The Preferred Error

June 11th, 2014
by reuben in heuristic

Last week emcrit proposed that we have lost our nerve: that we fail to act when action is called for, that we tend to commit errors of omission, rather than errors of commission, and so we should toughen up, give ourselves permission to act, provide maximally aggressive care everywhere. A chorus responded with the obvious objection that we are doing way, way too much and that we are causing massive amounts of harm with overtesting, overdiagnosing, and overtreating.

I review hundreds of high-risk cases per month, and in patients who have bad outcomes, we do often conclude that the bad outcome could have been prevented by doing more. It really does seem as though there is a reluctance by non-surgeons to perform dangerous procedures, and that this reluctance often results in harm.

The easiest way to explain this discrepancy is that maximally aggressive care everywhere might be a reasonable paradigm if everywhere for you is a resuscitation bay (cue Casey).  But of course M.A.C.E., if interpreted as when in doubt, do more is an unreasonable paradigm even in the resus bay–we don’t want to do more, we want to do the right amount. Part of knowing the right amount is knowing medicine, and part of it is knowing yourself. Most of us tend toward overtesting and overtreating, but under-resuscitating (most of us but not all of us–we’ve all run into clinicians whose threshold to do dangerous procedures is too low, they are way scarier). This is why there is a lot of wisdom to contradictory rules of thumb like don’t just do something, stand there and if you’re not sure whether to intubate, intubate.

When you spend a lot of time reviewing cases, you start to think about the patient in front of you from the perspective of the person reviewing the chart next week; this mindset has spawned a useful cognitive strategy I call the preferred error. If you make the right choice, or the patient does well, fantastic. What matters is when you’re wrong, or there’s harm. So consider the consequences of being wrong on both sides of the decision, and determine which course of action fails better.

Looking at if you’re not sure whether to intubate, intubate from the future backward, its rationale becomes obvious. If you intubate a patient who doesn’t need to be intubated, how much harm is done? Some harm. And there’s the slight chance that you will fail to intubate and cause harm by trying, but this is quite unlikely. Now consider, what if you don’t intubate, but it turns out the patient needed to be intubated–how much harm is done? Potentially a lot of harm when that patients later requires a crash intubation, which is much more dangerous.

preferred error pic

The preferred error considers how much harm if you’re wrong, but you must also consider how likely you are to be wrong, and factor that in. The hyperadrenergic patient–hypertensive, tachycardic, hyperthermic, agitated–has a differential filled with dangerous conditions, and it may take some time to sort out. You’re contemplating alcohol withdrawal, you think there’s a 30% chance that this is alcohol withdrawal. Should you treat for alcohol withdrawal? Consider what would happen if you treat with benzodiazepines, and he didn’t have alcohol withdrawal: not harmless, but probably minimal harm. And how likely is it that he doesn’t have alcohol withdrawal? About 70%, so 70% chance you might cause minimal harm. But what if you don’t treat with benzos, and the patient does turn out to have alcohol withdrawal? Very bad, lots of harm, the patient will get a lot sicker, might seize, might need a crash intubation. So 30% chance of causing a lot of harm if you don’t treat. Treat. Lots of tough decisions become easier when you consider the preferred error.

Lastly, when you’re still not sure what to do, you can hedge, and hedging means prepare. In the severe asthmatic you’re nervous about but you think you can turn around, but you’re not sure, and you really don’t want to intubate, but someone told you if you’re not sure whether to intubate, intubate, the way to manage that risk is get everything ready to intubate. Fully prepare, cognitively and materially, to intubate, as you throw every asthma therapy you’ve got at the patient. Preparation gives you the chance to be right, while minimizing the harm if you’re wrong. Preparation is the respect we pay to risk.

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