Difficulty in managing the airway is the most important cause of anesthesia-related morbidity and mortality. In the American Society of Anesthesiologists (ASA) Closed Claims Project, 6% of all claims concerned airway injury.¹ Difficult intubation was a factor in only 39% of airway injury claims. Eighty-seven percent of the airway injuries were temporary, and 8% resulted in death. In 21%, the standard of care was inappropriate (Table 51-1). Female patients, elective surgery, and outpatient procedures had higher rates of injury. There was no difference in ASA physical status classification and obesity among those with airway injuries during general anesthesia.

TABLE 51-1 Severity of Injury and Standard of Care

International studies exploring the incidence of complications during general anesthesia have been published in the United Kingdom,^2,³ Australia,⁴ and France.⁵ The procedural problems and airway complications found in these studies are summarized in Table 51-2.

TABLE 51-2 Procedural Problems and Airway Complications Encountered During General Anesthesia

The inability to secure the airway and subsequent failure of oxygenation constitute a life-threatening complication. In absence of major oxygen (O₂) reserves, failure of oxygenation leads to hypoxia, followed by brain damage, cardiovascular breakdown, and death. As soon as oxygenation is no longer achievable, tissue damage is initiated, and irreversible injury occurs in a few minutes. The ultimate goal of airway management is oxygenation of the patient, not placement of an endotracheal tube (ETT).

Some complications are dramatic and immediately life-threatening (e.g., unrecognized esophageal intubation, tracheal rupture); some are severe and long-lasting (e.g., nerve injuries), and some are painful for the patient (e.g., sore throat). Good clinical practice aims to avoid all of these complications.

A History of the Patient and Examination

Serious complications of airway management may result from not recognizing the level of airway difficulties. For example, it is impossible to clear an airway problem at the level of the vocal cords or the upper trachea when using a supralaryngeal airway device (SAD). These cases should be managed with endotracheal intubation or with a transglottic or transtracheal airway. Similarly, fiberoptically guided intubation may not prove beneficial in cases of bleeding and vomiting.

To minimize injury to the patient, the anesthesiologist should examine the airway carefully, identify potential problems, devise a plan that involves the least risk for injury, and have a backup plan that can be instituted immediately if needed. Common sense should prevail at all times. Lessons learned from difficult cases should be used to modify daily practice and minimize future problems associated with airway management.

The first step in managing patients with difficult airways is to establish a specific algorithm for the anesthesia department by accepting the existing ASA algorithm or adapting it to the requirements of the specific patient population of the department. The first step in this algorithm is identification of patients with difficult airways during the preoperative examination. Most patients have the typical physical signs or history of a difficult airway and are easily identified. Although a few patients have none of these signs, they remain at risk for a difficult airway, and we should focus on them. Unfortunately, a reliable test for detecting all patients at risk does not exist. The sensitivity and specificity of all existing tests are rather low. The anesthesiologist must be alert to all possibilities, because airway difficulties may occur at any time.

All tests should be performed in a standardized manner for every patient to prevent errors in the results. Practitioners should understand the functions and limits of each test. Combinations of simple tests or the application of more complex tests may increase the predictive value of the preanesthesia examination findings.^6,⁷ In uncertain cases, the preoperative evaluation of the airway can use fiberoptic devices under local anesthesia. Test and physical examination results must be documented, especially when the examiner is not the person administering anesthesia during the procedure.

B Omission, Commission, and Communication

In anesthesia practice, errors of omission are more common than errors of commission. Errors of omission include failure to recognize the magnitude of a problem, make appropriate observations, or act in a timely manner. Errors of commission include trauma to the lips, nose, or laryngotracheal mucosa; forcing sharp instruments into areas in which they do not belong; and introducing air or secretions into regions of the body in which further complications will ensue. The primary goal of anesthesiologists is to ensure the safety and well-being of their patients, and they are usually careful in performing the technical aspects of their jobs. The most frequent cause of fatal errors in medical practice, especially in the field of airway management, is to ignore inadequate experience and skills and not call for help.

C Planning and Scheduling

Many complications of airway management result from insufficient communication between the members of the medical team and improper coordination of patients in the operating room schedule. A patient with known difficult airway problems should be scheduled at a time when the most experienced anesthesiologists and surgeons are available. Communication among the entire staff is paramount to create optimal conditions for the patient′s safety.

Delayed recognition of complications leads to delayed therapy. Inadequate monitoring, nonfunctional equipment, and untrained staff have been linked to airway catastrophes. For optimal airway management, a difficult airway cart must be available, as recommended in the ASA guidelines. The cart should include additional devices and specialized equipment for managing all airway problems.

II Complications with Supralaryngeal Airway Devices

A Mask Ventilation

The difficult mask ventilation is an underestimated aspect of managing a difficult airway. Ventilation using a bag-mask breathing system is an essential task of the trained anesthesiologist, and it may be life-saving for the patient. The “cannot intubate, cannot ventilate” (CICV) scenario represents the most extreme type of airway problem.⁸ Mask ventilation is used at the beginning of most cases of general anesthesia. Although the mask and the technique may seem benign, each can cause problems.

1 The Sterilization Process

Many of the devices used to ventilate the patient and secure the airway are disposable, but some equipment is reusable. All devices should be checked before use, and reusable items should be free of residual cleaning agents. Masks may have pinhole defects in their air-filled bladders, allowing air leaks or extravasation of cleaning fluid. In one case report, the fluid caused severe burning and irritation to the patient’s eyes,⁹ and another patient contracted chemical conjunctivitis from residual glutaraldehyde on an anesthesia mask.¹⁰ If ethylene oxide, a common cleaning solution, adheres to reusable surfaces, it can cause serious mucosal injury. Water added to ethylene oxide forms ethylene glycol, a known irritant. Residual glutaraldehyde on an improperly rinsed laryngoscope blade caused massive tongue swelling and life-threatening allergic glossitis.¹¹ Care must be taken to thoroughly rinse the suction channel of a fiberoptic bronchoscope (FOB) after cleaning. Residual agents may drip out of the FOB port into the larynx or trachea, causing severe chemical burns.

2 Mechanical Difficulties

A mask is typically applied to a patient’s face before induction of general anesthesia. Preoxygenation of the patient is the first step in securing the airway. The mask should be applied during spontaneous breathing, before drugs are given. During placement, direct contact of the rigid parts of the mask with the bridge of the nose or mandible should be avoided because they are at particular risk for compromised blood flow.¹¹ Bruising and soft tissue damage may occur in these regions with excessive pressure, and pressure damage to the mental nerves as they exit from the foramina has been implicated in lower lip numbness in two patients.¹² Care must be taken to avoid contact with the eyes to prevent corneal abrasions, retinal artery occlusions, and blindness. As induction proceeds, firmer mask pressure and stronger lifting pressure on the angle of the mandible become necessary to maintain a tight mask fit and secure the airway. Pressure on the soft tissue of the submandibular region may obstruct the airway, especially in small children, or it can damage the mandibular branch of the facial nerve, resulting in transient facial nerve paralysis.¹³

Occasionally, the base of the tongue may fall back into the oral pharynx during induction and obstruct the airway. Oropharyngeal airways must be gently inserted into the mouth to avoid injury, such as broken teeth or mucosal tears. Improper placement may worsen airway obstruction by forcing the tongue backward. Equal care should be given to the placement of nasopharyngeal airways to avoid bleeding and epistaxis.

Before insertion of an oropharyngeal or nasopharyngeal airway, the oropharyngeal space should be enlarged. During conventional mask ventilation, the mandible is pressed against the maxilla, blocking condylar motion and hindering sufficient mouth opening and maximal extension of the base of the tongue. The mouth is opened and the mandible gently drawn forward and upward to displace the base of the tongue to a ventral position and increase the oropharyngeal space.

The lifting pressure applied to the angle of the mandible is sometimes sufficient to subluxate the temporomandibular joint (TMJ). Patients may experience persistent pain or bruising at these points and may have chronic dislocation of the jaw, which can cause severe discomfort.

Positive airway pressure can force air into the stomach instead of the trachea, producing gastric distention, difficult ventilation, and increased likelihood of regurgitation. Cricoid pressure can help to reduce the amount of air being forced into the stomach. The ability to achieve adequate mask ventilation should be assessed preoperatively. Independent risk factors for difficult mask ventilation are the presence of a beard, increased body mass index, lack of teeth, age older than 55 years, history of snoring or sleep apnea, limited mandibular protrusion test, male gender, Mallampati class III or IV (used to predict ease of intubation), and airway masses or tumors.¹⁴

Other factors may make mask ventilation difficult or impossible, such as large tongues, facial burns or deformities, stridor, or nasal polyposis. In these cases, it may be best to avoid mask ventilation and perform awake fiberoptic intubation. Patients with trauma to the pharyngeal mucosa may be at risk for subcutaneous emphysema.

Laryngoceles may manifest as or cause upper airway obstruction during induction of anesthesia. Congenital factors contribute to development of laryngoceles, and persons who play wind instruments also may be at risk because high intrapharyngeal pressures can weaken soft tissue and cause laryngoceles in the lateral pharynx.^15,¹⁶

3 Prolonged Mask Ventilation

Because mask ventilation offers no protection against silent regurgitation, the anesthesiologist should be vigilant for questionable airway noise, coughing, or bucking. Transparent masks allow visualization of the mouth and early identification of vomitus. Extra care should be taken to avoid undue pressure on vulnerable parts of the face. When continuous positive airway pressure (CPAP) is applied to patients with basilar skull fractures, pneumocephalus may occur.^17,¹⁸ At least one case report identified positive airway pressure as the cause of bilateral otorrhagia.¹⁹

Mask ventilation is relatively contraindicated in nonfasting patients, intestinal obstruction, head-low position, extreme obesity, tracheoesophageal fistula, and massive naso-oropharyngeal bleeding, although it may be life-saving when other airway devices fail. Especially in pediatric cases, it may be necessary to avoid hypoxia.²⁰

Adequate monitoring during mask ventilation includes observation of chest movement, pulse oximetry, measurement of end-tidal carbon dioxide (ETCO₂), and breathing pressure control. In infants, a precordial placed stethoscope is recommended.

B Laryngeal Mask Airway

The laryngeal mask airway (LMA), a device designed for upper airway management, is a cross between a face mask and an ETT. The LMA has been used in millions of patients and has been accepted as a safe technique in many types of surgical procedures. With use of the LMA, muscle relaxation is unnecessary, laryngoscopy is avoided, and hemodynamic changes are minimized during insertion. The LMA has a clear advantage when laryngeal trauma must be minimized (e.g., in operatic singers), when a standard mask fit is impossible, and when light planes of anesthesia are desired.²¹ It has proved valuable in situations in which mask ventilation is unexpectedly difficult and direct laryngoscopy impossible, and it may be used as a conduit for a fiberoptic intubation with a standard ETT.²² Use of the device is an integral part of the ASA difficult airway algorithm.²³

Placing the LMA correctly can be difficult in some patients. The mask may fold on itself, and pressure on the epiglottis can push the device down into the glottic opening, or the epiglottis may become entrapped in the laryngeal inlet of the mask. The tip of the epiglottis may fold into the vocal cords, increasing the work of breathing and producing coughing, laryngospasm, or complete airway obstruction. Excess lubricant can leak into the trachea, promoting coughing or laryngospasm.²⁴ Regardless of the problems encountered in placing the LMA, airway patency is usually maintained. An inadequate mouth opening (<1.5 cm), inadequate anesthesia depth, insertion with a not fully deflated cuff, inadequate size of LMA, inadequate force during insertion, and inadequate volumes for cuff inflation can cause malpositioning of the LMA.

