May 072017

Video laryngoscopy provides beautiful close-up views of the larynx, by navigating a sensor past the tongue and pharyngeal tissues that can obstruct direct laryngoscopy views. These visual advantages led to its wide adoption by anesthesiologists, emergency physicians, and intensivists after video laryngoscopy's introduction in the late 1990s.

The intuition that better visualization must result in improved intubation rates -- and some evidence suggesting this was so -- led to inclusion of video laryngoscopy in the American Society of Anesthesiologists' 2013 difficult airway algorithm. For example, in a small randomized trial of 153 patients at one academic center, use of a GlideScope improved first pass intubation rates substantially (74% vs 40%), without an increase in complications.

But others noted that video laryngoscopic intubations seemed to take longer, with the patients becoming seriously hypoxemic or possibly dying more often, compared to direct laryngoscopy. A randomized trial in JAMA adds to those worries.

Authors randomized 371 adults at 7 French academic centers to undergo urgent intubation by either video or direct laryngoscopy with a Mac blade. All patients were preoxygenated and induced according to a protocol which included neuromuscular blockers. The primary outcome was successful intubation on the first attempt (confirmed by capnography).

There was no significant difference between groups in success of first-pass intubation (68% for video, 70% for direct laryngoscopy), nor in time to intubation (median 3 minutes in both groups).

However, severe life-threatening complications (e.g., cardiac arrest, severe hypoxemia) occurred in almost 1 in 10 of the patients intubated by video laryngoscopy, vs. 1 in 35 of direct laryngoscopy patients (9.5% vs 2.8%, P=.01). This was not a pre-specified analysis.

The vast majority of patients (>80%) were intubated by supervised trainees, who had a low experience level with either video or direct laryngoscopy. They used the McGrath MAC video laryngoscope (Medtronic) exclusively, without a stylet in the ET tube.

Any concerns arising from the MACMAN trial may not be widely applicable in the U.S., where the vast majority of patients undergoing urgent endotracheal intubation are intubated not by supervised trainees, but by pulmonologist-intensivists or anesthesiologists practicing in non-academic hospitals.

The trial's exclusive use of the McGrath MAC video laryngoscope means its results can't necessarily be applied to other video laryngoscopes (GlideScope, et al). The McGrath device was partly chosen here because of its lower expense; GlideScope's larger video screen provides clearer views of the glottis.

Might clearer views with video laryngoscopy paradoxically increase risk? Some experts theorize that physicians become entranced by the beautiful images on the video laryngoscope screen, are falsely reassured of safety, take longer in completing an intubation pass than with urgent direct laryngoscopy, and get into trouble more often. While median intubation times were equal between video and direct laryngoscopy in MACMAN, the greater proportion of patients experiencing severe hypoxemia during video laryngoscopy lends some credence to this concern.

Another single-academic-center study showed no difference in intubation success between video and direct laryngoscopy among 150 patients, despite better views with video.

Broad conclusions about video laryngoscopy based on MACMAN seem unjustified, because of the variability between the McGrath and other available video laryngoscopes, and the study's use of inexperienced operators (albeit supervised).

One piece of advice seems prudent during video laryngoscopy: limit to the barest minimum the apneic time between epochs of bag-mask ventilation, no matter how pretty the view on the screen.

Read more:

Video Laryngoscopy vs Direct Laryngoscopy on Successful First-Pass Orotracheal Intubation Among ICU Patients. A Randomized Clinical Trial. JAMA. 2017;317(5):483-493.

Video Laryngoscopy in the Intensive Care Unit. Seeing Is Believing, But That Does Not Mean It’s True (Editorial).

Effect of video laryngoscopy on trauma patient survival: a randomized controlled trial. J Trauma Acute Care Surg. 2013 Aug;75(2):212-9.

A comparison of GlideScope video laryngoscopy versus direct laryngoscopy intubation in the emergency department. Acad Emerg Med. 2009 Sep;16(9):866-71.

Comparison of video laryngoscopy versus direct laryngoscopy during urgent endotracheal intubation: a randomized controlled trial.  Crit Care Med. 2015 Mar;43(3):636-41.

Randomized Trial of Video Laryngoscopy for Endotracheal Intubation of Critically Ill Adults. Crit Care Med. 2016 Nov;44(11):1980-1987.

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Video laryngoscopy was no better than directly intubating in the ICU, and may have been worse (MACMAN)