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News on blood

This article originally appeared in BMJ USA

The Roman physician Galen (ca 130 - 200 CE), considered second only to Hippocrates as a founder of medicine, focused much of his attention on blood. He believed that blood was produced in the liver, that it passed through the heart only once, that it was consumed in the tissues of the body, and that it was imbued with "spirits." His doctrines remained unchallenged for 1400 years, until William Harvey disproved many of them in his treatise "On the motion of the heart and blood in animals" (1628).

Although Galen did not always get it right, his legacy includes the introduction of experimentation to medicine. Experimentation continues on blood and its constituents, as shown in this issue of BMJ USA. One component of blood is HbA_1c. In a prospective study of 4662 men, Khaw et al show that glycated hemoglobin levels are positively associated with cardiovascular mortality throughout the range of elevatedand "normal"levels of HbA_1c (BMJ USA p 95). In an accompanying editorial, Barrett-Connor and Wingard write that this finding "implies that glucose control for coronary heart disease prevention should begin in those with impaired glucose tolerance, and . . . points to the desirability of shifting the entire population glycaemia curve to the left" (BMJ USA p 79).

Another constituent of blood is C reactive protein. Pepys and Berger review how C reactive protein can be helpful in clinical management (BMJ USA p 82). It is commonly used as an acute-phase marker of tissue injury, infection, and inflammation. But recent evidence indicates that levels of C reactive protein correlate with future risk of coronary events, stroke, and peripheral vascular disease. A sensitive assay for the protein may become a new risk assessment marker for cardiovascular disease.

Blood can be harmful when it clots at the wrong time or in the wrong place. Are long-haul airplane flights a cause of thromboembolic disease? Many people probably think so, after the widespread publicity given to the death of a 27-year-old woman from a pulmonary embolism after she disembarked from a flight between Australia and London. Geroulakos points out that "there is only circumstantial, but no epidemiological, evidence connecting air travel with venous thrombosis" (BMJ USA p 80).

Blood is at the center of one of the most contentious ethical dilemmas in clinical practice: the traditional refusal of Jehovah's Witnesses to accept transfusions of blood and blood products. Muramoto explores recent changes in church policy that may allow the use of various blood products in some Jehovah's Witnesses (BMJ USA p 125).

This issue of BMJ USA includes another paper from the BMJ 's Christmas edition. Chen et al report on three diabetic patients whose pet dogs display unusual behavior before or during their owners' hypoglycemic episodes (BMJ USA p 134). But there is no word from the authors as to whether the dogs' behavioral changes correlate with their owners' HbA_1c levels.

Glycated haemoglobin and mortality:

Paper (BMJ USA p 95) http://bmj.com/cgi/content/full/322/7277/15

Editorial (BMJ USA p 79) http://bmj.com/cgi/content/full/322/7277/5

C reactive protein (BMJ USA p 82) http://bmj.com/cgi/content/full/322/7277/82

Air travel and thrombosis (BMJ USA p 80) http://bmj.com/cgi/content/full/322/7280/188

Blood products and Jehovah's Witnesses (BMJ USA p 125) http://bmj.com/cgi/content/full/322/7277/37

Dogs and their hypoglycaemic owners (BMJ USA p 134) http://bmj.com/cgi/content/full/322/7276/1565