title: Predictors and clinical outcomes from failed Laryngeal Mask Airway Unique™: a study of 15,795 patients.
abstract: BACKGROUND
  Although the estimated risk of life-threatening adverse respiratory events during supraglottic airway device use is rare, the reported rate of events leading to failure of the airway device is 0.2-8%. Little is known about the risk-adjusted prediction of Laryngeal Mask Airway failure requiring rescue tracheal intubation and its impact on patient outcomes.
  
  
  METHODS
  All adult patients in whom a laryngeal mask airway (LMA Unique™, uLMA™; LMA North America, Inc., San Diego, CA) was used in ambulatory and nonambulatory anesthesia settings were included. The primary outcome was uLMA™ failure, defined as an airway event requiring uLMA™ removal and tracheal intubation. The secondary outcomes were the incidence of difficult mask ventilation and unplanned hospital admissions.
  
  
  RESULTS
  Of the 15,795 cases included in our study, 170 (1.1%) experienced the primary outcome of uLMA™ failure. More than 60% of patients with uLMA™ failure experienced significant hypoxia, hypercapnia, or airway obstruction, whereas 42% presented with inadequate ventilation related to leak. Four independent risk factors for failed uLMA™ were identified: surgical table rotation, male sex, poor dentition, and increased body mass index. A 3-fold increased incidence of difficult mask ventilation was observed in patients with uLMA™ failure. Among outpatients with uLMA™ failure, 13.7% had unplanned hospital admission, 5.6% of whom needed intensive care for persistent hypoxemia.
  
  
  CONCLUSIONS
  The study supports the use of the uLMA™ as an effective supraglottic airway device with a relatively low failure rate. However, there are clinically relevant consequences of uLMA™ failure, as evidenced by the high rate of acute respiratory events and need for unplanned hospital admissions.
authors.affiliation: Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA. rsatyak@med.umich.edu
authors.forename: Satya Krishna
authors.initials: SK
authors.lastname: Ramachandran
authors.forename: Michael R
authors.initials: MR
authors.lastname: Mathis
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Tremper
authors.forename: Amy M
authors.initials: AM
authors.lastname: Shanks
authors.forename: Sachin
authors.initials: S
authors.lastname: Kheterpal
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000556:Ambulatory Surgical Procedures; D015992:Body Mass Index; D016208:Databases, Factual; D005260:Female; D005544:Forecasting; D006801:Humans; D007442:Intubation, Intratracheal; D017214:Laryngeal Masks / Q000009:adverse effects*; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D019990:Perioperative Care; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects; D017211:Treatment Failure; D016896:Treatment Outcome