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Many different anesthesia techniques have been advocated for microlaryngeal endoscopic surgery (see Chapter 42 ). The goal is to provide the surgeon with a clear view, an immobile field, and room to work. The objectives are to protect the trachea, ensure good ventilation and oxygenation, minimize secretions and reflexes, and promote rapid awakening and return of protective airway reflexes. Morrison and associates[94] described the advantages and disadvantages of these techniques.
Routine premedication should be avoided. An antisialagogue such as glycopyrrolate to facilitate drying of oral secretions may be helpful. Titrated intravenous administration of 1-mg increments of midazolam with monitoring may be performed in the preinduction area.
Preoperative decisions about tracheal intubation and anesthesia management depend on whether the abnormality is a small vocal cord polyp, a potentially obstructing lesion such as papillomatosis, or a large and friable supraglottic tumor that will completely obstruct the glottic opening. If there is any question about the airway, direct laryngoscopic examination should be performed[133] [134] in an awake patient to assess the difficulty of intubation.
A small, long (5 mm × 31 cm) endotracheal tube with a high-volume low-pressure cuff can be used without obscuring the surgeon's view.[94] [135] The posterior commissure area can be inspected at extubation or by moving the tube aside. The use of a small endotracheal tube allows for monitoring of end-tidal CO2 , application of positive-pressure ventilation, and protection of the trachea.[136]
Another method of providing anesthesia for microlaryngoscopy places a small catheter between the vocal cords for insufflation of anesthetic gases at high flow rates. This technique does not protect the trachea or allow for the use of positive-pressure ventilation. High concentrations of the inhaled anesthetic must be used to overcome atmospheric dilution, and exhaled gas is blown back at the surgeon and into the operating room. Motion of the vocal cords may also occur.
Jet ventilation using Venturi entrainment provides ventilation without the use of an endotracheal tube,[94] [137] and the surgeon therefore has an unobstructed view of the larynx. Keeping the tip of the jet within the laryngoscope avoids airway barotrauma. Alignment of the laryngoscope with the tracheal axis is essential. The vocal cords need to be relaxed fully, and pathologic conditions in the airway must not be so large that they obstruct airflow. Motion of the chest wall must be monitored at all times. Ventilation begins at low pressure (30 to 50 psi). Inspiration lasts 1.5 seconds, passive expiration lasts 6 seconds, and the ventilatory rate is 6 to 7 breaths/min. The jet Venturi technique is contraindicated in children, obese patients, and patients with bullous emphysema. When large tumors are present in the airway, debulking of the tumor under general endotracheal anesthesia should be accomplished first. The jet technique may force blood or tumor tissue into the lungs.
An apneic technique involving alternate tracheal intubation and no tube during endoscopic removal of papillomas in children has been used successfully by Weisberger and Miner.[138] Babinski and coauthors [139] described the use of high-frequency positive-pressure ventilation during anesthesia for laryngoscopy. Small tidal volumes provide good gas exchange at low airway pressure. Respiratory rates of 60 breaths/min at 60 to 100 psi are provided by means of a stiff 3.5- to 4.0-mm catheter placed through the vocal cords. The risk of barotrauma and pneumothorax is lower, especially in patients with obstructive airway disease.
Good muscle relaxation is essential. Succinylcholine infusion may be considered for very brief cases. If the procedure is expected to last at least 30 minutes, use of a neuromuscular blocking drug such as vecuronium, rocuronium, or mivacurium for tracheal intubation allows return of muscle strength and spontaneous respiration for safe extubation.
Stimulation of the larynx can produce hypertension, tachycardia, and arrhythmias. Intravenous or topical application of lidocaine and small doses of fentanyl (1 to 2 µg/kg IV) moderate the sympathetic response. β-Blockers may also be helpful.
