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

Diseases

Limited temporomandibular joint mobility

Limited atlanto-occipital and atlantoaxial joint mobility

Unstable cervical spine

Limited laryngeal mobility

Postoperative or post-traumatic rigidity of the soft tissue of mouth and neck

Congenital, postoperative, post-traumatic anomalies of face and neck

Abscesses and tumors in face and neck

Paradontosis

Phlegmon of the floor of the mouth and of the neck

Epiglottitis

Mediastinitis

Stenosis of the upper airway

Enlarged goiter

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

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