cord papillomas and laryngeal webs, resection of redundant subglottic tissue, and coagulation of hemangiomas.

Preoperative Considerations

Appropriate equipment should include a laser-resistant endotracheal tube, and other endotracheal tubes for emergency situations should be available. Anesthesia during laser surgery may be administered with or without an endotracheal tube. All standard PVC endotracheal tubes are flammable and can ignite and vaporize when in contact with the laser beam. Some surgeons may prefer using a Dedo or Marshall laryngoscope and intermittent ventilation with a Sanders ventilator. The Sanders ventilator is a jet ventilator that delivers oxygen under 50 psi directly through a port in the laryngoscope.

Intraoperative Considerations

• The eyes of a patient must be protected by taping them shut, followed by the application of wet gauze pads and a metal shield in order to prevent laser penetration of eyes. All operating room personnel should wear special protective glasses.
• Airway fires are a risk with laser surgery, and a plan of action is necessary. In some centers the tracheal balloon is filled with methylene blue; hence rupture of the balloon is an early indication of a hazard. Both oxygen and nitrous oxide support combustion, and hence a mixture of 30% oxygen and nitrogen may be used. If a fire occurs, ventilation should be discontinued, oxygen turned off, and the tube removed. If the flame persists, the field should be flooded with normal saline. Direct examination of the pharynx and larynx will evaluate the extent of the burn.
• If a Dedo or Marshall laryngoscope is used, then maintenance anesthesia can be accomplished with an IV anesthetic to prevent anesthetizing the surgeon.
• The patient should be reintubated with a regular endotracheal tube after the bronchoscope is removed.
• Use of the Sanders jet ventilator is associated with the risk of pneumothorax and pneumomediastinum due to rupture of alveolar blebs or a bronchus.

Postoperative Considerations

• In the event of an airway fire, the patient should be monitored for at least 24 hours. Steroids and antibiotics should be considered for severe burns.
• If respiratory problems are encountered, then patients should be observed in an intensive care setting.

Epiglottitis

Acute epiglottitis is one of the most feared upper airway disease in children and adult. It is an infectious disease caused by Haemophilus influenzae type B. It can progress rapidly from sore throat to airway obstruction to respiratory failure and death if proper diagnosis and treatment are delayed. Patients are usually between 2 and 7 years of age, although epiglottitis has been reported in younger children and adults. Characteristic signs and symptoms of acute epiglottitis include:

• sudden onset of fever, dysphagia, drooling, thick muffled voice, and preference for the sitting position with the head extended and leaning forward;
• retractions, labored breathing, and cyanosis, which may be observed in cases where respiratory obstruction is present.

Preoperative Considerations

• Do not attempt direct visualization of the epiglottis in the unanesthetized patient. This could lead to airway compromise and death.
• Do not attempt excessive blood draws that will excite the patient. Keep the patient calm. The differential resulting from negative pressure inside and atmospheric pressure outside the extrathoracic airway results in slight narrowing during normal inspiration. During inspiration the pressure differential is exaggerated in the patient with airway obstruction. This dynamic collapse of the airway may become life-threatening in the struggling and agitated patient.

Intraoperative Considerations

• If the patient is a child, then a parent should be allowed into the operating room to keep the patient calm.
• An emergency airway cart and tracheostomy tray should be available and open.
• Induce anesthesia with halothane or sevoflurane maintaining spontaneous ventilation. Secure the airway.

Postoperative Considerations

• Postoperative care should be in the ICU for continued observation and radiographic confirmation of tube placement.
• Tracheal extubation is usually attempted 48–72 hours later when a significant leak around the endotracheal tube is present and visual inspection of the larynx by flexible fiberoptic bronchoscopy confirms reduction in swelling of the epiglottis and surrounding tissues.

Parotid Gland Surgery

Parotid gland surgery is usually performed for tumors but can also be performed for infectious disorders. Some diseases of parotid gland have been associated with the use of alcohol; hence these patients may exhibit the signs and symptoms of alcohol-related diseases. The surgeries are performed under general anesthesia, and in most cases, the facial nerve will need to be preserved and hence nerve monitoring is necessary. When a radical parotidectomy is done, the facial nerve may be sacrificed and reconstructed with a graft from the contralateral greater auricular nerve.

