Airway Anatomy + Sensory Block Targets

V3 → lingual nerve → anterior 2/3 of tongue (general sensation, not taste — taste is via chorda tympani from CN VII), floor of mouth.

The lingual nerve also carries sensation from the lingual gingiva.

Block technique: topicalize tongue + palate with 4% lidocaine spray or viscous lidocaine swish-and-spit; lingual nerve block at the floor of mouth (rarely done — topical sufficient).

CN IX supplies posterior 1/3 of tongue (general AND taste — unlike anterior 2/3), tonsillar fossa, soft palate (with V2), oropharynx, and the upper pharyngeal portion of the larynx down to the level of the epiglottis.

This is the nerve responsible for the GAG REFLEX — blocking it is essential for awake intubation.

Alternative: topicalize the posterior pharynx with nebulized 4% lidocaine.

SUPERIOR LARYNGEAL NERVE (SLN): the INTERNAL branch is purely sensory + supplies the supraglottic region (epiglottis, vallecula, aryepiglottic folds, false cords, mucosa above the vocal cords).

The EXTERNAL branch of SLN is motor to the cricothyroid muscle only.

RECURRENT LARYNGEAL NERVE (RLN): supplies SENSATION below the vocal cords (subglottis + trachea) AND MOTOR to all intrinsic laryngeal muscles EXCEPT cricothyroid (which the external SLN handles).

Mnemonic: 'all intrinsic muscles by the RLN except cricothyroid by SLN external'; 'above the cords sensory = SLN internal, below the cords sensory = RLN'.

💉Technique: identify the greater cornu of the hyoid bone (palpable, lateral); 'walk' a 25-gauge needle off the inferior border of the greater cornu, advance 1-2 mm through the thyrohyoid membrane, aspirate (avoid carotid laterally — vessels are lateral to the cornu), inject 2 mL of 2% lidocaine.

Repeat on contralateral side.

Blocks sensation from epiglottis to vocal cord level.

NOT sufficient alone for awake intubation — must also block the gag reflex (CN IX via topical or block) and the trachea (transtracheal injection).

Technique: palpate the cricothyroid membrane (between the thyroid and cricoid cartilages, in the midline).

Insert a 22-gauge needle in the midline, perpendicular to the skin, advance until air aspirated.

Have the patient TAKE A DEEP BREATH; on the next inspiration, inject 3-4 mL of 4% lidocaine rapidly — the patient will cough, spreading the local anesthetic up and down the trachea + cords.

Withdraw needle quickly to avoid laceration during cough.

NASAL passage anesthesia for nasal fiberoptic: cotton pledgets soaked in 4% lidocaine + phenylephrine 0.5% (or oxymetazoline) placed in each nostril for 5-10 min — reaches the sphenopalatine ganglion at the back of the nasal cavity (autonomic + sensory hub) + anterior ethmoidal nerve (sensory).

Phenylephrine vasoconstricts to reduce bleeding + open the nasal passage.

SPHENOPALATINE GANGLION block via the greater palatine canal (transoral) for chronic facial pain — rarely used for airway purposes.

CERVICAL PLEXUS (C2-C4) for awake carotid endarterectomy + neck surgery: superficial cervical plexus block at the midpoint of the posterior border of the sternocleidomastoid; deep cervical plexus at C2-C3-C4 transverse processes — beware of vertebral artery + intrathecal injection.