Where’s Wally? Finding that Patient

Having advanced teams is no damn good if you’re not doing your best to get them to the patient where they might add value. Dr Alan Garner returns with reflections on recent publications on this coming out of Europe. It’s a bit of a passion of his. 

 

Advanced capability prehospital medical teams may well be great, but they are an expensive resource that needs to be matched to the patients that are most likely to benefit. But these patients represent a very small percentage of the total numbers of calls to ambulance services so a way of accurately filtering the calls is critical to optimising the utilisation of such teams.

This of course means an accurate case identification system is required to dispatch these teams to the right patients, and preferably only the right patients. This is a kind of ‘Where’s (severely injured) Wally?’, all day, every day.  It is really hard to pick which of the red striped shirts is blood and the signal to noise ratio about the same as a Where’s Wally picture.  In NSW only about one in every 250 calls to Ambulance is a severely injured patient.

When it comes to dispatch of advanced capability medical teams (rather than which patient should go direct to a trauma centre – the two things are not necessarily the same) there is not a huge amount of literature out there yet.  This has been identified as a priority research area for HEMS.

Wally
Even with the empty seats, it’s hard work.

Hence I was really interested in a new paper just published by the people from EMRS Scotland on case identification in severe trauma.  Those who follow The Collective will be aware of my interest in this area from the work we have done in dispatch in NSW that arose as a spin off from the Head Injury Retrieval Trial, particularly in children.   You can find an earlier post on this here.

What the Scots did was move one of their clinicians who work on the service, either a paramedic or retrieval practitioner, into the control centre to look for cases that might benefit from an advance medical team response.  Prior to this move the case identification was done by non-clinical dispatchers with some oversight from paramedics and nurses who were not involved in provision of the Scottish retrieval service.   They used a simple before and after methodology to see how many of the severe trauma cases that occurred in Scotland were identified by the new system including the EMRS clinician versus the old system with the control room staff only.

The result was an improvement in sensitivity for major trauma that increased from 11.3% to 25.9%. Although 25.9% does not sound great it is possible that the new system identified almost all the severe trauma that was in the areas that the EMRS responds to.  EMRS are not dispatched to urban areas in close proximity to major hospitals but injuries occurring in these areas were not excluded from the analysis. Since Scotland has a predominantly urban population it is very likely that most trauma occurs in urban areas (like it does in NSW) so if they are identifying a quarter of all the severe trauma cases this may represent almost all the severe trauma that is in their response area.  Unfortunately this is not examined in the paper (I mean you can’t always cover everything) and more studies will be needed to clarify this.

Regardless of this methodological issue they more than doubled their case identification rate by putting a member of the EMRS team in control of identifying the cases.  Such systems are common in the UK.  As far as I am aware the first to publish this were London HEMS in early 90s where they were able to demonstrate a really dramatic improvement in sensitivity when they put one of the flight paramedics into the central control room. So this is not a new bit of learning. It’s reinforcing what we should know.

Stories we have heard before…

When we started the Head Injury Retrieval trial 13 years ago we had something like the London system in mind.  By accident we stumbled upon an improvement though.  Between 1989 when London HEMS set up their system and 2004 when we were planning the trial the internet had arrived.  We were able to build a system where the crew at the helicopter base was able to screen the calls and identify the cases directly from the Ambulance computer system rather than putting a flight paramedic into the control centre.

This contributed to the trial HEMS system being the fastest reported to date in the world medical literature.  We could get airborne about 3 minutes faster than the reports out of London and we’re pretty confident this was related to the ability to do multiple things simultaneously because it was all happening on base. At the same time as a clinically involved crew member was looking at the details of the case, aviators could start identifying potential landing sites and making plans. The pilot could head to the helo and start the checks even as that was happening. An experienced crew of 4 looking at cases also allows plenty of bouncing things off each other. There’s just a bunch of seemingly little stuff you can start working on that adds up to a significant bit of time-saving.

The trial system was however shut down at the end of the trial in 2011, and dispatch in NSW is now done by control room staff who are not involved in service provision.