Propofol induction (2 mg/kg IV) and infusion (10 mg/kg/hr) combined with fentanyl (1 to 2 µg/kg IV) supplementation, topical anesthesia of the larynx, and appropriate muscle relaxation have been used for microlaryngoscopy procedures. [140] The use of remifentanil can lead to faster recovery.[141] Monitoring is important because the incidence of myocardial infarction or ischemia after microlaryngoscopic procedures has been reported to be 1.5% to 4.0%.[142]
CO2 and neodymium:yttrium aluminum garnet (Nd:YAG) lasers are frequently used for microsurgery on the upper airway and trachea (see Chapter 67 ). The surgical advantages of using lasers include less bleeding, the ability to coagulate small vessels, maintenance of sterile conditions, less tissue reaction, increased precision of dissection, preservation of normal tissue, and in the case of Nd:YAG lasers, the ability to transmit the beam by fiberoptics. Van der Spek and associates[143] and Hermens and colleagues[144] reviewed the physics and medical uses of lasers, including their safety and implications for anesthesia management.
The American Society for Testing and Materials Subcommittee F29.02.10 developed guidelines for the provision of safe anesthesia during laser surgery on the upper airway. These guidelines compare and comment on the advantages and disadvantages of several anesthetic techniques and laser-resistant endotracheal tubes.[145] McRae reviewed laser use in airway surgery.[102]
Light amplification by stimulated emission of radiation (LASER) produces a beam of light that is monochromatic and coherent. Lasers exist in the infrared, visible, and ultraviolet regions of the spectrum. Light can be focused into an extremely small point, thereby achieving a very high power density. This beam is capable of vaporizing biologic tissue. Each laser medium emits radiation of a specific wavelength, which determines how the beam will interact with biologic tissue. Lasers are operated in short pulses, long pulses, or continuously. The continuous-wave CO2 laser, which produces radiation with a wavelength of 10,600 nm, is strongly absorbed by water and damages tissue surfaces to a depth of 0.2 mm. For this reason, the CO2 laser is suitable for removing lesions on the vocal cords and in the larynx.
The Nd:YAG laser, a short-pulsed, high-powered glass laser producing light with a wavelength of 1064 nm, can be transmitted by fiberoptics. Energy from Nd:YAG or argon (wavelength of 500 nm) lasers is absorbed preferentially by hemoglobin and pigmented tissue, has deep, penetrating effects, and is useful in treating detached retinas.
Moist gauze covering should protect nontarget tissue. Alignment of the laser should be checked, and immobility of the patient should be maintained. Operating room personnel should wear appropriate glasses or goggles to absorb the wavelength emitted by the laser in use. Instruments used with lasers should have a dull matte finish to decrease reflection.
Lasers can ignite materials used in anesthesia practice. The CO2 laser can penetrate an endotracheal tube and ignite a fire, supported by oxygen and N2 O.[146] Inhalation of smoke can cause chemical injury, bronchospasm, edema, and respiratory failure. Red rubber tubes burn and produce carbon monoxide gas. Burning polyvinyl chloride tubes produce hydrogen chloride, a pulmonary toxin.
In 1979, the reported incidence of airway fires during CO2 laser surgery was 0.4%.[144] [147] With the use of recommended equipment, techniques, and gas mixtures,[145] airway fires should be rare. During laser surgery on the airway, not more than 30% oxygen in nitrogen or helium should be used. N2 O supports combustion, as does oxygen. Sixty percent helium is an effective fire quencher,[148] and the use of protected endotracheal tubes reduces the risk of fire.[149] Commercially available laser-safe tubes should be used. They may be metal, aluminum, or copper foil-wrapped,[150] laser-resistant materials [151] or double-cuffed silicone-coated metal tubes. These tubes may be recommended as being resistant to the CO2 laser but not to the Nd:YAG laser.[152]
An alternative is to use a Venturi ventilation technique without an endotracheal tube.[137] Fire in the airway can still be a risk, however, because tissue may dry up and ignite in the high flow of oxygen.
Treatment of airway fires requires removal of the burning endotracheal tube, reintubation of the trachea, and flushing of the pharynx with cold saline. A rigid bronchoscope checks for damage and the presence of foreign bodies. Humidified gas, steroids, antibiotics, controlled ventilation, and tracheostomy may be necessary. Monitoring includes the use of chest radiographs, pulse oximetry, ECG, and analysis of arterial blood gases (see Chapter 67 ).
