Regional Blocks

Regional anesthesia is defined here as direct injection into or around the nerves supplying a specific anatomical or surgical site. Regional anesthesia in the head and neck follows many of the principles discussed in the previous sections. A full pre-operative evaluation should be completed. In a cooperative patient, regional anesthesia with or without supplemental sedation and analgesia will often provide excellent anesthesia. The procedure needs to be relatively short, because although the duration of the block may be fairly long, it is often difficult for even a sedated patient to remain cooperative and comfortable for an extended length of time. Depending on the extent and site of surgery, restriction of oral intake prior to the procedure is recommended according to the guidelines for MAC and general anesthesia. Deeper sedation or even general anesthesia may be required if the regional block and light sedation are inadequate.

The local anesthetics used in regional anesthesia have already been discussed. Care should be taken not to exceed the recommended dosages. Large volumes of @

Regional Block Scalp
Figure 1 Distribution of sensory nerves of the scalp as they become subfascial. (From Ref. 9.)

the injection may occasionally be required for the institution of large field blocks and it may be necessary to dilute the concentration of the anesthetic. In a field block, it may be necessary to supplement the anesthetic with epinephrine to achieve an adequate duration of anesthesia and hemostasis.

The general complications of local anesthesia have been described and only complications limited to the specific technique will be discussed here. Many of these blocks can be achieved by a variety of techniques. The most common methods of achieving the blocks will be discussed according to site.

Scalp

The primary sensory innervation of the scalp is by the cervical nerves and the trigem-inal nerve. The supraorbital, supratrochlear, and zygomaticotemporal nerves supply the forehead and occiput. The temporomandibular and the auriculotemporal branches of the trigeminal nerve innervate the temporal regions. The greater and lesser occipital nerves, which are distal branches of the cervical nerves, innervate the occipital and parietal regions. These nerves originate deep and enter a subfascial ^

o plane on a line encircling the head that passes above the ear and through the occiput and glabella (Fig. 1). The regional block is accomplished by subcutaneous injection |

of a large volume of (usually) diluted lidocaine with epinephrine. This infiltration will anesthetize the skin, fascia, and pericranium. Anesthesia is obtained in a skull cap distribution (Fig. 2). @

Figure 2 Region of anesthesia in a regional scalp block. (From Ref. 9.)

Forehead

The face and anterior scalp are innervated by the trigeminal nerve. Cervical nerves innervate posterior portions of the scalp as well as the neck and lower portions of the jaw. Operations on the forehead and scalp are possible using blocks of the supratrochlear and supraorbital nerves. These nerves are located in the supraorbital ridge/foramen of the frontal bone (Fig. 3). One to two milliliters of local anesthesia is injected in the region. It is sometimes difficult to locate the supraorbital foramen but it is helpful to note that the supraorbital, infraorbital, and mental foramina all lie in a straight line approximately 2.5 cm from the midline of the face. In neutral gaze, the pupils will also lie in this line. When large or midline lesions are to be excised, a bilateral block may be performed.

Possible complications include unusual swelling and ecchymoses around the orbit. This is usually secondary to either a large volume of anesthesia being injected or hemorrhage from the supraorbital vessels. It is usually self-limited and requires no specific treatment.

Infraorbital Nerve

An infraorbital nerve block can facilitate operations upon the lower eyelid, lateral aspect of the nose, the mucous membranes around the upper incisors, and the cuspid

Palpebral Nerve
Figure 3 Location of supraorbital notch/foramen.

teeth. The infraorbital nerve emerges from the infraorbital foramen and divides into the inferior palpebral nerve, the external nasal nerve, the internal nasal nerve, and the superior labial nerve. The infraorbital nerve lies 2.5 cm from the midline of the face in the frontal process of the maxillary bone (Fig. 4). It is usually numbed with the injection of 2.5 ml of 1% lidocaine. This can be accomplished via either a sublabial injection or direct percutaneous injection. Care should be taken not to inject in the orbital cavity because hemorrhage may occur. Bilateral blocks may be required for lesions near the midline.

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