Preparation of the Patient for Awake Intubation


KEY POINTS

  • When faced with a difficult airway (DA), awake intubation is the gold standard for airway management.

  • There are no absolute contraindications to awake intubation other than patient refusal, or a patient who is unable to cooperate (e.g., a child, a patient with an intellectual disability, or an intoxicated, combative patient).

  • Preparation begins with a careful history and physical examination and a detailed discussion of the procedure with the patient.

  • The goals of premedication are to alleviate anxiety, provide a clear and dry airway, protect against the risk of aspiration, and enable adequate topicalization.

  • The nasal mucosa and nasopharynx are highly vascular. When a patient requires nasotracheal intubation, adequate vasoconstriction is essential because bleeding can make visualization of the larynx extremely difficult.

  • Sedation may be accomplished with benzodiazepines, opioids, or intravenous hypnotics, either alone or in combination; these agents must be titrated carefully to maintain cooperation and adequate spontaneous ventilation.

  • Adequate topicalization of the airway with local anesthetics is the key to a successful awake intubation. When using local anesthetics, the practitioner must be familiar with the speed of onset, duration of action, optimal concentration, maximum recommended dosage, and signs and symptoms of toxicity.

  • If airway topicalization is insufficient, airway nerve blocks may be employed to supplement airway anesthesia.

  • Many choices are involved when preparing for awake intubation. Safety should be the primary consideration.

Introduction

The American Society of Anesthesiologists (ASA) Practice Guidelines for Management of the Difficult Airway (ASA DA Guidelines), together with the airway management guidelines of several other international anesthesiology societies, advocate for the consideration of airway management before induction of general anesthesia (awake intubation) as a primary strategy for management of the predicted difficult airway (DA). Although awake fiberoptic or flexible scope intubation (FSI) has traditionally been the technique of choice for awake intubation, awake video-assisted laryngoscopy (VAL) has gained acceptance.

Regardless of the intubation technique, however, awake tracheal intubation is considered the gold standard for management of the DA for the following reasons: ,

  • Spontaneous ventilation is maintained.

  • Patency of the airway is maintained by upper pharyngeal muscle tone.

  • The larynx does not move to a more anterior position, as it does after induction of anesthesia, resulting in an easier intubation.

Awake intubation can also be used for the patient with cervical spine pathology to allow for neurologic monitoring during and after the intubation procedure. An awake patient is also able to monitor his or her own neurologic symptoms to guard against further neurologic injury. In the unstable cervical spine, care must be taken to ensure that the topicalization and intubation do not result in coughing because this could result in further injury.

Another indication for awake intubation is the patient at high risk for pulmonary aspiration, particularly when the airway assessment predicts difficulty with airway management. With careful topicalization and the avoidance or judicious use of sedation, the patient can protect his or her own airway from aspiration during the intubation process.

A summary of the general indications for awake intubation is presented in Box 13.1 . There are no absolute contraindications to awake intubation other than patient refusal, or a patient who is unable to cooperate (e.g., a child, a patient with an intellectual disability, or an intoxicated, combative patient). Although allergy to local anesthetics has been cited as a contraindication to awake intubation, awake intubation without the use of local anesthetics has been reported utilizing sedation with remifentanil or dexmedetomidine (see later discussion).

Box 13.1
Indications for Awake Intubation
From Kopman AF, Wollman SB, Ross K, et al. Awake endotracheal intubation: a review of 267 cases. Anesth Analg. 1975;54:323–327; Thomas JL. Awake intubation: indications, techniques and a review of 25 patients. Anaesthesia. 1969;24:28–35; Bailenson G, Turbin J, Berman R. Awake intubation: indications and technique. Anesth Prog. 1967;14:272–278.

  • 1.

    Previous history of difficult intubation

  • 2.

    Anticipated difficult airway (DA) based on physical examination:

    Small mouth opening

    Receding mandible/micrognathia

    Macroglossia

    Short, muscular neck

    Limited range of motion of the neck (rheumatoid arthritis, ankylosing spondylitis, prior cervical fusion)

    Congenital airway anomalies

    Morbid obesity

    Pathology involving the airway (tracheomalacia)

    Airway masses (malignancy of the tongue, tonsils, or larynx; large goiter; mediastinal mass)

    Upper airway obstruction

  • 3.

    Unstable cervical spine

  • 4.

    Trauma to the face or upper airway

  • 5.

    Anticipated difficult mask ventilation

  • 6.

    Severe risk of aspiration

  • 7.

    Severe hemodynamic instability

  • 8.

    Respiratory failure

Preoperative Preparations

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 .

