Further Reading
1.4 Anesthesia
1.4.2 Regional Anesthesia Techniques
● Stage 3 : also known as “surgical plane,” where procedural stimulation causes minimal, if any, cardiovascular and/or respiratory changes.
● Stage 4 : massive anesthetic overdose that causes severe depression of brainstem activity leading to respiratory and/or cardiovascular collapse.
This stage should never be reached as it may be lethal even with ap- propriate cardiovascular and/or respiratory support.
Further Reading
Barash PG, Cullen BF, Stoelting RK, et al. Clinical Anesthesia. 6th ed. Philadelphia, PA:
Lippincott Williams & Wilkins; 2009
Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology. 4th ed. New York:
McGraw-Hill Medical; 2005
advanced laterally along the brow. A total of 8 mL of local anesthetic is ap- plied from the glabella to the lateral edge of each brow.
Greater and Lesser Occipital Nerves Indications: closure of lacerations
By blocking the greater and lesser occipital nerves, the posterior scalp can be anesthetized. By placing a track of local anesthetic from the mastoid process to the inion (i.e., external occipital protuberance) along the high- est nuchal line from each side, both the greater and lesser occipital nerves will receive a dose of local anesthetic and the posterior scalp will become anesthetized.
A large skin wheal is placed over the mastoid process on each side using a 27-gauge needle. Then through this wheal, a wheal is placed from the mastoid process to the inion using a 25-gauge Quincke needle that is bent to facilitate a superficial injection.
Infraorbital Nerve
Indications: closure of lacerations, facial surgery
The maxillary division of the trigeminal nerve innervates the midface, from the inferior portion of the orbit to the mandible. This area includes the area overlying the zygoma, the maxilla, and most of the nose, as well as the philtrum and the hard and soft palate.
The infraorbital foramen is palpable 2 to 3 mm below the rim of the orbit, just medial to the equator of the orbit. A small-gauge needle is used to inject local anesthesia just outside the foramen. Avoid injection into the foramen as the nerve is located in a confined space.
A small amount (2–4 mL) of local anesthetic is sufficient and it should be injected based on which area is to be anesthetized, i.e., emphasize above the foramen for lower lid work, medial to the foramen for lateral nasal work, and inferomedial to the foramen for work on the philtrum.
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Blocks of the Neck
Superficial Cervical PlexusThe cervical plexus is composed of four nerve roots, C 1 –C 4 , and terminates in four branches: lesser occipital, great auricular, transverse cervical, and supraclavicular nerves. The terminal branches emerge superficially at the posterior border of the sternocleidomastoid (SCM) muscle along the mid- portion of the muscle.
This is a purely cutaneous nerve block; there is no motor block with the superficial cervical plexus block. Neuromonitoring and stimulation of the recurrent laryngeal nerve is not compromised when using this block.
The patient is positioned in the seated position. A line connecting the insertion of the SCM at the midpoint of the clavicle to the mastoid process along the posterior muscle border designates the path in which subcutane- ous local anesthetic should be injected. Initially, 3 to 5 mL of local anesthetic is injected at the midpoint of the SCM using a 27-gauge needle. Using a
25-gauge Quincke point spinal needle, subcutaneous injections are then performed from this initial injection site in caudad and cephalad directions along the posterior edge of the SCM. Infiltration along these paths should require 6 to 8 mL of anesthetic in each direction. Aspiration prior to injec- tion is important to avoid intravascular injection.
Deep Cervical Plexus
The deep cervical plexus (DCP) is the collection of the C 2 –C 4 nerve roots as they exit the “gutter” formed by the transverse process of the respec- tive vertebrae. By injecting prior to the division of the cervical roots into dorsal and ventral spinal nerves, a more complete blockade of the ipsilateral neck is achieved—including both sensory and motor elements. This is not commonly used for otolaryngology procedures.
The patient is seated upright in a high Fowler position with a small towel behind the shoulders. The above-mentioned line is drawn between the mastoid process and the anterior tubercle of C 6 , which is palpable in the vast majority of patients. A line parallel to this is drawn 1.5 cm behind the first, and the posterior tubercle is palpated on C 2 , C 3 , and C 4 . Deep palpa- tion can be uncomfortable and a light touch is indicated. After a small skin wheal with a 27-gauge needle, a short (2.5 cm) blunt needle is advanced to the posterior process of each of the three vertebrae and then “walked”
laterally and anterior to the posterior tubercle. An advance of 1 mm be- yond the bony tubercle will suffice. It is not uncommon for the patient to describe a light paresthesia in the dermatome of the root being blocked.
