As everyone knows, fresh human blood rejuvenated Dracula no end: stored blood simply would not do for him.
Blood has long been a fluid endowed with mystic significance. Only comparatively recently in human history have people donated it to strangers with anything like a good grace. I once worked in a remote country, much given to drunkenness, where people would only give blood to their relatives, though fortunately they lived in large families. A man there once had an accident requiring rapid and repeated transfusion. His family had all been at a party. After transfusion, he himself was drunk.
It has long been thought that the longer human blood had been stored in blood banks, the less good its quality. There were two papers in a recent edition of the New England Journal of Medicine that tested this hypothesis, which (within limits, of course) turned out to be false, as so many hypotheses do. I think most people would instinctively feel, because it stands to reason, that fresh blood is best; we agree with Dracula.
Normally, blood is taken from donors, treated chemically and tested for viruses and refrigerated. In practice it is not kept more than six weeks, though this period is to an extent arbitrary and by convention. In the first trial, conducted in Canada, Britain, France, the Netherlands and Belgium, critically ill patients in need of blood transfusions were allocated randomly to receive either blood that was less than a week old or blood that was three weeks old.
One short passage in the paper was slightly troubling from the point of view of medical ethics: “At sites where deferred consent was permitted, written informed consent was obtained from the patient or surrogate decision maker as soon as possible after enrollment.” This appears to mean, unless I have misunderstood, that consent was retrospective, in other words that the patients were asked “Do you consent to having been experimented upon?” Even where such consent was not given, refusal was all but pointless, for they were then asked whether, nevertheless, they consented to the use of the data gathered in their case.
The experiment was relatively innocuous, but if the participants had been given access to the first statement in the second paragraph of the paper before they were experimented on, they might well have refused: “A systematic review of 18 observational studies involving a total of 409,840 patients and three randomized, controlled trials involving a total of 126 patients suggested that the transfusion of older red cells, as compared with newer red cells, was associated with a 16% increase in the risk of death.” The impression that this created might not have been counteracted for them by being told in the next sentence that a more recent controlled trial showed no such excess of deaths. Would you – would I – have given informed consent to participate in such a trial?
Happily in the event, there was no difference in the outcome of the 2430 patients who took part in the trial. Fresh blood did not conduce to better survival than stored blood. Indeed, those patients who were given stored blood had a lower death rate, though not significantly so. The authors admit limitations to their study: their patients were a mixed lot, with many different conditions, and so the results may have concealed differences in sub-groups. Moreover, their fresh blood could have been still fresher, and that might have made a difference.
If fresh blood were needed anywhere, you might suppose, it would be in cardiac surgery. But a second paper, American this time, that reported a trial in 1481 patients, showed the same thing: that fresh blood was not superior to stored. What stands to reason, or is thought on instinct to stand to reason, may not be so.