Intubation is the most commonly used method of securing a patient’s airway during surgical procedures and is a mainstay of management of patients in acute respiratory failure or who have altered mental status. Complications of endotracheal intubation can result from direct laryngoscopy, from pressure of the endotracheal tube or cuff on the airway and on surrounding structures, and from extubation.¹ There are numerous structures in the oropharynx, laryngopharynx, larynx, and trachea that are susceptible to potential damage (Fig. 55-1). This chapter discusses notable complications of endotracheal intubation, as well as their precipitating causes and perioperative management. These can be subdivided temporally: acute or chronic, depending on whether they occur at the time of intubation or whether they occur secondary to prolonged intubation.² Table 55-1 provides a comprehensive list of acute and chronic complications; a number of these are discussed in detail in this chapter.

Several factors are likely to increase the risk of pharyngeal and laryngeal complications. These factors may be related to the skills of the provider, the airway equipment, the patient’s anatomy, the emergent nature of the intubation, unanticipated difficulty encountered during intubation, or a combination of these. The provider plays a role in the risk of endotracheal intubation based on his or her knowledge, skill, and experience.² In addition, the equipment used for endotracheal intubation can affect the outcome. An inappropriately sized endotracheal tube, or the use of stylets or bougies, increases a patient’s risk of airway trauma.² The provider’s initial evaluation of the airway is a key element in avoidance of, and preparation for, a difficult intubation and the airway trauma that may result from it. Patient-related risk factors for airway trauma related to endotracheal intubation include a small larynx, cervical spine pathology, and difficult airway as assessed by the Mallampati score. It is also important to be mindful that routine intubation can cause trauma to the laryngeal soft tissues; a closed claims study demonstrated that 80% of laryngeal injuries occurred during routine intubation.³,⁴ Therefore, under the best circumstances and in the hands of the most experienced operator, complications may still occur.

Failed or misplaced intubations are some of the most commonly encountered complications of endotracheal intubation. Incorrect placement of the endotracheal tube may result in esophageal or bronchial intubations, which must be recognized and corrected promptly. Esophageal intubation may be recognized simply by auscultation of air in the abdomen, and lack of breath sounds, or lack of persistent end-tidal carbon dioxide (ETCO₂) with ventilation. Of note, transient ETCO₂ can be detected despite an esophageal intubation if the patient recently consumed a carbonated beverage. Sequelae of esophageal intubation are serious including hypoxia, brain death, myocardial infarction, and cardiac arrest.⁵,⁶,⁷

Bronchial intubation occurs when the endotracheal tube is placed in one of the mainstem bronchi, usually on the right due to its more vertical orientation as compared with the left. Infants and children are at higher risk of bronchial intubation due to the smaller distance between the vocal cords and carina. An endobronchial intubation can occur immediately after intubation, when the endotracheal tube is advanced too far. Endobronchial intubation only ventilates and oxygenates one lung, which leads to atelectasis, ventilation-perfusion mismatch, and hypoxia. If the patient has unequal breath sounds in both lungs, the endotracheal tube can be slightly pulled back. During the surgery or in the intensive care unit, the endotracheal tube is also at risk of migrating into a bronchus when the patient’s position is changed. For example, placing a patient in the Trendelenburg position can advance a tube that was initially in the distal trachea into the right mainstem bronchus.⁸ Usually, this event presents as elevated airway pressures and oxygen desaturation. Knowing the original depth of the tube when correct placement was confirmed can be useful for determining the length of endotracheal tube to pull back.

