Preparation of the Patient for Awake Intubation

Chart Review

Whenever possible, previous anesthetic records should be examined, especially those involving airway management. ^, Information regarding ease of mask ventilation, effective ventilation using a supraglottic airway device (SGA), and previously successful intubation techniques are particularly valuable. One should be alert for evidence of reactions to local anesthetics or respiratory depression with minimal doses of sedatives. All available anesthetic records should be reviewed, if possible; although the most recent intubation may have been routine, prior intubations may have been difficult. One should also note the surgical procedures involved—previous intubations may have been routine; however, the operation subsequently performed may have rendered the airway difficult.

When reviewing the chart, one should focus on four important features:

• 1.

  Degree of difficulty of tracheal intubation (the difficulty encountered and the method used)

• 2.

  Positioning of the patient during laryngoscopy (e.g., sniffing position, use of a ramp)

• 3.

  Equipment used (even if the intubation was performed routinely in one attempt, a videolaryngoscope [VL] or a flexible intubation scope [FIS] may have been used, potentially masking a DA)

• 4.

  Whether the technique that was used is a familiar one (one should not attempt to learn a new technique on a DA)

For patients with head and neck pathology having otorhinolaryngologic surgery, the ear, nose, and throat (ENT) surgeon’s notes should be reviewed in detail, with specific attention to characterizations of the patient’s airway, as well as any findings from nasopharyngeal laryngoscopy performed earlier. Imaging of the airway (e.g., computed tomography), if performed, should also be examined before formalizing an airway management plan.

The Patient Interview

After the medical records have been reviewed, a careful patient history should be obtained with particular attention to symptoms that may indicate airway obstruction, such as stridor or paroxysmal nocturnal dyspnea. The preoperative interview should also address the possibility of events having occurred since the last anesthetic that may impact ease of intubation, such as weight gain, airway radiation, facial cosmetic surgery, or worsening temporomandibular joint disorder or rheumatoid arthritis.

Once the anesthesia practitioner has made the decision that awake intubation is necessary, communication with the patient and psychological preparation are of the utmost importance to maximize the odds for a successful awake intubation. In a careful, unhurried manner, the anesthesiologist should describe to the patient conventional intubation contrasted with awake intubation and focus on the fact that, although the former is easier and less time consuming, the latter is safer in light of the patient’s own anatomy or condition. The anesthesiologist should present him- or herself as a knowledgeable, caring physician who is willing to take extra measures to ensure the patient’s safety and comfort. Recommendations should be presented to the patient with conviction, and if the patient is skeptical about proceeding as such, assistance from the surgeon may be enlisted. Because the patient has an established relationship with their surgeon, the surgeon’s reinforcement of the anesthesiologist’s opinion may be quite helpful. If this and subsequent discussion with the patient are unsuccessful, the anesthesiologist should document these efforts in the chart.

Complications of awake intubation should also be presented, including local anesthetic toxicity, airway trauma, epistaxis, discomfort, coughing or gagging, and failure to secure the airway. ^, The possibility of recall of the intubation procedure should be discussed; the incidence of recall after awake intubation varies depending on the different sedative agents used and their dosage. Recall rates as low as 0% and as high as 90% have been reported; however, higher rates of recall do not seem to be associated with patient dissatisfaction.

Staff

According to the ASA DA Guidelines, there should be “at least one additional individual who is immediately available to serve as an assistant in difficult airway management.” Whenever possible, it is preferable to have a second member of the anesthesia care team who can assist in the monitoring, ventilation, and pharmacotherapy of the patient and can provide an extra set of hands during the intubation procedure. For patients in extremis and those who refuse awake intubation, a surgeon trained in performing a surgical airway should be available with a tracheostomy/cricothyrotomy tray, ready to perform an emergency surgical airway, if necessary.

Monitors

During awake intubation, the routine use of electrocardiography (ECG), pulse oximetry, noninvasive blood pressure monitoring, and capnography is required as part of standard, basic intraoperative monitoring. Depending on the patient’s cardiovascular history and hemodynamic status, invasive hemodynamic monitoring may be necessary before awake intubation. Specific indications include hemodynamic instability, severe ischemic or valvular heart disease, and a patient for whom hypertension and tachycardia are potentially dangerous (e.g., the patient with aortic dissection or intracerebral aneurysm).

Supplemental Oxygen

The ASA DA Guidelines encourage the clinician to actively pursue opportunities to administer supplemental oxygen throughout the process of DA management, whenever possible. Arterial hypoxemia has been well documented during bronchoscopy and is associated with increased cardiac strain and dysrhythmias. In addition, sedation administered to supplement topicalization for awake intubation may result in unintended respiratory depression or apnea. Preoxygenation and supplemental oxygen delivery during the awake intubation procedure (including sedation, topicalization, intubation, and extubation) can prevent the onset of hypoxemia.

