Beware Transfusions

New Scientist:

Blood transfusion became a mainstay of medicine during the two world wars, where it was used as a last resort to save soldiers who had suffered massive blood loss. But now, far from being restricted to catastrophic bleeding, transfusions are routinely used as an optional treatment, most commonly for patients in intensive care or undergoing major surgery. … The rationale behind such blood transfusions seems incontrovertible. Red cells deliver vital oxygen to tissues, and seriously ill patients who are also anaemic fare less well, so a transfusion should help. Those assumptions went untested for the better part of a century.

Things started to change in 1999 with a randomised controlled trial on 838 critical care patients in Canada that used haemoglobin levels to determine when a blood transfusion was given. Normal levels of haemoglobin … range from 120 to 170 grams per litre. A normal haematocrit – the proportion of red cells in the blood – ranges from 36 to 50 per cent.  Doctors decide whether to give a transfusion based on a number of factors, including haemoglobin levels and haematocrit, and the patient’s overall robustness. Many guidelines exist, and practice varies from one hospital or doctor to another, but it is common for patients to receive transfusions when their haemoglobin dips to between 70 and 100 g/l or their haematocrit to 21 to 30 per cent.

But the Canadian study found significantly fewer patients died in hospital, 22 versus 28 per cent, if they received transfusions only when their haemoglobin fell below 70 g/l rather than when it fell below 100 g/l.


A more recent study has found that in heart attack patients with haematocrits of over 25 per cent, a transfusion is associated with more than three times the risk of death or a second heart attack within 30 days compared with not having a transfusion (Journal of the American Medical Association, vol 292, p 1555).

For almost 9000 patients who had heart surgery in the UK between 1996 and 2003, receiving a red cell transfusion was associated with three times the risk of dying in the following year and an almost sixfold risk of dying within 30 days of surgery compared with not receiving one. …

"There is virtually no high-quality study in surgery, or intensive or acute care – outside of when you are bleeding to death – that shows that blood transfusion is beneficial, and many that show it is bad for you," says Gavin Murphy, a cardiac surgeon at the Bristol Heart Institute, who ran the UK study.

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  • Ken

    Is this really surprising? How many things in medicine and in life generally are just taken to be true because ‘it makes sense’? I am never surprised to find out that common sense is wrong and always push to have any assumptions made rigorously tested and verified. I understand that we do not have the resources to test all assumptions, but there are many things that can be tested that have major implications. And many of the assumptions are never questioned, much less tested. While I understand a lack of testing, why does it take so long for someone to ask a basic question like: are blood transfusions typically good or bad for patients?

  • http://yudkowsky.net/ Eliezer Yudkowsky

    Duly noted.

    Have you thought of compiling these posts into a short, fast book called “Medicine Without Evidence: 100 Things To Avoid” or some such?

  • Jess Riedel

    I can’t see the utility of advertising the results of these studies to the audience of Overcoming Bias. Announcing this isn’t going to change anything about how medical research is done, but it will potentially lead patients to unnecessarily fear blood transfusions based on studies which they don’t understand. Who among us is going to remember the details of the sample population, and whether these results will apply to us in any given situation in the future? All that will come of this post is a vague notion for some readers that blood transfusions are potentially “bad”.

    If you think there is a tendency in the medical research community to leave common sense beliefs unquestioned, then this is an argument you need to take up with people who have the ability to improve the current system.

  • http://hanson.gmu.edu Robin Hanson

    Jess, reread that last quote – avoid it unless you are “bleeding to death.” Yes perhaps someone who is bleeding to death will mistakenly avoid a transfusion to their harm, it is far more likely that readers will avoid them in other situations, to their benefit.

  • Kynan Shook

    All this study says is that further study is warranted. Specifically, “Given the disparity in results between our study and other observational studies, … a randomized trial … is warranted to guide clinical practice.” Absent more advice, this article really says nothing. They do note that the sample of people who received transfusions were, on average, older, sicker, and weighed less. Although they say they account for these factors, neither I nor the average individual has the knowledge to evaluate these claims – and you never know whether they missed a risk factor somewhere.

