Block of the sphenopalatine ganglion may be used to provide regional anesthesia for nasal and dental surgery or for fiberoptic airway management. It may also be used in the management of acute migraine, acute cluster headache, and facial neuralgia.
For the transnasal approach, the patient is placed supine. With a cotton tip soaked in 4% lidocaine or 10% cocaine, the first applicator is passed along the upper border of the first turbinate until contact is made
with the posterior pharyngeal wall. A second soaked cotton tip is passed along the upper border of the middle turbinate. These should be left in place for 20 minutes.
For the greater palatine foramen approach ( Fig. 20-18 ), the greater palatine foramen is located in the hard plate medial to the third molar. A fine needle is advanced 3 to 5 cm through the foramen in a caudad and slightly posterior trajectory. The maxillary nerve lies just superior to the ganglion and a paresthesia may be elicited. After aspiration, 2 mL of local anesthetic is injected incrementally.
GLOSSOPHARYNGEAL (CNIX) BLOCK
With the peristyloid approach, owing to the presence of anatomic structures close to the glossopharyngeal nerve, there is an extremely high risk of accidental intravascular injection or spread to the vagus, hypoglossal, and accessory nerves.
With the patient in a supine position, the head is rotated to the side opposite the one to be blocked ( Fig. 20-19 ). The landmark for needle insertion is a point between the posterior border of the mandible and the tip of the mastoid process. A 23-G needle is advanced until the styloid process is contacted. The needle is then withdrawn slightly and walked off the styloid process a further depth of 1 cm. After careful aspiration, 3 to 4 mL of local anesthetic is injected in increments. An alternative technique has been described using an ultrasonically guided needle directed at the glossopharyngeal nerve as it runs anterior to the internal carotid artery. This is intended to reduce the risk of puncture of the vessels. An intraoral approach has been described. This requires adequate mouth opening, a tongue depressor, and a long 22-G (spinal) needle. The needle is inserted submucosally in the caudad portion of the posterior tonsillar pillar, or, alternatively, to a depth of 5 mm through the anterior tonsillar pillar. After aspiration, 5 mL of local anesthetic is injected. This approach can also be used during topical anesthesia of the airway. Alternatively, Krause's forceps holding local anesthetic soaked pledgets are rested in the piriform fossae for 3 minutes. This also blocks the superior laryngeal nerve.
Superior and Recurrent Laryngeal Nerve (CN X) Blocks Including Airway Blocks. All anesthesiologists encounter patients with difficult airways. Regional airway blocks are essential in managing these situations safely.
Superior Laryngeal Nerve Block. With the patient supine, the hyoid bone is displaced to the side to be blocked, which makes the hyoid bone more prominent. A short, fine needle is directed toward the lateral aspect of the hyoid bone and walked off the inferior margin a depth of 1 to 2 mm until it pierces the thyrohyoid ligament. Aspiration is performed to ensure that the airway has not been entered. Injection of 2 to 3 mL of local anesthetic is sufficient. This process should be repeated on the other side to anesthetize the glottis above the true vocal cords ( Fig. 20-20 ).
Recurrent Laryngeal Nerve Block. Transtracheal injection anesthetizes the airway below the true vocal cords. A 22-G needle is inserted through the cricothyroid membrane in the midline. Once air is freely aspirated, 4 mL of 4% lidocaine is injected rapidly and the needle withdrawn. This usually produces coughing. The coughing spreads the anesthetic above the vocal cords, often making a separate superior laryngeal nerve block unnecessary. Coughing could be undesirable in someone with raised intracranial pressure, and hematoma may occur if injection is not made in the midline. Pulmonary aspiration may also theoretically be a risk once the block has been performed.
Anterolateral Approach to the Recurrent Laryngeal Nerve. Blockade of both sides would produce bilateral vocal cord paralysis and should not be performed. Block of the recurrent laryngeal nerve can be undertaken for pain due to malignancy at the level of the first tracheal ring. A 22-G needle is passed to the posterolateral margin of the tracheal ring and 3 to 5 mL of local anesthetic is injected.
Figure 20-19 Point of entry on the skin for glossopharyngeal nerve block just posterior to the mandible and anterior to mastoid process.
Figure 20-20 The internal and external branches of the superior laryngeal nerve are blocked below the apex of the hyoid bone. (I) The needle penetrates the thyrohyoid membrane and is directed toward the greater cornu of the hyoid bone for superior laryngeal nerve block. Through the same point of entry, the needle can be directed into the larynx for transtracheal spray. (II) The needle enters at the greater cornu of the hyoid bone. (III) The usual approach for transtracheal spray is to insert the needle into the larynx through the thyrohyoid membrane.
Stellate Ganglion Block. Stellate ganglion block is indicated in circulatory disturbances of the upper limb (e.g., Raynaud's phenomenon). The stellate ganglion is approached most readily from the front via a paratracheal approach (see Chapter 33 ). The sympathetic chain lies on both the C6 and the C7 transverse processes and can easily be reached using a short, 3-cm needle. The position of the C7 transverse process is determined by placing a mark 3 cm lateral to the middle of the clavicular notch and 3 cm vertical to the clavicle. The carotid sheath and sternomastoid are retracted laterally as the needle is inserted perpendicularly through the mark to contact the bone. The needle is then slightly withdrawn, and, after aspiration, a small test dose of local anesthetic is injected. Stellate ganglion blocks carry the significant risk of total spinal anesthesia.11«
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