Box 13.2
Suggested Contents of the Portable Unit for Difficult Airway Management
Modified from Apfelbaum JL, Hagberg CA, Caplan RA, et al. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology. 2013;118(2):251–270.

  • 1.

    Rigid laryngoscope blades of alternative designs and sizes from those routinely used; may include a rigid fiberoptic laryngoscope

  • 2.

    Videolaryngoscopes (with both Macintosh-shaped blades and highly curved or distally angulated blades)

  • 3.

    Endotracheal tubes (ETTs) of assorted sizes and styles, such as the Parker Flex-Tip tube (Parker Medical, Highlands Ranch, CO)

  • 4.

    ETT guides, such as semirigid stylets, ventilating tube changers, light wands, and forceps designed to manipulate the distal portion of the ETT

  • 5.

    Supraglottic airways of assorted sizes and styles, such as the intubating laryngeal mask airway

  • 6.

    FSI equipment

  • 7.

    Equipment suitable for emergency surgical airway access (e.g., cricothyrotomy)

  • 8.

    An exhaled CO 2 detector

The items listed represent suggestions. The contents of the portable storage unit should be customized to meet the specific needs, preferences, and skills of the practitioner and the healthcare facility.

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.

Premedication and Sedation

Before awake intubation, premedication is commonly employed to alleviate anxiety, provide a clear and dry airway, protect against the risk of aspiration, and enable adequate topicalization of the airway. The pharmacologic agents most commonly used in preparation for awake intubation include antisialagogues, mucosal vasoconstrictors, aspiration prophylaxis agents, and sedatives/hypnotics.

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 .

TABLE 13.1
Pharmacologic Characteristics of Anticholinergic Drugs
Drug Tachycardia Antisialagogue Effect Sedation
Glycopyrrolate ++ ++ 0
Scopolamine + +++ +++
Atropine +++ + +
0, No effect; +, minimal effect; ++, moderate effect; +++, marked effect.
Modified from Stoelting RK, Flood P, Rathmell JP, Shafer S. Stoelting’s Handbook of Pharmacology and Physiology in Anesthetic Practice . 3rd ed. Wolters Kluwer Health; 2015:144.

Glycopyrrolate

Glycopyrrolate (0.2 to 0.4 mg intravenous [IV] or intramuscular [IM]) is the anticholinergic of choice for most clinical circumstances because of its marked antisialagogic effect and rapid onset after IV dosing of 1 to 2 minutes; the onset after IM dosing is 20 to 30 minutes. It has a moderate vagolytic effect, which lasts 2 to 4 hours; its antisialagogic effect lasts longer. Glycopyrrolate is devoid of central nervous system (CNS) effects because its quaternary amine structure prevents passage through the blood-brain barrier.

Scopolamine

Scopolamine (0.4 mg IV or IM) has an onset of 5 to 10 minutes after IV dosing and 30 to 60 minutes after IM. The duration of action is about 2 hours after IV dosing and 4 to 6 hours after IM dosing. In addition to being a very effective antisialagogue, scopolamine has very potent CNS effects, with sedative and amnestic properties. In some patients, however, this may lead to restlessness, delirium, and prolonged emergence following short procedures. Because it is the least vagolytic of the anticholinergics in clinical use, it may be the drug of choice for patients in whom tachycardia is contraindicated. Scopolamine for injection was discontinued by the sole manufacturer in the United States in 2015 with no plans for reintroduction.

Atropine

Atropine (0.4 to 0.6 mg IV or IM) has a rapid onset after IV administration of 1 minute; the onset after IM dosing is 15 to 20 minutes. Atropine produces only a mild antisialagogic effect but causes significant tachycardia because of its potent vagolytic effects. As such, it is not an ideal drug for use in drying the airway. As a tertiary amine, it easily crosses the blood-brain barrier and causes mild sedation. It may occasionally cause delirium, especially in elderly patients.

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.

Antacids

Preoperative administration of a nonparticulate antacid, such as sodium citrate, provides effective buffering of gastric acid pH. Total gastric volume is increased, but this effect is offset by an increase in the pH of gastric fluid so that, if aspiration occurs, morbidity and mortality are significantly lower. One disadvantage of sodium citrate is the potential to cause emesis because of its unpleasant taste. The use of particulate antacids, such as magnesium trisilicate, is not recommended for prophylaxis.

