What prevents our blood from freezing

When the blood "freezes"

My blood froze in my veins, some people say when they report a great horror. This expression certainly does not mean one thing: the cold death in northern Siberia or the Arctic. A few hours after the last breath, however, the body's blood would actually be frozen in the freezing cold. However, this is about something that makes a second variant of the saying clearer: "My blood is stuck in my veins."

We sometimes have this feeling when we are very afraid - suddenly. A sudden rustling in the bushes when we are still walking in a gloomy forest in the twilight of the evening - then we are as if hit by a blow. Or as soon as a dog barks at us unexpectedly when we turn the corner of the house.

"Suddenly" and "as if hit by a blow" - there is more truth in this than we can imagine. Because intense fear or even internal panic can actually cause our blood to clot and thus promote a life-threatening blood clot, because it promotes a stroke, or a heart attack.

First of all, there is an important survival mechanism behind this. "Some fibrin, a water-insoluble protein substance, which is immediately dissolved again," says Roland von Känel, chief physician of the department for psychosomatic medicine at the University Hospital in Bern, continuously develops in human blood.

In the case of acute stress, however, not only is blood clotting stimulated, i.e. more fibrin than usual is formed. The antagonist of this process, fibrinolysis (fibrin dissolution), is also increasing. However, the coagulation side is activated a little more than fibrinolysis, which - to put it casually - makes the blood slightly thicker.

“From an evolutionary point of view, that also makes sense,” adds the Swiss expert on psychosomatic bodily processes. "Because if our ancestors were stressed by attackers or wild animals and either had to fight or flee and get injured in the process, it was of course an advantage if the blood coagulated as quickly as possible and the wound was closed so that one did not bleed to death." Blood transfusions After all, there was no such thing as centuries or even millennia ago, and women who were stressed about childbirth have always been happy when their blood quickly thickens, the blood loss is less and the chance of survival is greater.

There are, however, "some factors that make the increased blood coagulation even more pronounced than would be physiologically sensible," notes von Känel. For example, if you have depression or a narrowed coronary artery or if you suffer from high blood pressure, blood coagulation outweighs clot dissolution under acute stress even more than in a healthy person. »If the blood pressure rises during mental or physical exertion, for example in a person with constricted heart vessels, the plaques deposited at the vascular bottleneck can tear open and the blood clot that forms on this wound is even more pronounced than without acute stress - and that can lead to a heart attack, ”the Bern doctor explains the problem.

People with chronic anxiety are also at risk, as Franziska Geiser, senior physician at the Bonn University Clinic and Polyclinic for Psychosomatic Medicine and Psychotherapy, and Ursula Harbrecht, senior physician at the University Institute for Experimental Hematology and Transfusion Medicine, have found out together with colleagues.

The two doctors were able to prove that people with a pronounced anxiety disorder are much more likely to have increased blood clotting than those who are mentally healthy. In addition, those affected carry up to four times the risk of dying from a heart condition.

Earlier surveys by questionnaire had already indicated that stress and fear tend to cause people's blood to clot. However, healthy people were interviewed. In contrast, the Bonn research team specifically examined anxiety patients. Geiser and Harbrecht compared the blood coagulation of 31 people who suffered from a severe form of panic disorder or a social phobia with that of a healthy control group of the same size.

In healthy people, both processes, blood clotting and fibrin dissolution, are roughly balanced. In the anxiety patients examined, however, the blood tended to thicken while at the same time fibrinolysis was inhibited - even though the test subjects were not injured - one ignores the prick when taking the blood. The possible consequences in extreme cases have already been mentioned: A clot forms that can clog a coronary artery or a cerebral vessel.

This does not mean, however, "that all patients with a pronounced anxiety disorder must now be afraid of suffering a heart attack," says Franziska Geiser, appeasing exaggerated worries. It only becomes dangerous when other risk factors are added - such as smoking or being overweight. Soothing for anxious people: Good psychotherapy can reduce the increased tendency to clot again - so that the lucky ones no longer have excessive blood stuck in their veins.

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