Contraindications for using an LMA include nonfasted patients, morbid obesity, need for high inspiratory pressures (>20 to 25 cm H₂O) in the presence of low pulmonary compliance or chronic obstructive pulmonary disease (COPD), acute abdomen, hiatal hernia, severe gastroesophageal reflux, Zenkers diverticulum, trauma, intoxication, airway problems at the glottic or infraglottic level, and thoracic trauma.

There is a close relationship between difficult intubation and traumatic intubation. In cases of difficult intubation (poor view of the vocal cords), the practitioner tends to increase the lifting forces of the laryngoscope blade, which can lead to damage of the intraoral tissues and osseous structures, thereby converting a difficult intubation into a traumatic intubation. Furthermore, the use of increased force can induce swelling, bleeding, or perforation as the intubation becomes more and more difficult and may turn into a “cannot intubate,” and possibly even a “cannot ventilate,” situation. If intubation fails after multiple attempts, another technique should be used in accordance with the airway management algorithm.¹⁵

Lip injuries include lacerations, hematomas, edema, and abrasions. They are usually secondary to inattentive laryngoscopy performed by inexperienced practitioners. Although these lesions are annoying to the patient, they are usually self-limited.

The incidence of dental injuries associated with anesthesia is more than 1:4,500.¹⁶ The maxillary central incisors are at most risk. Fifty percent of dental trauma occurs during laryngoscopy, with 23% following extubation, 8% during
emergence, and 5% associated with regional anesthesia. Dental trauma is also associated with LMA devices and oropharyngeal airways. These injuries are most common in small children, patients with periodontal disease or fixed dental work, and patients in whom intubation is difficult. Preexisting dental pathology (protrusion of the upper incisors, carious teeth, paradentosis or periodontitis) should be thoroughly explored before induction of anesthesia, and the patient must be advised of the risk of dental damage. Although tooth guards may obstruct vision, their use is indicated in certain situations.

In the event that an entire tooth is avulsed, it should be retrieved and saved in a moist gauze or in normal saline. Aspiration of the tooth can induce serious complications requiring bronchoscopy for removal. With a rapid response from an oral surgeon or dentist, an intact tooth can often be reimplanted and saved, but only when performed within 1 hour.

Massive tongue swelling, or macroglossia, has been reported in numerous instances in both adult and pediatric patients. Although macroglossia (occasionally of life-threatening proportions) is associated with angiotensinconverting enzyme inhibitors, some cases have occurred while a bite block was in place and when there was substantial neck flexion during endotracheal intubation. Loss of tongue sensation is possible after a compression injury to the lingual nerve during forceful laryngoscopy or after LMA placement with an overinflated or malpositioned cuff. A reduced sense of taste and cyanosis of the tongue caused by lingual artery compression are additional injuries that can be incurred by using an oversized, malpositioned, or overinflated LMA.

Damage to the uvula (edema and necrosis) is usually associated with an endotracheal tube, oropharyngeal and nasopharyngeal airways, an LMA, an alternative supraglottic airway device, or by overzealous use of a suction catheter. Sore throat, odynophagia, painful swallowing, coughing, foreign body sensation, and serious life-threatening airway obstruction have been reported.

The incidence of sore throat after intubation is approximately 40% to >65% when blood is noted on the airway instruments.¹⁷ The incidence of sore throat following LMA placement is 20% to 42%, depending on cuff inflation, and 8% with face mask ventilation.¹⁸ Additionally, when comparing a double-lumen tube with an endobronchial blocker, Knoll et al., determined that significant postoperative hoarseness occurred more frequently in the double-lumen group: 44% versus 17%, respectively. The cumulative number of days with hoarseness and sore throat were significantly increased in the double-lumen group compared with the blocker group. Sore throat did not differ significantly between groups, but the overall incidence in this study was 41%.¹⁹ Fortunately, pain on swallowing usually lasts no more than 24 to 48 hours. Topical anesthesia, such as lidocaine jelly, applied to the endotracheal tube does not lessen the incidence of this problem and may actually worsen it.