Numerous complications are associated with the LMA. Perhaps the greatest limitation is the inability of the LMA to protect against pulmonary aspiration and regurgitation of gastric contents. Because the LMA does not isolate the trachea from the esophagus, its use is risky when the patient has a full stomach or when high airway pressures are necessary for positive-pressure ventilation. The overall risk of aspiration and regurgitation using the LMA seems to be in the same low range as endotracheal intubation when the indications and contraindications for the LMA are respected.²⁵ The risk of aspiration, which is a consequence of the device’s design, should be weighed against the advantages of the LMA in cases of difficult intubation and ventilation. Other complications have been reported with the use of the LMA. Their incidence and severity depend on the user’s skills and experience, depth of anesthesia, and anatomic or pathologic factors.²⁶

Failure to insert the LMA results from inadequate anesthesia depth, suboptimal head and neck position, incorrect mask deflation, failure to follow the palatopharyngeal curve during insertion, inadequate depth of insertion, cricoid pressure, and oral variations such as large tonsils. Laryngeal spasm and coughing result from inadequate anesthesia depth, tip impaction against the glottis, and aspiration. Mask leaks or the inability to ventilate the lungs results from inadequate anesthesia depth, malpositioned mask, inadequate size of the mask, and high airway pressure. A displacement of the LMA after insertion is caused by inadequate anesthesia depth, a pulled or twisted tube, and inadequate mask size. Problems during recovery are removal of the LMA at an inappropriate anesthesia depth, laryngospasm and coughing when oral secretions enter the larynx after cuff deflation, tube occlusion caused by biting, and regurgitation. Effects on pharyngolaryngeal reflexes such as laryngeal spasm, coughing, gagging, bronchospasm, breath-holding, and retching may be associated with LMA use.

The incidence of sore throat with this device is between 17% and 26%.²⁷ The incidence of failed placement is 1% to 5%, although this rate tends to decrease with increasing operator experience.²⁸ The LMA cuff is permeable to nitrous oxide and carbon dioxide, which results in substantial increases in cuff pressure and volume during prolonged procedures.^29,³⁰

Several case reports mention edema of the epiglottis, uvula, posterior pharyngeal wall, and vocal cords; in the worst cases, these conditions have led to airway obstruction.³¹^–³³ Nerve paralysis (i.e., lingual, recurrent, hypoglossal, and glossopharyngeal), postobstructive pulmonary edema, tongue cyanosis, and transient dysarthria have been reported. Cuff-pressure control can reduce at least some of these complications.^27,³⁴^–³⁷ Other problems with the LMA include dislodgment, kinking, and foreign bodies in the tube, leading to airway obstruction.³⁸

Newer designs of the LMA were developed to increase comfort, handling, or safety in various situations. To minimize the risk of aspiration and regurgitation, the ProSeal laryngeal mask airway (PLMA), which has an esophageal vent, was released in 2000.³⁹ It isolates the glottis from the upper esophagus when correctly positioned, which further protects the airway.^40,⁴¹ Some cases with gastric insufflation with a malpositioned PLMA were reported.^42,⁴³

The intubating laryngeal mask airway (ILMA) was designed to overcome unexpected difficult laryngoscopic intubation. Use of the ILMA has been successful in patients with difficult airways.^44,⁴⁵ Tracheal intubation through the ILMA using special ETTs is easier than with the standard LMA, and the success rate for blind insertion of a tube through the ILMA is more than 90%.^46,⁴⁷ Branthwaite reported a case of larynx perforation leading to mediastinitis and the patient’s death.⁴⁸ Fiberoptically guided insertion of an ETT through an LMA has had the highest success rate for intubation and the lowest rate for damage of laryngeal structures.

Modifications of extraglottic airways combine features of various LMAs. For example, the LMA Supreme combines the Fastrach intubating laryngeal mask airway (ILMA-Fastrach) shape with the PLMA gastric port, resulting in a higher rate of success on first attempt at insertion and lower leak pressures, and the LMA I-Gel supraglottic airway is a single-use device without an inflatable cuff.^49,⁵⁰ Other devices, such as the LMA C-Trach, use integrated fiberoptic channels to visualize the glottic region.⁵¹ Overall rates of complications are similar to those described earlier.

Classic contraindications to using an LMA include nonfasted patients, extreme obesity, necessity of high breathing pressures (20 to 25 cm H₂O) in the presence of low pulmonary compliance or chronic obstructive pulmonary disease (COPD), acute abdomen, hiatal hernia, Zenker’s diverticulum, trauma, intoxication, airway problems at the glottic or infraglottic level, and thoracic trauma. Nevertheless, the LMA’s successors, particularly those with a channel for the insertion of a gastric tube, have led to more liberal use of LMA devices.⁵²^–⁵⁴

C Esophageal-Tracheal Combitube

The esophageal-tracheal Combitube is an esophagotracheal, double-lumen airway designed for emergency use when standard airway management measures have failed.^55,⁵⁶ Use in elective surgery has been reported.⁵⁷^–⁶⁰

The device is inserted blindly into the mouth and advanced to preset markings. The distal tube is usually positioned within the esophagus at this point. A distal cuff is inflated within the esophagus, and a large-volume proximal cuff is inflated inside the pharynx. Ventilation is then attempted through the esophageal tube because esophageal intubation occurs in approximately 96% of insertions. If ventilation through this lumen fails, ventilation is attempted through the tracheal lumen. The device is designed for single use, but a study of multiple uses of the Combitube found no problems with the reprocessing.⁶¹ Another study warned against reuse because insufficient cleaning may lead to transmission of iatrogenic infections.⁶²

The 37-F (small adult) Combitube is not recommended for patients shorter than 120 cm, and the 41-F Combitube is not recommended for patients shorter than 150 cm. Disregarding those recommendations may induce serious esophageal injury. Further contraindications to using a Combitube are intact gag reflexes, ingestion of caustic substances, known esophageal disease, airway problems at the glottic or infraglottic level, and latex allergy.⁵⁶

The Combitube has major disadvantages because of its design. It can be used for a maximum of 8 hours (tracheobronchial care is difficult through the Combitube), suctioning of the trachea is not possible with the device in the esophageal position (may become problematic with copious tracheal secretions), it may injure pharyngeal and esophageal soft tissues, and no pediatric sizes are available.

Complications have been reported with use of the Combitube. In two patients, the device was inserted too far, causing the large pharyngeal cuff to lie directly over the glottis and obstruct the upper airway.⁶³ This was easily resolved by partially withdrawing the Combitube until breath sounds were auscultated. Tongue discoloration has been reported while the pharyngeal cuff was inflated, but it usually resolves immediately without further adverse sequelae after the cuff is deflated. The Combitube has been linked to glossopharyngeal and hypoglossal nerve dysfunction, esophageal rupture, subcutaneous emphysema, pneumomediastinum, pneumoperitoneum, and tracheal and esophageal injury and bleeding.⁶⁴^–⁶⁶ Esophageal lacerations were most likely caused by incorrect use; in both cases, the distal cuff was overblocked, and the larger Combitube (41 F) was used in a small patient. Despite their disadvantages, the Combitube and the EasyTube are widely accepted as devices for managing the difficult airway.

D Other Supraglottic Airway Devices

Many devices are available for managing the airway at the supraglottic level: cuffed oropharyngeal airway (COPA), laryngeal tube (LT), LaryVent, glottic aperture seal airway (GO2 airway), Cobra perilaryngeal airway (CobraPLA), and King Laryngeal Tube Suction (LTS).⁶⁷^–⁶⁹ Overall, they seem to cause complications and physiologic alterations similar to those found with the LMA.^70,⁷¹ The devices were designed for separating the airway from the esophageus but do not efficiently protect the airway from regurgitation and aspiration. They share several advantages and disadvantages. Contraindications include nonfasted patients, gastroesophageal reflux, hiatal hernia, pregnancy, obesity, reduced pulmonary compliance, glottic and infraglottic stenosis, and a mechanical obstruction of the oropharynx. Most complications arise from dislodgment, overblocking the cuff, and insufficient depth of anesthesia. Most of the devices were developed in the past few years, and acceptance in routine practice has varied.

Another concern is the wide range of supraglottic devices. In addition to the limited storage space provided on the airway management cart, it seems impossible to maintain regular and sufficient training with all devices for all practitioners. Many complications in airway management are caused by operator inexperience and by inadequate or nonfunctional equipment. The recommendation for all anesthesiologists is to select a few devices that are used routinely or for which practitioners are well trained.

III Complications with Intubation

A Endotracheal Intubation

1 Anatomic Requirements

Successful oral intubation requires four anatomic traits: adequate mouth opening, sufficient pharyngeal space (determined by visualization of the hypopharynx), compliant submandibular tissue (determined by measuring the thyromental distance), and adequate atlanto-occipital extension.⁷² If the patient’s anatomy is compromised in any of these factors, intubation will be difficult. For optimal conditions, a free view to the vocal cords is necessary, and introduction of the ETT should be easily performed.

The opening to the airway may prove inadequate because of facial scars, TMJ disease, macroglossia, or dental disease. Nasal intubation techniques, such as blind or fiberoptic approaches, may overcome this problem. A fiberoptic technique is preferred because blind techniques are associated with a high incidence of complications.

The pharyngeal space may be limited by tumors, abscesses, edema, and surgical or traumatic disruption. If the anatomy is distorted, the anesthesiologist must optimize the view of the vocal cords. Awake intubation may be necessary, and it should be considered whenever the pharyngeal space is limited. If direct laryngoscopy is performed, the patient should be placed in the sniffing position, and a styletted ETT should be considered. Every effort—backward-upward-rightward pressure (BURP) or optimal external laryngeal manipulation (OELM)—should be made to optimize visualization and identification of the laryngeal and pharyngeal structures.^73,⁷⁴

Compliance of the submandibular space is essential to ensure that the tongue can be placed out of the way to view the glottis. Compliance may be decreased by scarring, changes caused by radiation, or localized infections. Extension of the atlanto-occipital region is necessary to lift the epiglottis off the posterior pharyngeal wall during direct laryngoscopy. A fused, fixed, or unstable spine may be rigid enough to impede visualization of the glottic structures. Awake intubation or fiberoptic techniques should be considered in these instances.

2 Laryngoscope Modifications and Rigid Optical Instruments

Laryngoscopes are designed for visualization of the vocal cords and for placement of the ETT into the trachea under direct vision. The two main types are the curved Macintosh blade and the straight blade (i.e., Miller with a curved tip and Wisconsin or Foregger with a straight tip). All blades are available in different sizes for every age of patients. The main injury caused by using laryngoscopes is damage to the teeth. In cases of inadequate visualization of the vocal cords, a change of the patient’s head position may lead to success. In some cases, a blade of inadequate size is responsible for intubation failure. An external laryngeal manipulation (e.g., BURP, OELM) may move the vocal cords into the line of vision and facilitate intubation.

Obtaining a view of the vocal cords with a conventional laryngoscope requires optimal positioning of the patient. With a flexible fiberscope, positioning is not an issue, and damage to the teeth is less likely. Similarly, with innovations such as the Glidescope video laryngoscope, Airtraq laryngoscope, McGrath video laryngoscope, Pentax Airway Scope (Pentax AWS), and Truview video laryngoscope, a video image of the oropharynx and the laryngeal inlet is transmitted from the camera in the tip of the blade and allows laryngoscopy and intubation in positions other than the sniffing position. The advantages of these instruments help to reduce the number of difficult or failed intubations and the incidence of dental damage. In studies on mannequins or patients with normal airways, these devices have been evaluated as better than or equal to the Macintosh laryngoscope, and data demonstrate successful intubation of patients with known or suspected difficult airways.^75,⁷⁶ Although visualization of the vocal cords has become easier, insertion of the intubation tube can be tricky. The monitor view reveals only the laryngeal inlet, and advancing the tube into the larynx may requires an introducer or a built-in guiding channel, which can make the instrument bulky and the technique more complicated than with a conventional laryngoscope. Several cases of pharyngeal injuries have been reported with the rigid stylet of the Glidescope .⁷⁷ Increased awareness of potential complications, better training and supervision, and appropriate equipment and patient selection can reduce the incidence of complications.

