Clinical Case 104: FAST Thinking

This is a trauma case.  I want to use this case to illustrate something about the way we think about trauma when it comes to making calls using ultrasound – specifically the FAST exam.  FAST exams are ubiquitous in modern ED practice – but if executed and interpreted poorly – they are potentially a source of error.

Now you may be aware that I am an US tragic – and when it comes to trauma I have been seriously drinking from the gel fountain.  OK – onto the case.

Typical Broome case:  a lot of unknown unknowns.  30 y.o male who is brought in by the Ambos after being found on the roadside.  Appears to be very drunk.  There wis a vague history from the Ambos that a few “innocent bystanders” saw our patient getting a “proper flogging” [being kicked and punched by a group of fellows].

On initial assessment there is not much to find externally – no bruises or lacerations .  His Obs are really very normal [BP 110/70,  pulse 80, RR = 12, breath alcohol level 0.3%…. normal for Broome].  He has a normal neurological examination [ which is of course the bluntest test in Medicine! ] And equally reassuringly has equal and reactive pupil responses.

Now it is a few hours since the injury and his belly is sore.  Despite his relatively pickled state he is really not wanting you to examine his belly at all.  He seems very tender though there is no distension or bruising.

So being me – it is time to get some gel onto the patient and find the badness.  The scan is basically negative, well almost.  The LUQ, pelvis and subxiphoid views are all normal… but. The RUQ view is just not quite right. Take a look and think – is this a positive, a tiny bit of free fluid? Or is it OK?  This is the sort of call you need to be really sure about when doing these bedside scans.

Because it would be easy to look at this and say – “it is OK” and move on, but if you cannot convince yourself of normality – then you need to act.  So what is it going to be?

So – here is the summary: a Very drunk man with normal obs.  Not a clear mechanism of injury – but we think he has been “flogged”.  Not much to find on examination.  And his FAST exam looks pretty good – but is that RUQ view as it ought to be?  It all hinges on this!

OK I ma going to leave it hanging there and wrap up the case in a few days.

Let me know – what will you do next?

If you are interested in the finer points of the FAST exam then I highly recommend Dr Laleh Gharabaghian’s Sonospot website, or check out her podcast with Scott Weingart on “Don’t Half Ass your FAST”

OK, after a few days to consider the FAST  – here is the conclusion to the case.  But first a rant about “half-arsing the FAST” [Love that line from Dr Laleh]

Obviously it would be a bad idea to make a call on a single still image from a FAST protocol – and yet I see this a lot!  I see a lot of Docs getting a little too focussed on getting a “text book picture” on the screen.  I think we should be exploring the area, as Laleh says: fanning through the whole potential space around Morison’s pouch and into he paracolic gutter if the gas allows.

Lots of folk use a single angle of attack – this often gives a nice image – but to be sure that you are not missing something down at the inferior edge of the liver – you need to look at it from a few sides.  This requires one to have a few tricks in the quiver – not just 4 “standard” points to cover.

Now – point number 2.  FAST (and a lot of bedside US) is not the most sensitive test – it requires a decent volume of haemoperitoneum to be present before you notice it.  So what does that mean in practical terms?  Well I looked at the image above – and thought: “it is nearly normal”.  There just might be a slip of blood there anterior to the kidney.  On a second fan through – I was convinced that there was something “not right”.  It was not clearly NEGATIVE.  Now human nature makes us want to think like this:  ‘if it is close to normal – it can’t be too bad.  Could it?’  But that is wrong – FAST is insensitive, so any subtle abnormality could potentially mean serious pathology.  When you interpret a FAST – you need to be certain of normality.  There is no room for “close enough” here.  And when I rescanned this patient – I was not certain.  So I decided to go onto CT.

So what did the CT show?

A slice from the CT

So – as you can see.  A small anomaly on the FAST can bely serious injury.

So – our patient remained stable and was managed conservatively.  HE did have a lipase bum and went onto develop some traumatic pancreatitis.  [ we would never blame the alcohol! ]

And for the record he had serial FAST scans which become more obviously positive over time.  One could even see the laceration with the aid of the CT!.  But that is not what FAST is about – you should not be looking for solid organ injury.

And here is the liver lesion on the subsequent Ultrasound

So remember – DON’T HALF_ASS YOUR FAST

Have a low threshold to call it “not normal”.

Scan like you are hunting for blood – not just taking a snapshot!

Repeat the scan if in doubt.  And remember to interpret in the clinical context – i.e.. a NORMAL FAST in a crashing patient means little.  You need to find the badness when the pressure is dropping – either in CT or the operating room!

Happy scanning – Casey