#PHJC – Man or machine? An experimental study of prehospital emergency amputation

The first physical meeting of the Prehospital Journal Club (PHJC) met last week at the University of Surrey and we had an incredible turnout. I was expecting a small but enthusiastic group of four or five, however we had closer to 50 people turn up, with a mix of undergraduate students, tutors, post-graduates, paramedics, child nurses and mental health nurses all ready to dive in to the literature! It was slightly overwhelming, yet incredibly encouraging to think that we have so many people willing to come in on their lunch breaks and days off to come and appraise the literature so we can make sure we’re evidence-based practitioners!

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I’m sorry it’s taken me over a week, but I’m really pleased to now write up the discussion we had. I’m really keen that the PHJC is in the spirit of FOAM and we don’t hoard this information to ourselves, but make it available for others to learn from and contribute to.

So, lets get straight in to the paper! If you haven’t read it, I encourage you to do so by clicking here!

Title: Man or machine? An experimental study of prehospital emergency amputation

Authors: Caroline Leech & Keith Porter.

Published in: Emergency Medicine Journal (EMJ)

During the journal club we used the critical appraisal checklist provided by the BestBETs website, which you can find if you click here.

As you might expect from the title, this study compared different techniques for performing prehospital emergency amputation. As noted in the introduction of the paper the need for prehospital amputation is an extremely rare event, however when the need arises it is a potentially life saving intervention. This is an intervention for prehospital enhanced care teams (HEMS, BASICS) and certainly in the UK, a physician led procedure.

Are the objectives of the study clearly stated?

Yes! The aims are clearly stated at the end of the introduction; to observe the results of four different techniques of lower limb amputation.

Technique 1 – surgical technique with a Gigli saw

Technique 2 – surgical technique with a hacksaw

Technique 3 – immediate amputation with a reciprocating saw

Technique 4 – immediate amputation with a Holmatro device

Is the study design suitable for the objectives?

Yes. I struggled to put the design of this study in to one of the conventional categories we normally use. It’s not a randomised controlled trial, as there was no randomisation involved, yet it was an experimental study as an intervention was intentionally introduced to the sample, rather than an observational study. So perhaps, as the authors mention, we can call it a small experimental study. If anyone has any better thoughts please comment below!

While the design has some known limitations (which we will come to), the JC came to the conclusion that the purpose of the study was (probably) not to give a final definitive answer as to what is the absolute best technique for prehospital amputation. For fun, during the JC, we spoke about what might be needed in order to come to some sort of answer like this. One could perhaps design a large adequately powered, international RCT, where patients needing prehospital amputation were randomised in to groups as to which technique they would receive and then we could compare results as to which was the superior technique. However (and it’s an enormous however), we live in the real world and we need to be pragmatic when it comes to research.  Professor Sir Keith Porter notes in one of the papers in the reference list (read it here – another great paper) that in 18 years of prehospital work he has performed three amputations. How long would the study have to run for in order to recruit enough participants? How much would it cost to run a trial for that long? Would it be ethical to randomise patients in to how their limbs were going to be amputated?! Would it be justifiable to put so many resources in to studying such a rare event?

This study provides some descriptive data on the observed results of the different techniques, which can be used to give the service providers who perform this intervention some alternative ideas when they are faced in these challenging situations.

Were the outcomes defined at the start of the study?

The primary and secondary outcomes are presented on page 3 in the methods section.

Primary outcome:

  1. Time from ‘knife to skin’ to full amputation with the limb disconnected
  2. Number of attempts
  3. The perceived risks to the rescuer or patient during the procedure

Secondary outcomes:

  1. Quality of skin, soft tissue and bone cut

 

Was this the right sample to answer the objectives & is the study large enough to achieve its objectives?

The sample used in this study were two fresh frozen cadavers with no preservative or arterial treatment. The two cadavers were of similar weight and size. Obviously there are some limitations here, but I think this is an appropriate sample to use for this type of study for it to achieve its objectives.

What are the limitations? The participants were dead and had been frozen, they were on (presumably) an operating table with adequate lighting and positioning rather than stuck in some machinery or entrapped in an upside down vehicle during the middle of the night in the poring rain; the number of samples is small, with two techniques performed on each cadaver (one technique per leg); the cadaver donors were elderly and may have had different bone density compared to a younger population; there was a low resting blood volume in the cadaveric specimens, therefore the study was unable to assess the amount of haemorrhage; there were none of the emotional or psychological baggage attached that would be present in a real life, no doubt stressful, situation etc. These are all acknowledged by the authors and I’ve just listed them from the paper.

 

Were all appropriate outcomes considered?

I’ve thought about this for a while and I can’t really think of any others that may have been missed. Please comment if you can!

Has ethical approval been obtained if appropriate?

