Laryngospasm mechanism


Laryngospasm: Stimulation of vagus nerve during light anesthesia (Superior Laryngeal n, pharyngeal br of vagus, recurrent laryngeal below cords). Muscles involved: lateral cricoarytenoid, thyroarytenoids (both from recurrent laryngeal), crycrothyroid (from external branch of superior laryngeal). Causes: hypocalcemia, painful stimuli, vagal hypertonicity, foreign body.

Airway Innvervation: The larynx is composed of nine cartilages, three paired and three unpaired and these cartilages contain within them the vocal cords. The movements of the larynx are controlled by the extrinsic muscles which move the larynx as a whole and the intrinsic muscles which move the various cartilages in relation to one another. The larynx is innervated bilaterally by the superior laryngeal nerve (supplies mucosa from the epiglottis to the level of the cords) and the recurrent laryngeal nerve (supplies mucosa below the cords), both branches of the vagus nerve (CN X). The recurrent laryngeal nerves supply all of the intrinsic muscles of the larynx except for the cricothyroid muscle and any damage to the recurrent laryngeal can result in vocal cord dysfunction. The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve.

Other nerves which may need to be anesthetized for awake fiberoptic intubations include the maxillary branch of the trigeminal nervewhich supplies sensory innervations to the nasopharynx and the glossopharyngeal nerve which supplies sensory innervations to the post 1/3 of the tongue, pharynx, and areas above the epiglottis.


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