Laryngoscopy requires deep anesthesia because it causes strong stimulation of physiologic reflexes, and respiratory, cardiovascular, and neurologic adverse effects are possible.⁷⁸ Hypertensive patients, pregnant patients with hypertension, and patients with ischemic heart disease are particularly at risk. Deep anesthesia, application of topical anesthetics, prevention of the sympathoadrenal response with drugs such as atropine or intravenous lidocaine, and minimizing mechanical stimulation can attenuate the adverse effects.

Laryngoscopes have been modified to optimize visualization of the vocal cords. The Corazelli-London and McCoy-Mirakuhr flexible-tip blades may achieve a better view of the glottis by drawing the epiglottis up.⁷⁹

Rigid optical instruments such as the Bonfils retromolar intubation fiberscope and its modifications,⁸⁰ the Bullard laryngoscope, and the intubation tracheoscope⁸¹ are not commonly used in anesthesiology. They require skilled handling, and experience should be gained in routine cases to apply to difficult airway situations. The rigid intubation tracheoscope, a familiar device in ear, nose, and throat surgery, has special indications and may be useful in the hands of anesthesiologists. Available in two sizes (child and adult), it consists of a battery-filled handle and a straight, rigid tube with a connection to a breathing bag or circuit. The rigid tracheoscope is useful for tumors, scars, and abscesses in the oropharynx, base of the tongue, and larynx and for aspirated foreign bodies.

The disadvantages of these instruments are a relatively closed view through the tube, a high risk of damage to the teeth and laryngeal structures, possible perforation of the hypopharynx, and risk of aspiration. High-flow oxygen insufflation through a port induced subcutaneous cervical and facial emphysema in one patient.⁸²

3 Difficult Intubation

Despite optimal positioning of the head and neck, the glottis is sometimes impossible to visualize, even in patients without obvious predisposing features.⁸³^–⁸⁵ Risk factors for difficult tracheal intubation include male sex, age between 40 and 59 years, and obesity.⁷² Anesthesiologists should be aware of the potential for a difficult intubation in the following circumstances:

A chin-to-thyroid cartilage distance of less than three finger breadths (about 7 cm) hampers visualization of the glottis.⁹⁰ A combination of tests may increase the predictive value of the preanesthesia examination results.^6,⁷ Causes for difficulty in securing the airway are shown in Box 51-1.^25,⁹¹ Computerized analysis of facial structure provides an accurate approach to predicting difficult intubation.⁹² Patients who proved difficult to intubate should be told about it and given written documentation so that they can notify future anesthesiologists. Patients should be registered with the MedicAlert Foundation.

Box 51-1

Miscellaneous Causes of Difficult Securing of the Airway

Symptoms

Dumpling voice

Hoarseness

Pathologic respiratory sound

Foreign body feeling

Odynophagia

Constitutional Factors

Modified from Krier C, Georgi R: Airway management: Is there more than one “gold standard”? Anasthesiol Intensivmed Notfallmed Schmerzther 36:193–194, 2001.

4 Nasotracheal Passage

a Cranial Intubation

Nasotracheal intubations are potentially hazardous. In patients with basilar skull fractures or certain facial fractures (e.g., LeFort II or III fractures), the ETT may be inadvertently introduced into the cranial vault (Fig. 51-1).⁹³ Fractures of the frontal part of the skull base with cerebrospinal rhinorrhea, intranasal abscesses or abscesses with intranasal expansion, choanal atresia, hyperplastic tonsils, tendency to uncontrollable nasal bleeding, and coagulopathies are considered contraindications to nasotracheal intubation. In a case of nasotracheal intubation, asystole occurred after the tube was introduced into the orbit.⁹⁴ However, if care is taken, the complication rates of oral and nasal intubation are not different.⁹⁵ Nasal intubation in a patient with a known or suspected skull fracture should be performed only by using fiberoptic bronchoscopy and with extreme caution in the inferior nasal meatus. For midfacial fractures with intact dura mater, it is possible to open the dura by manipulation during nasotracheal intubation.

Figure 51-1 Intracranial nasotracheal tube (computer enhanced).

(From Horellou MF, Mathe D, Feiss P: A hazard of naso-tracheal intubation. Anaesthesia 33:73, 1978.)

b Nasal Injury

Nasotracheal intubation may be problematic in the presence of hypertrophic turbinates, extreme deviation of the nasal septum, prominences on the nasal septum, chronic infections in the nasal cavity, and nasal polyposis. Minor bruising occurs in 54% of nasal intubations and most commonly involves the mucosa overlying the inferior turbinate and the adjacent septum.⁹⁶ If epistaxis occurs, the ETT cuff should be inflated and remain in the nostril to tamponade the bleeding.

The nasal mucosa must be vasoconstricted before instrumentation.⁹⁷ Some agents used for this purpose are 0.5% phenylephrine in 4% lidocaine or 0.1% xylometazoline. A 4% solution of cocaine may be associated with severe adverse effects and is no longer recommended for vasoconstriction. The risk of nasal injury can be minimized with the use of a small, well-lubricated ETT with a flexible tip that has been soaked in warm water.⁹⁸

Possible complications of nasotracheal intubation are dislodgment of nasal polyps,⁸⁸ dislodgment of nasal turbinates,^99,¹⁰⁰ adenoidectomy, injury of the nasal septum, perforation of the piriform sinus, and the epiglottic vallecula. In case of injury to the piriform sinus, the internal branch of the superior laryngeal nerve, soft tissue of the pharynx, the larynx, and the superior laryngeal vessels may be damaged. Tears in the pharyngeal mucosa can mature into retropharyngeal abscesses.¹⁰¹ Nasotracheal tubes may dissect and run behind the posterior pharyngeal wall. Patients with an obstructed nasal passage due to convoluted turbinates are at increased risk for this complication. One case of external compression of the nasotracheal tube due to the displaced bony fragments of multiple Le Fort fractures was reported.¹⁰²

Delayed complications of nasotracheal intubation include pharyngitis, rhinitis, and synechia between the nasal septum and inferior turbinate bone. After the tube is secured in the trachea, ensure that it is also secured properly at the level of the nostril. Distortion of the nares can lead to ischemia, skin necrosis, or nasal adhesions.

Even without gross trauma, mechanical damage to the superficial epithelial layers caused by nasal intubation results in mucociliary slowing in 65% of patients and bacteremia in another 5.5%.^103,¹⁰⁴ The most common organisms introduced into the blood are nasopharyngeal commensal organisms (e.g., Streptococcus viridans), which can cause endocarditis and systemic infection. Even short-term intubation has caused nasal septal and retropharyngeal abscesses. Acute otitis media has occurred in 13% of nasally intubated neonates.¹⁰⁵ Paranasal sinusitis has been reported, most commonly occurring with nasal intubation for more than 5 days.^106,¹⁰⁷ Infection may be related to sustained edema and occlusion of the sinus drainage pathways. Prompt diagnosis is critical, and paranasal sinusitis should be suspected in any patient with facial tenderness, pain, or purulent nasal discharge or in any nasally intubated patient who develops sepsis with no other obvious source. A careful examination of the patient is necessary, but the success of a previous cosmetic operation should not be endangered. The nasal structures must be checked again postoperatively.

c Foreign Bodies

The nostrils are common sites for entry of foreign bodies. Small children, known for placing small objects into their orifices, find the nostrils one of the most accessible sites. More than 80% of patients who aspirated a foreign body are children, and most were between 1 and 3 years old.¹⁰⁸^–¹¹⁰ Foreign body aspiration is the cause of death of 7% of children younger than 4 years.

Smith and colleagues reported a rhinolith that was dislodged during nasotracheal intubation.¹¹¹ The mass had formed around the rubber tire of a toy car that the patient had placed in his nose 30 years earlier. Nasotracheal intubation can dislodge similar foreign bodies that may obstruct the ETT, pharynx, or trachea. If a nasal foreign body is known or suspected, it should be gently dislodged, advanced into the oral pharynx, and retrieved before intubation. Mask ventilation may also dislodge foreign bodies to the lower parts of the airway.

5 Traumatic Intubation

Difficult intubations often are traumatic intubations. In a case of difficult intubation, the practitioner tends to increase the lifting forces of the laryngoscope blade, which may damage the intraoral tissues and osseous structures. When the operator continues to intubate the patient many times without changing his approach or technique, difficult intubation is changing to traumatic intubation. Use of increasing forces causes swelling, bleeding, or perforation, and the intubation becomes more and more difficult. It may end in a CICV situation. We recommend a maximum of three attempts to achieve intubation using a laryngoscope. If intubation fails after three attempts, another airway-securing technique should be used following the airway management algorithm.

a Lip Trauma

Lip injuries, which are typically found on the right upper lip, include lacerations, hematomas, edema, and teeth marks. They are usually caused by inattentive laryngoscopy performed by inexperienced practitioners, the laryngoscope blade, and the teeth. Although these lesions are annoying to the patient, they are usually self-limited.

b Dental Trauma

The incidence of dental injuries associated with anesthesia is greater than 1 case in 4500 procedures.¹¹² Maxillary central incisors are most at risk; 50% of these injuries happen during laryngoscopy, 23% after extubation, 8% during extubation, and 5% in the context of regional anesthesia. Dental injuries are also associated with the use of LMAs and oropharyngeal airways. With insufficient anesthesia, depth biting against the tube is possible. Dental injuries are most common in small children, patients with periodontal disease (in which structural support is poor) or fixed dental work (e.g., bridges, capped teeth), protrusion of the upper incisors (i.e., overbite), carious teeth, and cases of difficult intubation. Preexisting dental pathology should be explored, and all loose, diseased, chipped, or capped teeth must be documented in the chart before anesthesia induction and intubation.¹¹³ The patient must be advised of the risk of dental damage. Tooth guards may be used, but they can be awkward and obstruct vision,¹¹⁴ although the time for intubation is not significantly longer.¹¹⁵

Fragments of chipped or partially broken teeth and completely avulsed teeth should be located and retrieved. Care should be taken to ensure that no foreign bodies slip into the pharynx to later become lodged in the esophagus or the larynx. Avulsed teeth should be saved in a moist gauze or in normal saline without cleaning them. Tooth aspiration may cause serious complications requiring rigid or flexible bronchoscopy for removal. With a rapid response from an oral surgeon or a dentist, an intact tooth often can be reimplanted and saved. The optimal time is within the first hour; thereafter, reimplantation success diminishes with increasing time.¹¹⁶

c Tongue Injury

Massive tongue swelling, or macroglossia, has been reported in adult and pediatric patients.^117,¹¹⁸ Some cases occurred while a bite block was in place, some happened with an oral airway and soft tissue compression of the chin, and some occurred with no protective device. The common denominator was that they all occurred when there was substantial neck flexion during endotracheal intubation and surgery was prolonged. Macroglossia results from obstructed venous and lymphatic drainage of the tongue, and it has been associated with angiotensin-converting enzyme inhibitors.¹¹⁹ In each case, the ETT might have severely compromised the circulation on the affected side of the tongue. One report described the sudden onset of tongue swelling after prolonged surgery to repair a cleft palate,¹²⁰ during which the tongue was retracted extensively. Obstruction of the submandibular duct by an ETT may lead to massive tongue swelling.¹²¹ Reduced sense of taste, cyanosis, or loss of tongue sensation is possible after compression of the lingual nerve or by lingual artery compression during forced intubation or associated with an oversized, malpositioned, or overinflated LMA.

