Blood Donation: The Vampirical Antihypertensive

19. December 2017

Donating blood is supposed to have a positive effect on high blood pressure. Patients with moderate hypertension benefited in particular. Recipients, however, must be prepared to deal with risks: young men are at an increased risk of dying if they receive blood from women who were previously pregnant.

Since ancient times, doctors have bled patients in order to cure many diseases. The procedure is also used in modern medicine. In cases of haemochromatosis doctors rely on blood extraction in order to remove excess iron deposits from the body.

Elevated amounts of erythrocytes ie. polycythaemia can also be positively influenced in this way, as red blood cells are then regularly eliminated. Doctors have now found out that blood donors with hypertension also benefit.

Bloodletting to beat hypertension


Bloodletting in 1340, depiction from Luttrell-Psalter © Wikipedia, CC0

Professor Andreas Michalsen, chief physician at Immanuel Hospital Berlin’s Department of Natural Medicine, recruited 292 blood donors for a study. Of these, 146 had blood pressure over 140/90 mmHg. Another 146 subjects with normal blood pressure levels served as controls. “In the hypertensive subjects a reduction in both systolic and diastolic blood pressure were measured directly after donation, “Michalsen summarises. After four donations the systolic levels fell from an average of 155.9 to 143.7 mmHg. Diastolic pressure dropped from an average of 91.4 to 84.5 mmHg. There was therein a clear correlation between the “dose” and the effect.

More frequent blood donations improved the result. Patients with moderate hypertension (grade 2 as according to the European Society of Hypertension) clearly benefited in particular. After four donations, their levels dropped by 17.1 mmHg systolic and 11,7 mmHg diastolic. According to Michalsen, the results are quite clinically relevant: “Lowering blood pressure by 10 mmHg systolic or 5 mmHg diastolic reduces the risk of stroke and ischaemic heart disease by up to 40 percent”. Participants without hypertension did not notice any significant changes.

Michalsen’s evaluation: “On the basis of the current evidence, I can make a recommendation in relative terms”. He adds: “That means, given that patients have no contraindications such as anaemia or iron deficiency, and ideally have somewhat elevated haematocrit and/or ferritin levels, I would recommend ‘bloodletting’ or that they donate blood”. This is especially relevant where there exists the individual desire to reduce medication, he says. The specialist adds: “Further studies are, however, necessary and desirable in order to answer questions relating to the best responders, the best bloodletting ‘dose” and the exact mechanism of action”.

How often should one donate blood? Everyone says something different

Patients want to know how often they should donate, given the benefits. In Germany, the interval is eight weeks. In the UK there is an established time period of twelve weeks for men and 16 weeks for women. Which is correct?

Emanuele Di Angelantonio from NHS Blood and Transplant, a group of experts in the British National Health Service healthcare system, has questioned this difference. She has together with colleagues evaluated data from more than 45,000 donors. All subjects were divided into three groups and received different recommendations:

  • Men were to donate blood every 12, 10 or 8 weeks.
  • For women, the intervals were 16, 14 or 12 weeks.

Shorter intervals, in keeping with the specified aim, led to more blood donation, without impairing the subjective well-being of the subjects. Taking a look at important laboratory parameters:

  • Men had a Hb-level of 14.3 g/dl (8 week interval) versus 14.6 g/dl (12 weeks). The lower limit is 13.5 g/dl.
  • For women, the figures were 13.1 g/dl (12 weeks) versus 13.2 g/dl (16 weeks). They are not supposed to fall below 12.5 g/dl.
  • ferritin levels in men were 25.7 μg/l (8 weeks) versus 36.3 μg/l (12 weeks), the lower limit being 20 μg/l.
  • Women had ferritin levels of 21.9 μg/l (12 weeks) versus 26.0 μg/l (16 weeks). They are not supposed to to fall below 15 μg/l.

Di Angelantonio therefore advises the occasional checking of ferritin levels when physicians are dealing with regular donors. Otherwise, she sees no relevant differences: citizens should be permitted to to have their vein tapped more often.

Deadly transfusion, unclear cause

While donors are in safe territory, recipients face some dangers. This particularly affects men under the age of 50 who receive donations from women who have previously been pregnant. For recipients of packed red blood cells the overall mortality risk was higher in the medium term, Camila Caram-Deelder reports. She conducts research at the Center for Clinical Transfusion Research, Sanquin Research, in the Dutch city Leiden.

The researcher evaluated data from 31,118 patients and 59,320 red blood cell transfusions. 88 percent of all donations came from men, 6 percent from women with at least one pregnancy in their history, and another 6 percent from women who had never been pregnant.

There were in statistical terms 101 deaths per 1,000 person-years and they differed considerably. Caram-Deelder provides a figure for male donors of 80 deaths per 1,000 person years. For female donors having had at least one pregnancy the figure was 101 deaths per 1,000 person-years. “Donors having previously been pregnant thus increased the risk of male recipients dying by 13 percent”, Caram-Deelder summarises. “This especially affects younger men under 50”.

How the risk comes about is largely unclear. Ritchard G. Cable from the American Red Cross Blood Services, Farmington, mentions TRALI in an editorial. The abbreviation TRALI stands for “transfusion-related acute lung damage due to immunological reactions”. Antibodies of the donor trigger an immune reaction against leukocytes of the recipient. During any pregnancy, the maternal immune system forms antibodies against the foetus, since half of its genetic material comes from the father, so it is foreign to the body. However rejection does not occur because the woman’s immune response to the father’s antigens is suppressed through various mechanisms. However even after birth the antibodies still remain present. Cable writes that TRALI would be out of the question as the sole explanation. The reaction involved here is an immediate one, which fails to match the clinical observations. The editorialist indicates that Caram-Deelder ultimately demonstrates no causality, but only a possible association. Further studies are required.

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