Esophageal perforation is a rarely reported complication of endotracheal intubation that occurs during unintentional esophageal intubation.⁹,¹⁰,¹¹,¹²,¹³,¹⁴ Most iatrogenic esophageal injuries occur during upper gastrointestinal endoscopy and esophageal dilation and usually involve the thoracic esophagus.¹⁵ However, esophageal injuries that occur secondary to endotracheal intubation are usually located in the cervical esophagus. The increased susceptibility of the cervical esophagus to injury is due to the lack of a reinforcing longitudinal muscle layer and the pressure of the cervical vertebrae on the esophagus during cricoid pressure and neck hyperextension.¹⁰ Hilmi et al10 published two cases reporting the occurrence of subcutaneous emphysema after unintentional esophageal intubation (Fig. 55-2). In both cases, perioperative endoscopy identified an esophageal tear in the posterior wall, in the cervical esophagus near the upper esophageal sphincter. Risk factors for esophageal perforation include operator experience, unanticipated difficult intubation, and the use of a rigid stylet.¹⁰,¹⁶ The most common clinical finding of esophageal perforation is subcutaneous emphysema in the neck or upper chest that becomes more obvious when the patient receives mask ventilation.¹⁰ The extent of the subcutaneous emphysema depends on the amount of air that enters the esophagus; patients who are readily ventilated will have less air entry into the esophagus than patients who are difficult to mask ventilate. Appropriate diagnostic tests include a chest radiograph and endoscopy for definitive diagnosis. Depending on the location, extent of the injury, development of
sepsis, and the patient’s overall medical condition, conservative nonsurgical management is generally preferred unless complications arise.¹⁰ Conservative management includes antibiotics, nasogastric suction, and total parenteral nutrition.

This important topic is discussed fully in other chapters of this book. (See Chapters 9-15.)

Both laryngoscopy and intubation can trigger the body’s sympathetic response, resulting in an increase in circulating catecholamines. This, in turn, can cause hypertension, various arrhythmias, increased intracranial pressure, and increased intraocular pressure. These complications could potentially lead to myocardial ischemia or infarction, congestive heart failure, or fatal arrhythmias.¹⁷ Risk factors for these complications include history of cardiovascular disease as well as prolonged laryngoscopy or multiple attempts at intubation. Medications frequently used to reduce the impact of these autonomic reflexes in an adult include pretreatment doses of intravenous lidocaine (50 mg) or intravenous fentanyl (100 to 200 mcg). The administration of short-acting beta-blockers such as esmolol before laryngoscopy can control hemodynamic responses to endotracheal intubation and prevent tachycardia.¹⁸

Injury to the spinal column or cord can occur with hyperextension of the cervical spine during intubation. In its worst case, it can result in quadriplegia. Patients most at risk of this complication include those with a history of cervical spine fracture, previous surgery to the cervical spine, tumors of the cervical spine, spinal malformations, osteoporosis, and trauma with suspected instability of the cervical spine.² For patients in these categories, the provider should consider fiberoptic intubation, or another means of managing the airway that would avoid significant cervical spine motion (see relevant chapters in the book on fiberoptic bronchoscopy for intubation, optical stylets, lightwands, prism/mirror-based devices, and rigid fiberoptic devices).

Corneal abrasion is a preventable complication of airway management that carries an incidence of 0.1% in nonophthalmologic surgery, though the etiology is not always apparent. 19 This complication can be caused by objects on the provider’s wrist or hanging from the provider’s neck or uniform chest pocket such as jewelry, a wristwatch, or an identification badge, resulting in direct trauma to the corneal epithelium.²⁰ One measure that can be used to protect the patient’s eyes during mask ventilation and intubation is to tape the eyelids closed after induction and before laryngoscopy. Soothing saline drops or methylcellulose drops overnight can manage a simple abrasion. For those with severe pain or changes in visual acuity, an ophthalmology consultation should be obtained. Antibiotics are usually not required, and patients are usually symptomfree the following morning.

The incidence of oral and pharyngeal injury during endotracheal intubation can be as high as 18%.²¹ Although not usually severe, trauma to the lips, teeth, tongue, and buccal mucosa may be painful and are of cosmetic concern to the patient. These types of injuries are more common with difficult intubations or poor laryngoscopic technique especially among beginners.²² Patients may complain of dysphagia or sore throat postoperatively. If the mucosal
lining of the posterior pharynx is disrupted, a pharyngeal abscess may develop.²³

Dental injuries are the most common complication of endotracheal intubation and the most common reason for lawsuits against anesthesiologists.²⁴,²⁵,²⁶,²⁷,²⁸,²⁹