Module 4: Medications - Advanced Knowledge

Airway anatomy

  nerves or their branches can selectively be blocked for an awake bronchoscopic intubation:

  1. Trigeminal nerve (CN V) (nasal cavity, mouth)

    The nasal cavity is entirely innervated by the trigeminal nerve.

    • Anterior ethmoidal nerve (from V1) – septum
    • Greater and lesser palatine nerves, from sphenopalatine ganglion in pterygopalatine fossa (V2)
    • Nasopalatine nerve, from sphenopalatine ganglion (V2) – septum
  2. Glossopharyngeal nerve (CN IX) (posterior 1/3 tongue, pharynx, valleculae, lingual surface of epiglottis and gag reflex)

    Gag reflex:

    • Elicited by stimulation of the glossopharyngeal nerve, efferent from vagus nerve
    • Abolished by bilateral block of glossopharyngeal nerve
  3. Vagus nerve (X) (larynx, trachea)

    The superior laryngeal nerve divides into internal and external branches.

    • Internal branch: sensation from epiglottis to above vocal cords
    • External branch: cricothyroid muscle

    Recurrent laryngeal nerve:

    • Given off the vagus nerve during it's intra-thoracic course (loops around ligamentum arteriosum on left and around subclavian artery on right)
    • Provides sensation of larynx below and including vocal cords and trachea. Motor to all intrinsic muscles of the larynx except cricothyroid muscle
    • Glottic closure reflex (exaggeration of this reflex = laryngospasm) – this is caused by stimulation of superior laryngeal nerve, efferent from recurrent laryngeal nerve

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Nerve blocks

Superior laryngeal nerve (sensation to larynx above vocal cords)

  • Blocked between hyoid bone and thyroid cartilage where it penetrates the thyrohyoid membrane
  • Place patient supine with maximal neck extension
  • Grab the hyoid between the thumb and index finger and firmly displace it towards the side to be blocked
  • Advance a 25g needle to the greater cornu then walk it off inferiorly and advance it a further 2 – 3mm
  • Inject 2 – 3ml and an additional 1ml as the needle is withdrawn (to block the external branch)

Glossopharyngeal nerve: (gag reflex and sensation from the oropharynx to the lingual surface of the epiglottis)

  • Usually blocked by the local anesthetic applied to the back of the tongue and throat
  • Can also be blocked by holding a local anesthetic soaked swab bilaterally at the palato-glossal arch (the rim of tissue than runs from the uvula to the base of the tongue)

The glossopharyngeal nerve can be blocked by holding swabs soaked in local anesthetic at the point indicated by the white arrow.

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Continue to: Module 5: Procedure