d Damage to the Uvula

Uvula trauma is usually associated with the use of ETTs, oropharyngeal and nasopharyngeal airways, LMAs,¹²² or Combitubes and with overzealous blind use of a suction catheter.¹²³ The results of damaging the uvula are edema and necrosis.¹²⁴ Sore throat, odynophagia, painful swallowing, coughing, foreign body sensation, and serious life-threatening airway obstruction are reported.¹²⁵

e Pharyngeal Mucosal Damage

A postoperative sore throat (POST) likely represents a broad constellation of signs and symptoms. The incidence of POST after intubation is higher than POST after LMA use and after face mask ventilation.^126,¹²⁷ The incidence of sore throat associated with the use of the Combitube was 48%.¹²⁸ Aggressive suctioning is probably a mitigating factor. The incidence is substantially higher in women and in patients undergoing thyroid surgery. No correlation was seen with factors such as age, use of muscle relaxants, type of narcotic used, number of intubation attempts, or duration of intubation. Small tube and cuff size and topical treatment and inhalation of steroids have a positive impact on POST.¹²⁹ However, pain on swallowing usually lasts no more than 24 to 48 hours and can be relieved in part by having the patient breathe humidified air.

f Laryngeal Trauma and Damage to the Vocal Cords

Trauma to the larynx may occur after endotracheal intubation. It depends on the intubator’s skill and the degree of difficulty. In one large study, 6.2% of patients sustained severe lesions, 4.5% had hematoma of the vocal cords, 1% had hematoma of the supraglottic region, and 1% sustained lacerations and scars of the vocal cord mucosa.¹³⁰ Recovery typically is prompt with conservative therapy.¹³¹ Hoarseness may appear 2 weeks postoperatively.¹³²

Granulations usually occur as a complication of long-term intubation. However, a small but significant number of patients sustain laryngeal injuries during short-term intubation.¹³³ Intubation can cause various degrees of laryngeal trauma, including thickening, edema, erythema, hematoma, and granuloma of the vocal folds.^134,¹³⁵ Injuries of the laryngeal muscles and suspensory ligaments are possible. The larynx should be inspected for injury before insertion of the ETT to document and treat preexistent lesions. Anesthesiologists should be vigilant in all cases of hoarseness, and patients should be examined by an otorhinolaryngologist preoperatively.

Arytenoid dislocation and subluxation have been reported as a rare complication of intubation.¹³⁶ Mitigating factors include traumatic and difficult intubations, repeated attempts at intubation, and attempted intubation using blind techniques such as light-guided intubation,¹³⁷ retrograde intubation, and use of the McCoy laryngoscope.¹³⁸ Early diagnosis and conservative or operative treatment are necessary,¹³⁹ because fibrosis with subsequent malpositioning and ankylosis may occur after 48 hours.

The vocal process of the arytenoid is the most common site of injury by the ETT because it is positioned between the vocal cords. Granuloma formation most commonly occurs at this site. The degree of injury worsens with increasing tube size and duration of intubation.¹⁴⁰

Many investigators have reported unilateral or bilateral vocal cord paralysis after intubation, which is usually temporary.¹⁴¹^–¹⁴⁴ One report associated vocal cord paralysis with use of ethylene oxide to sterilize ETTs.¹⁴⁵ Hoarseness occurs with unilateral paralysis, whereas respiratory obstruction occurs with bilateral problems. The most likely source of injury is an ETT cuff malpositioned in the subglottic larynx with pressure on the recurrent laryngeal nerve.^142,¹⁴³ Permanent voice change after intubation because of external laryngeal nerve trauma has been reported in up to 3% of patients undergoing surgery at sites other than the head or neck. The incidence may be decreased by avoiding overinflation of the ETT cuff and by placing the ETT at least 15 mm below the vocal cords.¹⁴² Eroded vocal cords may adhere to one another, eventually forming synechiae. This is a potential problem when airflow between the vocal cords has been compromised as a result of tracheostomy.¹⁴⁶ Surgical correction is usually necessary.

g Tracheobronchial Trauma

Tracheal trauma has many causes.¹⁴⁷ Injury may result from an overinflated ETT cuff, inadequate tube size, or malpositioned tube tip, laryngoscope, stylet, tube exchanger, or related equipment. Predisposing factors include anatomic difficulties; blind or hurried intubation; inadequate positioning; poor visualization; and most commonly, inexperience of the intubator. The presence of an ETT may lead to edema, desquamation, inflammation, and ulceration of the airway.¹⁴⁸ The severity of the injury may be related to the duration of intubation, although this relationship is not well established.¹⁴⁹ Any irritating stimulus, such as pressure from an oversized ETT, dry inhaled gases, allergic reactions to inhaled sprays, or chemical irritation from residual cleaning solutions, can initiate an inflammatory response and cause mucosal edema in the larynx or trachea. Edema after extubation limits the lumen diameter and increases airway resistance. Small children are most susceptible to this problem, in which a sudden increase in airway resistance results from laryngotracheobronchitis or croup. Almost 4% of children 1 to 3 years old develop croup after tracheal intubation.^150,¹⁵¹ Mechanical trauma may result from sharp objects within the trachea, such as a stylet tip that extends beyond the length of the ETT. Tracheal ruptures, especially after emergency intubation, were reported.¹⁵² One case of a bronchial rupture caused by an ETT exchanger was reported.¹⁵³

ETT cuffs inflated to a pressure greater than that of the capillary perfusion may devitalize the tracheal mucosa, leading to ulceration, necrosis, and loss of structural integrity.¹⁵⁴ Ulceration can occur at even lower pressures in hypotensive patients. The need for increasing cuff volumes to maintain a seal is an ominous sign that heralds tracheomalacia.¹⁵⁵ Massive gastric distention in an intubated patient may signal the presence of a tracheoesophageal fistula as the cuff progressively erodes into the esophagus.¹⁵⁶ Any patient with more than 10 mL of blood in the ETT without a known cause should be assessed for a tracheocarotid fistula.¹⁵⁷ The various nerves in this region of the neck are also at risk. Erosion of the ETT into the paratracheal nerves may result in dysphonia, hoarseness, and laryngeal incompetence. Tracheomalacia results from erosion confined to the tracheal cartilages. The anesthesiologist must inflate the ETT cuff only as much as necessary to ensure an adequate airway seal. When nitrous oxide is used during a lengthy surgical procedure, the pressure in the cuff should be checked by a cuff pressure control device. In the presence of 70% nitrous oxide, intracuff pressures take an average of 12 minutes to increase to levels that are potentially high enough to cause tracheal ischemia.¹⁵⁴ The cuff pressure should not exceed 25 cm H₂O. Increasing cuff pressure caused by surgical manipulations can be observed and prevented by using a cuff pressure control device.

Tracheal intubation may erode the tracheal mucosa, leading to scar tissue, which ultimately retracts and leads to stenoses of the trachea, larynx, or nares. The reported incidence of granulomas is 1 case in every 800 to 20,000 intubations.^158,¹⁵⁹ They are more common in women than in men and occur rarely in children. The most common site of erosion is along the posterior laryngeal wall, where granulation tissue easily overgrows. Side effects of granulomas include cough, hoarseness, and throat pain. The growths may be prevented by minimizing the trauma associated with laryngoscopy and intubation. When granulomas occur, surgical excision is usually required.

Membranes and webs may eventually replace tracheal and laryngeal ulcers. These growths are commonly thick and gray. Care should be taken while intubating patients with these lesions because inadvertent detachment may result in respiratory obstruction or bleeding into the airway. With time, the inflammatory process associated with laryngeal ulcers may extend to the laryngeal cartilage. If this occurs, the cartilage may become inflamed (i.e., chondritis) or softened (i.e., chondromalacia).

Several months after prolonged tracheal intubation, tracheal stenosis and fibrosis may occur. This usually represents the end stage of a progression from tracheal wall erosion to cartilaginous weakening to healing with fibrosis.¹⁴⁷ Stenoses typically occur at the site of an inflated cuff, although they may occur at the ETT tip. Symptoms include a nonproductive cough, dyspnea, and signs of respiratory obstruction. Dilation of the stenosis is curative in its early stages. However, surgical correction may be necessary after the tracheal lumen has been reduced to 4 to 5 mm.^160,¹⁶¹

Supraglottic complications induced by long-term intubation may be prevented by early tracheostomy. There is no evidence supporting an ideal time for tracheostomy in long-term ventilated patients.

h Barotrauma

Barotrauma results from high-pressure distention of intrapulmonary structures. High-flow insufflation techniques in which small catheters are used distal to the larynx are most often associated with barotrauma. These problems are common in microlaryngeal surgery when jet ventilation is used.¹⁶²^–¹⁶⁶ Direct impingement of the catheter tip on the tracheal mucosa may also cause barotrauma.¹⁶⁴ Edema or hematoma may occur if the jet of air strikes the mucosa of the larynx or the vocal cords, leading to laryngospasm. When air leaks into the peribronchial tissues, it can traverse into the subcutaneous space, the lung interstitium, or the pleural and pericardial cavities. Pneumomediastinum or tension pneumothorax and possibly tamponade are the results, and chest tubes may be necessary. Progressive accumulation of air may cause loss of pulmonary compliance, loss of ventilatory volume, or if the accumulation is large enough, overdistension of lung tissue with cardiopulmonary compromise and, finally, impossible ventilation. Safety mechanisms should be in place to prevent high-pressure airflow in the event that intrapulmonary pressures become excessive. For diseased pulmonary tissue, the least possible airway pressure should be used to prevent parenchymal blowout. This advice also applies to patients with blunt thoracic trauma who have subcutaneous emphysema. They should be presumed to have a bronchial leak unless proved otherwise. Barotrauma may also result from upper airway obstruction during jet ventilation.¹⁶⁷

i Nerve Injuries

Laryngoscopy and cuffed supraglottic airway devices may cause periodic or permanent nerve injury. Lingual, recurrent, hypoglossal, and glossopharyngeal nerve paralysis have been described for LMA devices, and neuropraxia with weakness, numbness, or paralysis of the tongue can occur after laryngoscopy.³⁴ After damage to the internal branch of the superior laryngeal nerve during a difficult intubation, two patients had signs of aspiration.¹⁶⁸

Malposition of the cuff or tube may be one reason for this rare damage. Ahmad and Yentis postulated that lingual nerve injury may occur where the nerve distal to its gingival branch is compressed by the LMA tubing against the side of the tongue.¹⁶⁹ In addition to the cases previously described, we observed one case of permanent anosmia after nasotracheal intubation with no pathologic findings.

j Spinal Cord and Vertebral Column Injury

Airway managing techniques such as chin lift, jaw thrust, and direct laryngoscopy transmit movement to the cervical spine. When a patient’s neck is fused, adequate neck extension may be impossible to obtain. Attempting to hyperextend the necks of these patients may result in cervical fractures and quadriplegia.¹⁷⁰ A head that is fixated in a cervical collar or halo does not allow neck extension and limits the successful use of direct laryngoscopy. Using a fiberoptic device to assist intubation should be considered in these cases. If immediate intubation is necessary, patients with an acute fracture of the back and neck may be supported by in-line cervical stabilization during careful intubation while protecting the head against excessive movement and fixing it in a safe position by a second person.¹⁷¹ C1 and C2 fractures seem to be particularly vulnerable because any degree of extension may compromise spinal cord function. Between 10% and 25% of spinal cord injuries occur because of improper immobilization of the vertebral column after trauma, and neurologic deterioration was associated with direct laryngoscopy in a patient with a cervical spine injury.¹⁷²^–¹⁷⁵

Several conditions, such as Down syndrome and rheumatoid arthritis, are associated with atlantoaxial instability.^176,¹⁷⁷ Excessive neck extension in a patient with an undiagnosed Arnold-Chiari malformation may cause worsening of cerebellar tonsil herniation.¹⁷⁸ Patients with underlying diseases such as connective tissue disorders, lytic bone tumors, and osteoporosis should be intubated carefully, and extreme neck extension should be avoided in every patient because of loss of muscle tone by curarizing drugs. A range-of-motion test and an assessment of neck extension should be performed before inducing anesthesia. A case of quadriplegia after bag-ventilation, direct laryngoscopy, and cricothyrotomy in a patient with an unrecognized cervical spine injury was reported.¹⁷⁵ Hastings found in a review of records of 150 patients with unstable cervical spine injury a 1.3% incidence of neurologic deterioration after elective surgery with tracheal intubation. Inadequate airway management may result in disaster of permanent spinal cord injury. Awake fiberoptic intubation should be considered when neck extension cannot be achieved without the risk of damage and time is not crucial. It is considered the safest method for airway management in patients with cervical spine injury, followed by LMA and the Combitube.¹⁷¹

k Eye Injuries

The ASA Closed Claims Project reported that the eye injuries were responsible for 3% of all claims; of these, 35% were related to corneal injuries, with corneal abrasions being the most common eye complication.¹⁷⁹ They are primarily caused by a face mask being placed on an open eye or by the eyelids not being completely closed during anesthesia.^180,¹⁸¹ Jewelry, identification cards, and loose-fitting watch bands have been implicated in scratching the eyeball.¹⁸² A stethoscope hanging from the neck of a clinician can fall forward and strike the patient’s eyes or forehead. Prevention consists of vigilance on the part of the anesthesiologist and application of adhesive tape over the closed eyelids. Especially during head and neck surgery, the eyelids should be taped closed, and the eyes should be covered carefully with soft eyepads.¹⁸³ Some clinicians routinely apply lubricating ointment to the inside of the eyelids, although this has not been proved to increase efficacy.