The authors note that ethical approval was not required as research involving previously collected, non-identifiable tissue samples in accordance with the terms of donor consent is excluded from the NHS research ethics approval

 

Was it clear what was measured, how it was measured and what were the outcomes?

For the first primary outcome – time from ‘knife to skin’ to full amputation with the limb disconnected, time was measured in seconds and provided in the results table.

The quality of the cut was measured by six independent raters using a grading score devised specifically for this study, therefore its validity is unknown. The mean scores of the grading is presented in the results table.

Something that was mentioned is that a consultant radiologist, who was masked to cutting technique, assessed a CT scan of the limbs post-procedure. However, I’m unsure how the radiologists assessment comes in to the results. The quality of skin, soft tissue and bone was measured using the grading scale by the unblinded raters, however it doesn’t mention where the radiologists assessment comes in to play, other than as a nice to know description. And it is nice to know!

Was the assessment of outcomes blinded?

No. The raters using the grading score were not blinded to which technique they were rating, therefore this could introduce detection bias. For instance, if a one of the raters had a preference or dislike for one of the techniques being used this may influence how they grade that technique.

The same could be said for performance bias. The surgical operator who performed the technique may have had a preference or dislike for one of the techniques and could have been extra careful to perform an excellent procedure, or not taken any care and been haphazard, taking less care on the technique they disliked. However, it would not have been feasible to blind the operator to which technique he would have been using!

 

Are the measurements valid & reliable?

The grading score used was designed specifically for this study, therefore its validity and reliability is untested and unknown. Therefore, we are unsure as to the extent of the grading score actually measuring what it’s supposed to and the degree as to which we would see consistent results. However, as there is not much research surrounding this area it is unsurprising that there is not an existing validated grading score that the raters could have used, therefore the only option would be to devise their own. Perhaps there is a tool that is used in surgical research for grading quality of cuts for amputations?

The paper also mentions that the operator used to perform the surgical techniques was highly skilled in amputation and not representative of the expected cohort of prehospital doctors that would be likely to be performing this in real life. Though not part of the study or the results, the authors note than when observing a group of non-surgical doctors performing the techniques investigated, the technical skill was found to be similar, but took up to a minute longer. The paper recommends prehospital doctors become familiar with and practice the skill of using the gigli saw.

The skill of the firefighters using their equipment was more likely to be generalisable, as though they were briefed beforehand, they were not given any specific direction or guidance.

Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?

The results are presented nicely in a table in the results section for the primary and secondary outcomes. As I mentioned earlier, I’m not sure how the results of the CT scan come in to the results, but it’s a nice piece of information to have.

Are there any statistics correctly performed and interpreted?

As the sample is so small and the data collected limited, some descriptive statistics (mean score of the grading criteria) are presented.

Are the results discussed in relation to existing knowledge on the subject and study objectives?

Yes. The authors mention that this is the first study to explore the feasibility of more than one method of prehospital lower limb amputation using fire service equipment, but they do reference other relevant papers that have been published and why some of their results may have differed from the current study (different equipment and surgical technique used).

Is the discussion biased?

No. The discussion gives a fair summary of the study, acknowledging the known limitations.

Are the author’s conclusions justified by the data?

Yes. The authors provide a sensible and reasonable conclusion based on the findings from the results. The conclusion states that prehospital amputation of the distal femur with the gigli saw and fire service hacksaw can be performed effectively and timely. The reciprocating saw, though providing the quickest amputation also carries the highest risk to safety. The Holmatro device can be used if only the fire service can access the patient (it also works underwater), but is not recommended as technique of first choice.

Does this paper help me answer my problem?

This paper certainly gives a lot of food for thought to those service providers who may have to perform a prehospital lower limb amputation. This paper adds to the current available evidence to help health care professionals make evidence-based decisions in an area that is very difficult to research.

Can any necessary changes be implemented in practice?

Perhaps an actual change in practice is not necessary, but an awareness for prehospital practitioners of alternative methods in extreme situations that could potentially save a life.

Are the study patients similar to your own?

As a paramedic, though extremely rare, it is certainly feasible that I could attend a job where the need for physician led emergency prehospital lower limb amputation could be needed. Though we’ve discussed the limitations of the paper, it still provides us with some ideas as to the feasibility of the techniques used. We can use our caution to interpret the results in light of a good critical appraisal.

Does the paper give any conclusions that will affect what you will offer or tell your patient?

At the end of the day, the decision of whether or how to amputate a patient’s lower limb won’t be mine to make (phew!). It will be with a more senior clinician, more than likely a doctor. Hopefully they will have read this paper and used the information, along with other current best research to make an evidence based decision.

 

 

We really enjoyed reading this paper and going through the questions from the critical appraisal checklist. We would really love to hear other people’s thoughts, so please feel free to comment below and keep the conversation going. I hope this has helped!

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