It is worth noting that the system used to identify severely injured children when HIRT was recruiting was associated with zero safety incidents of even a minor nature, no unintended dual responses by physician teams and zero cost.  But it doubled the rate of identification of severely injured children for physician team response and decreased time to a paediatric trauma centre by half an hour.

It is now seven years since this case identification system was discontinued by the powers that be and there is still no suggestion that it will be recommenced. This is despite the mounting evidence of system deterioration and concerns about inevitable missed cases and delayed responses resulting in poor clinical outcomes.

Meanwhile, elsewhere…

It is notable that other services are now commencing the direct screening by HEMS crew case identification system.  Have a look at this article on the Great North Air Ambulance in the north of England. It sounds like exactly the process we used during the Head Injury Trial to identify severely injured children in Sydney more than a decade ago.

This comment from Andy Mawson, Operations Manager for Great North Air Ambulance is central to the whole thing:

“It’s an extra set of eyes to make sure we are getting to the right patients in the fastest possible time. Essentially we’re working in support of the teams within the NWAS control centre, it’s a great example of collaborative working.”

The system used to identify severely injured children during the head injury trial in Sydney was collaborative too, not competitive.  There were extra eyes looking for the same cases rather than one set of eyes looking at the whole state of NSW trying to find severely injured Wally across four different control centres.   How can this not be better?

But this is a refinement of the system the Scots studied; putting case identification into the hands of clinicians that provide the services is the core of the system. Why does this work?  I think the clinicians directly involved in provision of advanced prehospital teams just understand the services they are dispatching better.  They understand the actual logistics of response and the capability that can be delivered on scene.  It seems that you need more than a set of guidelines to do this sorting quickly and effectively.  The “gestalt” that comes from actual provision of these services is required to lift the dispatch system to the next level.

Sydney previously had a case identification system that was world leading and is now being replicated in other places like the north of England.  Sydney also had the fastest physician staffed HEMS yet reported in the world literature to go with it.

But the case identification system was switched off and the effective service area of the HEMS halved.  Missed cases and delayed activations occur frequently.

So after all this, the same questions from my last post on this topic in August 2016 still apply:

“You might ask why such a hugely effective system was discontinued in the first place.

You might ask why it has not been reinstated given the subsequent evidence.

And they would be very good questions.”

 

[Sound of silence].

 

Notes:

We are always interested in people’s clever thoughts on tricky topics. So hit those comments if you have things to say.

Now, the first of those papers on the paediatric tasking happening with the crew watching the screens is this one:

Garner A, Lee A, Weatherall A. Physician staffed helicopter emergency medical service dispatch via centralised control or by crew – case identification rates and effect on the Sydney paediatric trauma system. Scand J Trauma Resusc Emerg Med. 2012;20:82. 

The follow-up which looked at the before and after state of play was this one:

Garner AA, Lee A, Weatherall A, Langcake M, Balogh ZJ. Physician staffed helicopter emergency medical service case identification – a before and after study in children. Scand J Trauma Resusc Emerg Med. 2016;24:92. 

That paper on priority areas for HEMS research is this one:

Fevang E, Lockey D, Thompson J et al. The top five research priorities in physician pre-hosopital critical care: a consensus report from a European research collaboration. Scand J Trauma Resusc Emerg Med. 2011;19:57.

The Scottish paper (which is not at all like the Scottish play) is this one:

Sinclair N, Swinton PA, Donald M, et al. Clinician tasking in ambulance control improves the identification of major trauma patients and pre-hospital critical care team tasking. Injury. 2018. doi: https://doi.org/10.1016/j.injury.2018.03.034

That original London was this one:

Coats TJ, Newton A. Call selection for the Helicopter Emergency Medical Service: implications for ambulance control. J R Soc Med. 1994;87:208-10. 

And that letter was by me and here is the reference:

Garner A. Pre-hospital and retrieval medicine clinical governance in Sydney and the inconvenient truth. Emerg. Med. Australasia. 2017;29:604-5. 