Laser surgery on the tracheobronchial tree is performed with the CO2 or Nd:YAG laser by means of a rigid bronchoscope. This instrument allows better visualization, access, control of bleeding, suctioning, and irrigation. [153] The literature on ventilation and anesthesia technique for bronchoscopic laser surgery is not consistent. After reviewing many techniques, Van der Spek and coauthors[143] discussed the advantages and disadvantages and described their own successful clinical practices.
Management of subglottic laser surgery presents challenges for the anesthesiologist. Bargainner and associates[154] analyzed these challenges and outlined safe methods with a ventilating laryngoscope and jet ventilation, in addition to discussing potential complications.
Either a CO2 laser or an Nd:YAG laser is used in subglottic laser surgery. The Nd:YAG laser penetrates tissue (4 to 5 mm), has hemostatic properties, and can be conducted by a single optic fiber. Even foil-wrapped and special laser-shielded endotracheal tubes have been perforated and ignited within 12 seconds during continuous Nd:YAG laser exposure.[155]
Postoperative considerations include head-up positioning to decrease edema and administration of humidified oxygen. If a Venturi jet technique has been used, complications such as pneumothorax or respiratory failure may occur within the first 2 hours. Steroids and racemic epinephrine may be helpful in controlling laryngeal edema.
Improved monitoring and postanesthesia care have reduced the mortality from tonsillectomy (see Chapter 60 ). The goal of anesthesia for tonsillectomy is to provide deep general anesthesia that prevents reflex-induced hypertension, tachycardia, and arrhythmias. Muscle relaxation is required to prevent bucking, coughing, or straining. Rapid recovery to consciousness and the return of protective airway reflexes are also desirable. The safest practice is probably to extubate the trachea when the patient is awake. Use of the reinforced, flexible laryngeal mask airway for tonsillectomies,[156] [157] [158] adenoidectomies, [159] and nasal surgery[160] provides excellent airway protection with less eventful recovery, cough, or airway obstruction on emergence.
Stridor and laryngospasm after adenotonsillectomy can be minimized by applying topical 2% lidocaine to the glottic and supraglottic areas before intubation. This treatment proved as effective as giving intravenous lidocaine (1 mg/kg) just before extubation, but without higher sedation scores.[161]
Preoperative evaluation includes checking for loose teeth, ensuring that aspirin has not been ingested recently, and determining coagulation variables. Premedication is not usually necessary.
A technique using fentanyl and a short-acting muscle relaxant with a volatile inhaled anesthetic is satisfactory. A topical spray of 4% lidocaine on the tonsil area will help decrease the anesthetic requirement, the incidence of arrhythmias, and postoperative stridor and laryngospasm.[161] [162] These patients should be well hydrated with a solution of balanced crystalloid (3 to 5 mL/kg/hr). Blood loss during tonsillectomy is difficult to estimate.
Patients with sickle cell disease are at higher risk for postoperative complications such as pneumonia, atelectasis, and vaso-occlusive crisis. Children with sickle cell disease presenting for elective tonsillectomy should be given a transfusion to reduce the hemoglobin S ratio to less than 40%.[163] Children with chronic adenotonsillar hypertrophy may also have associated undiagnosed obstructive sleep apnea syndrome and are at increased risk for postoperative respiratory complications.[164] Patients with Down syndrome may have large tongues and unstable atlanto-occipital joints and require more careful perioperative airway management.[165]
Tracheal extubation usually occurs in the operating room when the patient is awake and protective airway reflexes are present. Some coughing should not interfere with surgical closure of the tonsillar bed.
Pediatric tonsil patients are placed in the "tonsil position" (i.e., on one side with the head slightly down) in the recovery area to allow blood or secretions to drain out rather than flow back onto the vocal cords. One hundred percent oxygen mist is given by facemask; the pulse oximeter, arterial blood pressure, and ECG are monitored routinely. Patients should be kept in the recovery room for at least 60 minutes. The pharynx should be rechecked directly for bleeding before discharge from the recovery room.