Trauma to the larynx and vocal cords is not uncommon following endotracheal intubation. Whether it occurs depends on the experience and skill of the intubator, as well as the degree of difficulty. In one large study, 6.2% of patients sustained severe lesions, 4.5% developed a hematoma of the vocal cords, 1% developed a hematoma of the supraglottic region, and 1% sustained lacerations and scars of the vocal cord mucosa.²⁰ Recovery is generally prompt with conservative therapy, although hoarseness may appear even after a 2-week interval.²¹ Granulations usually occur as a complication of long-term intubation but can also be a result of short-term intubation. Injuries of the laryngeal muscles and suspensory ligaments are also possible. Patients with hoarseness should be examined preoperatively by an ENT specialist.

Arytenoid dislocation and subluxation have been reported as rare complications.²² Mitigating factors include traumatic and difficult intubations, repeated attempts at intubation, and attempted intubation using blind techniques such as light-guided intubation, retrograde intubation, and the use of the McCoy laryngoscope (Penlon Limited, Abingdon, UK). However, these complications are also found after easy intubations. Early diagnosis and operative repositioning of arytenoid dislocation is necessary, because fibrosation with consecutive malposition and ankylosis can occur after 48 hours.

Numerous investigators have reported vocal cord paralysis after intubation with no obvious source of injury. Paralysis may be unilateral (hoarseness) or bilateral (respiratory obstruction). The most likely source of injury is a malpositioned endotracheal tube cuff in the subglottic larynx which exerts pressure on the recurrent laryngeal nerve. Permanent voice change due to external laryngeal nerve trauma following intubation results in up to 3% of patients undergoing surgery in sites other than the head or neck. However, vocal cord paralysis after intubation is usually temporary. Its incidence can be decreased by avoiding overinflation of the endotracheal tube cuff and by placing the endotracheal tube at least 15 mm below the vocal cords. Vocal cord paralysis may also have a central origin. Eroded vocal cords can adhere together, eventually forming synechiae. Surgical correction is usually necessary.

Tracheobronchial trauma has various causes. Injury can result from an overinflated endotracheal tube cuff, inadequate tube size, malpositioned tube tip, laryngoscope,
stylet, tube exchanger, or related equipment. Predisposing factors include anatomic difficulties, blind or hurried intubation, inadequate positioning, poor visualization, or, most commonly, an inexperienced intubator. Edema after extubation decreases the lumen diameter and increases airway resistance. Small children are most susceptible to this problem; almost 4% of children within the age group of 1 to 3 years develop croup following endotracheal intubation. Tracheal rupture, especially after emergency intubation, has been reported, as well as a bronchial rupture secondary to the use of an endotracheal tube exchanger.²³

Endotracheal tube cuffs inflated to a pressure greater than that of the capillary perfusion may devitalize the tracheal mucosa and lead to ulceration, necrosis, and loss of structural integrity. Ulceration can result at even lower pressures in hypotensive patients. The need for increasing cuff volumes to maintain a seal is an ominous sign of developing tracheomalacia. The various nerves in this region of the neck are also at risk. Erosion of the endotracheal tube into the paratracheal nerves can produce dysphonia, hoarseness, and laryngeal incompetence. Tracheomalacia results from erosion confined to the tracheal cartilages. It is imperative that the anesthesiologist inflates the cuff of the endotracheal tube only as much as is necessary to ensure an adequate airway seal. If using nitrous oxide during a lengthy surgical procedure, the pressure in the endotracheal tube cuff should be checked by a cuff pressure control device. The cuff pressure should not exceed 25 cm H₂O.

The incidence of granulomas has been reported to range from 1:800²⁴ to 1:20,000.²⁵ Endotracheal intubation prolonged for several months can produce tracheal stenosis and fibrosis, typically at the site of an inflated cuff and sometimes at the location of the endotracheal tube tip. Dilation of the stenosis is curative if it is caught in its early stages. However, surgical correction may be necessary once the tracheal lumen has been reduced to 4 to 5 mm.

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