Saturday, February 18, 2012

Intubation and Mis-en-place.

Back when I was a paramedic-wannabe, one of the experienced medics showed me his elaborate way of arranging his equipment at the start of the shift, including where he placed pre-torn pieces of tape, ready at a moment's notice to secure an IV line. He called this process "tape karma." It was a catchy phrase, and I respected his ritualistic attention to preparation.

In a similar way, line cooks in restaurants prepare for the chaos of a Saturday evening rush by meticulously preparing their station. The arrangement, known as mis-en-place (Roland can help you out with pronunciation!), is personal and exact; ingredients collected, utensils readied, and stations cleaned. As per Anthony Bourdain:
What exactly is this mystical mise-en-place I keep going on about? Why are some line cooks driven to apoplexy at the pinching of even a few grains of salt, a pinch of parsley? Because it’s ours. Because we set it up the way we want it. Because it’s like our knives, about which you hear the comment: ‘Don’t touch my [duck], don’t touch my knife."
Someone messed with the mis. (Thanks Evan!)
If line cooks are going to be fanatical about how they prepare your duck a l'orange, perhaps you should develop your own airway mis-en place. That is, a systematic preparation for each intubation attempt that is ritualistic and practiced.

I submit that these 5 items should form the core of your "airway mis." Add or substitute as you see fit, but regardless, get your mis in gear!
If you let your mise-en-place run down, get dirty and disorganized, you’ll quickly find yourself spinning in place and calling for backup. I worked with a chef who used to step behind the line to a dirty cook’s station in the middle of a rush to explain why the offending cook was falling behind. He’d press his palm down on the cutting board, which was littered with peppercorns, spattered sauce, bits of parsley, bread crumbs and the usual flotsam and jetsam that accumulates quickly on a station if not constantly wiped away with a moist side towel. “You see this?” he’d inquire, raising his palm so that the cook could see the bits of dirt and scraps sticking to his chef’s palm. “That’s what the inside of your head looks like now.”

1. Head elevation:
This simple maneuver is frequently skipped, but can really improve visualization of the larynx. In a person of normal habitus, place enough padding (folded towels or sheets) under the occiput to elevate the head 7 cm off the bed. There are a few ways to explain this, but the best is empiric - it is proven to improve the glottic view. In Levitan 2003, the authors compared the laryngoscopic view with the patient laying flat, with the head up by 7cm, and somewhere in the middle.


The amount of the glottis that could be seen went from about 30% when laying flat, to 80% with head elevation. Now, you can't do this with the trauma patients, but in the medical patients, you're wasting time and left arm strength if you don't grab a folded sheet to shove under the head.

"And teal arrows! Grab me 3 or 4 teal arrows!

2. Ramping:
Now, a little folded towel isn't gonna help you when you're about to intubate this:


Because of all the excess tissue in her lower back, her neck and chest have about the same geometric relationship when she is supine as this lady does...


... in her fancy yoga pose. The red triangle schematically represents adipose, demonstrating how the neck gets flexed in obese patients. You need to get these folks "uncrunched" before you get your laryngoscope ready. You need to ramp them!

The idea is that you create a triangular wedge that elevates the upper back and shoulders off the bed. Once you have corrected the neck-chest relationship, you also have to ensure that you have head elevation as well. In practice it looks like this:


Note how the external ear meatus is level with the sternal notch - this relationship is key to creating good intubating conditions. With significant obesity, a good deal of effort may have to be made to achieve this alignment:


That's a lot of laundry. But, if you've ever skipped this part in an obese patient, and found it difficult to even get the laryngoscope blade in the mouth because the handle was getting caught up on the chest, you'll recognize the wisdom of this approach immediately.

3. Tube & Stylet Shaping:
This only applies to direct laryngoscopy - using the Glidescope requires modification!

The odd thing about medicine is that there can be so little evidence in some areas (hypertensive urgency, anyone?), while there is plenty in other areas, such as how to shape the ET tube and stylet.

There are a number of reasons that an ET tube that is bent in a "hockey stick" form (straight down to the cuff, then bent upwards) improves visualization and placement. There is some variation, however, with how much bend is required. Levitan and pals intubated a few cadavers, using ET tubes and stylets bent into a "hockey stick" shape with angles ranging from 25° to 60°. 


What they found was that an angle sharper than 35° increased the difficulty of tube passage significantly - at 60°, over half of the ET passage attempts were rated "impossible!"


4. Cricoid pressure is misunderstood:


Simply put:

Cricoid pressure ≠ BURP maneuver ≠ Laryngeal manipulation

The two cartilaginous structures are structurally distinct, are attached to surrounding anatomy in different ways, and respond to manipulation in distinct manners.
  • Cricoid pressure, in which the cricoid cartilage is displayed posteriorly, is not mean to aid visualization, but to prevent passive regurgitation during RSI.
  • The Backwards-Upwards-Rightwards-Pressure (BURP) maneuver employs manipulation of the laryngeal cartilage. It is performed by an unguided assistant, and is intended to improve visualization.
  • External laryngeal manipulation (of the laryngeal cartilage) is performed by the laryngoscopist with their free right hand, also to improve the view.
Most importantly, cricoid pressure may be very difficult to apply correctly, and do little to prevent aspiration even when done perfectly. Furthermore, it may worsen the chances of successful intubation. In a review of the risks and benefits of the cricoid pressure (or Sellick's maneuver),  Ellis and Harris reviewed a mountain of literature. This an essential paper for every EM physician, and I'll email a PDF to anyone who wants it. They found that:
  • "Recent anatomic investigations on live patients undermine the conclusions of initial cadaver studies validating the technique."
  • "Cricoid pressure consistently reduces tidal volume and increases peak inspiratory pressures when applied during bag-valve-mask ventilation, and even controlled, well applied cricoid pressure can adversely effect ventilation and cause airway obstruction."
  • "There is solid evidence that cricoid pressure is applied inconsistently in all intubating environments. Indeed, if we are not able to perform it as recommended (ie, without excessive force at the correct location) whether or not it is a useful technique becomes a secondary argument."
They conclude that:
Given that the risks of cricoid pressure worsening laryngeal view and reducing airway patency have been well described, we recommend that the removal of cricoid pressure be an immediate consideration if there is any difficulty either intubating or ventilating the ED patient.
While that review was based on a systematic review of the literature, the same authors then conducted a study of their own, looking at the benefit of switching between cricoid and laryngeal maneuvers during intubation attempts. One table well-summarizes their findings:

CP = cricoid pressure, BLM = external (bimanual) laryngeal manipulation
So, know the differences in these maneuvers, how and when to best apply them, and understand when to switch between them!

5. Pull the Cheek:
So you're almost there - you see the cords, the #8 is in your right and your attending is shouting "What do you see?" in your ear. As you start to send it home, though, the mouth starts looking a bit crowded, and you lose sight of the precious cords. What to do?

Put your attending to work - ask them to pull the right cheek to the side, creating more room to visualize and place the tube.

I tell ya', it's like finding $10 in your just-washed scrubs - free money!

4 comments:

  1. Love it! On my list I add a nasal cannula for apneic oxygenation on everyone.

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    1. I just read the Weingart paper, and it really is a great resource - another essential EM paper! Here, I just wanted to limit the topics to those central to the act of placing the tube, preparing for success on the first attempt.

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  2. http://sinaiem.org/files/conference_docs/lectures/Levitan.mp4

    awesome Levitan lecture from Sinai EM

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    1. Cool!

      I'll admit it - this post consisted of just taking a bunch of Levitan's stuff, and adding some pictures I got off of Google image.

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