Intraoperative complications from tonsillectomy consist of arrhythmias caused by increased levels of endogenous epinephrine from light general anesthesia, sensitization of the myocardium to catecholamines by halothane, and hypercapnia. Postoperative complications consist of poor respiratory function and continued bleeding. Patients with a history of obstructive sleep apnea must be extubated awake and observed closely in the recovery room for depressed respiratory function.[166] [167]
Although postoperative bleeding is the most serious complication, persistent vomiting and poor oral intake are the most common reasons for unscheduled overnight admission after ambulatory surgery. The incidence of PONV can be as high as 70% during the first 24 hours after tonsillectomy.[168] Many different antiemetic regimens have been advocated to minimize PONV after tonsillectomy surgery.[169] [170] [171] Pappas and colleagues[172] noted that a preoperative dose of dexamethasone decreased the incidence of PONV after tonsillectomy in children.
Although metoclopramide may help empty the stomach, it does not seem to have specific antiemetic properties as ondansetron does in preventing PONV after tonsillectomy.[173] Withholding oral fluids postoperatively from children undergoing day surgery reduces the incidence of vomiting. [174] It is important to develop anesthetic techniques and to use appropriate antiemetics and recovery protocols to minimize vomiting after tonsillectomy. Avoid meperidine, decompress the stomach, discontinue N2 O, [175] administer an antiemetic regimen, keep the patient well hydrated, and do not force oral fluids.
The incidence of post-tonsillectomy bleeding requiring surgery is 0.3% to 0.6%. This complication usually occurs within 6 hours of surgery,[176] and the extent of blood loss is generally underestimated. No premedication should be given. Coagulation should be tested, if possible, and blood should be typed and crossmatched. The patient should be well hydrated through a reliable intravenous line. Most problems before induction are caused by hypovolemia and airway obstruction.
At induction of anesthesia, an additional person should be available to provide good suctioning of blood. Rapid-sequence induction of anesthesia with the application of cricoid pressure and slight head-down positioning of the patient will protect the trachea and glottis from aspiration. After induction, a nasogastric tube may be placed and removed. As with elective tonsillectomy, extubation is safest with the patient awake.
A peritonsillar abscess can cause pain, trismus, dysphagia, and respiratory obstruction. Often, the abscess can be drained by incision or needle aspiration under local anesthesia. The risks of general anesthesia include further respiratory obstruction, difficult endotracheal intubation, and rupture of the abscess with spilling of pus into the airway.
Planning of general anesthesia for a peritonsillar abscess may include preoperative decompression of the abscess to minimize the risk of rupture. A difficult intubation should be expected because of distorted anatomy, edema, and incomplete resolution of trismus. Endotracheal intubation must be performed slowly, carefully, and gently. If the abscess is right sided, a left-sided approach for laryngoscopy may be indicated. If airway obstruction is expected, one of three options should be selected: awake intubation under direct vision, mask induction with the patient breathing spontaneously, or elective tracheostomy.
Ludwig's angina is a cellulitis of the submandibular and sublingual spaces, possibly including the anterior compartments of the neck.[177] Visualization of the glottic opening is frequently impossible. General anesthesia is contraindicated if stridor occurs at rest. Therefore, tracheostomy with local anesthesia through the cellulites may be the safest way to secure the airway. Decompression under cervical block has also been described.[178]
Adult epiglottitis occurs in 1 per 100,000 adults per year.[179] Causes include infection, trauma, and irradiation. Symptoms are a sore throat, dysphagia, a muffled voice, and respiratory distress. Careful inhalation induction plus titrated intravenous sedation before rigid bronchoscopy or endotracheal intubation is the recommended technique.[180] [181] The use of steroids is controversial, but they may help in cases of angioedema. [182] Racemic epinephrine is not necessarily useful.
Aspiration of a foreign body into the trachea is a common cause of sudden onset of obstructive breathing, croupy cough, hoarseness, or wheezing in young children. Several reviews have described in detail the problems and precautions of anesthesia management.[94] [132] Dislodging the foreign body into the upper part of the trachea can convert partial obstruction into total obstruction.
During severe airway obstruction, the anesthesiologist should consider either direct laryngoscopy in an awake patient or a rigid bronchoscopic examination without the application of positive pressure. Most of these cases occur in children. Usually, gentle mask induction without cricoid pressure or positive-pressure ventilation is the preferred induction technique.[183] [184] Kosloske[185] routinely uses muscle paralysis and controlled ventilation. The surgeon must be prepared to perform an emergency tracheostomy or cricothyrotomy if partial obstruction suddenly becomes complete.
