CHAPTER 9 Oral and Facial Anesthesia
This discussion involves both intraoral and extraoral anesthetic techniques. Therefore, an understanding of regional anatomy is crucial to properly perform these infiltrations and nerve blocks. The sensory innervation of the face and oral cavity is primarily from the trigeminal nerve (fifth cranial nerve). This nerve is divided into ophthalmic (V1), maxillary (V2), and mandibular branches (V3; Figs. 9-1 and 9-2).
Contraindications
• Risk of hematoma (e.g., in patients with hemophilia or anticoagulant use); trauma to vascular bundles can increase risk of bleeding and hematoma (relative contraindication)
Complications
See Chapter 5, Local and Topical Anesthetic Complications.
• Syncope: Most common untoward reaction to anesthetic injections, often resulting from pain during the injection. A semisupine or supine position and slow injection technique are recommended.
• Broken needle: Very rare, but it is best to always leave some needle showing and not to “bury” to the hub when injecting.
• Hematoma: Rare, often resulting from torn capillaries or vessels that are punctured during injection.
• Persistent paresthesia: Occurs after the anesthetic should have worn off. Indicates damage to the nerve from physical or local chemical trauma. Can be temporary or permanent.
• Ischemic ulcer: Usually resulting from vasoconstrictor use in relatively avascular tissue (e.g., subperiosteally in the hard palate). Skin is very vascular, and ischemia is extremely rare when local anesthetic with epinephrine of a low concentration (1/100,000 or 1/200,000) is used.
• Blanching: Occurs at the site of injection because of pressure of anesthetic and vasoconstriction. If remote from the injection site, then it is probably due to inadvertent intravascular injection. No treatment is needed.
• Tachycardia: Can occur from pain of injection, but it is most likely due to intravascular injection or rapid absorption of local anesthetic with epinephrine.
• Paralysis: Results from inadvertent anesthesia of facial nerve (seventh cranial nerve). It is usually temporary. If longer-acting anesthetics such as bupivacaine are used and the patient cannot close the eyelid, the lid can be taped down (to avoid dryness of the eye) until the anesthetic wears off.
• Visual disturbance: Rare, probably due to vascular spasm or intraarterial injection. Normal vision usually returns in about 30 minutes.
Equipment
-inch (25- to 30-gauge) needle• Local anesthetic, such as 2% lidocaine with or without 1 : 100,000 epinephrine, or 0.5% bupivacaine with or without 1 : 200,000 epinephrine
• Mepivacaine (pKa 7.6; may give better anesthesia in infected tissue, which usually has an acidic environment [pKa <7.5])
General Technique
1 Anesthetic solution is usually deposited just above the bone around the nerve trunks in the submucosa or subcutaneous tissue, where the nerves exit from the bone itself (e.g., supraorbital, infraorbital, or mental nerves). This technique is known as a supraperiosteal injection. It may be approached from either an intraoral or extraoral route, depending on the nerve block desired.
2 If going through facial skin, clean the skin with alcohol. If giving local anesthetic to repair traumatic lacerations, clean thoroughly with normal saline. Tent or support the tissue and slowly infiltrate (for 30–60 seconds) into the area to be addressed. Identify landmarks before infiltration; they can become “ballooned” and hard to appreciate after local anesthetic is given.
