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Sacks MD, Marsh D. Paediatric Anaesthesia 2000; 10:435-37.

Review: A 4-year old boy underwent a lower-extremity orthopedic procedure under general anesthesia supplemented by a caudal epidural block. Following induction of anesthesia, a size 2 LMA was inserted, and the LMA cuff was inflated with 7 ml of air. Anesthesia was maintained with isoflurane and nitrous oxide. At the conclusion of the 90-minute procedure, the LMA was removed prior to emergence. Marked inspiratory stridor developed during emergence and was unresponsive to positive pressure or racemic epinephrine. Microlaryngobronchoscopy confirmed poor abduction of the vocal cords, and persistent stridor necessitated tracheal intubation. The following day the trachea was extubated without further problems. The patient's transient stridor was attributed to bilateral recurrent laryngeal nerve neuropraxia, resulting from nerve compression by the LMA.

Comments: Although a relatively rare complication, neuropraxia has been observed in adults managed with an LMA. This is the first case report involving a child. Other reports attributed neuorpraxia to nerve compression by an overinflated or malpositioned LMA cuff. Diffusion of nitrous oxide into the LMA cuff may contribute to cuff overinflation and excessive pressure on the surrounding tissue. The LMA Instruction Manual warns against cuff overinflation and recommends monitoring intracuff pressure. Other techniques, e.g., inflating the cuff with the inspired anesthetic gas mixture or periodically deflating the cuff to the minimum effective volume, have been suggested. The LMA is used widely in pediatric anesthesia practice. This report describes a rare but serious complication and discusses techniques to avoid it.

Reviewed by: John T. Algren, MD
Vanderbilt Children's Hospital, Nashville, TN