Why were they so leechy-keen?

December 23, 2005 11:03 PM

While reading this excellent thread, an interesting question popped into my mind - why was bloodletting so popular for so long when it so obviously doesn't work?

According to this page, bloodletting was popular for over a millenium-and-a-half. Although I understand that they had a whole philosophy behind it, couldn't any casual observer have just said, "Well, we bled him/her, and it doesn't look like they've gotten any better. Come to think of it, I've never seen anyone get better as a result of bloodletting. Y'know what? I don't think this bloodletting stuff really works!"

posted by Afroblanco to health & fitness (27 comments total)

Except that some people do get better, sometimes, and whenever that happens, the success is attributed to the bloodletting. When they get worse, well, maybe it just doesn't work all the time. Common logical fallacy, frequently found in, oh, religion.
posted by trevyn at 11:06 PM on December 23, 2005

I can't find any corroboration, but I seem to recall that bloodletting (the really-lose-a-lot-of-blood kind, not the leeches or small lettings kind) does actually reduce fever, though not for long. If this is true, the short term symptom supression might have further fueled the idea.
posted by fvw at 11:13 PM on December 23, 2005

Except that some people do get better, sometimes, and whenever that happens, the success is attributed to the bloodletting. When they get worse, well, maybe it just doesn't work all the time. Common logical fallacy, frequently found in, oh, religion.
posted by trevyn at 11:06 PM PST on December 23

This is true, though I'd have used the example of homeopathy instead. They didn't really do double-blind controlled experiments back in the day, unfortunately.
posted by Optimus Chyme at 11:25 PM on December 23, 2005

I seem to remember from some brief early medicinal studies that the act was spiritually associated, too. Cleansing out bad juju from the blood also helped cleanse your soul. Actions with spiritual connotations always tend to last longer than one would anticipate otherwise.
posted by symphonik at 11:29 PM on December 23, 2005

There are some arguments for the efficacy of bloodletting in certain situations, but it seems likely that the placebo effect was responsible for some of the perceived benefits:

Medical historians say that it is impossible to divine the real reason bleeding seemed to 'work," and that to use a modern explanation would be a gross oversimplification. The perceived power of physicians wielding such an invasive procedure likely had a potent placebo effect, said Dr. David Jones, who teaches in the science, technology, and society program at the Massachusetts Institute of Technology.

And:

One reason for the continued popularity of bloodletting (and purging) was that, while anatomical knowledge, surgical and diagnostic skills increased tremendously in Europe from the 17th century, the key to curing disease remained elusive and the underlying belief was that it was better to give any treatment than nothing at all. The psychological benefit of bloodletting to the patient (a placebo effect) outweighed the physiological problems it caused.

There are also places where bloodletting is still practiced for basically the same reasons symphonik describes.
posted by Aster at 11:53 PM on December 23, 2005

I know this isn't really bloodletting, but what about acupuncture? At least in Korea, even now, very minor bloodletting (a drop of blood or so) is accepted as a general Korean-medicine cure for stuck 'chi' (indigestion/stuck stomach).

I've never heard of this being discussed outside of Korea, so here's my description of it: indigestion, as a result of eating too fast/eating too much foreign foods that aren't compatible with your system/eating bad foods is seen as a result of having stuck chi/ki ('ki' or 'gee' is the Korean pronunciation). To cure this, the subject's right hand is held down, the arm is swept down as to rush the blood towards the fingers, and the finger (usually the thumb) is wound a few turns with thread as to keep the blood in the finger temporarily. A sterilized needle/acupuncture needle is used to create a small nick in the skin around where the straight side of the fingernail meets the skin -- near the 'corners' of your fingernail, and on the more fleshy part. The thumb is then squeezed until the blood stops comes out (which is about a drop of blood), and then daubed away with tissue; if the blood is dark dark red and doesn't squeeze out very well, then that's further proof that your chi/ki was indeed stuck.

In Eastern medicine/Korean medicine there are certain lines of ki/chi throughout your body in which ki/chi flows -- if you step into any Chinatown acupuncture shop you'll probably find miniature people and wall-diagrams depicting politically-correct people with dots all over their bodies. Those dots are related to certain ailments/parts of the body, and are acupuncture points, or 경혈 in korea.

