Knowledge of the relevant airway anatomy and innervation is essential to successful airway anesthesia (Figures 52-1 and 52-2).
Figure 52-1. Upper Airway Anatomy and Innervation
Reproduced from Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology. 4th ed. Figures 5-1 and 5-3. Available at: http://www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.
Figure 52-2. Innervation of the Larynx
Reproduced with permission from Brown DL. Atlas of Regional Anesthesia. 4th ed. Philadelphia: Saunders; 2010:193. © Elsevier.
Nerves of the Airway with Area of Innervation
|Nerve||Relevant sensory innervation|
|Trigeminal||Mucus membranes of the nose, superior and inferior surfaces of the hard and soft palate, anterior two thirds of tongue|
|Glossopharyngeal||Posterior one third of tongue, vallecula, anterior surface of the epiglottis, walls of pharynx, tonsils|
|Superior laryngeal||Base of the tongue, epiglottis, aryepiglottic folds, arytenoids|
|Recurrent laryngeal||Larynx below the vocal cords, trachea|
- Consent the patient for the procedure, taking care to explain in simple language what will happen and answering any questions. A calm and informed patient is more likely to cooperate than one who is confused and frightened
- Sedation for patient comfort is often critical, but take care to carefully titrate medications such as midazolam (1–3 mg IV) or fentanyl (25–50 μg IV) that may cause respiratory depression. Dexmedetomidine, an alpha 2 agonist with sedative but not respiratory depressive properties, may be considered (may start IV at 4 μg/kg/h, and then decrease to 1.5–2 μg/kg/h once patient becomes visibly sedated)
- Antisialagogues (e.g., glycopyrrolate 0.2–0.4 mg IV, caution in tachycardic patients) to decrease oral secretions may be useful to improve the effectiveness of topicalization and to improve fiber-optic visualization
- Alert the OR staff to the possibility of a difficult intubation. Be sure to discuss with the surgeon the possibility of needing a surgical airway. Consider asking a colleague to assist during the procedure. An extra pair of hands can be the difference between success and a poor outcome
- Anesthetizing the airway may be accomplished by topicalization, invasive airway blocks, or a combination of the two techniques
- Involves application of local anesthetic directly to the mucosa
- May be accomplished in a variety of ways:
- Atomizer—local anesthetic (e.g., 5–10 mL of 2% lidocaine) is dispersed via an atomizer device (e.g., Mucosal Atomizer Device [MAD], Wolfe Troy Medical, Inc.) into a fine mist and directly sprayed onto the desired mucosa
- Nebulizer—local anesthetic (e.g. 8 mL of 2% lidocaine) is placed into breathing treatment nebulizer and the patient inhales the resultant mist
- Commercially prepared benzocaine sprays such as Hurricaine®—three brief 1-second sprays are usually sufficient. (Note: Benzocaine may cause methemoglobinemia; do not spray for more than 3 seconds!)