Effect of Laryngoscope Blade Size on First Pass Success of Tracheal Intubation in Critically Ill Adults.

Tracheal intubation (TI) is a common procedure in critical care, often performed with a Macintosh curved blade used for direct laryngoscopy (DL). Minimal evidence informs the choice between Macintosh blade sizes during TI. We hypothesized that Macintosh 4 blade would have higher first-attempt success than Macintosh 3 blade during DL.
Design: Retrospective analysis using a propensity score and inverse probability weighting of data from six prior multicenter randomized trials.
Setting and Participants: Adult patients who underwent nonelective TI at participating emergency departments and ICUs. We compared the first-pass success of TI with DL in subjects intubated with a size 4 Macintosh blade on the first TI attempt to subjects with a size 3 Macintosh blade on the first TI attempt.
Main Results: Among 979 subjects, 592 (60.5%) had TI using DL with a Macintosh blade, of whom 362 (37%) were intubated with a size 4 blade and 222 (22.7%) with a size 3 blade. We used inverse probability weighting with a propensity score for analyzing data. We found that patients intubated with a size 4 blade had a worse (higher) Cormack-Lehane grade of glottic view than patients intubated with a size 3 blade (adjusted odds ratio [aOR], 1.458; 95% CI, 1.064-2.003; p = 0.02). Patients intubated with a size 4 blade had a lower first pass success than those with a size 3 blade (71.1% vs 81.2%; aOR, 0.566; 95% CI, 0.372-0.850; p = 0.01).
Conclusions and Relevance: In critically ill adults undergoing TI using DL with a Macintosh blade, patients intubated using a size 4 blade on first attempt had a worse glottic view and a lower first pass success than patients intubated with a size 3 Macintosh blade. Further prospective studies are needed to examine the optimal approach to selecting laryngoscope blade size during TI of critically ill adults.
Competing Interests: Dr. Khan has received research funding from Eli Lilly, AstraZeneca, Regeneron pharmaceuticals, United Therapeutics, Johnson & Johnson, Dompe Pharmaceuticals, and 4D Medical, as site Principal Investigator for research enrollment, and consulting fees from Dompe Pharmaceuticals for clinical trial design. The remaining authors have disclosed that they do not have any potential conflicts of interest.
(Copyright © 2023 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the Society of Critical Care Medicine.)