To the Editor:—
Lingual nerve injury is an uncommon complication of anesthetic airway management. 1–8We report the first case of transient bilateral lingual and glossopharyngeal nerve injury after use of a cuffed oropharyngeal airway (COPA).
A healthy 32-yr-old female with a height of 164 cm and a weight of 65 kg was anesthetized for suction and curettage after spontaneous abortion. Anesthesia was induced using 2.5 mg/kg propofol and 1 μg/kg remifentanil. A 9-cm COPA was inserted easily, and the cuff was inflated with 30 ml air, according to the recommendations of the manufacturer, and secured with ribbon. Because of an audible leak during manual ventilation, 8 ml air was added subsequently into the cuff of the device. Anesthesia was maintained using nitrous oxide–oxygen (50/50) and remifentanil (0.5 μg · kg−1· min−1). At the time of recovery, the COPA was removed, i.e. , 20 min after its insertion. The patient immediately reported numbness of the entire tongue. Neurologic examination showed decreases in temperature and in response to light touch and pin prick in the presulcal and postsulcal parts of the tongue, indicating lingual and glossopharyngeal nerve injury. There was neither a motor function deficit nor intraoral trauma. The symptoms resolved spontaneously within 2 h after the operation.
This uncommon complication of the lingual nerve previously described with a laryngeal mask airway is not surprising. 1,2,4,6Anesthetic airway management with both laryngeal mask airway and COPA uses pharyngeal cuff inflation, which causes an increase of oropharyngeal soft tissue pressure. Excessive pressure exerted against the oropharyngeal mucosa could explain the injury of superficial nerves, such as the lingual nerve and the lingual branch of the glossopharyngeal nerve. Over the styloglossus muscle, these nerves are close to each other and can be injured simultaneously. 9,10In the case we report, the 8 ml air added into the cuff of the COPA overinflated the cuff by 25% of the maximum volume recommended by the manufacturer (COPA size 9, 30 ml), and was probably the cause of excessive pressure exerted against the oropharyngeal mucosa. With an 11-cm COPA, Brimacombe et al. 11recently showed that even with an inflated volume according to the recommendation of the manufacturer, pharyngeal mucosal perfusion is decreased and decreases further with additional volume. Moreover, nitrous oxide, even used during a brief period, could increase the cuff pressure further. A 30-min exposure to 66% N2O in oxygen induces a 30-mmHg mean increase in laryngeal mask airway cuff pressure. 12
In conclusion, this case shows the natural course of lingual nerve injury after misuse of the COPA, which is typical of acute compression because of its brief duration and subsequent resolution. The fact remains that the COPA inflated cuff volume recommendation must be followed. In case of air leakage, a change to a larger-sized COPA is probably better than a moderate overinflation of the cuff.
*Hopital Bretonneau, Tours, France. firstname.lastname@example.org