Use of a laryngoscope, held sideways, as an aid in perforsming an intraoral glossopharyngeal nerve block.

Sir,

Anesthetizing the glossopharyngeal nerve (GPN) is an important component in achieving successful airway anesthesia and is necessary for both awake oral and nasal tracheal intubations. The clinician should recall that the GPN is the IX cranial nerve and that it innervates the posterior third of the tongue, epiglottis, as well as the soft palate.[1]

Anatomically, the intraoral GPN nerve block can be accomplished by injection of local anesthesia at the base of either the anterior or posterior tonsillarpillars.[2] This can be facilitated by using a laryngoscope, held sideways, for medial retraction of the tongue [Figure 1]. It is the authors’ observation that this provides excellent visualization of these structures; with less potential for gagging then traditional caudal tongue retraction. When held in this manner, the laryngoscope subsequently also functions as a bite block. Typically, a 22 to 25 gauge Quincke point spinal needle is then used to inject 4 to 5 ml of 2% lidocaine. For patients with small mouths, limited inter-incisor distance, or with mild to moderate trismus, pediatric laryngoscopes may be used. Furthermore, Miller laryngoscope blades, which are usually narrower than Macintosh, may also be advantageous.

Figure 1

By holding a laryngoscope sideways, the tongue can be retracted medially. This facilitates the visualization of either the poster or anterior tonsillar pillars during the administration of an intraoral glossopharyngeal nerve block a period

In addition, the use of a video laryngoscope such as the Glidescope® may also facilitate proper localization. This device may also be educationally valuable.

For those patients with severe trismus, the extraoral GPN block may be necessary.[1] Careful aspiration is always essential with either the intraoral or extraoral approaches; as the GPN is located near the carotid artery.

In addition, “redundant” local analgesic techniques, with topicalization of the tongue as well as nebulized lidocaine, are beneficial prior to performing this block. Use of both the transtracheal and superior laryngeal nerve blocks are also indispensable for awake tracheal intubation. Whereas topical anesthesia, of the sphenopalatine ganglion and nasal mucosa, are additionally needed for awake nasal intubation. Judicious use of intravenous sedatives may also be beneficial.[1] Pretreatment with sodium citrate and metoclopramide is necessary if a “full stomach” or gastroesophageal reflux is known or suspected.[3]

The patient's ability to tolerate either a traditional Berman or Guedel oral airway may be used as an indication of adequate overall intraoral anesthesia. Fiberoptic-compatible oral airways should also be available.[4]

It should be noted that awake intubation can be accomplished with a traditional laryngoscope, video laryngoscope, or fiberoptic bronchoscope. “Blind” intubation techniques can also be employed. These may be facilitated with the use of an “intubation whistle” or by the auscultation of breath sounds emanating from the proximal end of the tracheal tube.[5]