After careful aspiration, 4 to 5 cc of local anesthetic (with epinephrine) is injected at each of the three levels. (C 2 , C 3 , C 4 ). The proximity to the spinal column and major vascular structures increases the risk of intrathecal or intravascular injection.
Specific Nerve Blocks for the Upper Airway
Maxillary Division of the Trigeminal Nerve (Sphenopalatine Ganglion)
● The transnasal topical approach to the sphenopalatine ganglion involves application of local anesthetic to the mucous membranes surrounding the ganglion.
● Position the patient supine with neck extension. A local anesthetic (typically 80 mg of 4% cocaine) is applied to each nostril. Cotton-tipped applicators soaked in 4% cocaine are gently swirled and advanced into the nares. Each applicator is advanced a little further than the one prior, and once placed the applicator is left there as successive applicators are introduced. Each nostril should receive four to seven applicators as the opening allows. The applicators should remain in the nares for at least 20 minutes allowing the local anesthetic to diffuse through the mucosa overlying the ganglion.
● The sphenopalatine ganglion can also be approached through the greater palatine foramen located at the posterior portion of the hard palate. In this approach, the patient is positioned in the supine position with the
neck extended. The foramina can be palpated medial to the gumline of the third molar. A small-gauge needle is advanced ⬍2.5 cm through the foramen in a superior and slightly posterior direction. To avoid an intravascular injection, aspirate prior to injection.
Glossopharyngeal Nerve
● The glossopharyngeal nerve (CN IX) exits the skull at the jugular foramen and passes between the internal jugular vein and the internal carotid ar- tery. It descends just dorsal to the styloid process before curving forward and anterior to innervate the palatine tonsil, the mucous membranes of the fauces and the base of the tongue. This nerve has motor, sensory, and autonomic components, and supplies lower motor neurons to the stylopharyngeus and parasympathetic innervation of the parotid and mucous glands.
Superior Laryngeal Branch of the Vagus Nerve
● The superior laryngeal nerve can be blocked as it passes into the thy- rohyoid membrane inferior to the greater cornu of the hyoid bone and superior to the greater cornu of the thyroid cartilage. This block will provide anesthesia to the glottis above the vocal folds.
● With the patient seated in an upright (high Fowler position) with a towel roll transversely laid behind the shoulders, the thyroid cartilage is palpated. It can be helpful to lightly displace the thyroid cartilage toward the side of the block. Using a small-gauge needle, 2 to 3 mL of local anesthetic is injected near the cartilaginous greater cornu. Aspi- ration prior to injection will confirm that the needle has not entered the supraglottic air column. This procedure is then repeated on the other side.
Topical Anesthesia of the Subglottic Airway
● The recurrent laryngeal branch of the vagus nerve pierces the subglottic trachea to innervate all the laryngeal muscles other than the cricothyroid muscle as well as provide sensory innervation to the subglottic mucosa.
● The patient is positioned in a high Fowler position with a towel roll laid transversely behind the shoulders. Moderate neck extension is help- ful. After skin disinfection, the thyroid cartilage is identified. The next palpable cartilage inferiorly is the cricoid cartilage. The palpable gap between these two structures overlies the cricothyroid membrane. A 22- gauge needle containing local anesthetic (2 to 4 mL 3% chloroprocaine or 2 to 4 mL 4% lidocaine) is advanced perpendicular to the skin while gentle aspiration is applied to the syringe plunger. Air will be freely aspi- rated when the needle penetrates the cricothyroid membrane, entering the trachea. The patient should be alerted that the injection will induce coughing. The local anesthetic should be rapidly administered and the needle withdrawn. The patient will cough and should be encouraged to do so several times to enhance spread of the anesthetic.
Further Reading
Barash PG, Cullen BF, Stoelting RK, et al. Clinical Anesthesia. 6th ed. Philadelphia, PA:
Lippincott Williams & Wilkins; 2009
Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology. 4th ed. New York:
McGraw-Hill Medical; 2005