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Describe the conduction of general and regional anesthesia for middle ear surgery.
The epinephrine given for control of bleeding is gener-ally combined with local anesthetics, which minimizes surgical stimulation from the operative site. Use of laryngo-tracheal anesthesia may eliminate endotracheal-tube-induced pain and coughing. The simultaneous employment of these two techniques markedly reduces inhalation agent requirements. Mild to moderate hypotension frequently ensues. Attempts at decreasing the inspired partial pressure of volatile anesthetic agent may be met with patient motion or bucking. The surgical result could be disastrous. Consequently, deep anesthesia must be maintained and the blood pressure supported with occasional small doses of ephedrine or phenylephrine. If hypotension persists, a low-dose infusion of phenylephrine may be helpful.
At the termination of surgery, emergence from anesthe-sia should ideally be free from coughing and straining in order that the tympanic membrane graft remains in place. Intravenous or intratracheal lidocaine may be used to help prevent these complications if the patient is not at increased risk for aspiration of gastric contents.
Regional anesthesia for radical tympanomastoidectomy and other similar procedures may be accomplished with lidocaine 1% with epinephrine 1:200,000 (5 μg/cc). To block the branches of the trigeminal nerve and the cervical plexus that innervate the auricle, multiple skin wheals connected by subcutaneous infiltration are made around the mastoid process. The total volume of local anesthesia is 5–8 mL. The superior two-thirds of the anterior surface of the auricle may be anesthetized by infiltrating local anesthesia over the posterior aspect of the zygoma and connecting the skin wheal with subcutaneous infiltration along the anterior border of the auricle to its inferior border. The auriculotemporal nerve supplies the anterior portion of the auditory canal and can be infiltrated with 2 mL at the osseous-cartilaginous region. The floor of the external auditory canal and the inferior portion of the tympanic membrane are supplied by the vagus nerve.
Two milliliters of local anesthetic is infiltrated in the inferior portion of the canal.
The remainder of the tympanic membrane may be anesthetized by direct application of 4% lidocaine spray or 4% cocaine. Occasionally, extensive radical mastoid surgery may require an incision that is more posterior. Consequently, the lesser occipital and greater occipital nerves may need to be blocked. Subcutaneous infiltration from the mastoid process to the greater occipital protuber-ance along the superior nuchal line will create adequate anesthesia. Five to eight milliliters of a local anesthetic will successfully accomplish this block.
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