(IANAEastern medicine doctor, so don't take my word for the factuality of what I just said. The fact is that this remedy is pretty well-known, and it works to some extent (I grew up with it), whether due to the placebo or not. Before you go about talking about the scientific validity of acupuncture, it's necessary to realize that this is a different science altogether...)
posted by provolot at 12:37 AM on December 24, 2005

Erk. Sorry for the hasty sentences.
posted by provolot at 12:37 AM on December 24, 2005

Here's a link to an interesting article on the present day use of maggots and leeches in medicine. Cutting edge stuff.
Maggots and Leeches: Old Medicine is New Again
posted by BoscosMom at 1:23 AM on December 24, 2005

You might also ask why we treated condition X with treatment Y in modern medicine, when it "obviously" didn't do any good.

For many years gastric ulcers were "known" to be caused by stress and diet and treated accordingly. Only they weren't, and whatever the diet and stress-based treatments were doing, it didn't cure them.

A hundred years from now people might be puzzling at the idea of treating cancer with chemotherapy when it "didn't work".
posted by AmbroseChapel at 3:38 AM on December 24, 2005

Diet. Craze.
posted by vanoakenfold at 3:52 AM on December 24, 2005

People do a lot of things that don't work, clasping their hands in prayers, acupuncture, magnet therapy etc... The question is not why, we know that--a bunch of human fallacies such as confirmation bias--but will we ever stop?
posted by JeNeSaisQuoi at 4:15 AM on December 24, 2005

I always thought it was do with balancing the 4 humours.
posted by the cuban at 4:52 AM on December 24, 2005

My grandmother has said that leeches helped her survive and recover from meningitis as a child (about 80 years ago)--that they helped reduce the swelling and inflammation. Leech saliva does, apparently, contain chemicals that can do that, and she certainly made it through with no permanent damage.
posted by needs more cowbell at 5:31 AM on December 24, 2005

From the AskMe archives: "Why were people in olden days so smart about some things, but so dense about others?"
posted by stupidsexyFlanders at 5:57 AM on December 24, 2005

There are benefits to bloodletting. I'm trying to get friends who have cholesterol or high blood pressure problems to donate blood regularly since I read (one or two years ago?) about possible medical benefits from blood donation.

It's possible that we were engineered to live through a bloody battle with man or beast every 6 months. That's just one possibility. Haven't kept up with the research but I think it's good for your humanity to donate blood anyway.

Google: medical benefits from blood donation
posted by 9000.68 at 7:05 AM on December 24, 2005

Well, think about the fact that the expelling of nearly every other single bodily fluid can bring about a subtle, or even a dramatic, improvement in the way one feels. You feel better after you expel mucus, tears, urine, feces, semen/vaginal fluid, vomit, even saliva. On this logic, the release of blood seems very likely to do the same thing.

This is just a hypothesis, but I think it makes some sense, if we can put ourselves into a pre-medical mindset. Such an idea would jibe pretty well with the idea of balancing the cour humors, as the cuban suggests above.
posted by Dr. Wu at 7:42 AM on December 24, 2005

If nothing else, leeching or bloodletting made the patient weak enough that they were willing to stay in bed, rest, and eat reasonably nourishing food. Unless it was done to excess, it probably didn't cause any irreparable damage. (And leeches do have some medical properties.)
posted by jlkr at 8:24 AM on December 24, 2005

Oxygen delivery in the resting state is maximized at a hematocrit of about 30-33; above this, the extra red cells simply slow down the progress of blood through the capillaries. People who don't bleed regularly have hematocrits of 42-48 (non-menstruating) or 39-42 (menstruating).

