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Anesthesia for Laryngeal Surgery in the Office

2000; Wiley; Volume: 110; Issue: 10 Linguagem: Inglês

10.1097/00005537-200010000-00040

1531-4995

Lucian Sulica, Andrew Blitzer,

Head and Neck Surgical Oncology

Regional anesthesia of the larynx is not commonly used by otolaryngologists, although it is not a new technique. It has been a part of the anesthesiologist's repertoire since at least 1951, used principally to facilitate awake intubations. 1. More recently, it has been proposed as an adjunct to transesophageal echocardiography and as a treatment for laryngospasm. 2., 3. It has been of limited use to the laryngeal surgeon because available surgical technologies such as the operating microscope and the CO2 laser have required a direct line of sight and laryngeal immobility, making suspension laryngoscopy under general anesthesia the approach of choice. However, indirect laryngeal surgery remains a feasible alternative, both in its traditional form and in combination with rigid or flexible endoscopic visualization. Vocal fold augmentation and biopsy, excision, or even laser ablation of lesions is possible. 4.-7. Modern indirect laryngeal surgery is based on the recovery of techniques that were nearly lost to the modern otolaryngologist. Before the advent of safe general anesthesia, most laryngeal procedures were performed perorally in fully conscious patients by a few skilled laryngoscopists able to handle both a mirror (in the nondominant hand) and an instrument. They developed an array of tools and procedures, some of which can be adapted to meet modern clinical needs. We have developed a standardized protocol to achieve laryngeal anesthesia, using medications common to most otolaryngologists' offices, that allows us to move many laryngeal procedures out of the hospital operating room and into the procedure suite of our clinic. This method has three basic components: bilateral superior laryngeal nerve block, topical anesthesia of the trachea via cricothyroid puncture, and peroral topical anesthesia of the larynx and pharynx. In our center it has proved safe, easily learned, and reliable. A discussion of our experience follows a description of our method. After giving informed consent for the planned procedure, the patient sits in a regular examination chair and faces straight ahead. The thyrohyoid space is found by palpation. A point halfway between the hyoid bone and the superior border of the thyroid cartilage, and halfway between the anterior midline and the superior cornu of the thyroid cartilage, is selected as the site for injection (Fig. 1). This corresponds to the place where the internal branch of the superior laryngeal nerve pierces the thyrohyoid membrane to enter the paraglottic space. The surgeon inserts a syringe with a 27-gauge needle and advances it gently until the characteristic springlike resistance of the thyrohyoid membrane, similar to a trampoline, is appreciated. Drawing back on the plunger ensures that the needle does not lie in either the lumen of the superior laryngeal artery or that of the pharynx or larynx. One to 2 mL of a solution of equal parts bupivacaine 0.25% and lidocaine 1% with epinephrine 1:100,000 is injected. Then this procedure is repeated at the same spot on the opposite side of the larynx. Every effort must be made not to penetrate the thyrohyoid membrane to avoid causing swelling of the supraglottis that can obscure the surgical site, or even endanger the airway. The tip and lingual surface of the epiglottis may retain some sensitivity following these injections. The injection of an additional milliliter of solution into the pre-epiglottic space at the thyroid notch eliminates this. The hyoid bone, the thyroid cartilage, and the cricoid cartilage are outlined. The point of injection to anesthetize the internal branch of the superior laryngeal nerve as it pierces the thyrohyoid membrane is marked with an "X." The circle marks the cricothyroid membrane at the point where it is punctured for intratracheal anesthesia. The square identifies the spot where the pre-epiglottic space is injected. A 30-gauge needle is used to instill 2 mL lidocaine 1% into the trachea via cricothyroid membrane puncture. The patient coughs, spreading the anesthetic throughout the trachea and the subglottis. We do not recommend the use of epinephrine-containing solution in the trachea. While the patient's tongue is gently held by the otolaryngologist, the patient is asked to phonate and a spray of topical lidocaine 4% is directed at the posterior wall of the pharynx. This provides additional anesthesia and inhibits gagging. The more patent side of the nose is anesthetized with aerosolized mixture of equal parts phenylephrine 0.25% and tetracaine 1% in the usual manner for transnasal fiberoptic flexible endoscopy. By the time topical agent is administered via nasal and oral routes, laryngeal anesthesia should be complete. Before beginning any procedure, the tip of the endoscope can be used to probe the vocal folds and the subglottic area to confirm this. Any remaining areas of sensitivity can be addressed by dripping lidocaine 1% directly onto them via the instrument port of the endoscope. The procedure described provides 45 to 60 minutes of profound anesthesia of the territory extending from the valleculae to the subglottis, during which the patient will tolerate soft-tissue biopsy, multiple injections into the vocal fold, or even CO2 laser ablation of respiratory tract papilloma. In the rare case where a vallecular lesion does not lie completely in the area of anesthesia, a transoral glossopharyngeal nerve block can augment the laryngeal block. 