By Alexander Niven, MD
Senior Associate Consultant, Division of Pulmonary/Critical Care Medicine, Mayo Clinic, Rochester, MN
Dr. Niven reports no financial relationships relevant to this field of study.
SYNOPSIS: In this large, multicenter, retrospective study, video laryngoscopy, the most common approach to failed airway management, demonstrated a high rate of success, even when difficult ventilation existed.
SOURCE: Aziz MF, Brambrink AM, Healy DW, et al. Success of intubation rescue techniques after failed direct laryngoscopy in adults. Anesthesiology 2016;125:656-666.
The failed airway, generally defined as clinical factors that complicate intubation or effective ventilation, is associated with significant morbidity and mortality. Current difficult airway guidelines recommend a systematic approach to airway assessment, patient and equipment preparation, and procedure planning to increase the rate of first attempt intubation success. However, the best rescue technique to manage the failed airway is less clear, and current data are limited to single center experiences, with little direct comparison between procedures.
Aziz et al wanted to determine the comparative effectiveness of five intubation rescue techniques suggested by the American Society of Anesthesiologists Difficult Airway Algorithm (video laryngoscopy, flexible fiberoptic laryngoscopy, lighted stylet, optical stylet, or supraglottic airway [SGA] as a conduit to intubation), and to test the hypothesis that video laryngoscopy (VL) was associated with a higher rate of success than other techniques.
The authors used a multicenter, retrospective, observational design made up of nine years of data from seven large U.S. tertiary care academic institutions compiled by the Multicenter Perioperative Outcomes Group. Electronic records from all adults with an unsuccessful tracheal intubation attempt using direct laryngoscopy (DL) followed by one of the five techniques of interest were included. The use of a bougie or introducer with DL was not included unless the DL attempt was abandoned. The primary outcome was the rate of successful intubation using each rescue technique. Secondary outcomes included success rates in difficult or impossible mask ventilation and associated airway complications.
A total of 1,427 cases met inclusion criteria from 346,861 electronic case records. Cases were managed by attending anesthesiologists, anesthesia residents, and certified nurse anesthetists, and most rescue intubations occurred after only one failed DL attempt (68%).
VL was the most common rescue technique (69%), followed by flexible fiberoptic intubation (11%), lighted stylet (8%), optical stylet (8%), and SGA (5%). The success rate with VL was very high (1,032 of 1,122 cases, 92% confidence interval [CI], 90-93%) and superior to all other techniques (77-78% for all methods, except 67% for optical stylet; P < 0.001 for all). Most VL cases employed a GlideScope (89%), Storz DCI or C-MAC (6%), or Bullard scope (4%), with similar high success rates (90-92%). Interestingly, VL was the preferred tool to intubate patients with difficult or impossible mask ventilation (107 of 155 cases, 69%) with equivalent success rates when compared to a SGA (88% vs. 83%; P = NS).
When VL was unsuccessful, airways were most often managed using flexible fiberoptic intubation (37.5%) or by return to DL with a bougie (18.75%). Although 52% of these airway management cases were associated with hypoxemia, difficult mask ventilation, or two failed DL attempts, only 28% had identified high-risk preoperative airway exam findings. Hypoxemia (SpO2 < 90% for more than one minute) occurred in 25% of rescue attempts, and rare pharyngeal injuries (12 cases) occurred only with the use of VL.
The authors’ conclusions support several well-documented principles associated with difficult airway management. The poor observed performance of the preoperative airway exam reminds us that anatomic findings alone are poor predictors of the difficult airway and must be combined with measures of physiologic derangement and operator experience using tools such as the MACOCHA Score to increase sensitivity in the ICU.
Aziz et al noted that operators frequently resorted to a rescue technique after only one DL attempt, and the utilization of VL in this setting tripled between 2004 and 2012. This trend reflects the growing availability of VL devices in operating rooms and ICUs and increasing familiarity with their use as both primary and rescue airway tools. As VL provides better glottic visualization over DL, it is logical that providers practiced in regular VL use would utilize this technique in high-pressure, failed airway situations with significant success.
It is important to note that the addition of a bougie to DL was employed successfully to rescue the vast majority of failed airways in another large single-institution study of urgent airway management. The decision to exclude these cases in the current analysis raises concerns that the role of VL potentially is overrepresented in this series. The small but associated incidence of pharyngeal injury with VL observed also is an important reminder that VL blades should be placed into the oropharynx under direct visualization prior to shifting attention to the video monitor.
VL was used frequently and successfully in failed airways in which ventilation is difficult, a situation in which current guidelines still recommend early SGA use to preserve oxygenation. The explanation of this surprising finding is less clear but underlines the weak evidence that supports this recommendation and the need for a prospective randomized trial to more effectively address this question.
This study demonstrates that providers are reaching for VL as a primary rescue tool for failed airways early and often as availability and facility have grown and with a high degree of success. This observation suggests that operators appropriately reach for the tools with which they are most comfortable in a crisis, but also emphasizes the need for better comparative studies to determine how best to employ the growing array of available advanced airway tools and better inform our guidelines for difficult airway management.
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