THE Laryngeal Mask Airway Supreme ™ (LMA-S ™; Laryngeal Mask Company Limited, Henley-on-Thames, United Kingdom) is a single-use supraglottic airway device developed as an alternative to the reusable laryngeal mask airway ProSeal ™ (Laryngeal Mask Company). Featuring an additional drain tube to suction gastric content, the LMA-S ™ may be used as a backup device in emergency situations. Indeed, its use has been described in difficult emergency intubation1and in cardiopulmonary resuscitation.2However, even backup devices have their limitations to consider. We report an unforeseen acute airway obstruction directly caused by the LMA-S ™.
Case Report
A 62-yr-old man with a body mass index of 30.2 kg/m2was scheduled for a resection of a malignant melanoma and sentinel lymph node of the left arm under general anesthesia at the Department of Plastic Surgery at the University Hospital Bern. After preoxigenation of more than 5 min, general anesthesia was induced IV (210 mg of propofol and 0.15 mg of fentanyl) and maintained IV with propofol and remifentanil to keep bispectral index between 40 and 60. Face mask ventilation was successful, and a LMA-S ™ (size 5) was introduced easily. The LMA-S ™ was cuffed, but ventilation was not possible. This was confirmed by missing end tidal CO2, no visible thorax movement, and no end expiratory tidal volumes. Fiberoptic bronchoscopy showed that the LMA-S ™ pushed the epiglottis down, resulting in obstruction of the glottis. Fiberoptic-controlled retraction of the LMA-S ™ reversed this situation, and a partial view of the glottic opening was noted, corresponding to a grade of 2 according to a fiberscopic rating suggested by Cook3and earlier described by Kapila.4Nevertheless, ventilation was still insufficient.
Although Spo2continued to be stable between 98 and 99% for the entire time, we decided to remove the LMA-S ™ and ventilate the patient by face mask, which was easily done. We then introduced the LMA-S ™ a second time. After cuff inflation, only tidal volumes below 300 ml were achieved. Auscultation revealed expiratory and inspiratory stridor over the trachea, and ventilation worsened. Fiberoptic bronchoscopy showed severe narrowing of the laryngeal inlet with barely visible vocal cords, which was interpreted as a supraglottic laryngeal edema.
We removed the LMA-S ™ again and intubated the patient (100 mg of succinylcholin) easily (Cormack Lehane grade 1). Surprisingly, no laryngeal swelling was revealed by direct laryngoscopy. Ventilation was sufficient, and surgery was performed without further events. The patient was extubated uneventfully 15 minutes postoperatively and some 2 h and 20 min after induction of anesthesia, and he was discharged to the recovery room without any further respiratory sequels.
Discussion
Laryngeal masks are used broadly for elective and emergency airway management and are an essential part of the American and European difficult airway management algorithm.5,6Due to their wide use, noticeable complications and side effects have been reported over the last years. The most common side effects are hoarseness and dysphagia. More threatening situations like impossible ventilation with desaturation are much less common. The rare reports of airway obstruction directly triggered by the laryngeal mask are swelling of the pharyngeal soft tissues caused by the leakage of irrigation fluid,7herniation of the laryngeal mask airway cuff,8–10foreign bodies (Ascaris lumbricoides11), and intermittent obstruction related to a vagal nerve stimulator.12
Similar to our case, Chin reported a case of increased airway pressure in a ProSeal ™ laryngeal mask airway13and related it to laryngeal edema. However, in a reply by Stix et al ., this case was associated with mechanical obstruction of the laryngeal inlet by the cuff and drain tube of the ProSeal ™.14
We primarily attributed the rapidly deteriorating ventilation to soft tissue swelling and edema caused by airway manipulation and the mechanical stimulus of the LMA-S ™ pushing down the epiglottis. This thesis was not confirmed; direct laryngoscopy after removal of the LMA-S ™ showed normal laryngeal anatomy without edema. Laryngeal spasm was also excluded as an underlying cause because a propofol bolus did not improve ventilation.
We therefore attribute this case of airway obstruction to mechanical obstruction of the laryngeal inlet by the cuff as described by Stix.14The inflated LMA-S ™ cuff displaced the cuneiform and corniculate cartilages medially, thereby narrowing the laryngeal inlet as observed during fiberoptic control, obstructing ventilation substantially.
In summary, laryngeal masks are often used as backup devices for the management of possible airway difficulties, and laryngeal masks have been life-saving in daily clinical practice over the years. Supraglottic airway devices are easy to introduce, and they provide a patent airway in most cases. Nevertheless, even newly developed types of laryngeal masks (as the LMA-S ™) may be cause for the obstruction of the laryngeal inlet when the mask displaces laryngeal cartilages medially, narrowing the laryngeal inlet. This is the first report of this phenomenon of medialization in a LMA-S ™.
Because laryngeal masks are important backup devices in the management of difficult airways, this infrequent cause of a laryngeal mask failure must be made known. Strategies to handle laryngeal mask failures might be included in the algorithms for difficult airway management, and backup strategies for the “backup device” laryngeal mask should be considered.
