Prophylactic i.v. metaraminol during spinal anesthesia for elective Cesarean delivery.

To the Editor: We read with interest the article by Hillerman et al.1 concerning laryngeal nerve identification during thyroid surgery using the laryngeal mask airway (LMA). Although postoperative voice changes are usually attributed to recurrent laryngeal nerve injury, the external branch of the superior laryngeal nerve (EBSLN) is also at risk since it runs close to the superior thyroid artery, which is ligated during surgery.2 Injury to the EBSLN occurs in 4–10%3,4 of patients and results in huskiness and voice fatigue since it is the only motor supply for the cricothyroid muscles, which tense the vocal cords. Identification of the EBSLN and individual ligation of the superior thyroid vessels are imperative to avoid injury. A particular problem during dissection is that the pharyngeal wall is soft and collapsible making exposure of the EBSLN difficult. A technique we discovered which overcomes this problem is to use the LMA to control the tension and position of the pharyngeal wall. The technique involves insertion of the LMA behind the tracheal tube and inflation of the cuff until the surgical conditions are optimal. The technique can also be used when the LMA is the ventilatory device, but the range of cuff volumes is more restricted since the seal with the pharynx must remain intact. We have used this technique on 17 patients and have had no problems with location of the EBSLN.