The science of this is called 'hemorrheology' if you want to Google further.

er, hematocrit is simply the percentage of blood volume occupied by red blood cells. If you bleed someone, they lose plasma and red blood cells, but the body quickly shifts water back into the intravascular space, so the hematocrit drops.
posted by ikkyu2 at 11:14 AM on December 24, 2005

Oxygen delivery in the resting state is maximized at a hematocrit of about 30-33

By what measure is oxygen delivery maximized? In a person with a healthy heart, oxygen delivery is dependent on metabolic demand with feedback loops involving cardiac output. With adequate cardiac reserve, it remains optimal even to quite low hematocrits, and the most practical physiological measure of this would be markers like the VO2, mixed venous oxygen saturation, the base deficit, and the serum lactate level, all of which remain steady to levels drastically below even a crit of 30. See here for one of many studies that reflect the fact that oxygen delivery in humans is a system evolved to provide "optimal" oxygen even after bleeding out a significant amount of blood. But there's no meaningful peak point in this oxygen delivery system. Instead it's really a plateau which dips off only with massive anemia and rather abnormally high viscosities/hematocrits.
posted by drpynchon at 11:59 AM on December 24, 2005

Aside to 9000.68: The Red Cross actually won't let you donate if your blood pressure is too high (systolic must be under 180, diastolic must be under 100).

We now return you to your regularly scheduled bloodletting.
posted by Aster at 12:41 PM on December 24, 2005

Bloodletting triggers the bodys healing response anti bodies anti coagulants immune system crude but effective for many things. Your Barber used to do this, the stripes on the pole symbolize veins and arteries the globe on the pole is the basin used to catch the blood
posted by hortense at 9:22 PM on December 24, 2005

Bloodletting triggers the bodys healing response anti bodies anti coagulants immune system crude but effective for many things.

Wow. There are still people in the civilized world who think bloodletting works. Go figure.

Aster's quotes are correct.
posted by languagehat at 7:34 AM on December 25, 2005

I am not recommending bloodletting. I am saying that a wound stimulates a bodys healing system, It is part of the fascinating history of barbers and surgeons. I am not a surgeon
but I am a barber.
posted by hortense at 4:56 PM on December 25, 2005

Thank you all for your answers. Excellent links, Aster and stupidsexyFlanders! I'm definitely going to be reading up on this a bit more.

What is most astounding to me is not that people practiced bloodletting at all - people do crazy stuff all the time - but the fact that it went on for so long. A millenium and a half is a long time to do something that, in most cases, puts the patient in worst condition then how they started.
posted by Afroblanco at 10:18 PM on December 25, 2005

In a person with a healthy heart, oxygen delivery is dependent on metabolic demand with feedback loops involving cardiac output.

Which is why I specified the 'resting state'. A hematocrit of 30-33 is where the oxygen capacity of blood balances off against the extra energy necessary to push blood with increased viscosity.

The determinants of blood viscosity include, in this order, plasma viscosity (related to protein constituents), hematocrit, red cell deformability, and red cell adherence (rouleax formation etc.). Of these, although plasma viscosity is the most important determinant, by far the most variability exists with respect to hematocrit. In other words, you can't alter plasma viscosity much. You can easily siphon off or add some red blood cells.

The reason I became interested in this is because of closed head injury, which is analogous but not identical to a resting state. There's some data to suggest that in closed head injury, where resistance to arteriolar flow can be critical (ICP and the Monroe-Kellie doctrine), survival and outcome is better at crits of 30 than at 45. Closed head injury is a situation in which tissue metabolic demand (injured brain) can skyrocket, without exercise or other cardiac stimuli being present.

No one's done the treatment trial, though. It's even been speculated that mannitol's effects in closed head trauma are due to its hemorrheologic effects, not its diuretic or edema-reducing effects (if any). Mannitol coats the surface proteins of red cells and pretty much eliminates red cell adhesion; it also increases the ionic strength of the blood it's dissolved in, causing fluid to leave the RBC and therefore increasing deformability significantly.
posted by ikkyu2 at 1:05 PM on December 26, 2005

I also have experience with some bloodletters who are also barbers, and I have to say it's been uniformly negative.
posted by ikkyu2 at 1:06 PM on December 26, 2005

Not to be too insensitive at this time of year, but an equally valid question could be: why was/is praying so popular when it so obviously doesn't work?

I've prayed the Trail Blazers won a championship each year since I was a kid, and they still haven't won one. Why does God hate me?
posted by pwb503 at 6:01 PM on December 26, 2005