Difficult Airway and Failed Extubation

Case Synopsis

An obese man (body mass index 40) sustained closed head injury, lung contusions, and C-spine injury after a fall from a tree. Tracheal intubation was performed by paramedics at the scene, and the patient was transported to the hospital. Three days later, the patient had satisfactory neurologic and respiratory recovery, but the neck collar was still in place. After meeting extubation criteria, his trachea was extubated. The patient immediately developed severe respiratory difficulty, and his oxygen saturation started to drop. Attempts to ventilate the lungs with a facemask were unsuccessful. As the patient lost consciousness, laryngoscopy was performed after removing the neck collar and applying in-line head stabilization. No laryngeal structures could be visualized.

Problem Analysis

Definition

Failed Extubation

Extubation failure is the inability to maintain adequate respiratory functions after endotracheal tube removal due to airway obstruction or hypoventilation. Without proper and timely management, it eventually leads to oxygen desaturation, hypoxemia, and respiratory failure. Immediate reintubation is needed until the underlying cause is treated and the patient can tolerate extubation. A crisis/near-miss situation may develop if reintubation proves difficult or fails. The American Society of Anesthesiologists (ASA) task force on the management of the difficult airway recommended preformulating an extubation strategy in patients who may be at risk of extubation failure and are known to have a difficult airway. The guidelines recommended a “staged extubation” strategy that can be achieved by using an airway device that functions as a “bridge” to full extubation and ensures continuous airway access in case reintubation is needed after removing the endotracheal tube.

Difficult Airway

A difficult airway is defined as a clinical situation in which a conventionally trained anesthesiologist experiences difficulty with facemask ventilation (FMV), difficulty with tracheal intubation, or both. Some patients with difficult FMV may be relatively easy to intubate, and vice versa. The common causes of airway management failures are listed in Box 139.1 .

BOX 139.1

Underlying Causes of Airway Management Failures

Inaccurate or incomplete preoperative airway assessment
Failure to predict:
- Ease/difficulty of mask ventilation
- Ease/difficulty of direct laryngoscopy/ tracheal intubation
- High-risk tracheal extubation
Unwillingness to abandon failed airway management plan
Failure to call for help early, when difficult airway is first apparent
Incomplete preparation of backup plan
Deterioration of performance under stress
Failure in judgment

Difficult Facemask Ventilation

Difficult FMV occurs when positive-pressure ventilation, by an unassisted anesthesiologist, fails to maintain oxygen saturation above 90% (with an inspired oxygen concentration of 100%) or the ventilation effort fails to prevent or reverse signs of inadequate gas exchange. Inadequate FMV occurs secondary to inadequate facemask seal, excessive gas leak, or excessive resistance to the ingress or egress of gas. Signs of inadequate facemask ventilation are listed in Box 139.2 .

BOX 139.2

Signs of Inadequate Facemask Ventilation

Insufficient or absent chest movement
Absent or inadequate breath sounds
Audible signs of airway obstruction, gastric air insufflation, or gastric dilation
Inadequate or decreasing oxygen saturation (late)
Cyanosis (late)
Absent, inadequate, or elevated end-tidal carbon dioxide
Absent or inadequate exhaled gas flow (spirometry)
Hemodynamic consequences of hypercarbia or hypoxemia (e.g., tachycardia, hypertension, dysrhythmias)—occur late, should not wait for them to diagnose inadequate facemask ventilation

Difficult Laryngoscopy and Intubation

Difficult laryngoscopy refers to the inability to visualize any portion of the vocal cords after multiple attempts using conventional rigid laryngoscopy. Difficult intubation occurs when endotracheal intubation requires multiple attempts, and failed intubation means failure to place the endotracheal tube after multiple attempts. The incidence of difficult laryngoscopy (more than two attempts) is between 0.5% and 2%. The first attempt must be optimized by providing an adequate depth of anesthesia, muscle relaxation, proper positioning of the head and neck, and application of external laryngeal manipulation if needed. Switching blades can sometimes improve visualization, and a straight laryngoscope blade may be more efficacious with an “anterior” larynx. Alternatively, a video laryngoscope can provide better visualization of the glottis. No more than two or three attempts should be made at direct laryngoscopy, because repeated attempts may worsen the patient’s outcome (e.g., conversion of a can-ventilate to a cannot-ventilate situation, or laryngeal edema causing glottic airway obstruction after tracheal extubation). FMV should be performed between intubation attempts, and laryngoscopy must be stopped if oxygen saturation drops below 90% to 92% (maintenance of oxygenation takes precedence). The most experienced anesthesiologist should perform the final attempt at direct laryngoscopy.

Recognition and Risk Assessment

Reviewing the patient’s prior anesthetic history and previous records of airway management (if available) is extremely helpful when formulating the airway management plan. Preanesthetic airway evaluation should be performed in all cases (including emergencies and monitored anesthesia care cases) to elicit predictors of potential difficulty if any is present. Predictors of difficult FMV, as well as some suggestions for dealing with them, are listed in Box 139.3 . Placing a laryngeal mask airway permits adequate ventilation in most of those patients and should be used early when a difficulty is encountered with FMV. Predictors of difficult laryngeal visualization with direct laryngoscopy are listed in Box 139.4 . Unfortunately, airway examination findings have low and variable sensitivity and marginal specificity; however, worrisome findings, particularly in combination, suggest a difficult laryngoscopy/intubation. For example, a Mallampati class higher than II in association with other airway findings signifies a potential difficulty during traditional direct laryngoscopy.

BOX 139.3

Predictors and Patient Factors Associated With Difficult Facemask Ventilation and Suggested Solutions

Facial Hair

Place adhesive plastic sheet, with mouth and naris openings, over facial hair to achieve better mask seal
Place oral, nasal, or laryngeal mask airway early

Edentulous

Consider leaving dentures in place until laryngoscopy to improve facemask seal
Place laryngeal mask airway early

Body Mass Index >30

Preoxygenate patient with continuous positive airway pressure, and use 20- to 30-degree reverse Trendelenburg position
- Increases time interval to desaturation after onset of apnea or difficult mask ventilation
- Reverse Trendelenburg “unloads” diaphragm, improving pulmonary compliance
Use laryngeal mask airway early for positive-pressure mask ventilation

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