Airway Blocks

Carin A. Hagberg

Innervation of the nasal and oropharyngeal and laryngeal cavities, as well as the trachea, depends on three pairs of cranial nerves: the trigeminal (V), vagus (X), and glossopharyngeal (IX). Consequently, there is no single nerve that can be blocked to produce complete anesthesia. Most of the nasal cavity innervation involves the sphenopalatine ganglion and the ethmoid nerve. Application of long cotton-tipped applicators soaked in 4% lidocaine with epinephrine or cocaine over the nasal mucosa allows a block of the sphenopalatine ganglion (applicator angled at 45° to the hard palate) and the anterior ethmoid nerve (applicator parallel to the dorsal surface of the nose).

The glossopharyngeal nerve provides sensory innervation of the oropharynx, including the posterior third of the tongue, anterior surface of the epiglottis, posterior and lateral walls of the pharynx, and the tonsillar pillars. The glossopharyngeal nerve also provides motor innervation to the stylopharyngeus muscle, involved in deglutition. The rest of the pharynx, as well as the upper larynx, vocal cords, and trachea, are innervated by the vagus nerve and its branches, especially the superior laryngeal and the recurrent laryngeal nerves.

Preparation of the patient includes the use of 0.4 to 0.8 mg intravenous (i.v.) glycopyrrolate administered 30 to 45 minutes prior to application of the local anesthetic to decrease the amount of secretions and the use of a vasoconstrictor for the nasal mucosa (1% phenylephrine) in the absence of contraindications.

The performance of airway blocks requires that the following be taken into consideration:

Adequate preparation, including a complete explanation to the patient and the surgeon of the reason for performing the airway nerve blocks, is essential for patient cooperation and comfort and for success of the procedure.
The risk-to-benefit ratio has to be established. The following should be considered: (a) an alternative plan, including the direct spray of local anesthetic solution using 4% lidocaine or 14% to 20% benzocaine (risk of methemoglobinemia) or indirect spray with a nebulizer using 4% lidocaine; (b) the time available; and (c) the patient’s condition, including level of consciousness and degree of respiratory depression and insufficiency.
The use of appropriate sedation using usually a combination of 2 to 5 mg midazolam and 50 to 150 mg fentanyl to maintain patient comfort. However, sedation should be
individually titrated so that verbal contact with the patient is maintained (oversedation may lead to hypoventilation, oxygen desaturation, and respiratory arrest).
These blocks should be practiced as much as possible in nonemergency situations to gain experience in performing airway blocks (often required for awake intubation), so that when their success is required for a difficult intubation or when an emergency arises, they can be performed appropriately.

Suggested Readings

Bourke DL, Katz J, Tonneson A. Nebulized anesthesia for awake endotracheal intubation. Anesthesiology 1985;63:690–692.

Douglas WW, Fairbanks VF. Methemoglobinemia induced by a topical anesthetic spray (Cetacaine). Chest 1977;71:587–591.

Fry WA. Techniques of topical anesthesia for bronchoscopy. Chest 1978;73:694–696.

Gotta AW, Sullivan CA. Anaesthesia of the upper airway using topical anesthetic and superior laryngeal nerve block. Br J Anaesth 1981;53:1055–1058.

Kopman AF, Wollman SB, Ross K, et al. Awake endotracheal intubation: a review of 267 cases. Anesth Analg 1975;54:323–327.

O’Hollander AA, Monteny E, Dewachter B, et al. Intubation under topical supra-glottic analgesia in unpremedicated and non-fasting patients: amnesic effects of sub-hypnotic doses of diazepam and Innovar. Can Anaesth Soc 1974;21:467–474.

Sidhu VS, Whitehead EM, Ainsworth QP, et al. A technique of awake fibreoptic intubation: experience in patients with cervical spine disease. Anaesthesia 1993;48:910–913.

A. Glossopharyngeal Nerve Block (Anterior Approach)

Patient Position: Supine.

Operator Position: The physician is situated on the contralateral side of the patient’s head.

Indications: Abolition of the gag reflex or hemodynamic response to laryngoscopy.

Needle Size: 25-gauge spinal needle.

Local Anesthetic Solution: 2% lidocaine.

Volume: 2 to 4 mL per side.

Anatomic Landmarks: The glossopharyngeal nerve, which emerges from the skull through the jugular foramen, travels along the lateral wall of the pharynx.

Approach and Technique: With the patient’s mouth wide open, a tongue blade held with the nondominant hand is introduced in the mouth to displace the tongue medially, creating a gutter between the tongue and the teeth. The gutter ends posteriorly in a cul-de-sac formed by the base of the palatoglossal arch. A 25-gauge spinal needle is inserted at the base of the cul-de-sac and advanced slightly (0.25 to 0.5 cm). After negative air and blood aspiration tests, 2 mL of 2% lidocaine is injected. The procedure is repeated on the other side (Fig. 19-1).

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