Fresh Air

Airway management is just a little bit different in kids. Sometimes it is tough. So wouldn’t you like more time to sort it out? Andrew Weatherall has a quick look at an exploration of THRIVE in kids.

There are plenty of challenges in paediatric anaesthesia. Little veins. Stressed parents. Plus every time you turn around there’s a new Pokémon to pretend you’re interested in.

One of the other challenges is constantly trying to extrapolate things from the adult literature to kids. Paediatrics is a niche game and all too often a new or rediscovered technique is described in adults and we’re left to try and figure out whether it makes sense for kids at all or which way to adjust it. Even if it does draw some research interest it’s often a long time down the track.

Which is why it’s pretty ace to see an Australian team publishing work relating to apnoeic oxygenation in kids. It’s about time kids got an earlier look in.

What did they do? 

The paper describes a small randomised trial on well kids (note, not the ones where you’d want it to work most) where humidified high flow nasal prong oxygen was administered after an agreed period of pre-oxygenation. They were aiming to produce the same sort of set-up as THRIVE (Transnasal Humidified Rapid-Insufflation Ventilatory Exchange). The kids were aged from 0 months up to 10 years and divided into 4 groups (0-6 months, 6-24 months, 2-5 years and 6-10 years) and if I read it right each age group had 12 total subjects (6 in each of the control group and the THRIVE group).

Once lined up and going ahead the kids underwent induction of anaesthesia then a period of pre oxygenation then either they lost the mask and got nothing (I’d insert a GIF of the Gene Wilder version of Willy Wonka saying “You get nothing” but I honestly don’t know how) or they got THRIVE. That’s the bit where the stopwatch started.

So… what’s the punchline? 

The punchline is typically the bit at the end of the joke designed to make you lau… oh, you mean in this research.

The apnoea time was longer. Quite a bit longer.

And that was the end of this post and everyone should do this forever and ever amen.

Actually no, wait a minute because there’s some subtle bits in there that I think are worth exploring.

1. Maybe if it works it’s worth more than adults

This point is well made in the paper, if briefly. Kids have a smaller FRC, higher metabolic demand and their airways have a pesky propensity to collapse. So if it does work the relative benefits of buying time might be even more notable.

2. This study does not test how preoxygenation is influenced by the nasal prongs

It is worth noting that the nasal prong technique here is not about the preoxygenation. Preoxygenation here was achieved via assisted ventilation with a bag-mask set-up. In the intervention arm the nasal prongs were not applied until after preoxygenation was done. So you cannot support the idea that putting the nasal prongs on, then trying to preoxygenate with the mask is a reasonable technique citing this study. There is evidence from a couple of small studies (here and here) that the nasal prongs disrupt the seal (in adults) and lead to lower expired oxygen levels during preoxygenation. The underlying assumption in this study is that excellent face-mask ventilation is the best way to achieve preoxygenation. This study of THRIVE doesn’t change this.

3. They didn’t test how long apnoeic time was extended

Huh? Wasn’t this the point of the study? Well yes. But also no.

In the 4 groups the apnoea time was extended 86.8 seconds, 88.7 seconds, 129.5 and 169.2 seconds as you moved up in ages. Except it was more than that. In the THRIVE group once they reached twice the published apnoea time, they ended the trial period for apnoeic oxygenation and recommenced face-mask ventilation. At that point the average peripheral oxygen saturation was 99.6%. All but one of the control group hit 92%. So we don’t know what the full extent of the increase in time was. It’s just… a lot.

4. They still did basic stuff

Beyond the face-mask ventilation point above, the authors also point out that they maintained jaw thrust as part of their apnoeic oxygenation technique. The opening of the airway might be very important and it’s a good reminder that if you’re going to try this technique you can’t forget things we’d consider basic.

5. It’s not really ventilatory exchange

They also checked out carbon dioxide and it kept right on rising at these rates of 1-2 L/kg/min oxygen. Depending on your patient (traumatic brain injury anyone) that could really matter. If this problem could be solved then this technique might actually have broader applications in procedures where there might be advantages to maintain oxygenation and ventilation without respiratory effort or airway instrumentation. That’s  a problem for future work. It’s an intriguing  prospect and is discussed in a heck of a lot more depth in the very good accompanying editorial.

