Interesting Airway Scenario

Carlos Danger

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Quite a bit has been written in the anesthesia literature about the unreliability of the Mallampati score as an indicator of the difficulty of intubation, and I had an interesting airway situation in the OR yesterday that illustrated it perfectly.

A 36 year old healthy male was coming in for vocal cord injections by ENT. These are cool cases because we'll (anesthesia) put the patient to sleep and then without securing the airway, turn the OR table so that the ENT surgeon has the airway. They'll place a rigid scope so that they can visualize the glottis, and the scope provides a channel for them to work through and for us to jet ventilate through. Usually we'll keep the patient relaxed with a sux drip, which is always fun.

I always look these patients up the day before because often they have complicated histories, and often they've been here before for these procedures and it can be very helpful to see how they were done previously. When I found this guys chart, I saw he had NOT had this procedure done before. He was 85kg and healthy. I did see that he'd had a hemithyroidectomy about a year and a half ago. Purely out of curiosity I decided to see if I could access his anesthesia record from that case (I should do that commonly, but I often don't). According to the anesthesia record, the patient was classified as a MP1 prior to induction, yet the CRNA had been unable to visualize the cords via DL and had only a grade 3 view with VL. Interesting, I thought. Probably was just a lazy MP evaluation and his airway was obscured by a goiter (hence needing the thyroid removal), which is gone now, so he'll be easy.

So I go see the patient in pre-op. Sure enough, he looks healthy and normal. MP is, in fact, a 1. He does have a slightly short TMD but not dramatic. Able to bite his upper lip, good neck and jaw ROM. He also has a short beard but nothing that will make him hard to mask. I did decide to have VL in the room, though I did not expect to need it.

So now we are in the OR. Put the monitors on, pre-oxygenate, start the propofol drip + give him a bolus of propofol, and mask him. First, he's hard to mask. Not real hard, but harder than I expected. Start the sux drip and give a bolus of sux. Still hard. Hmm. Oh well. Turn the table, now I'm masking him from below and he's still hard to hold a seal on, though I am getting good air exchange. Remove the mask so ENT can instrument the airway.....and they can't visualize the glottis. It took almost 15 minutes of them re-positioning their scope and eventually going down 2 sizes before they could get a decent view. Almost unheard of in a healthy, normal-looking patient for ENT to have such trouble. He jetted fine and the rest of the procedure was uneventful.

This is not the first time I've been surprised at the difficulty of DL on a given patient, but certainly it was the first time that the degree of difficulty was so dramatically different from what I expected. This was a young, healthy guy with perfectly normal-looking anatomy, who would have presented a real problem to me if I'd ever had to RSI him in the field.

Moral of the story: place very little faith in your assessment of airway difficulty. The assessments are still worth doing, because they are quick and easy and can alert you to obvious issues. But they are very insensitive tests....never ever assume an airway will not be difficult just because the patient "looks fine".
 

Aprz

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If there was a like button, I'd click it. I am about to go to sleep now so I didn't research much about the reliability of Mallampati. I have never thought about the reliability of it before! First, I found something that said it's more reliable when the patient is supine? Maybe that's the issue? And I didn't find anything about the actual reliability/sensitivity of the Mallampati for bad airways, but I only tried Googling for like 1-2 minutes so no serious Google-fu. The case you are describing n=1. In your experience, have you found it to be unreliable for determining easy or difficulty airways to make you say that it's very insensitive and to place little faith in it? Perhaps the real take away is that it isn't a perfect assessment?
 
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Carlos Danger

Carlos Danger

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If there was a like button, I'd click it. I am about to go to sleep now so I didn't research much about the reliability of Mallampati. I have never thought about the reliability of it before! First, I found something that said it's more reliable when the patient is supine? Maybe that's the issue? And I didn't find anything about the actual reliability/sensitivity of the Mallampati for bad airways, but I only tried Googling for like 1-2 minutes so no serious Google-fu. The case you are describing n=1. In your experience, have you found it to be unreliable for determining easy or difficulty airways to make you say that it's very insensitive and to place little faith in it? Perhaps the real take away is that it isn't a perfect assessment?

The MP test should actually be done with the patient sitting upright, not supine.

It's not just my experience at issue; there has been a fair amount of research on this and the literature is pretty clear that the MP test is unreliable on it's own. You can get a fair amount of accuracy by combining the the MP test with several other indicators, like jaw protrusion, TMD, HMD, and neck mobility, but none of those by themselves tell you much at all.
 

Handsome Robb

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I'm a MP1 and needed VL for my tube during my surgery because of my ROM in my neck or lack thereof.

Great post.
 

Smash

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Nice. Is there a reason for using a sux drip rather than say roc with a suggamadex chaser? Just curious (edit: aside from the cost of suggamadex)
 
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Carlos Danger

Carlos Danger

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Is there a reason for using a sux drip rather than say roc with a suggamadex chaser?

Good question.

Suggamadex unfortunately still isn't available in the US.....:cool:

Sux drips work really well for these cases because they are on very quickly, give a very dense block, then are off very quickly without having to deal with the hassle and side effects of a typical reversal cocktail. Plus, sux is dirt cheap.

For peds, we often do use roc. It's a little harder to use though, because you have to give a big enough dose to have a dense block at the vocal cords, but these are short cases so you can't give too much, because you can't safely reverse a depolarizer until it is starting to wear off, and the bigger the dose (to get the dense block), the longer it takes to start to wear off. And then you have to deal with the timing and side effects of reversal. And roc is still relatively expensive here.