Although these injuries typically heal within 24 hours, they are usually painful and can lead to corneal ulceration. An immediate ophthalmologic consultation is recommended. Local anesthetics should not be applied because they can delay regeneration of the epithelium and may promote keratitis. Treatment consists of allowing the injured eye to rest by use of an eye patch and applying an antibiotic ointment.

l Temporomandibular Joint Injuries

TMJ anatomy is special in that one side cannot be moved without the other side. Both joints represent a functional unit, and injuries to one TMJ affect the other side. Opening the mouth is a combination of rotary and translational movement in the joint. The rotary movement allows only a mouth opening of about 25 mm; the maximal opening is achieved by the translational movement. Pathologic changes such as bone cysts, rheumatid arthritis, and atrophy of the mandible due to age can reduce the joint mobility and may lead to fractures. Rupture of the lateral ligament is possible. TMJ injuries are caused by increasing forces during laryngoscopy to optimize the view of the vocal cords. Limited mouth opening, pain in the joint, lateral deviation of the mandible (e.g., unilateral luxation), protrusion of the mandible (e.g., bilateral luxation), and lockjaw (e.g., fixation after joint luxation) may occur. Most reported cases of TMJ injury were not associated with difficult airway.¹⁸⁴

m Damage to the Nose

Some injuries to the nose and endonasal structures were described previously. Using anatomically preformed tubes for head and neck surgery or compression of the nasal wing may lead to necrosis in the worse cases (Fig. 51-2). Wrapping the tube with foam material at the nasal wing level and careful nursing in cases of long-term intubation may reduce or avoid this complication.

Figure 51-2 Necrosis of right nasal wing after 3 days of intubation with an anatomic, preformed tube.

6 Esophageal Intubation

a Endotracheal Tube Placement

When visualization of the glottis is difficult, the ETT may inadvertently be introduced into the esophagus. Esophageal intubation is more common among inexperienced practitioners, but it may also occur in the hands of experienced stuff members. Intubating the esophagus is not disastrous, but failing to detect and correct the condition is. Recognition of this error must be rapid to avoid the adverse effects of prolonged hypoxia. A closed claims analysis of adverse anesthesia events reported that 18% of respiratory-related claims involved esophageal intubation.¹⁸⁵ Preoxygenation can help alleviate this problem by allowing a longer apneic period for tracheal intubation and by delaying the onset of hypoxemia. End-tidal CO₂ capnography is essential in confirming endotracheal placement of the tube. Capnography should be available wherever intubation is performed. In out-of-hospital practice and emergency medicine, where capnography may not be available, calorimetric single-use CO₂ detectors or an esophageal detector device can help to identify failed intubation in 94.6%.¹⁸⁶ Esophageal intubation can briefly produce an end-tidal CO₂ capnogram (e.g., in presence of CO₂-containing drinks in the stomach), but the waveform diminishes rapidly after three to five breaths.^187,¹⁸⁸ Fiberoptic control is another safe way to confirm the correct position of the tube. Other signs, such as equal bilateral breath sounds, symmetrical bilateral chest wall movement, epigastric auscultation and observation, and tube condensation, are potentially misleading.¹⁸⁹ A misplaced tube should remain in place while the trachea is correctly intubated. This helps to identify the correct orifice for intubation and protects the trachea from invasion by regurgitated stomach contents. Once proper endotracheal intubation is achieved after an esophageal intubation, the stomach should be suctioned to minimize vomiting, gastric perforation, or compromise of ventilation.

b Esophageal Perforation and Retropharyngeal Abscess

Perforation of the esophagus has been reported on several occasions.¹⁹⁰^–¹⁹⁸ It seems most likely to occur when inexperienced clinicians handle emergency situations, when intubation is difficult, or in presence of esophageal pathology. Perforation occurs most commonly over the cricopharyngeus muscle on the posterior esophageal wall, where the esophagus is narrow and thin. Subcutaneous emphysema, pneumothorax, fever, cellulitis, cyanosis, throat pain, mediastinitis, empyema, pericarditis, and death can occur. Early detection and treatment of the condition are critical because the mortality rate of mediastinitis is more than 50%. An esophageal perforation should be suspected in any patient with a fever, sore throat, and subcutaneous emphysema after a difficult intubation.

A case report identified a traumatic tracheal perforation through the esophagus in a patient with a difficult intubation.¹⁹⁹ Cases of esophageal perforation have been associated with the use of an esophageal-tracheal Combitube.^65,⁶⁶

7 Bronchial Intubation

a Use of an Endotracheal Tube

Bronchial intubation is common and sometimes difficult to identify. Asymmetrical chest expansion, unilateral absence of breath sounds (especially on the left side), and eventual arterial blood gas abnormalities are diagnostic features. Bronchial intubation (preferentially right-sided) is more common in newborns and children, because of the small distance between the carina and the glottis. The position of the tip of the tube should be carefully monitored in children. If bronchial intubation goes undetected, it may lead to atelectasis, hypoxia, and pulmonary edema.²⁰⁰ Transillumination of the neck with a lightwand can assist in tube location,²⁰¹ although not in cases of obesity and large goiter. Fiberoptic control is the best tool to detect proper position of the tube. The ETT may be deliberately advanced into a main stem bronchus and withdrawn until bilateral breath sounds are auscultated.

The tip of the ETT may move between 3.8 and 6.4 cm during flexion or extension of the patient’s head as the patient is positioned for surgery (Fig. 51-3).²⁰² It is easy to remember that the tip of the ETT moves in the same direction as the patient’s nose. If the patient’s neck is flexed, the nose is pointed downward, and the ETT advances farther into the trachea. The tube moves away from the carina an average of 0.7 cm during lateral rotation of the head. Care should be taken in case of cleft palate surgery or tonsillectomy. Special blades used by the surgeon to achieve a direct view may move the ETT forward during positioning the blade. A stethoscope placed on the left chest helps to identify an endobronchial tube that is being displaced.

Figure 51-3 The mean movement of an endotracheal tube with flexion and extension of the neck from a neutral position. The mean tube movement between flexion and extension is one third to one fourth of the length of a normal adult trachea (12 ± 3 cm).

(From Conrardy PA, Goodman LR, Lainge F, et al: Alteration of endotracheal tube position: Flexion and extension of the neck. Crit Care Med 4:8, 1976.)

When inadvertent bronchial intubation is discovered, the tube should be withdrawn several centimeters and the lungs inflated sufficiently to expand any atelectatic areas. In cases of chronic atelectasis, bronchoscopy may be required to remove mucous plugs. This problem can be avoided by measuring the length of the ETT alongside the patient before intubation. The tip of the tube should ideally be at least 2 cm above the carina, which may be approximated at the sternal angle (of Louis) adjacent to the junction of the sternum with the second rib. Appropriate orotracheal tube depths are 21 cm from the teeth in adult women and 23 cm in adult men, and nasotracheal tube depths are 25 cm in women and 27 cm in men from the nares.²⁰³

b Use of A Double-Lumen Tube

Safe limits for the placement of double-lumen tubes have been outlined by Benumof and colleagues.²⁰⁴ Modern FOBs have removed the guesswork surrounding endotracheal-bronchial tube tip location. The double-lumen tube may be inserted blindly into the appropriate bronchus, followed by bronchoscopic confirmation of its position, or the bronchoscope may be inserted initially and used as a stylet over which the double-lumen tube is advanced. Fiberoptic bronchoscopy significantly reduces malposition of the double-lumen tube, and its routine use is recommended after intubation, changing patient’s position, increasing ventilation pressure, and irregular auscultation sounds. However, even in the best of hands, tracheobronchial injuries occur.²⁰⁵ Bronchial rupture is a serious complication that requires immediate attention. Using double-lumen tubes that are too large may be the cause of bronchial trauma.²⁰⁶ The 37- to 39-F double-lumen tubes are recommended for women, and the 39- to 41-F tubes are recommended for men.

B Maintenance of the Endotracheal Tube

1 Airway Obstruction

A patent airway is an absolute requirement for safe anesthesia. Airway obstruction can occur at any time during administration of general anesthesia, particularly in prolonged operations or in patients with predisposing anatomic abnormalities. Airway obstruction should be considered when an intubated patient has diminished breath sounds associated with increasing peak inspiratory pressures. Obstruction can result from diverse factors,²⁰⁷ including a sharp bend or kink in the ETT, a tube that has been bitten closed, or a tube that is obstructed with mucus, blood, foreign bodies, or lubricant.^208,²⁰⁹ The ETT may become warm with continued use during prolonged procedures; under these circumstances, the tube may kink and become obstructed. Many clinicians mistakenly treat the patient for bronchospasm when the turbulent air movement comes from the ETT, not from the patient. At least two cases have been reported in which the plastic coating on a stylet sheared off and occluded the lumen of an ETT.^210,²¹¹ In another case, a tube was obstructed by the prominent knuckle of an aortic arch.²¹² Nitrous oxide can cause expansion of gas bubbles trapped in the walls of an ETT, leading to airway obstruction.²¹³

The cuff of an ETT can cause airway obstruction. An overinflated cuff may compress the bevel of the ETT against the tracheal wall, occluding its tip.²¹⁴ The cuff may also herniate over the tip of the tube and cause an obstruction.²¹⁵ When faced with any of these problems, the best solution is to pass a suction catheter or an FOB down the lumen of the ETT and attempt to clear it. If the tube is totally obstructed, passage of a stylet may be tried. Total obstruction that cannot be remedied quickly requires removal of the tube, and the patient should be reintubated as rapidly as possible. The ETT and connecting hoses should be supported and, if necessary, taped to prevent kinking caused by their own weight. Inspiratory gases should be humidified during long anesthesia to prevent tube obstruction from dried secretions.

Unusual causes of airway obstruction have been reported. In two patients, complete airway obstruction occurred secondary to achalasia and esophageal dilation.^216,²¹⁷ Two cases of tension hydrothorax that caused airway obstruction during laparoscopic surgery have been reported. The first patient had malignant ascites that, when combined with a pneumoperitoneum, led to a rapid accumulation of pleural fluid with respiratory and cardiovascular compromise.²¹⁸ The second case occurred during operative hysteroscopy when a large volume of glycine was absorbed through opened myometrial vessels under high intraabdominal pressure.²¹⁹ In each case, more than 1.5 L of clear fluid was drained once chest tubes were placed.

