Why did bloodletting became standard practice of medical care in the first place and how did it remain so for centuries despite its obvious and immediate detrimental effects?

by EasternEuropeanIAMA

I'm aware donating blood regularly can be good for you. However the health benefits of donating blood are seen long term and would be (I assume) very difficult to see/prove with the level on medical knowledge available at the time bloodletting was a thing.

Also, people with high blood pressure can get an immediate (tho short) lessening of symptoms from loosing some blood. But chronic stress, obesity, and metabolic syndrome were hardly prevalent conditions back then to render bloodletting useful for that purpose.

So... what gives?

BedsideRounds

I answered this question a while back. I also produced a two-part podcast series in partnership with the American College of Physicians on how debates and bloodletting essentially led to modern medicine: Let It Bleed and Blood on the Tracks.

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But a view key points:

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  • Bloodletting became the standard of care because it was "bioplausible" in the nosological model of the time, humoralism. That is, you could rebalance blood by literally training blood
  • It also became the standard of care because it likely made people feel better, either by the placebo effect (we know now that more intense interventions produce larger placebos), and because it very likely did lower preload and provide immediate relief in a variety of forms of heart failure
  • Rheumatic heart disease was FAR more common in the pre-antibiotic era, and mitral stenosis from rheumatic disease (and subsequent heart failure) would have been far more common.
  • You are correct about how the effects of bloodletting were "difficult to prove" -- the first population study on a medical intervention in history was done by Pierre Louis to examine whether or not bloodletting was effective in pneumonia. The fallout of this study (and a second one in England a few decades later) essentially led to the decline of widespread bloodletting.

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Let me know if you have any questions.