Laryngeal and subglottic edema may last for 24 hours after removal of a foreign body. Close observation and the use of humidified oxygen are suggested during this recovery period.
Difficult intubations are usually caused by anatomic abnormalities such as micrognathia, limited jaw motion, or congenital syndromes ( Chapter 42 ). Other causes of difficult intubations include obesity, acromegaly, cervical spine problems, rheumatoid arthritis, and even gastric reflux.[186] Evaluation of the head, neck, mandible, tongue, teeth, and oropharynx can help predict a potentially difficult intubation. Various strategies have been devised to assess the airway.[187] [188] [189] [190] [191] They often have high sensitivity but low predictive value and may fail to predict difficult intubations accurately.
A compromised airway implies partial obstruction to airflow and the risk of total obstruction if further airway narrowing occurs. Pathologic conditions above the glottis prevent a clear view of the glottic opening, whereas subglottic lesions permit a good view of the vocal cords, but require careful placement of a small endotracheal tube or bronchoscope. All compromised airways are difficult intubations, but not all difficult intubations occur in patients with compromised airways.
A large percentage of serious anesthesia accidents involve some aspect of airway mismanagement. In a closed claims analysis, Cheney and coauthors [192] reported that most respiratory complications involved an inability to intubate, esophageal intubation, or inadequate ventilation. The American Society of Anesthesiologists developed a practice algorithm for safe management of the difficult airway.[193] Crosby and colleagues[194] reviewed the causes, techniques, and problems associated with difficult airways. Benumof and Scheller[195] [196] described the management of a difficult adult airway with emphasis on awake intubation techniques[133] and the use of transtracheal jet ventilation (TTJV).[197] These authors noted that the incidence of "cannot ventilate—cannot intubate" situations may be as high as 1 per 5000 anesthesics.[196] Proper response to these emergency situations involves the use of an intubating laryngeal mask airway,[198] [199] [200] the Combitube (Kendall-Sheridan, Argyle, NY), a TTJV, or a tracheostomy. Sofferman and associates[201] discussed alternatives for the management of a lost airway during induction of anesthesia in head and neck surgery, including use of the laryngeal mask airway and Combitube. A combined technique using an anterior commissure laryngoscope and gum elastic bougie is preferred for the special circumstances of patients requiring otolaryngologic surgery.
Regional blocks of the oropharynx, larynx, and glottis facilitate awake intubation (see Chapter 42 and Chapter 44 ). Preparation of patients for awake intubation includes premedication, topicalization, and nerve blocks from the nasal cavity to the trachea, including sphenopalatine, glossopharyngeal, and superior laryngeal nerve blocks.[133] [202] [203] The glossopharyngeal nerve supplies sensory innervation for the posterior third of the tongue, the oropharynx, the tonsillar area, and the gag reflex. This nerve can be blocked by infiltration of 3 mL of 2% lidocaine posterior to the palatopharyngeal fold at its midpoint, 1 cm deep to the mucosa of the lateral pharyngeal wall. Paralysis of the pharyngeal muscles and relaxation of the base of the tongue may cause some respiratory obstruction.[204] [205] If a glossopharyngeal nerve block is used with blockade of the superior laryngeal nerve for awake intubation, the latter procedure should be performed first to avoid respiratory obstruction.
The internal branch of the superior laryngeal nerve lies just below the mucosa in the depth of the piriform fossa. A topical block of this nerve can be performed by applying local anesthetic for 3 to 5 minutes to the piriform fossa mucosa.[133]
An external approach to block the superior laryngeal nerve may be used in the absence of neck tumor or infection. A 23-gauge needle is placed 1 cm medial to the superior cornu of the hyoid bone and directed caudad to pierce the thyrohyoid membrane. After aspiration, 2 mL of local anesthetic is injected. Blockade of the superior laryngeal nerve anesthetizes all laryngeal mucous membranes above the rima glottidis, including the epiglottic and arytenoepiglottic folds. This block should be used with caution in patients with a full stomach because it removes some protective reflexes. A maxillary nerve block can interrupt sensory innervation to the nasal cavity in preparation for nasotracheal intubation. The mandibular nerve can be blocked from an external approach. This block eliminates masseter muscle tone, relaxes the jaw, and minimizes biting by an awake, but uncooperative patient. Loss of masseter tone may cause partial upper airway obstruction.