2 Disconnection and Dislodgment

A common and serious complication of tracheal intubation is disconnection of the ETT from the remainder of the anesthesia circuit. This was identified as the most common critical incident in a study of anesthesia-related human errors and equipment failures.²²⁰ A trained anesthesiologist usually identifies this problem immediately. The low-pressure alarm sounds first, and the patient’s breath sounds become absent. However, if the ventilator continues to function normally, the physician may be unaware of the nature of the problem. Disconnections are most likely to occur if the connections are made of dissimilar materials, if the patient’s head is turned away from the anesthesiologist, or if the airway connections are hidden beneath the surgical drapes. Alarms to signal airway disconnection are included on all modern anesthesia machines, and their signals should be taken seriously.

Connections between the ETT and the breathing circuit should be checked and reinforced at the outset, before the anesthesiologist loses visual control of the airway. There should be no tension on the connections from the weight of the corrugated tubing or the drapes on the tubing. Members of the surgical team should be discouraged from inadvertently leaning on any portion of the breathing circuit. The exact site of disconnection should be ascertained rapidly by checking each connection, beginning at the patient’s airway and moving proximally back to the machine.²²¹ Nonetheless, the anesthesiologist must have a prearranged plan in mind in the event that an airway is inadvertently disconnected or dislodged during surgery.

3 Circuit Leaks

Leaks in an air delivery circuit can cause hypoventilation and dilution of the inspired gases by entry of room air into the system. With an ascending bellows system, such as that found in newer models of anesthesia machines, the bellows do not rise completely during exhalation if there is a leak. This situation indicates that the circuit leak exceeds the inflow of fresh gas. Older machines with a descending bellows system do not provide such a visual clue and appear to function normally. The anesthesiologist should be vigilant at all times for signs of a circuit leak. The inspired oxygen concentration measured at the gas sampling port is reduced because of dilution with room air, and the partial pressure of end-tidal CO₂ increases. Cyanosis, decreased oxygen saturation (SpO₂), or hypertension and tachycardia associated with hypercapnia may be the presenting signs, although each of these is typically a late finding.

Mnemonics such as COVER ABCD–A SWIFT CHECK may help to diagnose and treat the conditions ²²²:

4 Laser Fires

Lasers are frequently used in the operating room to ablate benign and neoplastic tissues in the airway. The use of special laser-guarded or metal tubes is recommended, and all inflammatory materials such as prosthetic teeth and nasogastric tubes should be removed. One of the most catastrophic events associated with their use is an airway fire, which occurs when the laser ignites the ETT.²²³^–²²⁵ The risk that a laser beam will contact the wall of an ETT is 1 : 2.²²⁶ Perforation of the tube may occur and produce a blowtorch-like flame. Oxygen-rich inspired gas concentrations fuel brisk ignition of the plastic in the ETT and can fuel a fire in both directions. The ETT acts as a blowtorch; the fire is fed by the combustible walls of the tube and is intensified by the high rate of oxygen flow. The heat and fumes of the burning plastic may cause severe damage to the airway. Treatment consists of immediately disconnecting the circuit from the ETT and removing the burning tube from the airway. If the tube is not burning or if complete loss of the airway may occur with removal of the tube, leaving the tube in situ should be considered. The fire should be extinguished with saline, and the patient should be supported by face mask ventilation. The airway should be evaluated for damage with bronchoscopy, and the appropriate supportive respiratory care should be given.

Many precautions can reduce the risk for an airway fire. If possible, placement of an ETT may be avoided altogether if air can be delivered through a ventilating laryngoscope, a jet ventilation system, or by intermittent apneic ventilation.²²⁷ If a tracheostomy tube is in place, ventilation may occur distal to the site of laser surgery. The choice of laser tubes should be consistent with the type of laser used. Blocking cuffs are particularly vulnerable to the laser beam. Covering the tube with saline-soaked gauze or noncombustible tape, using a positive end-expiratory pressure (PEEP) of 5 to 10 cm H₂O to prevent aspiration of material in case of cuff puncture, and filling the cuff with saline to act as extinguisher in the event of puncture are measures that can protect the patient’s airway.^228,²²⁹ Placing a dye, such as methylene blue, in the saline can further alert the anesthesiologist, because in the event of a fire, a stream that is the color of the dye will be emitted.

Nitrous oxide should be avoided because it supports combustion. Oxygen concentrations should never exceed 40% for the same reason.^230,²³¹

C Special Techniques

Iv Complications with Infraglottic Procedures

Infraglottic airway access is the last step in the ASA airway management algorithm. When tracheal intubation is impossible, a patient’s airway is compromised, and the patient’s condition deteriorates into a CICV situation threatening brain damage or death, life-saving steps must be undertaken immediately. There are no contraindications for infraglottic procedures in these critical situations. The most severe complication is failure to establish an airway before damage or death occurs. Complications arise because the decision to progress to a surgical airway is not made soon enough or because the procedure is performed too slowly. In all cases of difficult airway, the practitioner should evaluate the possibility of an infraglottic airway access. Difficult anatomic situations, marked scars, abscesses, and morbid obesity may limit infraglottic access techniques.

Infraglottic airway techniques are suitable for emergency situations, and they are indicated for oxygenation and ventilation of anesthetized patients. Surgical procedures of the upper airway, laryngeal surgery, and diagnostic procedures have been successfully managed with this technique.

A Translaryngeal Airway

1 Retrograde Wire Intubation

Retrograde wire intubation is an excellent technique for securing a difficult airway. It can be used when anatomic limitations obscure the glottic opening. Because the technique is blind, it is important to exercise caution and not worsen any preexisting conditions. The technique has variations, such as using the FOB by passing the wire through the suction channel or through a tube exchanger.²³⁸

Although simple in concept, the basic technique has numerous problems and potential complications. The procedure takes some time to perform and should not be considered under emergency circumstances unless the practitioner is very experienced. The tip of the ETT has been known to get caught on the glottic structures. The problem may be alleviated somewhat by using a tapered dilator inside the ETT or by using an epidural catheter as the wire to assist with passing the ETT through the glottis. Bleeding may occur at the site of the tracheal puncture in quantities sufficient to cause a tracheal clot or airway obstruction. Cases of severe hemoptysis with resultant hypoxia, cardiopulmonary arrest, arrhythmias, and death after retrograde wire intubation have been reported.²³⁹^–²⁴² Subcutaneous emphysema localized to the area of the transtracheal needle puncture is common but usually self-limited. In severe cases, the air may track back through the fascial planes of the neck, leading to tracheal compression with resultant airway compromise, pneumomediastinum, and pneumothorax.^243,²⁴⁴ Laryngospasm may result from irritation by the retrograde wire unless the vocal cords are anesthetized or relaxed. Other, less common complications include esophageal perforations, tracheal hematoma, laryngeal edema, infections, tracheitis, tracheal fistulas, trigeminal nerve injury, and vocal cord damage.^245,²⁴⁶ The complications reported with retrograde wire intubation were most often associated with multiple attempts, large-gauge needles, and untrained staff members in emergency settings.²⁴⁷

2 Cricothyrotomy

Two methods are described: the surgical cricothyrotomy (using a scalpel) and the needle cricothyrotomy (using a needle set). In both procedures, the cricothyroid membrane must be perforated. Acute complications include bleeding (especially during surgical cricothyrotomy), misplacement of the tube (especially after needle cricothyrotomy), failure of airway access, wound infection, displaced cartilage fractures, and laryngotracheal separation.²⁴⁸ Other complications include breaking and bending of the needle, subcutaneous emphysema, pneumothorax, pneumomediastinum, and pneumopericardium. When cricothyrotomy is performed in the case of total upper airway obstruction, barotrauma may occur because of expiratory blockade.

Granulation tissue around the tracheostomy site, subglottic stenosis, massive laryngeal mucosa trauma, endolaryngeal hematoma and laceration, vocal cord paralysis, hoarseness, and thyroid cartilage fracture with dysphasia are direct long-term complications. Indirect long-term complications include brain damage or mental impairment due to hypoxia when the cricothyrotomy takes more than 2 to 3 minutes.

Every emergency translaryngeal airway should be changed to a formal tracheostomy as soon as possible. Subglottic stenosis is a delayed complication, especially in children.

B Transtracheal Airway

1 Transtracheal Jet Ventilation

One emergency method is transtracheal jet ventilation (TTJV), which is accomplished by introducing a small, percutaneous catheter into the trachea and insufflating the respiratory tract with high-pressure oxygen over a jet ventilator or a hand jet device (e.g., VBM Manujet). Although this technique may be helpful in critical situations, life-threatening problems are associated with it.

To accomplish TTJV, a long, large-bore catheter is advanced through the cricothyroid membrane into the trachea. If this catheter is displaced from the trachea, subcutaneous emphysema, hypoventilation, pneumomediastinum, pneumothorax, severe abdominal distention, or death may result.¹⁶⁴ On the basis of normal skin compliance, a 4-inch catheter may be pulled into the subcutaneous space by applying traction to its proximal end. The hub of the TTJV catheter must be continuously pressed firmly against the skin.

Barotrauma is a potential complication of TTJV.^249,²⁵⁰ Oxygen delivered through a transtracheal catheter must be able to escape the lungs freely, or overdistention and pulmonary rupture may occur.^251,²⁵² Any changes in breath sounds, chest wall expansion, or hemodynamics should be considered to result from pneumothorax. In cases of total airway obstruction, the risk for pneumothorax is greatly increased because gas cannot escape from the lungs in a normal manner. Strong consideration should be given to placing a second transtracheal egress catheter in these circumstances. Laryngospasm can impede the outward flow of oxygen from the trachea. It should be prevented by providing adequate local anesthesia to the neighboring structures or by relaxing the patient.²⁵⁰ If the larynx is obstructed by a foreign body, only low-flow oxygen should be delivered until safe egress of gas is established. Inadvertent placement of a gas delivery line into the gastrointestinal tract may result in complications and may cause gastric rupture, esophageal perforation, bleeding, hematoma, and hemoptysis.^253,²⁵⁴

Damage to the tracheal mucosa may occur in patients who are managed with long-term TTJV, especially if the gas is not humidified.²⁵⁵ The possibility of tracheal mucosal ulceration should be considered in any patient if nonhumidified TTJV is attempted through single-orifice catheters for a prolonged period.

2 Percutaneous Dilatational Tracheostomy

Percutaneous dilatational tracheostomy is not primarily recommended for emergency use. With further development, these insertion techniques became faster and appeared to be suitable for emergency situations in skilled hands.²⁵⁶^–²⁶⁰ Different sets are available.

Bleeding, subcutaneous and mediastinal emphysema, pneumothorax, airway obstruction, aspiration, infection, and death are early complications. Accidental extubation is a serious complication, because replacement of the cannula may be impossible. In this situation, orotracheal intubation or a translaryngeal oxygenation is required.²⁶¹ Bacteremia also has been reported.²⁶²

Delayed complications include tracheal stenosis, scars, hoarseness, and tracheoesophageal and tracheocutaneous fistulas. The incidence of injury for percutaneous dilatational tracheostomy is 2%, which is lower than for formal tracheostomy.

3 Formal Tracheostomy

A formal tracheostomy is rarely recommended in emergency situations. Various types of instruments, assistance, and sterile conditions are required, and the tracheostomy should be performed only by a trained surgeon.