8. Although sensation does not return to normal for about 3 hours (1.5 hours if bupivacaine is not used), the patient cannot cooperate with noxious manipulation of the vocal folds for longer than about an hour. An inadequately prepared individual can find complete laryngeal anesthesia a disturbing phenomenon because it can create the sensation of airway obstruction. However, we find that the well-coached patient requires no more than gentle reassurance to adjust without drama. In rare cases of extreme anxiety, diazepam 2 mg given by mouth 30 minutes before the procedure has been useful. Not only breathing but also voice remains intact throughout the period of anesthesia, although we have noticed that the occasional patient loses control of pitch when speaking, probably from inadvertent anesthesia of the external branch of the superior laryngeal nerve. This has always been a transient effect. Deglutition is clearly impaired, and the patient must be cued to spit or swallow from time to time as accumulating secretions or blood interfere with the procedure. We have found the preoperative administration of an anti-sialogogue like glycopyrrolate helpful in minimizing this problem. Obviously, the patient should be told to eat or drink nothing after the procedure until sensation returns to normal. A similar method of anesthesia, but omitting the superior laryngeal nerve block, has been described for diagnostic endoscopy of the airway to the carina and for indirect laryngeal surgery. 4., 9. We have found that the nerve block adds further to patient comfort and is particularly useful in prolonged procedures. The technique has been in use at our center for approximately 5 years. In performing more than 50 procedures, we have had no serious complications. This is in part a result of careful selection of patients. Patients with borderline airways, for instance, are handled in the operating room. Nevertheless, many patients undergo regional laryngeal anesthesia and awake indirect laryngeal surgery specifically because significant comorbidity exists and they have been judged high-risk general anesthesia candidates. These have included patients with renal insufficiency, ischemic heart disease, and seizure disorders. In such cases, the surgeon must remain acutely conscious of the systemic toxicities of the various agents used and adjust mixtures and quantities as indicated. The most common complication from the anesthetic procedure itself, rather than from the surgery, is ecchymosis at the site of injection. We have not seen formation of a hematoma, either subcutaneously or submucosally. Penetration of the larynx by secretions is clearly observed during procedures, but this has not created problems for our patients. On one occasion, a patient has had a vasovagal response to injection that resolved without intervention. This phenomenon has been reported by other authors. 10. This could be explained by diffusion of anesthetic to the carotid bulb or the main trunk of the vagus. For this reason, and as a point of general principle, we believe that it is important to keep the amount of injected anesthetic to a minimum. A technique for superior laryngeal nerve block has been reported which requires injection of 8 mL lidocaine 1% at the greater cornu of the hyoid. 11. We have found this excessive. As the surgeon's experience with the technique grows, particularly in the identification of the thyrohyoid membrane by the characteristic "trampoline" resistance, the total volume of lidocaine required falls to about 2 mL. We also disagree with the authors of an anatomical cadaver study in which methylene blue was substituted for lidocaine. 12. They concluded that, in fact, the anesthetic comes to rest in the paraglottic space. Were this so, we would expect to see occasional vocal fold paresis. To date, we have not seen one, nor have we seen swelling or distortion of the laryngeal mucosa. However, as noted above, temporary cricothyroid muscle paresis occurs, strongly suggesting that the anesthetic collects and acts external to the thyrohyoid membrane. The method of laryngeal anesthesia described in this report has been remarkably reliable and effective, even in inexperienced hands. Applied with caution, it has proved safe, and it has allowed us to take full advantage of both new and old technologies to perform a wide range of laryngeal procedures with less delay, less risk, and less cost than the heretofore standard direct laryngoscopy under general anesthesia.