Once, a woman arrested while I was drawing up the local anaesthetic before inserting an intravenous cannula. Asystole. Dead. A few times around the algorithm made no difference, and the operating list was considerably shorter than planned. Apart from occasional angina, she'd been fine preoperatively; I'd anaesthetised her without incident 6 weeks previously.
Lucky, wasn't I? Five minutes later it would have been my fault, with my nasty anaesthetic drugs. And who could think anything else? Anaesthetist injects drug; patient dies: res ipsa loquitur — ‘the thing speaks for itself’. Except that in this case the thing spoke incorrectly.
I tell this story frequently. It is one of the most important lessons, not just in medicine but in life: no matter how obvious, association is not necessarily causation, it may just be coincidence. Sir Austin Bradford Hill famously wrote about ascribing cause to disease in 1965, listing nine criteria: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experimental evidence, and analogy. Unfortunately, only one — temporality — seems to matter to the public and the media; witness MMR. For some scare stories, mobile phones being the best example of the moment, even temporality is irrelevant, all that matters is the existence of something about which not everything is known. But even Bradford Hill can let us down, because he can't tell us anything about single cases: yes, hypoxia causes fetal cerebral damage; it fits all the criteria — but that doesn't mean damage is necessarily due to hypoxia. On balance, I'd rather be an anaesthetist than an obstetrician.
The world is full of coincidence. I read an article in the Journal of Medical Ethics about the science and art of medicine in which the writer had written ‘evidence-based decisions … are like computer-generated symphonies in the style of Mozart — correct but lifeless’. The same day, in an article about computer simulation in Nature I read, ‘the computer would not be able to generate a single beautiful melody until we can define one’. Of course, it could have been the conjunction of Jupiter and Saturn in my star sign that influenced me to read those two articles on the same afternoon, but it is more likely it was just coincidence.
Which is not to say that coincidence, as with my poor old lady, isn't sometimes a bummer. A friend was drilling into a wall and all the lights went out. Assuming, not unnaturally, that he'd drilled through an electric cable, he stripped all the plaster off the wall. No cable. Coincidentally, the kettle had fused and tripped the circuit breaker.
- © British Journal of General Practice, 2005.