Traditional preoxygenation (≥3 minutes of tidal volume ventilation) or fast-track preoxygenation (i.e., four vital-capacity breaths in 30 seconds) is effective in delaying arterial desaturation during subsequent apnea. Supplemental oxygen has been shown to delay circulatory arrest resulting from local anesthetic toxicity in animals.

Oxygen delivery by nasal cannula can easily be administered during orotracheal intubation, regardless of the intubation technique. During nasotracheal intubation, the nasal cannula can be placed over the mouth. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) via high-flow nasal cannula is associated with decreased incidence of desaturation during awake intubation and is considered the technique of choice when available (see Chapter 15 ). ^{, ,} In a patient in extremis, transtracheal jet ventilation (TTJV) can be used to administer oxygen while a definitive airway is established. ^{, ,}

Airway Equipment

The ASA DA Guidelines recommend the ready availability of a portable storage unit that contains specialized equipment for DA management. The concept of preassembled carts for emergency situations is not new; examples include crash carts for cardiac arrest and malignant hyperthermia carts. Suggested contents of this portable unit are listed in Box 13.2 .

Many techniques can be used to secure the airway in the awake patient. Direct laryngoscopy (DL), VAL, intubating laryngeal mask airways (ILMAs), FSI, rigid fiberoptic laryngoscopy, retrograde intubation, lighted stylets, and blind nasal intubations have all been used successfully to perform awake intubation. ^{, , ,} No matter which technique is selected, all of the necessary equipment should be prepared ahead of time and readily available, when needed. The practitioner should also have several backup modalities in mind with the required equipment available, in case the initial technique used is ineffective.

Antisialagogues

One of the goals of premedication for awake intubation is drying of the airway. Secretions can obscure the view of the glottis, especially when an FIS or VL is being used to intubate. In addition, secretions can prevent local anesthetics from reaching intended areas, resulting in failed sensory blockade, or they can wash away and dilute local anesthetics, diminishing their potency and duration of action.

The medications most often used for their antisialagogic properties are the anticholinergics, which inhibit salivary and bronchial secretions by way of their antimuscarinic effects. They should be administered as early as possible for maximal effect (preferably at least 30 minutes in advance) because they do not eliminate existing secretions but rather prevent new secretion formation. The anticholinergics most often used in clinical practice are glycopyrrolate, scopolamine, and atropine. A summary of their pharmacologic properties is presented in Table 13.1 .

Nasal Mucosal Vasoconstrictors

The nasal mucosa and nasopharynx are highly vascular. When a patient requires nasotracheal intubation, adequate vasoconstriction is essential for preventing epistaxis. Blood in the nasal passage can make visualization of the larynx extremely difficult, especially during FSI. Nasal mucosal vasoconstrictors should be applied 15 minutes before nasal intubation. One commonly used agent is 4% cocaine, which has vasoconstrictive as well as local anesthetic effects (see later discussion). Alternatively, a mixture of lidocaine 3% and phenylephrine 0.25% can be made by combining lidocaine 4% and phenylephrine 1% in a 3:1 ratio. This combination has anesthetic and vasoconstrictive properties similar to those of cocaine and can be used as a substitute. This mixture can be either sprayed intranasally or applied with cotton-tipped applicators. Commercially available nasal decongestants containing either oxymetazoline 0.05% (Afrin) or phenylephrine 0.5% (Neo-Synephrine) may also be applied to nasal mucosa. The usual dose is two sprays in each nostril.

Aspiration Prophylaxis

Routine prophylaxis against aspiration pneumonitis is not recommended for healthy patients who are appropriately fasted. However, it may be beneficial in patients with risk factors for aspiration, such as a full stomach, symptomatic gastroesophageal reflux disease, gastrointestinal motility disorders, morbid obesity, diabetic gastroparesis, or pregnancy. In these patients, nonparticulate antacids, histamine (H ₂ )-receptor antagonists, and metoclopramide may be used alone or in combination.

Sedatives/Hypnotics

Depending on the clinical circumstance, IV sedation may be useful in allowing the patient to tolerate awake intubation by providing anxiolysis, amnesia, and analgesia. Benzodiazepines, opioids, hypnotics, α ₂ -agonists, and neuroleptics can be used alone or in combination. These agents should be carefully titrated to effect, because oversedation can render a patient uncooperative and make awake intubation more difficult. Spontaneous respiration with adequate oxygenation and ventilation should always be maintained. Extreme caution should be taken in the presence of critical airway obstruction, because awake muscle tone is sometimes necessary in these patients to maintain airway patency. In these situations, sedation should be used sparingly or avoided altogether. Avoidance of oversedation is also important in the patient with a full stomach, because an awake patient can protect his or her own airway if regurgitation should occur. See Table 13.2 for a summary of sedative regimens for awake intubation.