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Mac 3 or Mac 4 for Intubation? | MacSize-ICU Results Surprising

September 8, 2022

Written by Aaron Lacy

Spoon Feed
There was an association with increased first attempt intubation success during direct laryngoscopy when using a Macintosh 3 laryngoscope blade compared to a Macintosh 4 blade.

Why does this matter?
We spend a lot of time researching, discussing, and Spoon-Feedin’ how we can optimize success during intubation. Bougies, Intubating LMAs, Video Laryngoscopy, and more are all fancy devices we can employ to help us succeed. But what if something as simple as laryngoscope blade size changed outcomes?

3 before 4?
This was a retrospective analysis of 2,139 intubations that occurred in French ICUs looking at outcomes of patients intubated via direct laryngoscopy with either a Macintosh blade 3 (n=629) or Mac 4 (n=1,510). The incidence of first-pass intubation after first DL attempt was significantly higher in the Mac 3 group (79.5% vs 72.3%, p = 0.0025). There were no reported adverse events or differences in Cormack-Lehane scores (p=0.48).

The authors also accounted for patient size (height) when analyzing the results. If the patient size and view was the same between groups, what explains the difference? The authors hypothesize that the longer blade length of a Mac 4 may make deft adjustments more difficult, and a wider blade might make tube delivery more difficult.

I was taught (and have blindly now repeated to residents) that it is better to start with a Mac 4 as you always can ‘back out’ to adjust your view but cannot magically make the Mac 3 blade longer if it’s not big enough. This was retrospective and only studied DL (vs VL), so it shouldn’t be practice-changing but hypothesis-generating. No RCT is easy, but in terms of cost and equipment, this topic is just begging for a motivated group to snatch it up… :).

Impact of Macintosh blade size on endotracheal intubation success in intensive care units: a retrospective multicenter observational MacSize-ICU study. Intensive Care Med. 2022 Aug 16. doi: 10.1007/s00134-022-06832-9. Online ahead of print.

What are your thoughts?