Bleeding is a complication of all surgical procedures, including airway access procedures. Minitracheostomy occasionally results in excessive bleeding into the airway, necessitating progression to full surgical tracheostomy.²⁶³ The inflated cuff used in formal tracheostomy prevents pulmonary aspiration of blood. In rare cases, the innominate artery can rupture into the trachea because of excessive pressure from the tracheostomy tube, with resultant massive hemorrhage into the airway. Air embolism during operative procedure is possible.

If an air leak occurs and the cervical skin has healed around the tracheostomy tube, air can escape into the subcutaneous spaces of the neck, resulting in subcutaneous emphysema. If the condition goes unrecognized and the patient is maintained on high-pressure mechanical ventilation, the air may track to other locations. Air escaping into the paratracheal spaces can result in a pneumomediastinum. Air released into the pleural cavity can result in a tension pneumothorax.

Tracheal stenosis is a complication of long-term tracheostomy. A tracheostomy tube can cause tracheal erosion, particularly into the esophagus (i.e., tracheoesophageal fistula) or the brachiocephalic artery. These tubes typically sit low in the trachea and are designed with a fixed curve. Tube pressure can damage the skin at the insertion site.

Accidental extubation and dislodgment of the cannula occurs occasionally, most often in the early postoperative period. If the cannula is inadvertently removed from a fresh tracheostomy, it should be replaced as quickly as possible. Infection, mediastinal sepsis, tracheal stenosis, and tracheomalacia are rare late complications.

V Physiologic Responses

The larynx has the greatest afferent nerve supply of the airway. Airway reflexes are important in protection of the airway. They must be suppressed for stress-free airway management, especially for endotracheal intubation. Intensive autonomic response may occur during placement, maintenance, and removal of all airway management devices.

A Hemodynamic Changes

Direct laryngoscopy and tracheal intubation are potent stimuli that may instigate an intense autonomic response.^264,²⁶⁵ Tachycardia, hypertension, arrhythmias, bronchospasm, and bronchorrhea are common; hypotension and bradycardia occur less often. Patients with preexisting hypertension are even more at risk when they are under stress.

Oczenski and colleagues showed that the insertion of a Combitube was associated with a significantly higher and longer-lasting increase in systolic, diastolic, and mean arterial pressure; heart rate; and plasma catecholamine concentration compared with insertion of a LMA and laryngoscopic endotracheal intubation (Fig. 51-4).²⁶⁶ Hemodynamic and catecholamine responses to insertion of an LMA are minimal.^267,²⁶⁸ The apparently sympathetically mediated responses to mechanical stimulation of larynx, trachea-carina, and bronchi may be completely or partially blocked by topical or intravenous lidocaine.²⁶⁹ The magnitude of stimuli to the upper airway depends on the number of attempts and the duration of intubation. In cases of difficult airway situations a higher increase of hemodynamic responses is anticipated. The hemodynamic response may also be blunted by giving opioids or short-acting selective β₁-blockers before laryngoscopy and intubation.²⁷⁰ Because many patients have coexisting cardiovascular disease and cannot meet increased myocardial oxygen demands, large hemodynamic responses must be prevented. More than 11% of patients with myocardial disease develop some degree of myocardial ischemia during intubation.²⁷¹ The key is to provide an adequate depth of anesthesia with intravenous or inhalational agents before instrumentation of the airway.

Figure 51-4 A and B, Heart rate and mean arterial blood pressure (MAP) at specified times (mean ± SD, n = 73) during insertion of the endotracheal tube (ET), laryngeal mask airway (LMA), and Combitube (CT).

(From Oczenski W, Krenn H, Dahaba AA, et al: Hemodynamic and catecholamine stress responses to insertion of the Combitube, laryngeal mask airway or tracheal intubation. Anesth Analg 88:1389, 1999.)

Fiberoptic intubation performed under sufficient local anesthesia and conscious sedation is an appropriate technique to prevent major hemodynamic changes during intubation. Minor hemodynamic changes and minor increases of plasma catecholamine concentration are nevertheless apparent in this technique. Fiberoptic intubation using a special mask adapter shows fewer hemodynamic changes than those caused by laryngoscopy after induction of anesthesia. The lowest cardiovascular responses were documented in patients after insertion of an LMA.²⁷²

B Laryngospasm

Laryngospasm is a protective reflex mediated by the vagus nerve. This reflex is an attempt to prevent aspiration of foreign bodies into the trachea. It may be provoked by movement of the cervical spine, pain, vocal cord irritation by secretions, or sudden stimulation while the patient is still in a light plane of anesthesia.²⁷³

In some cases of laryngospasm, the patient makes respiratory efforts but cannot move air in or out of the lungs. If direct laryngoscopy was performed, the vocal cords would be completely adducted. However, laryngospasm involves more than spastic closure of the vocal cords. An infolding of the arytenoids and the aryepiglottic folds occurs; these structures are subsequently covered by the epiglottis.²⁷⁴ Malpositioning, incorrect insertion of an LMA, secretions or blood in the airway, and inadequate depth of anesthesia during intubation or extubation of the LMA or tracheal tube may induce laryngospasm. It may also occur during fiberoptic intubation performed in unanesthetized or subanesthetized laryngeal structures. A firm jaw thrust can sometimes break the spasm—the hyoid is elevated, thereby stretching the epiglottis and aryepiglottic folds to open the forced closure.

The stimulus should be removed, a change of airway should be considered, and secretions should be suctioned away. Positive mask pressure with 100% oxygen may help by distending the pharynx or vocal cords, but this technique is not always adequate. Gentle chest compression in children may also help.²⁷⁵ Deepening the anesthesia with small doses of propofol (0.25 to 0.8 mg/kg given intravenously can treat laryngospasm in 76.9%) or treatment with a short-acting muscle relaxant (0.1 to 3 mg/kg of succinylcholine) are the most promising ways to break the spasm.²⁷⁶

C Bronchospasm

Tracheal irritation from the ETT can cause bronchospasm that is sufficiently severe to prevent air movement throughout the lungs.²⁷⁷ Approximately 80% of the measurable resistance to airflow occurs in the large central airways; the remaining 20% occurs in the smaller peripheral bronchioles.²⁷⁸ The incidence of intraoperative bronchospasm is almost 9% with endotracheal intubation, 0,13% with an LMA, but almost 0% with mask ventilation.^279,²⁸⁰ Poor correlation is seen with age, sex, duration or severity of reactive airway disease, duration of anesthesia, or the forced expiratory volume in 1 second.²⁷⁹ Other factors that may contribute to bronchospasm include inhaled stimulants, release of allergic mediators, viral infections, exercise, or pharmacologic factors (including beta-blockers, prostaglandin inhibitors, and anticholinesterases). Bronchospasm may occur during fiberoptic intubation if parts of subglottic airway are insufficiently anesthetized. The spasm can be treated with inhalation of epinephrine or isoproterenol or a β₂-agonist (e.g., albuterol, metaproterenol, or terbutaline) or by deepening the level of a volatile anesthetic.

D Coughing and Bucking

Two additional adverse responses to intubation are coughing and bucking on the ETT.²⁸¹ These responses are potentially hazardous in cases of increased intracranial pressure,²⁸² intracranial vascular anomalies, open-globe injuries, or ophthalmologic surgery or in cases in which increased intra-abdominal pressure may rupture an abdominal incision.²⁸³ Intubating a patient only when an adequate depth of anesthesia has been achieved helps to prevent this reflex.

Coughing and bucking occur less frequently with the LMA. However, in the case of lubricant globules on the anterior surface of the cuff, light anesthesia, and malpositioning, they may be observed.

E Vomiting, Regurgitation, and Aspiration

The overall incidence of aspiration during general anesthesia has been reported as 1 in 2131 procedures (in Sweden) to 1 in 14,150 procedures (in France). The incidence in the United States was 1 in 3216 procedures. The associated mortality rate was 1 in 71,829 cases in the United States.²⁸⁴ A meta-analysis of 547 publications concerning use of the LMA suggested that the overall incidence of pulmonary aspiration was about 2 in 10,000 cases.²⁸⁵

The ETT and Combitube are most effective in preventing pulmonary aspiration. To reduce the risk of pulmonary aspiration, some airway management devices, such as the ProSeal-LMA and the Laryngeal Tube S, were redesigned.

In any patient considered to have a full stomach, the likelihood of vomiting in response to irritation of the airway is increased, and aspiration of stomach contents is a constant concern. Aspiration leads to coughing, laryngospasm, and bronchospasm, assuming that protective reflexes are intact. Hypertonia, bradycardia, asystole, and hypoxia may occur. The magnitude of pulmonary reactions depends on the type and quantity of the aspirated material.²⁸⁶

The Sellick maneuver, or cricoid pressure (CP), is controversial. Although some strongly endorse the technique and trust its effectiveness, others think that CP should be abandoned because it adds to patients’ risks with no evidence of gained benefit. Other practitioners apply CP because they think it is a low-risk technique that may work in some patients. The future of CP use lies in the answer to the question of whether it is effective in preventing regurgitation or an unnecessary hazard. Because aspiration is a rare event, a study to confirm the preventive effect of CP may not be feasible.

It is possible to completely obstruct the airway with CP. CP has resulted in airway obstruction in patients with lingual tonsils, lingual thyroid glands,²⁸⁷ and undiagnosed laryngeal trauma.²⁸⁸ If any doubt exists about the success of an oral intubation, awake techniques should be considered under these circumstances.²⁸⁹

F Intraocular Pressure Changes

Intraocular pressure increases during direct laryngoscopy and extubation, but not during LMA insertion.^290,²⁹¹ Decreased intraocular pressure was observed under tracheal intubation during general anesthesia with propofol and with sevoflurane, both combined with remifentanil.²⁹²

Sufentanil is effective in preventing intraocular pressure increases caused by rapid-sequence induction with succinylcholine; alternatively rocuronium can be used.²⁹³ Increased intraocular pressure should be strictly avoided in patients with penetrating eye injuries.

G Intracranial Pressure Changes

Intracranial pressure markedly and transiently rises during laryngoscopy and endotracheal intubation. Patients with head injury are at risk from this increase because it reduces cerebral perfusion and may increase the likelihood of secondary brain damage.²⁹⁴ Fiberoptic bronchoscopy produces a substantial but transient increase of intracranial pressure.²⁹⁵ Deep anesthesia during induction can prevent these adverse effects.

H Apnea

Apnea may be a reflex response to tracheal irritation from the ETT or other airway techniques. Extraneous reasons for the apnea—for example, if the patient is a premature or term neonate,²⁹⁶ has had induction drugs or excessive narcotics, or has a reflux response to light levels of anesthesia—should be ruled out initially. If no clear reason exists for the patient’s lack of respiratory effort, mechanical ventilation can be initiated, and spontaneous ventilation can be attempted later.

I Latex Allergy

Of anaphylaxis episodes occurring during surgical procedures, 16.6% are related to latex allergies.²⁹⁷ To prevent anaphylaxis during anesthesia and surgery, the patient’s history should be evaluated preoperatively. There is no therapy for latex allergy, and avoidance of latex-containing products is mandatory for predisposed individuals.²⁹⁸ Latex allergy affects 8% of the U.S. general population and has a prevalence of 30% among health care workers.^299,³⁰⁰ There has been an increase in the incidence of type I and IV latex sensitivity in the general population, from 1% in 1980 to 8% in 1996.³⁰¹ The prevalence of latex sensitivity among anesthesiologists is about 12.5%, and the prevalence of allergy is 2.4%.³⁰²

Patients with spina bifida, rubber industry workers, atopic patients, and patients with a history of many operations are most at risk.³⁰³ Patients with certain exotic food allergies may also have a coexisting latex allergy³⁰⁴; in one study, the rate was 86%.³⁰⁵

Patients with type I hypersensitivity are at risk for anaphylaxis with hypotension, rash, and bronchospasm. Type I hypersensitivity symptoms are localized contact urticaria with pruritus and edema. Generalized reactions are rash or hives, tearing, rhinitis, hoarseness, dyspnea, nausea, vomiting, bronchospasm, abdominal cramping, and diarrhea.