 

 

Things that Go Up Kids’ Noses – THRIVE and Paeds

Nasal prongs seem pretty popular for lots of things these days. So how about their use in kids. There’s a couple of papers out there on its use in the paralysed patient and Dr Andrew Weatherall is here to splice them together. 

Isn’t it supposed to be the kids who stuff things up their noses? Have we just seen them do it so often we started wondering about the possibilities ourselves?

Let’s assume not. It’s more a case of people finally getting around to testing things out on kids when they’ve been running with them in adults for quite some time. This time it is THRIVE and that ever so desirable feature of endless maintenance of oxygen saturations while we get around to the ensnorkelling we’ve planned.

In principle that makes plenty of sense. The normal kid is more likely to rapidly desaturate than the normal adult. Physiology is pretty insistent on that. Plus we know people find paediatric intubation tricky so dropping the stress by avoiding the slide of the plethysmograph tone down that digital scale is probably a worthy pursuit.

So how about we look at two papers examining just this issue – does THRIVE employed in the little people stop those saturations from … not thriving??

travis-essinger-479636-unsplash
Fancy, nose-cramming air is what we’re dealing with really

Australian Angles

First up is this paper published by Humphreys et al, who work out of Brisbane. They did a small RCT on well kids with 24 in the control arm and 24 receiving 100% THRIVE. The kids fell between the ages of 0 and 10 years of age and are reported in the age groups 0-6 months, 6-24 months, 2-5 years and 6-10 years (with a total of 12 in each age range, meaning 6 in the controls and 6 in the THRIVE group within each age group – got it?)

The routine went something like *induction of anaesthesia* –> pre-oxygenation by doing that whole bag-mask ventilation bit –> the mask disappeared and THRIVE was added or nothing was added –> start the stopwatch.

You’ll note that, like the other paper we’ll mention, this is not about patients who are spontaneously ventilating. That’s a completely different thing.

In this group though the period of the saturations staying up was longer. Across the age groups the extension in apnoeic time was 86.8 seconds (0-6 months), 88.7 seconds (6-24 months), 129.5 seconds (2-5 yeas) and 169.2 seconds (6-10 years).

Right, lock it up. Everyone should have nasal prongs. All the time. It’d stop peanuts ending up there too.

Except there’s more pesky nuance in this paper. Like:

1. It’s not for pre-oxygenation

It’s worth noting that the preoxygenation here was all about face-mask ventilation with a good seal. They added THRIVE after that bit and started the clock. This is not entirely surprising because we know that nasal prongs compromise seals in adults and that’s only more likely with kids.

So if you were thinking that you should set up those nasal prongs from the before time zero, you need to think again. THRIVE for preoxygenation is not something tested here, and you shouldn’t assume it’d be better than good face-mask technique.

2. They didn’t test the duration that it worked for apnoea

All they said was it’s ‘more’. ‘Wait,’ you might say, ‘you mean they didn’t test the thing that was the point of study?’

Well not really because the cut-off was ‘twice the previously noted time to desaturation’. So they tested that they could reach the ‘double or nothing’ limit, but didn’t test the full extension. In the THRIVE groups the average saturation when they stopped the clock was 99.6%.

So I guess be reassured that it was likely to be really a heck of a lot of time.

3. Basic things were part of the procedure

For this study there was a lot of basics being done well. Throughout apnoeic oxygenation they weren’t doing things like airway instrumentation, suction, intubation or, I assume, anything much beyond chatting about the weekend and watching the clock. They did jaw thrust, a basic manoeuvre likely to optimise the impact of THRIVE. So maybe we should remember that all those things we are also interested in were not part of the picture.

And Now an Update from the Swiss

What if you didn’t make your cut-off ‘2 times the other cut-off we knew about’? How long could you go?

Well a Swiss crew with no interest in being neutral on the topic I guess have done a study comparing low flow nasal oxygen (0.2 L/kg/min) with THRIVE at either 100% or 30% FiO2 with 20 in each group. And they found … (wait for it…..) 100% THRIVE prolongs apnoea time.

