Evidence-based medicine (EBM): the pesky little man on your shoulder

Posted on 21st May 2013 by Karan Chhabra

Your patient has mild hypertension. What should you do?
Treat the hypertension.
Okay, how should you treat the hypertension?
Well, let’s start with HCTZ, that’s well tolerated.
What will that do?
It’s a diuretic; it’ll help her get rid of the extra volume.
Okay, what will that do?
It’ll lower her blood pressure.
Okay, what will that do?
What do you mean, what will that do?
What will lowering her blood pressure do?
It’ll lower her blood pressure! Seriously—who are you anyway?

Thankfully, once we’re all done with this business of medical training, we probably won’t have someone like that on our shoulders. But the question “what will that do?” is an important one, one that won’t go away once we’re fully-fledged practitioners. And frighteningly, as much as our knowledge of the body progresses, we often don’t know.

The funny truth is, treating that hypertension probably won’t do anything at all for your patient. It sounds ludicrous—how many presentations have we sat through on the disastrous consequences of hypertension?—but, in many cases, it is absolutely true. To be more specific, in mildly hypertensive patients without any past cardiovascular problems, pharmaceutically treating hypertension doesn’t have any effects on cardiovascular morbidity or mortality.

This information comes from a systematic review of four randomized controlled trials—the “gold standard” of evidence—and data from 8,912 patients conducted by the Cochrane Hypertension Group [1]. Not only did it show that the four trials, together, showed no significant effects on mortality and morbidity, but it also showed that 9% of patients discontinued hypertension therapy because of its adverse effects.

How does this make any sense? One could come up with any number of physiologic mechanisms. But it ultimately doesn’t matter a whole lot. Because as physicians, what we should be concerned about is our patients’ well-being—and in that respect, we know what we need to know. In this particular example, we don’t really have evidence that using drugs to treat our patient will help her live longer or better. But we do have evidence that a good number of patients suffer side effects, and (directly or indirectly) all of them will suffer their cost. These are harms that we know about, and weighed against benefits we’re unsure of, we should probably give that HCTZ a second thought.

Of course, that doesn’t mean hypertension isn’t a bad thing, or that we should let it go unaddressed. But our patients have a right to know that by getting on anti-hypertensive medications, they have a 9% chance of suffering adverse effects, and only a .78% chance of avoiding a cardiovascular event (in the absolute best case scenario) [1]. They have a right to know that they might be better served with lifestyle modification than with drugs.

Why does any of this matter? Evidence-based medicine (EBM) represents that annoying little man on our shoulder, constantly questioning the benefits of our treatment decisions. EBM recognizes that we might not always know the body’s secrets, why it responds to things the way it does. In fact, of 3,000 treatments tested in research, it turns out that we don’t even know whether 50% are effective [2]. But EBM acknowledges that we have a shortcut—measuring what the body does, in all its complexity, rather than trying to explain away every bit of it. That’s not to say we don’t need to learn physiology, pharmacology, and all that other good stuff. They tell us what’s wrong with our patient and suggest many ways to address it. What the pesky man on our shoulder does is help us work with our patients to pick that one thing that will address their problem best.

Links:

[1] Diao D, Wright JM, Cundiff DK, Gueyffier F. Pharmacotherapy for mild hypertension. Cochrane Database of Systematic Reviews 2012, Issue 8. Art. No.: CD006742. DOI: 10.1002/14651858.CD006742.pub2.

[2] “What Conclusions Has Clinical Evidence Drawn about What Works, What Doesn’t Based on Randomised Controlled Trial Evidence?” Clinical Evidence. British Medical Journal, Web. 17 Jan. 2013. http://clinicalevidence.bmj.com/x/set/static/cms/efficacy-categorisations.html

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