Histamine Receptor Antagonists

H 2 -receptor antagonists selectively and competitively inhibit secretion of hydrogen ion (H + ) by gastric parietal cells and also decrease the secretion of gastric fluid. With IV administration of cimetidine 300 mg, famotidine 20 mg, or ranitidine 50 mg, peak effects are achieved within 30 to 60 minutes, increasing gastric pH and decreasing gastric volume. , Of the three, ranitidine is probably the drug of choice because it has fewer adverse effects, greater efficacy, and a longer duration of action. ,

Proton Pump Inhibitors

Proton pump inhibitors (PPIs), such as pantoprazole, lansoprazole, and omeprazole, have not been shown to be as effective as H 2 -receptor antagonists at increasing gastric pH and decreasing gastric volume preoperatively, particularly when administered orally. , PPIs may have a role in aspiration prophylaxis for the patient on chronic H 2 -receptor antagonist therapy.

Metoclopramide

Metoclopramide is a cholinergic agent and dopamine (D 2 )-receptor antagonist that stimulates motility of the upper gastrointestinal tract and increases lower esophageal sphincter tone. The net effect is accelerated gastric emptying with minimal effect on gastric pH. The standard adult dose is 10 mg IV. Onset after IV administration is rapid, within 1 to 3 minutes, and its effects may persist for up to 2 hours. Metoclopramide can precipitate extrapyramidal symptoms and should be avoided in patients with Parkinson disease.

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.

TABLE 13.2
Sedative Drugs for Awake Airway Management
Drug Class Sedative Dose Notes
Midazolam Benzodiazepine 1–2 mg IV, repeated prn (0.025–0.1 mg/kg) Frequently used in combination with fentanyl
Fentanyl Opioid 25–200 µg IV (0.5–2 µg/kg) Usually used in combination with other agents (e.g., midazolam, propofol)
Alfentanil Opioid 500–1500 µg IV (10–30 µg/kg) Faster onset, shorter duration than fentanyl
Remifentanil Opioid Bolus 0.5 µg/kg IV followed by an infusion of 0.1 µg/kg/min Infusion can subsequently be titrated by 0.025 µg/kg/min to 0.05 µg/kg/min in 5-minute intervals to achieve adequate sedation
Propofol Hypnotic 0.25 mg/kg IV, in intermittent boluses
or
Continuous IV infusion of 25–75 µg/kg/min, titrated to effect
Can also be used in combination with remifentanil (decrease dose of both drugs)
Ketamine Hypnotic 0.2–0.8 mg/kg IV Pretreat with antisialagogue
Consider administration of midazolam to attenuate undesirable psychological effects
Dexmedetomidine Alpha-2 agonist Bolus 1 µg/kg IV over 10 minutes, followed by an infusion of 0.2–0.7 µg/kg/h Reduce dose in the elderly and in patients with depressed cardiac function
From Artime CA, Hagberg CA. Airway management in the adult. In: Gropper MA, Miller RD, eds. Miller’s Anesthesia. 9th ed. Elsevier; 2020:1373–1412.

Benzodiazepines

Benzodiazepines, via their action at the γ-aminobutyric acid (GABA)–benzodiazepine receptor complex, have hypnotic, sedative, anxiolytic, and amnestic properties. They have also been shown to depress upper airway reflex sensitivity, a property that is desirable for awake intubation. Benzodiazepines are frequently used to achieve sedation for awake intubation in combination with opioids, and they are used for their amnestic and anxiolytic effects when other sedatives (e.g., dexmedetomidine, ketamine, remifentanil) are chosen as the primary agent. , Three benzodiazepine receptor agonists are commonly used in anesthesia practice: midazolam, diazepam, and lorazepam.

Midazolam

Because of its more rapid onset and relatively short duration, midazolam is the most commonly used agent. Sedation with midazolam is achieved with doses of 0.5 to 1 mg IV repeated until the desired level of sedation is achieved. The IM dose is 0.07 to 0.1 mg/kg. Onset is rapid, with peak effect usually achieved within 2 to 3 minutes of IV administration. The duration of action is 20 to 30 minutes, with termination of effect resulting primarily from redistribution. Although recovery is rapid, the elimination half-life is 1.7 to 3.6 hours, with increases noted in patients with cirrhosis, congestive heart failure, renal failure, or morbid obesity, as well as in the elderly. It is extensively metabolized by the liver and renally eliminated as glucuronide conjugates. ,

Diazepam and Lorazepam

Diazepam has a slightly slower onset and longer duration of action than midazolam and has been shown to be a less potent amnestic. , , It can cause pain on IV injection and has the added risk of thrombophlebitis. Lorazepam possesses more profound sedating and amnestic properties; however, it is less suitable for sedation during awake intubation because these effects are slower in onset and longer lasting than with either midazolam or diazepam.

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