The trachea and vocal cord area can be anesthetized either by atomizer from above or by transtracheal injection. Sensory innervation is supplied by the vagus nerve via the recurrent laryngeal nerve. These nerves run along the tracheoesophageal groove and supply both sensory fibers and motor fibers to the intrinsic muscles of the larynx. Bilateral recurrent laryngeal nerve blocks can result in vocal cord paralysis and airway obstruction.
Direct laryngoscopy, bronchoscopy, or tracheal intubation can be performed in an awake patient with minimal discomfort or risk after a topical laryngeal block.
Difficult direct laryngoscopy occurs in 1.5% to 8.5% of general anesthetics, and failed intubation occurs in 0.13% to 0.3%.[194] Initial methods for dealing with these unexpected situations include the following: external laryngeal manipulation[206] or backward, upward, and rightward laryngeal displacement[207] to bring the glottis into view; use of a stylet; repositioning of the head; change of the laryngoscope blade; and the use of special blades.[208] A flexion-flexion position of the head and neck may achieve glottal exposure. The flexion-flexion position aligns the oral and pharyngeal cavities to facilitate direct view of the vocal cords. Extension of the head at the atlanto-occipital joint leads to backward displacement of the tongue base into the airway. Further options include the intubating laryngeal mask airway,[195] [199] [200] [209] the use of a rigid or flexible fiberoptic scope,[210] [211] or nasotracheal intubation. Parmet and coworkers[212] found that the laryngeal mask airway provided rescue ventilation without complications in 94% of cases of unanticipated difficult intubation and ventilation. Less than 50% of blind nasotracheal intubations succeed on the first attempt. Furthermore, bleeding and trauma often occur after several attempts.
Other methods involve the use of a light wand,[213] [214] a rigid bronchoscope, the Combitube,[215] or a retrograde catheter technique.[208] [213] The Combitube has been associated with esophageal rupture and should be inserted carefully, under direct vision whenever possible.[216] Skill should be attained in routine cases before relying on these methods for a difficult intubation. Fiberoptic equipment must be used often enough in routine situations to be reliable during intubation of abnormal airways.[217] [218] The fiberoptic scope has been useful during nasotracheal intubations in rheumatoid arthritis patients who have trismus or spondylosis. Chapter 42 also discusses difficult endotracheal intubations.
Several investigators have provided guidelines for the safe evaluation and management of patients with compromised airways.[129] [194] [195] [196] [208] [209] [219] [220] [221] Clinical signs and symptoms such as stridor, tachypnea, cyanosis, anxiety, sternal retractions, diaphoresis, and tachycardia are usually present. Patients with chronically abnormal airways learn to adapt their breathing and vocalization to limited airflow. Before attempting any method of intubating a compromised airway, as much information as possible should be gathered. Such information consists of radiographs, computed tomographic or magnetic resonance imaging scans, old records, history, and physical examinations.
Patients with compromised airways must not be given general anesthesia or muscle relaxants unless control of the airway is ensured. Awake intubation should be performed under direct vision in patients with uncertain pathologic processes. Safe techniques for managing compromised airways include awake direct laryngoscopy after topical laryngeal block,[133] [134] awake fiberoptic,[217] tracheostomy under local anesthesia, TTJV through a cricothyroid puncture, or emergency cricothyrotomy.[222]
TTJV is a quick, easy, safe solution to the problem of "cannot ventilate/intubate." Various methods of providing TTJV are possible. It is recommended that TTJV be available for every anesthetizing location. The incidence of serious complications from the elective use of TTJV is relatively low, and such complications are usually related to tissue emphysema or pneumothorax. The risk of barotrauma and gas trapping from TTJV is increased when upper airway obstruction limits the ability to expel TTJV gas from the lungs.[197]
Tracheostomy may be necessary for upper airway obstruction, loss of protective airway reflexes, or chronic aspiration caused by vocal cord paralysis (see Chapter 63 and Chapter 75 ).[223] Other reasons are that endotracheal intubation is not feasible, stridor is present at rest, patency of the airway is lost, or an unstable foreign body is present in the airway. A tracheostomy after major head and neck surgery sometimes ensures smoother postoperative recovery.
