TBI | The Collective

Not that long ago Dr Alan Garner described the process for developing Carebundles as part of trying to deliver the best care and measure it at the same time. Here’s the first of the follow-up posts: on TBI.

The isolated severe traumatic brain injury bundle

As a follow up to our blog about Carebundles and their general utility in Prehospital and Retrieval Medicine we thought we might go through each of the bundles that we are using in Sydney and discuss our rationale for why we included the items we did and the evidence base for them. We hope this process will provide us with some open peer review of our criteria across an international cohort of our colleagues which can only be good for us.

The first thing to note is simply a repeat of my previous post. It is hard to get good evidence in the space we work in and much of the data is extrapolated forward from in-hospital practice. Mere geography alone should not affect pathophysiology so this approach is biologically plausible but we acknowledge it is not ideal. To quote from the previous post:

“We then turned to the evidence based consensus guidelines, Cochrane reviews and good quality RCTs to define the Carebundle items. This is a sobering process as you realise just how few interventions there are that have good evidence to back them up. This is particularly true for prehospital care where we are often operating in an evidence free zone. In many cases we had no choice but to go with the consensus (or best guess as I like to call it). We decided that we would include intubation for unconscious trauma patients for example despite the evidence not being all that strong and in many cases contradictory.”

So let’s look at our bundle items for isolated severe head injury (GCS <9) and why we chose them:

Intubation and mechanical ventilation

As I have already stated the evidence here is not strong. However it certainly allows better control of both oxygenation and ventilation (PaCO₂) so it makes sense and is the in-hospital standard of care. We also know that we can do this safely and extremely rapidly without delaying in-hospital care (CT scan in particular). Given we are not delaying subsequent care it seems reasonable to intubate these patients on scene given the other advantages.

We carry a small ventilator to every case. There is some observational evidence that PaCO₂ outside of the normal range is bad for head injuries and that we are crap at providing consistent ventilation by hand so this made sense to us.

ETCO₂30-35mmHg

Again see Davis’ papers on this subject. We are wanting low normal range (in the 35-40mmHg range) but we don’t have formal blood gases available to us in our rapid response urban operation in Sydney (we do in our longer distance transports in other parts of Australia and internationally). We therefore assume there will be a small gradient from arterial to alveolar and aimed for an ETCO₂ that was likely to get our arterial level in the zone we were aiming for.

Monitoring

Our minimum is ECG, SpO₂, non-invasive blood pressure and waveform, quantitative ETCO₂. These are the minimum standards for managing an intubated patient in our part of the world as covered by the specialty colleges. .

Venous access

There is definitely no randomised controlled trial that shows that prehospital venous access improves outcome from severe head injury (or anything else that I know of either). However it really goes with intubation as above. We aim for pharmacologically smooth intubations without desaturation or hypotension. We need a line to achieve this.

C-spine immobilisation

Note that this does not say a rigid collar, just immobilisation which can be achieved in a number of ways. There is of course evidence that collars impede venous return and therefore it is possible they have an adverse effect mediated by effects on cerebral perfusion pressure. The consensus guidelines still cite the evidence of C spine injury associated with severe head injury so neck immobilisation made our list. We’re actively reviewing what to do when we arrive at a patient already with a rigid collar in place.

Analgesia

No evidence that I am aware of that prehospital analgesia changes outcome for patients with severe TBI, even in terms of subsequent post traumatic stress disorder in survivors. Unconscious (but not completely obtunded patients) still feel and respond to pain however. Of course it may also mitigate the risk of hypertension potentially exacerbating intracranial haemorrhage so again a biologically plausible mechanism for a benefit. I think we mainly included this one as it is what we would want for ourselves & our families.

Head elevation (External Auditory Meatus above JVP)

This is again extrapolated forward from standard in-hospital care. We need to get the brain above the effect of venous pressure to maximise cerebral perfusion. No prehospital studies on outcome (recurrent theme) but seems reasonable.

