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Fentanyl, Ketamine & Rocuronium: The Regimen for Trauma
Interview with Prof Richard Lyon regarding the Fentanyl, Ketamine & Rocuronium Regimen for trauma
Professor Richard Lyon is a consultant in emergency medicine and pre-hospital care at the Royal Infirmary of Edinburgh. He is also a consultant and director of research and innovation at Air Ambulance Kent Surrey Sussex. Professor Lyon, what in your view are the most important factors in devising an RSI regime? Sure. So I think the first thing to think about is why we are anaesthetising these patients in the first place. And of course, the majority of the patients that we anaesthetise on the side of the road are those with blunt neurotrauma. And of course, that’s where the evidence is strongest that an early RSI is beneficial.
So when thinking about the drugs that you’re going to use for the RSI, it’s got to be safe. That is absolutely paramount. And it’s to be safe from a pharmacological point of view, but also from a systems point of view. And that’s really what led us to thinking about this research is that, well, how can we have a safe regimen for our blunt neurotrauma patients? But then the next thing is we want it to be effective. So we really want to have as smooth an anaesthetic as possible, particularly for those neurotrauma patients. So we don’t want a big ICP raise. And then when we come back to the safety aspects, of course, the poly trauma patients may be bleeding.
They may be hemodynamically unstable. So we really need a simple regimen that is easy to use and that can be used by multiple people– so safe, effective, and simple. What were the issues with the etomidate and suxamethonium regime? So etomidate and sux was used firstly by London’s Air Ambulance, and then spreading really across the country as the standard anaesthetic protocol for many, many years. And in some ways, it was excellent. And it was excellent in its simplicity. It was simple in that you either gave a syringe full of etomidate, 20 milligrammes, or a reduced dose of etomidate, half a syringe. So your only two options were one syringe versus half a syringe and a syringe full of sux.
So in terms of ticking the simplicity box, well, we’re there. From a safety point of view, actually, it was pretty good as well, because from a cardiovascular stability point of view, it was quite hard with the regime like that to render a patient hypotensive, even if you overcooked it and got it wrong. But where it didn’t work so well was on the effective part. So what we noticed was clearly, there’s no analgesia in there. And we were noticing big spikes in blood pressure, big spikes in heart rate, certainly a concern that we were causing a rise in ICP around laryngoscopy in particular.
And all that sort of concern coincided with around the time that studies were coming out showing that ketamine really wasn’t this sort of devil drug in terms of pushing up ICP that it had had concerns about. So that really led us to think, right, well, etomidate and sux is OK, but could we do this better? Why did you select fentanyl, ketamine, and rocuronium as a new regime to introduce? Why not propofol and thiopentone, for example? [INAUDIBLE] Sure. So I should probably highlight it wasn’t me personally that selected it. It was a group of very esteemed pre-hospital physicians, paramedics, anaesthetists that devised the regimen. And I guess it was devised because ketamine obviously is nicely cardiovascularly stable.
It’s been used for decades in trauma care, and it has a long-established record of use in the military, for example. And it works very well in those hypovolemic hypotensive patients. There was concern that in itself might not have that analgesic cover particularly for laryngoscopy. And that’s where fentanyl came into its own. And we can come onto that. But that’s probably one of the bigger unanswered questions, really, is how badly that fentanyl does need to sit there. And then the rocuronium was really another evolution. Sux is that sort of dirty drug. There’s some patients you wouldn’t want to use it in. You’re having to wait for circulations.
You obviously have to top it up and switch it out for another muscle relaxant. And some pre-hospital studies were trickling out that showed that using rocuronium actually gave a better first part intubation rate and gave better intubation conditions. So Air Ambulance Kent Surrey Sussex was the first to adopt this new regimen in the 3, 2, 1 dosing with a 1, 1, 1 dosing as a reduced cardiovascular instability dose. And obviously we’re trying to mirror that simplicity. And that’s what our landmark study really looked at, was comparing the old versus the new. How did you set about investigating the effectiveness of the new regime? How did you design that comparison? Yeah, it’s a great question.
