There’s no finesse to putting in a laryngeal mask, right? You just throw it in and it doesn’t matter what it is, yes? Maybe no. A quick look through things supraglottic with Andrew Weatherall.
Supraglottic airways are the one bit of airway management that’s a free pass, right? No skill required, do it with your eyes closed and hanging upside down I bet.
Well it’s true that these incredibly useful bits of kit are very forgiving. In fact when you go and look at papers assessing the rates of weird positioning of laryngeal masks or other devices you sort of start to realise you’ve been relying on a bit of good fortune a lot of the time when it just works out.
There is actually some finesse that can get you there more reliably and achieve better results though. Even enough to chew up a whole post on.
Well yes, why now? Why have a look at this point? Well an interesting paper just hit Anaesthesia which attempts to come up with the answer on just what is the best paediatric supraglottic device.
It’s interesting in part because it uses a review methodology called network meta-analysis (or mixed treatment comparison) which aims to combine both papers that directly compare devices against each other and the indirect comparisons (so that you can compare the devices even when they weren’t measured against each other in the original individual papers). If you want more the accompanying editorial is worth a look.
Now when I hear descriptions of a stats technique like that there is a bit of me that becomes the guy standing at the edge of the magic show with my arms muttering about trickery. At the same time they describe a transparent attempt to wrestle with one of the enduring problems in paeds airway research – there just aren’t that many papers and the ones there are don’t have that many numbers.
So let’s give them a listening because I bet the stats bit was actually really tricky and they published a thing that looks like a 2D version of a sculpture I tried to make in design once.
Which one should you choose then?
Well this particular review found a few things:
- The i-gel and Proseal laryngeal mask airway (PLMA) showed better oropharyngeal leak pressures than the LMA Classic. This is perhaps not surprising.
- They found a much higher risk of device failure with the i-gel compared to things in common clinical use (like the LMA Classic, LMA Unique and LMA Proseal). As in the former ones had failure rates of 0.36%, 0.49% and 0.5% and the i-gel came in at 3.4%.
- Failure at first attempt was highest in those under 10 kg.
- The i-gel looks like it had less blood staining than the others.
Now you might notice that there are only a few names there. This is mostly due to some devices not being in studies deemed good enough to allow comparisons despite 16 devices in total being covered (the Ambu AuraGain didn’t make it to the oropharyngeal leak pressure analysis or the first insertion success/failure look for example).
So they plump on the Proseal mostly on the basis of that device failure (and given they quote 2.5% as the rate of device failure you need to get below, that makes sense).
But does that quite get you to the choice for you? Well the accompanying editorial has a go at getting that sorted too. They suggest that although the first pass failure rates aren’t encouraging with 2nd generation supraglottic airways, as they offer gastric drainage, better seals and are better conduits for intubation you should still go with these.
For most of us, that’s not the important stuff
The thing is a lot of us don’t get much say over which devices we choose. That’s particularly the case if you’re a trainee or practitioner working in multiple spots. Sometimes even when you might have more say some realities just come into play. I get to work in a big hospital in a wealthy country and choosing an i-gel as the routine supraglottic airway option isn’t something we can contemplate.
The thing I’d really like is a list of the techniques that make it more likely I’ll have success placing that SGA and preferably for pretty much every device. So I’m making one. It might not have everything but it’s at least a start for people to look at and maybe improve on.
1. Get the depth right
Well I didn’t say these suggestions were going to be earth shattering just practical. Depth of anaesthesia at insertion matters. At least it matters if you’re not using muscle relaxation. So take a combination of the agent you’ve chosen, give it the time to work and then do a check with a serious jaw thrust. If they don’t respond to that, you’re probably safe to move on.
2. More jaw thrust
So much of the paediatric airway is about managing the tongue. This goes for these devices too and jaw thrust helps clear that tongue. Proper jaw thrust creating that true Neanderthal biting look make a huge difference to success of insertion.
3. Pump that cuff
OK this one applies to those that aren’t auto-pressured (like the Classics as an example). There is some evidence that partial inflation (rather than the initially suggested deflation with the tip in a particular orientation) results in faster success rates. For 2nd generation devices this isn’t so much the issue obviously (particularly for the i-gel you might have guessed.
4. Use that palate
Remembering the aim is to get past the tongue then staying along the palate is an obvious way to make that work out. This one turns up in descriptions of the best approach for putting in all sorts of devices including the Classic, Proseal and i-gel. It’s almost like it might work. For the Proseal there isn’t much
5. Introduce a twist
A twist is another move that can help. Ghai and crew explored this with the Classic previously and found that inserting the LMA initially upside down (with the ventilating side facing the hard palate) resulted in higher first-time insertion success. If you consider the profile presenting itself to get past that tongue again I guess that makes sense. This was by comparison to inserting the device in a lateral orientation and lateral performed better than the standard orientation.
The full rotation might be tough with some of the more rigid or preformed devices, but lateral remains an option for these. Definitely one to keep up the sleeve.
6. Manage the cuff pressure
For devices where you have an inflation step, the “until it pops forward” end point seems to result in pressures higher than you need. Actually monitoring the pressure is worthwhile, particularly as mid-range pressures (40-55 cmH2O) actually seem to result in a better oropharyngeal seal.
7. Check it’s in a good spot
This is always easiest if the patient is spontaneously ventilating so you can clinically assess the effort of breathing and listen for evidence of obstruction. Further check of ventilation pressures and seal are also par for the course and worth doing again if you have to transfer the patient or reposition.
8. Tape it in
I am a little surprised I’m mentioning this but a couple of papers mentioned this as a novelty item. I’m surprised because I’ve never seen someone not secure the supraglottic airway with tape. However it clearly doesn’t happen and at least one paper on i-gels pointed out that without the tape they found issues with the i-gel slowly coming out of the mouth.
So tape it. Of course you need to tape to hold without stretching the tape to the skin because this will produce rotational torque on the LMA. Torque = twisting = slow loss of position = that annoying device that just won’t sit right. So lay it on and gently form onto the device.
9. Watch that head position
I actually didn’t find much in the literature specifically covering this, bar one paper suggesting the seal with a Proseal actually improved when rotating the head for myringotomy.
So 9? There were 9 things to mention for supraglottic airway placement?
And that’s probably not even a full list. It’s almost like there are ways to do the basic things better. Including all the ones I probably missed.
You should definitely check out the reading stuff here because the source literature always has a wealth of good stuff.
You could also consider adding tips. Tips are good. That’s what the comments are for.
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That image is available for use at unsplash.com and was posted by Daniele Levis Pelusi.
Let’s kick off with one of the things that
That big review is this one:
And the editorial is this one:
Here’s something on cuff inflation to get it in:
And here’s a few on ideal cuff pressure:
Choi K-W, Lee J-R, Oh J-T, Kim DW. The randomised crossover comparison of airway sealing with the laryngeal mask airway Supreme at three different intracuff pressures in children. Pediatr Anesth. 2014;24:1080-7.
That twisting one is here:
And here’s a few on the i-gel in paeds:
Beylacq L, Bordes M, Semjen F, Cros A-M. The i-gel, a single-use supraglottic airway device with a non-inflatable cuff and an oesophageal vent: an observational study in children. Acta Anaesthesia Scand. 2009;53:376-9.
Theiler LG, Kleine-Brueggeney M, Luepold B, et al. Performance of the Pediatric-sized i-gel Compared with the Ambu AuraOnce Laryngeal Mask in Anesthetized and Ventilated Children. Anesthesiol. 2011;115:102-110.
And a few on the ProSeal:
Did you get this far? Then maybe you’d like to enjoy this pedestrian crossing. Seriously, check it out.