SpO₂ >93%

All the large observation data sets about this quote 90% as the magic number (See Randal Chestnut and Michael Fearnside’s classic papers on this topic for example). We were simply conservative and aimed a bit higher at the inflection point of the Hb dissociation curve as desaturation occurs so rapidly below this point. I note that the Germans (ADAC) are aiming for 95% presumably due to similar thinking.

Systolic Blood Pressure >110mmHg

Again the classic papers talk about 90mmHg for this item, although if you look at the Brain Trauma Foundation guidelines, they suggest a preference for a higher target, even though they can’t say exactly where to land. Guidelines out of Italy have also recommended this sort of target previously. Again this seems to make sense from a cerebral perfusion pressure point of view.

Blood sugar level

We mandate that this be documented for all patients. Our trauma population like most other parts of the developed world is becoming older and co-morbidities are increasingly common. This one is too embarrassing to miss.

Scene time <25 mins

One fifth of patients with severe head injury have a drainable haematoma. We want to maintain a sense of urgency among our teams. Again, we recognise that there are times when circumstances stop the team achieving this. The key thing is maintaining that sense that forward momentum can be significant for the patient.

Transport direct to trauma centre

All based on observational data but taking severe trauma patients direct to designated specialist trauma centres is standard of care internationally. Even the UK have got in on the act recently.

Conditional item

Hypertonic saline if neurologically deteriorating or lateralising signs

This one is going to be controversial. Again based on beneficial effects on ICP in the ICU setting rather than hard evidence of improved outcomes. We chose hypertonic saline over mannitol as there is less electrolyte disturbance and hypotension. We are targeting the neurologically deteriorating and lateralising signs group as they may have drainable lesions and we are trying to buy time to surgical evacuation. That is the theory anyway.

This is our audit sheet that the doctors complete post mission. You will note that it contains space for the team to comment on variations from the bundle so that we can identify the reasons that we are unable to meet our management targets.

Screen Shot 2016-05-17 at 10.10.19 PM copy — Here it is in all its documentation glory.

Although the bundle is designed for patients with GCS<9 in reality we intubate a lot of head injury patients with GCS 9-12 as well for various reasons. We do not consider application of the bundle mandatory in this group but if they do intubate the patient we encourage our teams to apply all the bundle items as well as completing an audit sheet post mission.

Did we get it right? As I said the lack of good evidence makes this process very sobering, so we would particularly welcome feedback. Next time I will have a look at our blunt multiple trauma bundle.

Notes and References:

One of the papers suggesting letting CO2 rise isn’t great:

Davis DP, Hoyt DB, Ochs, M, et al. The Effect of Paramedic Rapid Sequence Intubation on Outcome in Patients with Severe Traumatic Brain Injury. J Trauma Infect Crit Care. 2003;54:444-53.

and

Davis DP, Peay J, Sise MJ, et al. The Impact of Prehospital Endotracheal Intubation on Outcome in Moderate to Severe Traumatic Brain Injury. J Trauma Infect Crit Care. 2005;58:933-9.

Here’s the Pubmed page for the paper on issues with manual ventilation which no one seems to have repeated:

Hurst JM, Davis K JR, Branson RD, Johannigman JA. Comparison of blood gases during transport using two methods of ventilatory support. J. Trauma. 1989;29:1637-40.

Do you remember this classic paper relating to hypoxia:

Chestnut RM, Marshall LF, Glauber MR, et al. The role of secondary brain injury in determining outcome from severe head injury. J Trauma. 1993;34:216-222.

And here are those BTF guidelines.

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There’s always a bit of extra reflection you can’t include in the discussion of a research paper. Dr Alan Garner reflects more on some of the challenges of doing research in prehospital medicine.

The main results of the Head Injury Retrieval Trial have now been published on-line in Emergency Medicine Journal. We have paid the open access fees so that the results are freely available to everyone in the spirit of FOAM. This was an important study that was eagerly awaited by many clinicians around the world.

The summary from my point of view as the chief investigator: an enormous opportunity wasted.

It is now nearly ten years since we commenced recruiting for the trial in May 2005. Significant achievements include obtaining funding for a trial that was ultimately to cost 20 million Australian Dollars to run. I am not aware of another prehospital trial that has come anywhere close to this. Hopefully this is a sign that prehospital care is now seen as worthy of the big research bucks.