  • Caledonian

    As I see it, the problem is not whether transfusions increase the risk of death. The problem is that there is no actual evidence that would allow us to conclude whether they’re likely to be harmful or beneficial – all we really have is speculation and tradition.

    Sadly, this problem is systemic – the vast majority of medicine either isn’t based in evidence at all, or only to a very limited degree. Even more troublesome remains the reality that most physicians have little to no capacity – in time, data, interest, or psychological willingness to doubt – to examine critically the techniques and treatments they were taught to use.

  • http://lightskyland.com Matthew C.

    Maybe the Jehovah’s Witnesses aren’t as crazy as we all thought. . . 🙂

  • http://www.hopeanon.typepapd.com Hopefully Anonymous

    A plan for a systematic review of medical and safety practices would be a good idea, in regular intervals. Kind of like how we do a census every 10 years. Actually a periodic, systematic review for all domains of knowledge and “common sense” might be a good idea.

  • Ping

    The Jehovah’s Witnesses remain exactly as crazy as we thought they were before knowing about this study. This study has no bearing on the fact that their opposition to blood transfusions is based on an infallible holy book, not on experimental observation.

  • Caledonian

    Certainly we have no grounds for regarding the Jehovah’s Witnesses as more credible than before. It’s just that the credibility of the people who oppose their claims has been reduced.

  • Constant

    I wonder what percentage of donated blood goes to harming the recipients. Do the many conscientious people who donate their own blood help others on balance?

  • eddie

    If I’m understanding this whole Bayes thing, then in fact the JWs aren’t as crazy as we thought. This study surely raises our belief that the infallible holy book is, in fact, infallible. Not by much, perhaps… but it still means that the JWs are very slightly less crazy than our priors indicated.

  • http://zooko.com Zooko

    I’m beginning to think (in large part due to “Good Calories, Bad Calories” by Gary Taubes, which is (so far) a tour de force historical analysis of how large-scale, mainstream, government-supported science can go completely wrong) that for much of health science, “Whatever the mainstream scientists thought between 1850 and 1950.” is at least as good a predictor as “Whatever the mainstream scientists think today.”. There seems to be a great deal of “scientific overreaching” that went on during the 20th which is now the established consensus tradition and has to be *disproven* before it will go away. I think studies such as the one cited in this article, and books such as Taubes, are the beginnings of this large scale process of re-examining and in many cases disproving the so-called science that was developed during the 20th.

  • http://www.econ.canterbury.ac.nz/eric Eric Crampton

    In prepping for the birth of our son, I asked our obstetrician whether we ought be doing autologous donations early to be ready in case of caesarean, as Ira promised to be a big boy. He told us that there would be no point as he won’t give transfusions unless things were dire and then there’d be no chance that we’d have stored up enough blood in advance to make a difference. He noted the Canadian study on the risks of transfusion.

    Chalk one up for the NZ medical system, where my private health insurance does not cover pregnancy but where paying $2,000 in advance gets me a very good obstetrician and no extra charge for the eventual caesarean.

  • Bob

    Define crazy?

  • Dihymo

    I have to disagree with the idea that a special party needs to hear this and that the other special party cannot use it correctly.

    #1 our curiosity, impartiality, and morality is being daily lobotomized
    #2 heuristics such as experts must hear and plebes must fear create #1 which leads to #3
    #3 a systemic as well as epidemic inability to act even when we are convinced that action must take place

    So I would say just QM is reality and CM is a hallucination, the social strata and hierarchy of responsibility is also a hallucination because there has been no upkeep. Curiosity and self examination are increasing discouraged favoring their licentious sisters vanity and relief of boredom.

    Let’s just say it’s amplitude distribution is as wide as a the wavelength of a photon of 1 hertz. It may have been true at one point but since no one bothered to examine and maintain it became spread out.

    I would say though that the title of the thread does much more probable harm than the content. We could say the same of the Beware Supplements thread. Both threads have latent and newly emerging biases, which I won’t get into.