Special Considerations

• Muscle relaxants should be avoided if nerve monitoring is used.
• Nasal intubation may be necessary if mandible has to be dislocated.

Nasal Surgery

A significant percentage of nasal surgery is performed for cosmetic purposes, although a large percentage is performed for functional restoration of the airway. Functional restoration is usually performed for either congenital or posttraumatic deviations of the septum. Nasal surgery is office based and performed with local anesthesia and IV sedation. Patients with nasal polyps and asthma often have a hypersensitivity to aspirin, which can precipitate bronchospasm.

Intraoperative and Postoperative Considerations

• The most important consideration is achieving profound vasoconstriction in the nares to control bleeding. This can be achieved with cocaine packs, local anesthetics, and epinephrine infiltration.
• Since these drugs have a profound effect on the cardiovascular system, a careful evaluation of the cardiovascular system is essential, especially for older patients or patients with known cardiac disease. A vasoconstrictor can also precipitate dysrhythmias.
• A moderate degree of controlled hypotension combined with head elevation decreases bleeding in the surgical site.
• Blood may passively enter the stomach. The placement of an oropharyngeal pack or suctioning of the stomach at the conclusion of surgery may attenuate postoperative retching and vomiting.

Ear Surgery

The ear and its associated structures are target organs for many pathological conditions. Perhaps most common is the placement of myringotomy tubes. Also on the rise are placement of cochlear implants and tympanoplasties. The surgeries usually require general anesthesia and, in some cases, rely on neuromonitoring. When nerve monitoring is necessary, muscle relaxants should not be used. In most cases of ear surgery, there is nausea and adequate pretreatment with antiemetics, and the use of anesthetics such as propofol and sevoflurane have been shown to reduce the incidence of nausea and vomiting.

Myringotomy and Tube Insertion

Special Considerations

• Premedication is not recommended because most sedative drugs will far outlast the duration of surgical procedure.
• Anesthesia may be effectively accomplished with a potent inhalation drug, oxygen, and N2O administered by mask.
• Pretreat for nausea and vomiting.

Middle Ear and Mastoid Surgery

Tympanoplasty and mastoidectomy are two of the most common procedures performed on the middle ear and accessory structures.

Special Considerations

• An oral or nasal RAE tube may be helpful in avoiding intrusion into the surgical field.
• Although not totally contraindicated, N2O should be discontinued at least 30 minutes before placement of a tympanic membrane graft to avoid pressure-related displacement.
• Extubation should be smooth to avoid straining, which may unseat the tympanic membrane graft or disrupt other repairs.

Postoperative Considerations

Postoperative nausea and vomiting are the most common postoperative problems. This can be reduced by:

• decompressing the stomach after induction of general anesthesia, thereby emptying the stomach of gas and fluid;
• limiting the use of opioids;
• using antiemetics.

Neck Surgery

Neck dissection may be complete, modified, or functional. The primary muscle involved is the sternocleidomastoid muscle, the primary nerve is cranial nerve XI, and the primary vascular structures are the internal and external jugular veins and the carotid artery. Often a neck dissection is performed for removal of a tumor and may also involve a partial or total glossectomy. Patients who present with such tumors may have a history of tobacco use and pulmonary disease and may need a preoperative pulmonary workup. In a high percentage of cases, the dissection may be bilateral and a tracheostomy may be performed to maintain a patent airway.

Special Considerations

• These patients may be a challenge to intubate if they have a history of radiation treatment to the larynx and pharynx or if they have a significant mass in the oral cavity.
• If nerve monitoring is used, then muscle relaxants should be avoided.
• Dissection around the carotid bulb may precipitate bradycardia, which may be treated with an injection of local anesthetic into the bulb or with IV atropine or glycopyrrolate.
• Laryngeal edema can be a significant problem if no drains are placed.

Postoperative Considerations

• Nerves injured include the facial nerve, resulting in a facial droop. In addition, injury to the recurrent laryngeal nerve can cause vocal cord dysfunction. If the injury is bilateral, this can lead to airway problems. Since the phrenic nerve also traverses through the operative field, paralysis of the hemidiaphragm can occur. If injury is bilateral, that breathing will be impaired.
• With low neck dissection, a pneumothorax can occur.
• Excessive coughing or agitation can result in hematoma formation and airway compromise.