When suggamadex eventually becomes available here, it will probably only be used for emergencies where sux is contraindicated, because it's gonna cost an arm and a leg. It almost certainly won't be used routinely in the OR.
 

wanderingmedic

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Remi, thanks for the post. Fascinating stuff.

If you had been a medic in the field, and had chosen to RSI this pt, it does not sound like you could have ever gotten the tube. What do you think you would have done to manage this pt's airway prehospital? How well do you think a supraglottic airway would have worked?

On another note, how do cases like this make you feel about prehospital RSI?

Thanks!
 

CANMAN

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Cool scenario thanks for the post. For our quaterly O.R. time we often rotate through the ENT room and to see some of the cases is quite interesting.
 
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Carlos Danger

Carlos Danger

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I'm glad you guys like the scenario. I wasn't sure how many people would appreciate the relevance of it to EMS.
 
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Carlos Danger

Carlos Danger

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If you had been a medic in the field, and had chosen to RSI this pt, it does not sound like you could have ever gotten the tube. What do you think you would have done to manage this pt's airway prehospital? How well do you think a supraglottic airway would have worked?

On another note, how do cases like this make you feel about prehospital RSI?

That is a great question. The answer is simple, though: BVM --> LMA

An LMA would likely have worked fine in this guy; if ENT had decided to abort their procedure I would have slid an LMA in and ventilated him through that until he woke up. LMA's often don't work great, but I've never seen one not work at all.

The biggest, most important thing that I've learned thus far in my anesthesia training that relates directly to prehospital is the critical importance of being really good at mask ventilation. Everything always comes back to that. If you can mask ventilate well, you can pretty safely paralyze almost anybody, because whether or not you are able to place a tube or LMA quickly becomes much less critical. On the other hand, if you aren't good at mask ventilation, you can't safely paralyze anyone. It really is the key to whether you are a safe and effective airway manager.

As far as RSI in the field, I do not support it as a routine paramedic intervention, both because it is a risky procedure that generally isn't necessary (the research shows us that it improves outcomes only in very select cases, and even then not by much), and because we simply aren't very good at airway management in the field (the research tells us that, too). However, there are obviously exceptions to that. Most HEMS/CCT and some ground EMS agencies do a solid job.
 

jwk

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The MP test should actually be done with the patient sitting upright, not supine.

It's not just my experience at issue; there has been a fair amount of research on this and the literature is pretty clear that the MP test is unreliable on it's own. You can get a fair amount of accuracy by combining the the MP test with several other indicators, like jaw protrusion, TMD, HMD, and neck mobility, but none of those by themselves tell you much at all.

MP score can really only be done on an awake and responsive patient as well, although I can generally look at a patient and make a good guess. That being said, I am always surprised at airways that I think will be difficult and end up being easy, and airways that would appear to be easy that are a total pain to deal with. I had my first truly difficult GlideScope intubation just this past week, although this was a guy that I expected to be difficult, and he didn't disappoint. On top of that, he had to be a nasal tube to accommodate the surgeon, so that made it that much more fun.

Remi is right about dropping back to an LMA or other supra-glottic airway device when an ETT is difficult. You can't put blinders on and tell yourself you've GOT to get an ETT in place. The only thing you've GOT to do is ventilate your patient, by whatever means.

The only downside to LMA's, and particularly LMA's for anesthesia, is that mask airways are truly becoming a lost art. A lot of people think they can mask someone, and they can't. I see it all the time when I go to codes on the floor and respiratory "thinks" they're bagging the patient adequately. I did anesthesia for 15 years before LMA's came out, so I can mask almost anyone because I had to way back when. Now at the first sign of difficulty, an LMA goes in. I used to do lots of cases with a mask, but because LMA's are so easy, that's become totally passe' at this point.
 
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Carlos Danger

Carlos Danger

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MP score can really only be done on an awake and responsive patient as well, although I can generally look at a patient and make a good guess.

Great point. Many or most of those who need to be intubated prehospitally won't be able to sit upright and cooperate with an MP exam anyway.
 

NomadicMedic

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Great point. Many or most of those who need to be intubated prehospitally won't be able to sit upright and cooperate with an MP exam anyway.


Yet we are still required to do a LEMONS and BONES assessment on every intubation. I'm very surprised that there hasn't been a new difficult intubation predictor set built for prehospital use.

The paradigm shifting rapidly hhowever. And in our service, I predict as video laryngoscopy is rolled out at the end of the summer, the standard will change to "two attempts with VL, if unsuccessful move to a supraglottic airway." End of story.
 

Merck

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"two attempts with VL, if unsuccessful move to a supraglottic airway." End of story.

That would be an unfortunate protocol. I only say this because I'm generally against any protocol that requires a strict approach to a dynamic situation. VL is great in patients for whom VL is great. But don't underestimate good ole fashioned DL. Visualization is easier with VL in general, but placement can be trickier that with a direct line of sight afforded by DL.

To speak to the initial post, the case is interesting and highlights that assessments are never 100% - a fact that increases with the stress of a situation. However, they are still very valid, even if they only serve to get people to pause and actually consider their approach and back up plans rather than just grab a laryngoscope and tube and go for it (which is common...)
 
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Carlos Danger

Carlos Danger

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I predict as video laryngoscopy is rolled out at the end of the summer, the standard will change to "two attempts with VL, if unsuccessful move to a supraglottic airway." End of story.

Honestly, I think that'd be a good guideline. Not perfect, but good.

I really think we should view SGA's as appropriate management in many more cases than we traditionally have.
 
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