Partial airway obstruction by a pediatric laryngeal mask airway.

Abstract

To the Editor: The use of a laryngeal mask airway (LMA) for airway management is common practice, especially in pediatric anesthesia. We describe an unusual problem encountered with a LMA. A 6-year-old boy was scheduled for circumcision under general anesthesia. Before induction of anesthesia, all material was checked and judged to be in good condition. Inhalational induction (sevoflurane, nitrous oxide) and insertion of a # 2 classic LMA was uneventful using a rotational insertion technique with a deflated cuff. In the beginning, the patient was breathing spontaneously without any problems. Over time, ETCO2 increased gradually up to 12 kPa. The boy showed increasing signs of airway obstruction with jugular retractions. As a misplacement of the LMA was assumed, the device was removed; immediately after removal, airway obstruction disappeared and spontaneous ventilation was uneventful. The examination of the LMA showed a detachment of the cuff weld near the tip of the LMA (Fig. 1). This detachment lead to a deformation of the distal part of the laryngeal cuff as well as to an increased cuff volume. Because of the use of nitrous oxide, diffusion could easily increase the cuff volume over time and obstruct the airway. After this incident, all our LMAs were checked regarding this problem, and another one with a slightly detached weld was found.Figure 1.: (A) # 2 LMA with detached plastic weld; (B) intact # 2 LMA.We reported this incident to the manufacturer, Intavent Orthofix, Germany. They declared it to be a “user’s fault.” We were told that the detachment of the plastic weld was due to overblocking the LMA cuff during the sterilization process. The overblocking is supposed to be caused by remaining air or moisture in the mask, which leads to volume expansion because of high temperature and negative pressure during sterilization. Such a defect in the plastic weld may pass unnoticed when returned from sterilization and preparation for further use. It may be difficult to notice the detachment of the weld as long as the cuff of the LMA is deflated. We suggest that each LMA should be thoroughly examined just prior to its use while doing the preoperative check of the anesthetic equipment. During inflation of the cuff, the plastic weld, especially at the tip of the LMA, should be carefully checked for any possible detachment. One should keep in mind that it is also possible that an initially small detachment will grow in size, as the volume of the cuff increases with the use of nitrous oxide, and the increased forces acting on the weld could result in further detachment. These precautions could help to detect any defects that might be present and thereby avoid a major problem. B. S. von Ungern-Sternberg, MD T. O. Erb, MD Department of Anesthesia, University of Basel/Children’s Hospital, Basel, Switzerland