Of course, the gold standard would have been to do a randomised clinical trial comparing the two regimens. And whilst it wouldn’t have been impossible, the challenges of doing RCTs in the pre-hospital setting are really big. I mean, they are really big. And it just wasn’t really an option at the time. And we knew that there was sufficient concern around etomidate and sux to change. And the fent/ket/roc was our best guess. So what we elected to do was actually to bring it in and then do a before and after comparison. So what we did was when we did bring it in, firstly, we made sure that we had really good data.
And we reviewed it very carefully on a case by case basis to make sure that we weren’t doing harm, and there wasn’t any unforeseen consequences in the first patients we did it on. And then once we felt we had enough numbers, we just did a comparison, the before and after, as best we could, obviously, with the constraints of not doing a randomised trial, particularly looking at those patients with head injuries and then comparing those with normal versus abnormal cardiovascular status pre-anaesthetic. What would lead you to consider a reduced dose RSI? And what would be your thoughts on omitting fentanyl altogether? Another great question. We don’t have all the answers.
And what we don’t have unfortunately is a nice prescriptive answer to that question. So in your, what I would call, standard low-GCS blunt neurotrauma patient who is cardiovascularly normal– having said that, we also know obviously a lot more now about vasoactive head injury, which is another complicating factor to consider. But in those patients, you don’t think of bleeding. The 3, 2, 1– or actually, recently, we’ve updated it again to 3, 2, 2– appears to work very well. Now where you would certainly consider reducing it is in the hypovolemic patient, so where you either know, or you have serious concern that this patient is bleeding, whether internally or externally. And that’s a clinical judgement call that you need to make.
I think it’s important to really think about it as a stepwise approach. So the stepwise approach is number one to say, well, why are we doing this anaesthetic? And is the head injury a component of that? And that will help you with the fentanyl decision. You step down from a 3, 2, 2 to 1, 1, 2. Then you would consider omitting the fentanyl. And much to the horror of many of my anaesthetic colleagues, we do roc-only RSIs. The other group of patients that we have found that are particularly sensitive to the regime is the elderly. And again, I can’t put an age on that. But you do need to be careful, thinking about frailty.
Those patients can be quite susceptible to it– so either reducing it or dosing it on a slightly lower weight than you would. So it’s a very clinically based decision that you just need to think about.
An induction with fentanyl, ketamine and rocuronium is the current standard regimen for pre-hospital trauma RSI. In this step Kat Hunter (KSS HEMS Doctor) outlines the drug dosing regimens and interviews Professor Richard Lyon (KSS Director of Research & Innovation) to learn how the regimen was developed and the evidence for its benefit.
The “3:2:2” Regimen
In trauma patients who are cardiovascularly stable and not grossly hypovolaemic, induction of anaesthesia is typically achieved with 3mcg/kg fentanyl, 2mg/kg ketamine and 2mg/kg rocuronium. This is commonly referred to as a “3:2:2” RSI and is an evolution of the more widespread “3:2:1” regime. The larger dose of rocuronium has been adopted in some services to obtain optimal intubating conditions, recognising that body weight can be difficult to estimate. A maximum induction dose of rocuronium 200mg is given, based on a maximum ideal body weight of 100kg.
Reduced Dose Regimens
In patients suspected to have hypovolaemia and in the elderly, the dose of fentanyl and ketamine should be significantly reduced, typically to 1 mcg/kg fentanyl, 1 mg/kg ketamine and 2mg/kg rocuronium (a “1:1:2” RSI).
In critically unstable patients, consideration can be given to omitting fentanyl resulting in an induction with 1mg/kg ketamine and 2mg/kg rocuronium (a “1:2” RSI).
In extremis, for severely hypovolaemic patients who are peri-arrest and unconscious, consideration can be given to a rocuronium only induction with 2mg/kg rocuronium.
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