9905972176_058687136b_o

We should probably aim for precision in calling things what they are or we’ll end up with sad situations like this where the animal gets called a giraffe instead of the more descriptive ‘stretch horse’.

6. This is not a thing about intubation

It might suggest apnoeic time through intubation is prolonged. It might make sense to you that this holds. They did not intubate though and difficult intubation is a further step away. We should keep in mind that once you add a laryngoscope or have to employ a supraglottic airway or do anything other than jaw thrust a patient with muscle relaxation, you’re doing something different than this. In particular adding suction to the mix is likely to change things a bit in the paediatric airway as you’ll be removing some of that flow. How much? Does it matter clinically? Well, who knows? That’s definitely something to keep in mind

So should we change everything?

After one study? Pffft, no. This is a single small study, interesting and informative as it is. It’s not ‘Kevin Bacon turns up to a very repressed town and changes the world with just one school dance’ revolutionary. Wait, I could have just said ‘Footlose revolutionary’. Everyone knows Footlose right?

This is a really interesting first step. We shouldn’t forget thought that the vast majority of cases of paediatric airway management are very straight forward. Plus difficult airways in kids are generally easy to predict. So for the paediatric anaesthetist looking at THRIVE or something like it there’s not much that suggests you should make it a routine move. However if you did hit an unexpectedly difficult airway it might just have a role. Likewise in known difficult airways it might well have some value.

That’s also not the same as making suggestions for places like emergency departments. Their experience of paeds airway management is different and there is a bit of work showing pretty high desaturation rates or issues around airway management (see here and here) that would argue more strongly for alternatives.

It’s pretty cool stuff from this crew in Brisbane and you’d guess they’ll follow with some more work. In the meantime I’ll probably take a few breaths of fresh air and have a think about when it might be worth adding.

Notes:

That picture was posted by Peter Miller under Creative Commons and is unaltered.

You’d better get on with the reading:

The paper in question is

Humphreys S, Lee-Archer P, Reyne G, et al. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) in children: a randomised controlled trial. BJA. 2017;118:232-8. 

The editorial that’s also worth a read is this one:

Jagannathan N, Burke N. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) in children: a step forward in apnoeic oxygenation, paradigm-shift in ventilation, or both? BJA. 2017;18:15-2.

Here’s those things on seals and nasal prongs again:

Groombridge C, Chin CW, Hanrahan B, Holdgate A. Assessment of Common Preoxygenation Strategies Outside of the Operating Room Environment. 2016;23:342-6. 

and

Hayes-Bradley C, Lewis A, Burns B, Miller M. Efficacy of Nasal Cannula Oxygen as a Preoxygenation Adjunct in Emergency Airway Management. Ann Emerg Med. 2016;68:174-80.

Want a bit more on difficult airway stats in kids? Try this one:

Fiadjoe JE, Nishisaki A, Jagannathan N, et al. Airway management complications in children with difficult tracheal intubation from the Pediatric Difficult Intubation (PeDI) registry: a prospective cohort analysis. The Lancet. 2016;4:37-48. 

Oh and here’s the stuff from Australian kids’ hospital EDs and their experience with airways:

Long E, Sabato S, Babl FE. Endotracheal intubation in the pediatric emergency department. Pediatric Anesthesia 2014;24:1204-11. doi: 10.1111/pan.12490

and this smaller one:

Löllgen RMC, Pontin J, Gow M, McCaskill ME. Adverse events and risk factors during emergency intubation in a tertiary paediatric emergency department. [Epub ahead of print] 2016. 

DOI: 10.1097/MEJ.0000000000000439

Meanwhile did you spot the obvious error with the giraffe/stretch horse thing?

That’s right, giraffes are a kind of antelope. The correct term is stretch antelope.

2 responses to “Fresh Air

  1. Pingback: Apnoeic oxygenation in kids | Prehospital and Retrieval Medicine - THE PHARM dedicated to the memory of Dr John Hinds·

  2. Pingback: Old School/New School – Updating Classic RSI | Songs or Stories·

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