A tracheostomy performed under general anesthesia provides the surgeon with an immobile, cooperative patient and allows a less hurried procedure. General anesthesia may be provided by means of a small endotracheal tube, a rigid bronchoscope, a facemask, a laryngeal mask airway, or a glottic aperture seal airway. [224] Intubation may be accomplished with the aid of a fiberoptic bronchoscope or an intubating laryngeal mask airway. Avoid muscle relaxants. Awake laryngoscopy allows evaluation of the airway to determine a safe course of action.
A tracheostomy with local anesthesia is safe but requires some patient cooperation. Bilateral superficial cervical plexus blockade can supplement local infiltration. Patient cooperation is best achieved through verbal reassurance by the anesthetist and not by heavy sedation. During the procedure, the anesthesiologist must attend to airway management, give 100% oxygen, and follow vital signs with full monitoring.
Coughing may be decreased by giving lidocaine (1.5 mg/kg IV) approximately 2 minutes before placement of the tracheostomy tube. Often, sudden reestablishment of a good airway results in rapid correction of hypercapnia, resolution of stress, a decrease in endogenous catecholamines, and subsequent hypotension. Postobstructive pulmonary edema can also occur and has been reported in a young adult with coronary artery disease subsequent to relief of airway obstruction.[225] A major early complication of tracheostomy is malpositioning of the tube. As soon as a tracheostomy tube is placed, end-tidal concentrations of CO2 , breath sounds, and oxygen saturation must be checked. A chest radiograph should be obtained to verify correct tube placement and the absence of pneumothorax. Other early complications of tracheostomy include bleeding and local emphysema, which are usually exacerbated if the patient coughs and struggles.
The most important of the late complications of long-term tracheostomy is tracheal stenosis at the cuff site or stoma.[226] The use of high-volume low-pressure cuffs minimizes this complication. During general anesthesia, N2 O diffuses into the tracheal cuffs within 60 to 90 minutes and causes increased cuff pressure.
A Montgomery T-tube[227] or Olympic tracheal button must be placed without tension. These devices have the
Postoperative care after tracheostomy requires the administration of humidified oxygen, careful intermittent suctioning of secretions, attention to sterile precautions, and adjustment of cuff pressure to maintain 15 to 20 mm Hg. Prolonged tracheal suctioning not preceded or followed by oxygenation can result in arrhythmias secondary to hypoxia. Moreover, the track from the stoma to the trachea is not fully established for 5 days. Therefore, changing the tube within 5 days of tracheostomy runs the risk of losing this track. Under these circumstances, a pediatric laryngoscope may be helpful in holding the tissue apart and facilitating visualization of the trachea. For emergency airway management, a laryngoscope and small endotracheal tube should be at the bedside of all patients who have recently undergone tracheostomy.
Cricothyrotomy is another method of establishing an airway quickly (within 1 to 2 minutes) in an emergency, life-threatening situation. The complication rate of 8.6% is less than that for emergency tracheostomy.[228] The trachea is entered directly through an incision in the cricothyroid membrane just below the vocal cords. Disadvantages include damage to the cricoid cartilage, bleeding, and the need for insertion of a small tube. Emergency cricothyrotomy is a temporary procedure that secures an airway until a definitive tracheostomy can be established.
No patient should sustain injury or death because of upper airway obstruction. At the very least, the cricothyroid membrane can be punctured with a 12- to 14-gauge needle to provide temporary oxygenation. This method of transtracheal ventilation through a large needle has been effective in preventing hypoxia and respiratory acidosis.[197] [229] Oxygen is provided by flushing oxygen at a rate of 15 L/min or by jet ventilation at a slow, intermittent rate of 6 breaths/min and an inspiratory-expiratory ratio of 1:4. This technique allows time for passive expiration through a narrow channel to avoid high airway pressure. High airway pressure decreases venous return and arterial blood pressure and increases the risk of pneumothorax.