OK there wasn’t much suspense there really.

Except again it was more subtle, and again cut-off matters. They had a cut-off to terminate on the basis of desaturation, but another at 10 minutes (as in ‘it’s 10 minutes and I’m bored let’s stop because those saturations are still great’) and the 3rd cut-off was if the transcutaneous CO2 hit 65 mmHg.

In the THRIVE 100% group no one desaturated, 4 hit 10 minutes and the other 16 had their nasal prongs ditched when they breached the CO2 target. This actually accords with the other paper where they also found that THRIVE doesn’t achieve ventilation and removal of CO2 in kids.

But at the end of this paper you still can’t say how long apnoea might be extended, at least when it comes to those saturations staying up.

Oh, and a couple of other points:

1. Pre-oxygenation was with face-mask ventilation. Again.

Again the nasal option had no role in the preoxygenation phase. They went with face-mask ventilation until the expired oxygen was 90% or above. Then they started the clock with the chosen nasal prong option going.

2. The other airway things done at the time were … none.

Yep. Once again this was just about the oxygen and the stopwatch. Nothing else was going on.

mihai-surdu-170005-unsplash
I mean this could be a visual metaphor for the need to appreciate their is still colour not just black and white when it comes to THRIVE or it could just be pretty, you choose. 

Let’s Think Clinically

So let’s imagine that we’ve actually got that paediatric patient in front of us. Maybe one who needs to get intubated before we get them out of wherever ‘in front of us’ is.

Let’s agree that maintaining oxygenation throughout is a good and noble goal. It’s not the only goal of course. We’d also like to make sure we make good choices around number of attempts, and for some patients (say the patient with intracranial pathology) we need to think about ventilation.

And we don’t have evidence that pre-oxygenation is aided by having THRIVE in place.

So assuming we’re going to do things standard to modern paediatric RSI like face-mask ventilation for a bit before we get going. There is at least a bit of  a question about whether THRIVE adds a huge amount.

What it undoubtedly adds is the confidence that saturations will stay up. That is something that lots of practitioners, particularly those not regularly intubating kids would find immensely reassuring.

There is a couple of caveats to keep in mind though.

There’s a risk to be aware of with THRIVE that those saturations staying interminably up might encourage tunnel vision on persisting with intubation when it’s not working out. It’s not too hard to imagine the scenario where the tube hasn’t passed straight down, but those saturations are OK so you persist a bit longer, and a bit longer, and now long enough that the airway is becoming traumatised and suddenly you’ve created a problem.

So this might be a cognitive challenge to have planned for in advance – how do you keep yourself to a limited number of attempts before re-evaluating and going to plan B (or C)? Do you make it a personal process or have others in the crew hold you to a maximum number of attempts or maximum duration of looking?

After all, THRIVE is going to get you to 10 minutes probably. But if you’re still conducting open negotiations with the glottic structures at 10 minutes, oxygenation is not the airway problem that should still be at the front of your mind. While you’re there, you might have to think about re-dosing anaesthetic agents too.

And the other key patient group is that one where intracranial pathology is an issue. Letting the CO2 rise for some patients is not a good plan because your TBI patient (as just one example) doesn’t need those cerebral vessels dilating and the intracranial pressure going up. For those patients, a step back to face-mask ventilation, or potentially placing a supraglottic airway,  to re-establish an ability to exchange CO2 is probably a better option.

So THRIVE might be great for some things. But whether it’s clinically better than an approach to the airway where really excellent pre-oxygenation is routine and good practices around face-mask ventilation are established seems like a line ball call.

I mean it’s still way better than a piece of Lego up the nose. But it remains an adjunct to the basic stuff, not a replacement.

Notes:

OK. That first 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. 

The second one out of Switzerland 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.

Did you want something on nasal prongs and seals? You could try this

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

or this

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.

We’re always interested in other thoughts so feel free to drop a comment.