# Blood transfusion question
**URL:** https://boards.straightdope.com/t/blood-transfusion-question/436711
**Category:** Factual Questions
**Created:** [February 7, 2008, 7:17pm UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711 "2008-02-07T19:17:41Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@susan](https://boards.straightdope.com/u/susan)
#### Post date: [February 7, 2008, 7:17pm UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/1 "2008-02-07T19:17:41Z")
A friend just had a transfusion of red cells for medication-induced anemia. At the infusion center, a nurse said, “There’s a chemical reaction in the new blood that takes about three days, so you won’t see much effect until then.” Would someone please undumb this statement? My efforts have been hampered by the vast tracts of also-dumb consumer-targeted transfusion pages on the web, which seem to amount to “why your doctor ordered this” and “don’t worry,” while avoiding any mention of what will happen and why or any medical terminology.
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### Author:  [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)
#### Post date: [February 8, 2008, 2:13am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/2 "2008-02-08T02:13:02Z")
[QUOTE=susan]
A friend just had a transfusion of red cells for medication-induced anemia. At the infusion center, a nurse said, “There’s a chemical reaction in the new blood that takes about three days, so you won’t see much effect until then.” Would someone please undumb this statement?
[/QUOTE]
I don’t think you can un-dumb dumbness.
Freshly transfused blood undergoes the same “chemical reactions” as the patient’s own blood, as far as oxygen-carrying capacity goes, and it should have an effect rapidly if the patient is symptomatic from anemia - as in minutes to hours, not three days.
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### Author:  [@susan](https://boards.straightdope.com/u/susan)
#### Post date: [February 8, 2008, 2:22am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/3 "2008-02-08T02:22:41Z")
Thanks, \*\*Jackmannii. \*\*My friend had no notable positive effects all day yesterday, but feels a little more energetic and mentally clearer today.
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### Author:  [@Vlad\_Igor](https://boards.straightdope.com/u/Vlad_Igor)
#### Post date: [February 8, 2008, 2:51am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/4 "2008-02-08T02:51:25Z")
When I worked in the clinical lab, we’d get an H/H (a purple-top tube of blood to check the hemoglobin and hematocrit) 15-30 minutes after a transfusion ended, and we’d see a positive change in both. I can’t think of anything that would take 3 days to react in the blood. It’s pretty dynamic, changing from second to second. The nurse might have concocted an answer to questions regarding the necessity of drawing a new sample every 72 hours if the patient is receiving multiple transfusions.
Vlad/Igor
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### Author:  [@WhyNot](https://boards.straightdope.com/u/WhyNot)
#### Post date: [February 8, 2008, 2:52am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/5 "2008-02-08T02:52:36Z")
I’m at a loss, as well. My daughter (who, admittedly, was something under four pounds at the time) visibly pinked up and started moving more when she got a blood transfusion - the transfusion took several hours to push in just a tiny bit of blood, but the effects were noticeable pretty much immediately.
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### Author:  [@artemis](https://boards.straightdope.com/u/artemis)
#### Post date: [February 8, 2008, 3:15am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/6 "2008-02-08T03:15:00Z")
[QUOTE=Vlad/Igor]
The nurse might have concocted an answer to questions regarding the necessity of drawing a new sample every 72 hours if the patient is receiving multiple transfusions.
[/QUOTE]
I suspect you’re right: the nurse is confusing the timing of an anamnestic response (which does generally take about three days to occur) with the the timing of the transfusion’s oxygen-carrying effects (which are more or less immediate).
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### Author:  [@susan](https://boards.straightdope.com/u/susan)
#### Post date: [February 8, 2008, 4:25am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/7 "2008-02-08T04:25:41Z")
Would you define “anamnestic” in this context for me, please?
Thanks, everyone. This is really helpful.
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### Author:  [@Vlad\_Igor](https://boards.straightdope.com/u/Vlad_Igor)
#### Post date: [February 9, 2008, 1:31am UTC](https://boards.straightdope.com/t/blood-transfusion-question/436711/8 "2008-02-09T01:31:34Z")
Anamnesis is a delayed transfusion reaction resulting from the production of antibodies that destroy the transfused red cells. Red blood cells have a large number of proteins on the cell surface, and perhaps 30-50 can illicit an antibody response. When the Blood Bank sets up a unit (or units) for transfusion, they not only test the patient serum for antibodies against these proteins, but they also test some of the donor red cells against the patient serum. On occasion, the antibody titer decreases, or fades, to undetectable levels and the lab tests are negative. But when transfused cells enter the patient, their immune system wakes up and cranks out antibodies. That is an anamnestic response, and takes 2-3 days to develop, hence the requirement for a new blood specimen 72 hours post-transfusion.
Vlad/Igor, BS MT(ASCP).