Complications of endotracheal intubation have been reviewed by many investigators[230] [231] [232] [233] (see Chapter 42 and Chapter 75 ). Injury is more likely in children, female patients, patients with poor dentition, and those undergoing difficult tracheal intubation. Blanc and Tremblay [230] listed more than 30 possible problems such as broken teeth, laceration and perforation of the pharynx, subluxation of arytenoid cartilage, hoarseness, sore throat, paralysis of the vocal cords, and nerve damage. The overall incidence of laryngeal injury after short-term intubation is 6.2%,[234] the most common injury being hematoma of the vocal cords (4.5%). Mucosal lacerations occur in approximately 1 in 1000 intubations.
Perforation of the trachea usually occurs during difficult intubations with the use of a stylet. If subcutaneous emphysema is noted after a difficult intubation, the patient must be evaluated for mediastinitis and pneumothorax.
Pharyngitis and sore throat after tracheal intubation are common. Even patients undergoing anesthesia by mask may complain of postoperative sore throat. This complication usually resolves within 72 hours. Causes include the use of dry gases, reaction to the lubricant, cuff pressure, patient motion while the tube is in place, repeated attempts at intubation, and excessive tube size. Hoarseness is another postintubation problem associated with tube size. Mild postoperative hoarseness usually resolves within 5 to 7 days, but hoarseness that persists beyond 7 days requires evaluation by an otolaryngologist.
Vocal cord paralysis from damage to the recurrent laryngeal nerve is a rare, but serious cause of hoarseness. This complication may occur as a result of the endotracheal tube cuff pressing the recurrent laryngeal nerve between the thyroid lamina and the arytenoid cartilage[233] or because of direct injury during head and neck surgery. Unilateral injury causes no respiratory obstruction. Bilateral recurrent nerve injury may result in respiratory distress, stridor, and complete obstruction. Both true vocal cords can become motionless and adducted. A tracheostomy may be required during the 6-week recovery period.
Use of the laryngeal mask airway does not necessarily avoid complications. Sore throats and even unilateral right hypoglossal nerve paralysis have been reported. [235]
Cocaine is a naturally occurring alkaloid of the Erythroxylon coca plant. It is a local anesthetic and an excellent vasoconstrictive agent and is used in intranasal surgery to provide anesthesia, decrease bleeding, and shrink congested mucous membranes.[236] Cocaine also has sympathomimetic effects: it sensitizes organs to epinephrine and blocks the reuptake of released epinephrine at peripheral nerve terminals.[237] Cocaine should be avoided in hypertensive patients and those taking monoamine oxidase inhibitors.
Intranasally applied cocaine is absorbed rapidly and reaches peak levels in 30 to 45 minutes. These levels remain elevated for at least 120 minutes. [238] Intranasal doses of 0.5 to 1 mg/kg have been found to increase the heart rate 10 beats/min and raise both systolic and diastolic blood pressure approximately 10 mm Hg.[239] Doses of 2 mg/kg sensitize myocardium to the arrhythmogenic effect of epinephrine. Doses of 5 to 10 mg/kg depress the heart.
In some patients, even small doses of 0.4 mg/kg may cause ventricular fibrillation, cardiac arrest, hypertension, tachycardia, or respiratory depression. The median lethal dose of orally administered cocaine is approximately 500 mg.[240] For intranasal administration of a 4% solution, the safe recommended maximum dose is approximately 1.5 mg/kg.
Each drop of a 4% solution contains about 3 mg of cocaine. Cocaine is absorbed from the laryngeal tracheal mucosa as rapidly as though it were injected intravenously. It is metabolized primarily through ester hydrolysis by plasma pseudocholinesterase and is also slowly detoxified in the liver and excreted unchanged by the kidney. Patients with pseudocholinesterase deficiency may be sensitive to cocaine.[241] The practice of adding epinephrine to cocaine is hazardous, and there is no evidence that such addition produces less bleeding at the site of surgery.
Phenylephrine is a potent α-adrenergic agonist used as a vasoconstrictor. Overdosage leads to severe hypertension and cardiovascular decompensation. [242] On March 10, 1998, the Commissioner of Health in New York state circulated a letter to all hospital administrators establishing guidelines for the use of phenylephrine in the operating room.[243] The guidelines included the following recommendations:
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