Ranting on risk

 It is a truth universally acknowledged, but not often stated, that clinical judgement is insufficient to exclude subarachnoid haemorrhage with acceptable certainty.

Why wax lyrical about the minutiae of the clinical assessment? Perhaps the neck was slightly stiff. Perhaps one pupil was slightly sluggish. What of it? Ultimately, when the patient came in complaining of a first episode of acute severe headache, we all knew that a CT was inevitable.

And, to boot, since we were sufficiently suspicious of subarachnoid haemorrhage to perform a CT, and in the absence of a compelling alternative explanation, we would be negligent not to then follow-up the normal scan with a lumbar puncture after 12 hours to look for xanthochromia. 

Is this intellectual bankruptcy?

Wise heads on the post-take ward round will cluck knowingly. 'Ah, rushed in with a scan, did we?' How infuriating! The luxury of the normal CT scan report is enabling of maddening arrogance.

The same is true of troponin. A 60 year old man, diabetic, hypertensive, hyperlipidaemic, has some chest pain. It wasn't sudden, it didn't occur on exertion, and it doesn't radiate. It's a niggling pain on the left chest, catching the breath, and it's been going on-and-off for a few days. Is this 'cardiac-sounding chest pain'? One could discuss at great length. My point is that I'm not sure it really matters. Even if you take the diabetes out of the history and ignore the 'atypical chest pain' angle, it would still be an act of bravery to discharge the patient without checking the troponin. If the test is negative, we will curse the fool who ordered it too hastily, when the patient 'clearly has simple musculoskeletal pain'. If it is positive, we will either give the 'usual ACS stuff' and head on down the route to an angiogram. 

The same is true of CTPA.

One of the first patients I ever saw was a man post hip replacement, short of breath, pleuritic chest pain, tachycardic, new AF, hypoxic. He didn't have a PE. 

One of the other – musculoskeletal pain, tenderness on palpation – widespread PE in right lung

I could go on, though I fear that I am sounding like a terrible cynic.

To be honest, I am.

We medics are not as clever as we might think.

All clinical judgements are imperfect. 

All investigations are imperfect.

All medical decisions are made with imperfect information, and on the balance of acceptable risk. 

It's not enough that we understand this, patients must too.

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