Contamination with latex during anesthesia is possible through direct contact by face mask, endotracheal and gastric tubes, gloves, syringes, and electrodes; through inhalation from contaminated circuits and room air; and through the parenteral path with latex-containing intravenous administration sets.

Most airway management devices are available as latex-free products. The oropharyngeal cuff of the Combitube contains latex; therefore, it is contraindicated in patients with known latex allergy. All anesthesiology departments should have a special latex-safe cart with all medical supplies and devices.

VI Complications with Extubation

Primary and secondary responses to extubation are possible. The primary effects are local and systemic responses (Box 51-2). The same responses after intubation may be observed at extubation. During intubation, the patient is more protected by anesthesia induction than during extubation, and the cardiovascular responses may be even more exaggerated. The most serious complication after extubation is acute airway obstruction. Decreased consciousness with central respiratory depression, decreased muscle tone, and tongue retraction to the postpharyngeal wall may lead to inspiratory or expiratory stridor, dyspnea, cyanosis, tachycardia, hypertension, agitation, and sweating. Laryngospasm is also possible, and urgent treatment is necessary to prevent hypoxia, brain damage, and death. Other complications after extubation are not caused by the removal of the tube itself; they are consequences of the previous intubation and the duration of tube placement, such as laryngitis, edema, ulcerations, granuloma, or synechia of the vocal cords. The quality of tracheal intubation contributes to laryngeal morbidity, and excellent conditions are less frequently associated with postoperative hoarseness and vocal cord sequelae.

Box 51-2

Pathophysiologic Effects of Tracheal Extubation

Primary Local Effects

Damage to the vocal cords

Arytenoid dislocation/luxation

Primary Systemic Effects

Cardiovascular System

Tachycardia

Increased systemic arterial pressure

Increased pulmonary arterial pressure

Secondary Effects

Central Nervous System

Increased intracranial pressure

Eyes

Increased intraocular pressure

Modified from Hartley M: Difficulties in tracheal extubation. In Latto IP, Vaughan RS, editors: Difficulties in tracheal intubation, London, 1997, Saunders.

A Hemodynamic Changes

Hemodynamic changes, including a 20% increase in heart rate and blood pressure, occur in most patients at the time of extubation,^306,³⁰⁷ and symptoms that are associated with sympathoadrenal activity should be expected. These changes are usually transient and rarely require treatment. Although most patients tolerate these hemodynamic responses well, patients with cardiac disease,²⁷¹ pregnancy-induced hypertension,³⁰⁸ and increased intracranial pressure may be at particular risk for life-threatening ischemic myocardial episodes.³⁰⁹ Patients with cardiac disease have had decreased ejection fractions at the time of extubation.³¹⁰ Management consists of extubation under deep anesthesia or pharmacologic therapy. Deep extubation is inappropriate for patients with a difficult airway, those at high risk for aspiration, and those with compromised airway access. Pharmacologic strategies emphasize the importance of decreasing the heart rate, such as with short-acting beta-blockers.³¹¹ Cerebral hemorrhage is possible. Using an LMA may significantly reduce local and cardiovascular responses at removal if the cuff pressure is minimized to avoid overstimulation of the patient.²⁶

B Laryngospasm

In a computer-aided study of 136,929 patients, the incidence of laryngospasm was 50 cases per 1000 children with bronchial asthma or airway infection and 25 cases per 1000 in children 1 to 3 months old after tracheal intubation had been performed.³¹²

The optimal course for treating laryngospasm is to avoid it in the first place. Treatment was described earlier. When laryngospasm is anticipated, the patient may undergo a deep extubation. A patient undergoing deep extubation should be placed in the lateral position with the head down to keep the vocal cords clear of secretions during emergence. It is best to extubate patients during a positive-pressure breath to remove residual secretions. Extubation during positive-pressure breath is the procedure of choice in children. A study showed that children could be safely extubated in deep anesthesia from a 1.5 minimum effective alveolar anesthetic concentration of sevoflurane or desflurane.³¹³ The study of Koga and colleagues showed that the rate of airway obstruction in patients extubated during deep anesthesia (17 of 20) was not higher than in patients extubated after regained consciousness (18 of 20).³¹⁴

C Laryngeal Edema

Laryngeal edema is an important cause of post-extubation obstruction, especially in neonates and infants. This condition has various causes and is classified as supraglottic, retroarytenoidal, or subglottic.³¹⁵ Supraglottic edema most commonly results from surgical manipulation, positioning, hematoma formation, overaggressive fluid management, impaired venous drainage, or coexisting conditions (e.g., preeclampsia, angioneurotic edema). Retroarytenoidal edema typically results from local trauma or irritation. Subglottic edema occurs most often in children, particularly neonates and infants. Factors associated with development of subglottic edema include traumatic intubation, intubation lasting longer than 1 hour, bucking on the ETT, changes in head position, or tight-fitting tubes. Laryngeal edema usually manifests as stridor within 30 to 60 minutes after extubation, although it may start as late as 6 hours after extubation. Regardless of the cause of laryngeal edema, management depends on the severity of the condition. Therapy consists of humidified oxygen, nebulized epinephrine, head-up positioning, and occasionally reintubation with a smaller ETT. The practice of administering parenteral steroids with the goal of preventing or reducing edema after long-term (>36 hours) ventilation may prove beneficial for adult patients, but routine administration for anesthesia is controversial.³¹⁶

D Laryngotracheal Trauma

Unlike trauma during intubation, airway trauma at the time of extubation is not well described. Arytenoid cartilage dislocation has been reported after difficult and routine intubations.^122,³¹⁷ Symptoms become apparent soon after extubation and may be mild (e.g., difficulty swallowing, voice changes) or major (e.g., complete airway obstruction). Management depends on the severity of the condition. Options include reintubation, arytenoid reduction, and tracheostomy. If laryngotracheal trauma is suspected, an otolaryngology consultation is warranted.

E Bronchospasm

In patients at risk for bronchospasm, the timing of extubation is important. These patients may be extubated during deep anesthesia (if this approach can be used safely) or when they are fully awake and their own airway reflexes are present. Although the degree of spasm in this condition may be severe, it is usually self-limited and short-lived.

F Negative-Pressure Pulmonary Edema

When airway obstruction occurs after extubation in the case of laryngospasm, negative-pressure pulmonary edema may occur in a spontaneously breathing patient. As a result of inspiratory effort against the closed glottis, these patients generate negative intrapleural pressure of more than 100 cm H₂O. Rib retraction with poor air movement, laryngospasm, and stridor may lead to the rare diagnosis. Increased left ventricular preload and afterload, altered pulmonary vascular resistance, increased adrenergic state, right ventricle dilation, intraventricular septum shift to the left, left ventricular diastolic dysfunction, increased left heart loading conditions, enhanced microvascular intramural hydrostatic pressure, negative pleural pressure, and transmission to the lung interstitium may result in a marked increase in transmural pressure, fluid filtration into the lung, and development of pulmonary edema.³¹⁸

Negative-pressure pulmonary edema is seen within minutes after extubation. Hemoptysis and alveolar hemorrhage are rare symptoms. Management involves removing the obstruction, supporting the patient with oxygen, monitoring the patient closely, and reducing the afterload. CPAP therapy is useful, and reintubation is rarely necessary. Most cases resolve spontaneously without further complications.

G Aspiration

Pulmonary aspiration of gastric contents is a constant threat for any patient who has a full stomach or is at risk for postoperative vomiting. Laryngeal function is altered for at least 4 hours after tracheal extubation.³¹⁹ Coughing is a physiologic response to protect the airway from aspiration. Depression of reflexes, along with the presence of residual anesthetic agents, places most recently extubated patients at risk. Aspiration is probably more prevalent than is currently thought. Most cases are so minor that they do not affect the patient’s postoperative course. Reducing gastric contents by suctioning through a gastric tube and extubation with the patient placed in the lateral position with a head-down tilt is the safest protection against aspiration. Perioperative problems, if they do occur, are usually attributed to factors such as atelectasis. Management consists of supportive measures. Depending on the extent of aspiration, measures include supportive care, ranging from administration of oxygen through a nasal cannula to reintubation with mechanical ventilation, and PEEP.

H Airway Compression

External compression of the airway after extubation may lead to obstruction. An excessively tight postoperative neck dressing is a cause of external compression that is easily resolved. A more ominous situation is a rapidly expanding hematoma close to the airway. This may occur after certain operations, such as carotid endarterectomy, and must be quickly diagnosed and treated before total airway obstruction occurs.³²⁰ Immediate surgical re-exploration is indicated, although the airway concerns for these patients should be approached with extreme caution. To minimize airway distortion, general anesthesia should be avoided until the wound is evacuated under local anesthesia. However, even after surgical drainage, airway obstruction may occur as the result of venous or lymphatic congestion. Any use of muscle relaxants during anesthesia induction in these patients may result in catastrophe, regardless of whether the wound was previously drained. Conservative options for managing the airway in this situation include awake fiberoptic intubation, surgical airways, or inhalation induction. Muscle relaxants should be avoided until the airway is secured.

External compression of the neck, such as chronic compression of a goiter, may also result from tracheomalacia.³²¹ This condition is usually seen after the goiter has been removed, although cases were reported in which the airway collapsed with induction or after extubation.^322,³²³ Airway obstruction in these patients becomes apparent soon after extubation. Management includes reintubation, surgical tracheal support (i.e., stenting), or tracheostomy below the level of obstruction.

I Difficult Extubation

Occasionally, ETTs are difficult to remove. Possible causes are failure to deflate the cuff, use of an oversized tube,³²⁴ adhesion of the tube to the tracheal wall,³²⁵ or transfixation of the tube by an inadvertent suture to a nearby organ, a wire, a screw placed in an oromaxillofacial operation, or a broken drill.³²⁶^–³²⁹ ³⁴⁰ Possible sequelae of these complications include airway leak, aspiration, tube obstruction, and trauma from attempts at forceful extubation. One case was reported in which a nasogastric tube made a loop around the ETT.³³⁰ In most cases, the problem arises from an inability to deflate the cuff, commonly as a result of failure in the cuff-deflating mechanism. If this problem occurs, the cuff should be punctured with a transtracheal needle. If tube fixation is suspected, the passage of the tube should be checked with a suction catheter or a fiberscope. Forceful removal of an ETT with the cuff inflated may result in damage to the vocal cords and arytenoid dislocation.

J Accidental Extubation

Accidental extubation during anesthesia has been reported with disposable tonsillectomy instruments,³³¹ change of the patient’s head position, and in neurosurgery with the patient in the knee-elbow position.³³² Most accidental extubations were reported from intensive care unit patients, for whom self-extubation was the most common incident (77% to 85%).³³³^–³³⁵ The rate of reintubation was 37% to 57%.³³³^–³³⁵ The requirement for reintubation is higher for patients with full ventilatory support than those during the weaning phase.

Patients at risk for accidental extubation are characterized by the absence of physical restraints, a high nurse-to-patient ratio, trips out of the intensive care unit (59%), light sedation (43%), use of bedside portable radiography, accidental removal of the nasogastric tube or tugging on the ETT, oral intubation, and insufficient sedation.³³⁶ Complications after accidental extubation may be hypoxia, hypercarbic respiratory failure, aspiration, retention of pulmonary secretion, arrhythmia, and tachycardia. To avoid unplanned extubation, tubes can be secured with special tube holders,³³⁷ with waterproof tape, and with fixation using a knot or a bow.^338,³³⁹

Reintubation may be very difficult, especially after a difficult intubation. The use of a Combitube or an LMA is required in some cases of inadequate access to the patient’s head in the intensive care setting.³⁴⁰