In the subsequent ten years world events have helped to drive increasing investment in prehospital trauma research, particularly conflicts in Iraq and Afghanistan and the perception that there were many preventable deaths. The US government has become a big investor in prehospital research that might lower battlefield mortality. The Brits on the other hand typically made some assumptions based on the evidence they had and got on with it. Higher levels of advanced interventions during evacuation as exemplified by the British MERT system in Afghanistan seem to be associated with better outcomes but the evidence is not high quality.

I am the first to acknowledge that randomised trials are inherently difficult when people are shooting at you. Most prehospital care is not quite that stressful but there remain significant barriers to conducting really high quality prehospital research. Taking the evidence you have and getting on with it is a practical approach but it is not a substitute for meticulously designed and executed high quality studies. Such studies often disprove the evidence from lower level studies. We all bemoan the lack of good data in prehospital care and recognise the requirement for better research.

When you’re only left with signals

The Head Injury Retrieval Trial taken in this context really is an opportunity wasted. There is a strong signal in the as-treated analysis of unconscious trauma patients that there is a significant difference in mortality associated with physician prehospital care. The Intention to treat (ITT) analyses was not significant however.

The potential reasons for the lack of difference in the Intention to Treat group is really best appreciated by looking at the difference in intervention rates in Table 2. Both treatment teams (additional physician or paramedic only) could intubate cold so we only report the rate of drug assisted intubation. This was by far the most common physician only intervention, and the one we have been suspecting to make the most difference to head injured patients. When you look at the rates receiving this intervention it was 10-14% in the paramedic only group due to the local ambulance service sending their own physician teams in a good percentage of patients, compared with 49-58% in the treatment group. If this really is the intervention that is going to make the difference, our chances of demonstrating that difference are not great unless the treatment effect is absolutely massive.

When the system you study changes

The Ambulance Service in NSW decided two and half years into the trial that they considered physician treatment to already have sufficient evidence to make it the standard of care. They partially replicated the trial case identification system to enhance identification of patients that they believed would benefit from dispatch of a physician (there’s more detail in the HIRT protocol paper).

This is not the first time that such a thing has happened. In the OPALS study of prehospital advanced life support in Canada in 2004 the original study design was a randomised trial (Callaham). It was however done as a cohort study owing to the belief of paramedics that it was unethical to withhold ALS despite absence of proof of its efficacy. We bemoan the lack of evidence but belief in the efficacy of established models of care make gathering high quality evidence impossible in many EMS systems. NSW has proved to be no exception.

Sydney remains a good place to do this work of course.

Where are we then?

So where does this leave Sydney? I think a quote from Prof Belinda Gabbe best sums up the situation. Prof Gabbe is a trauma researcher from Monash who has published much on the Victorian trauma system and was brought in as an external expert to review the HIRT outcome data during a recent review of the EMS helicopter system in New South Wales. Her comment was:

“As shown by the HIRT study, physician staffed retrieval teams are now an established component of standard care in the Sydney prehospital system. The opportunity to answer the key hypothesis posed by the study in this setting has therefore been lost and recommendation of another trial is not justified. Future trials of HIRT type schemes will therefore need to focus on other settings such as other Australian jurisdictions, where physician staffed retrieval teams are currently not a component of standard care”.

The only jurisdiction in Australia with enough patients to make such a study viable that does not already use physicians routinely is Victoria. Such a study would be particularly interesting as the recent randomised trial of paramedic RSI from that state found absolutely no difference in mortality, the area where the HIRT trial indicates there well may be a difference. Any potential trial funder would want some certainty that history would not repeat itself in the standard care arm however.

In NSW though, the question of whether physician care makes a difference to patient outcome is now a moot point. It is now the standard of care – HIRT has definitively demonstrated this if nothing else. All we can do now is determine the best way of providing that care. We have more to publish from the data set that provides significant insights into this question so watch this space.

References:

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Tag Archives: TBI

A Bundle for TBI

HIRT – Studying a Non-Standard System that Ended up as Standard

A Hive Mind for Prehospital and Retrieval Med