Fresh Air 2 – An Update on THRIVE in kids

It’s not that long ago that a post went up on the merits of THRIVE in little people went up. You can have a read right here. There’s another paper just out which kind of says ¯\_(ツ)_/¯ it seems … or does it?

There are some things that just take up too much time. Data back-ups. Morning TV. (Yes, I mean all of it because it lacks the requisite value to justify any of its existence.)

And sometimes you have to wait minutes for coffee and that is usually a time critical intervention.

And don’t even get me started on reading. Who has time for making your eyeballs work that hard? I mean you’d have to be mental to read all the way through a thi… wait, I take that back. You should definitely keep reading this particular thing.

But it’s a bit of a drag that you don’t even just get to read the headlines or the abstract version because then you’d be short changed. Like if you only read the abstract for this latest thing on THRIVE.

What it says on the box

Another trial trying to see if the THRIVE worth really remembering is the clinical version and not the Santa Cruz reggae band  is not at all a bad thing. Particularly when it’s looking at kids who are all to often the forgotten (or too difficult) research group.

So we should all be delighted that this group had a good look at whether THRIVE increases apnoea time versus your run of the mill nasal oxygen. They had a solid look too. Sixty patients in the 1-6 year age range (and 10-20 kg)  with 20 in the 0.2 L/kg/min oxygen group, 20 getting THRIVE (humidified at 2 L/kg/min) with 100% oxygen and 20 getting THRIVE rates with 30% oxygen.

Then you go to read the key bits in the 4 minutes you have spare for ‘bettering yourself by reading’ in you busy week and the abstract conclusion says “High  flow 100% oxygen (2 litres/kg/min) administered via nasal cannulas did not extend safe apnoea time for children weighing 10-20 kg compared with low-flow nasal canal oxygen (0.2 L/kg/min). No ventilatory effect was observed with THRIVE at 2.0 L/kg/min.”

And I guess you think ¯\_(ツ)_/¯ “Why did I waste precious eyeball lubrication and lack of blinking on that when it doesn’t even work?” [Shakes nasal cannulae furiously at the oncoming storm.]

Except that sort of isn’t really the message here. You actually have to read the whole thing.

Nitty gritty

I am not going to go over the reasons that kids might be even more in need of things that help keep oxygenation happening while you do the critical intervention bit. The paper does have quite a nice summary though, just before it gets into the bit about approval from the Cantonal Ethics Committee. (Disappointingly the Cantonal Ethics Committee refers to the ethics committee for a Canton in Switzerland, not a committee entirely administered by Eric Cantona, the footballer. Though happily, also not governed by Eric’s personal ethical beliefs if you look at those first couple of ‘highlights’.)

There are a few key components of the way they went about this that make a big difference to how to take it:

  • Their main aim was to see if they could extend safe apnoea time and the second aim was to investigate the rate of increase of transcutaneous carbon dioxide during apnoea.
  • After patients were anaesthetised, bag-mask ventilation was the game until the expired oxygen concentration was > 90% (and of course saturations were 100% and the transcutaneous CO2 was 30-40 mmHg). So pre-oxygenation was again nothing to do with the nostril-peeling nasal prongs and this study is absolutely not about using THRIVE in the setting of airway endoscopy or situations where the breathing is spontaneous. Those questions are for another study.
  • There were three criteria for defining the termination of apnoea time:
    • Oxygen saturations hitting 95%.
    • Transcutaneous CO2 hitting 65 mmHg.
    • Apnoea time reaching 10 minutes (cross-reference the other work mentioned in the discussion here which reports desaturation to 90% in 119 seconds in infants up to 23 months and after 160 s in 2-5 year olds).

So let’s keep those criteria in mind because they are going to matter when we see how long before they need to come up for air.

martin-sattler-167489-unsplash

Crunch those numbers

The median apnoea time ended up being 6.9 minutes (5.7-7.8)  in the low flow group, 7.6 minutes (6.2-9.1) in the 100% THRIVE group and 3.0 (2.4-3.7) minutes in the 30% THRIVE group. That 30% group aren’t going to be in this chat for long it seems.

There’s another bit to look at though and that’s the reason they declared apnoea done. In the 30% THRIVE group all apnoeas were declared done because the patient hit that 95% desaturation threshold. In a median time of 160 seconds. Oh, sorry. I said we wouldn’t mention that group again. Let’s move on.

In the low flow oxygen group, 2 patients hit 10 minutes, 3 desaturated and the other 13 hit the transcutaneous CO2 threshold.

Then in the THRIVE 100% group the total number of desaturations was identical to the number of truly brilliant albums we can expect from members of  the Iglesias family: 0.

4 patients hit the magic 10 minute mark (small numbers but double the low flow group) leaving the other 16 to have their apnoea terminated because of transcutaneous CO2 getting up there.

You’d have to take those numbers as pretty suggestive of a much longer time to desaturation with the 100% THRIVE, though this study isn’t quite set up to address that.

They did demonstrate something about that second aim along the way too. The transcutaneous CO2 pretty much hiked up the same for everyone in this study, which does genuinely seem to be adding to the picture of the ventilatory benefits not being there as is apparently the case in adults.

 

Clinical Cut-Offs

The real question here is what do you actually do with results such as these? A bit like that other paper by Humphreys et al. we have been given information which tells us something about THRIVE but leaves off some of the clinical nuance.

What? We have to read and think? The outrages never cease.

A large amount of paeds airways that are difficult are predictable and occur in otherwise well kids. So if the patients are otherwise well, will a transient jump in CO2 have a meaningful impact on that child, or is the physiological cutoff point that matters somewhere out beyond that 10 minute mark, giving you plenty of time to do the ensnorkelling*?

The authors don’t really go into why that cut-off was chosen. It’s certainly a safe choice in a world of uncertainty. In clinical use though for most patients how much should that higher CO2 worry us just because it’s a higher CO2 for these few minutes?

 

Cut-offs that matter

No this is not about jean couture in dance movies from the ’90s. Or *cough* earlier.

There are other cut-off points that aren’t physiological that really matter. What I’d be more interested in is where you are up to you in your airway management plan if you’ve hit 7 minutes after apnoea (assuming you chose muscle relaxation for your known difficult airway case) and intubation still hasn’t happened.

By that point it would certainly be critically important to have a sense of how much rough treatment the airway structures have had, and where you are up to in your optimisation of conditions to achieve your airway goals.

Because if you’ve hit 7 minutes I would hope you are not doing exactly the same thing. You should be planning your next appropriate moves to maintain safe respiratory parameters. Otherwise you’re in the space that hamsters going for the electrified cheese occupy and fixation error is your co-pilot.

So that’s one little note of caution to sound when it comes to THRIVE. It certainly seems to postpone desaturation. It’s important we use that time in the patient’s best interest though, rather than thinking “everything’s coming up THRIVE because those saturations are up and I can just keep trucking”.

Or what about this situation…?

What about the patient where you really do think CO2 matters? Let’s say a patient with a head injury or some other reason not to dilate the blood vessels inside their head.

I can see how in that patient group, the lack of CO2 clearance is something to really consider. In those cases, accepting an apnoea time that corresponds with a transcutaneous CO2 hitting 65 mmHg is probably also not a particularly sensible choice.

In those patients you should be thinking about an airway management plan that ensures CO2 removal well before you approach the median times stated here. In which case we’re back to the trusty bag-mask ventilation option or maybe a supraglottic airway.

The Wrap

So was that abstract a fair summary of the story? I can’t argue the facts in what’s written, but it’s also not as simple as “is time to desaturation longer yes or no please tick a box”.

THRIVE at 100% does seem to give you a longer time to desaturation than other nasal prong options, either with lower 100% flows or THRIVE at 30% inspired oxygen. And this might provide a safety margin for one element of airway management – maintenance of oxygenation.

But we shouldn’t lose sight of the fact that it doesn’t guarantee the patient is safe. It’s one tool among many to use to make the best airway management plan for the patient in front of us.

Because the cut-off isn’t just about saturations, or when the CO2 hits a certain point, or the 10 minute timer telling us everyone else is bored.

Clinical end-points are not always the same as research endpoints. And reading to the end  of the paper is only the first part of getting to the end of the story with your patient.

Oh, and someone better come up with another acronym. See without that CO2 being exchanged, you end up with THRI…? And Transnasal Humidified Oxygen Cramming just doesn’t seem like people will get on board.

 

Notes:

Yes, *ensnorkelling should absolutely be the internationally accepted word for providing a breathing tube in the internal aspect of the airway. Join me. Dream.

The image of that diver is unchanged from the Creative Commons offerings of unsplash.com, which is where this excellent image from Martin Sattler came from.

Now, the paper of interest again is this one:

Riva T, Pedersen TH, Seiler S, et al. Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) for oxygenation of children during apnoea: a prospective randomised controlled trial. BJA. 2018;120(3):592-99.

That Humphreys paper is this one:

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. 

Oh, and did you read all the way to the end? Then perhaps you will enjoy some time to recover while heading down a mountain with Danny McCaskill.

 

 

 

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