19Feb

Hemostasis and disorders of the blood coagulation system

Coagulopathy, increased or decreased platelet aggregation, DIC syndrome - all these are violations of the hemostasis system( blood coagulation in the body).Most violations of hemostasis occur during pregnancy, as during this period all systems are activated, and with excessive initial hyperactivity in the uterus microthrombi may form. What is it - hemostasis, and what are the violations in the system, read in this material.

Primary and secondary hemostasis: a combination of

mechanisms When we talk about blood coagulation in our home, we discuss the mechanisms of hemostasis - one of the most important systems of the body. Hemostasis is a biological system that maintains the liquid state of blood in the body in the norm and is responsible for stopping bleeding if the integrity of the vessels is damaged. That is, our body is programmed by nature in order not to lose a single drop of blood in vain.

There are two mechanisms of hemostasis( blood clotting), namely:

  • vascular-platelet( primary);
  • coagulation( secondary).

Only with a full-fledged combination of primary and secondary hemostasis mechanisms is it possible to operate the system efficiently. Platelets take an active part in coagulation hemostasis, without them the final stage of the formation of a full thrombus - retraction of the blood clot is impossible. When wounds of both small and large vessels there is a formation of a platelet plug with subsequent coagulation of blood, the organization of a fibrin clot, and then - restoration of the lumen of the vessels due to fibrinolysis - dissolution of the fibrin clot.

To ensure that blood flow in the normal state is not violated, and if necessary, effective blood clotting occurs, it is necessary to maintain a balance between plasma, platelet and tissue factors that promote coagulation and inhibit it. If this balance is broken, bleeding occurs( hemorrhagic diathesis), or thrombosis.

Constant haemostatic plug ( "red blood clot") is formed by the formation of thrombin. Thrombin causes irreversible platelet aggregation and fibrin deposition on the clots formed at the site of the injury. Fibrinotharbocyte mesh serves as a barrier preventing further leakage of blood from the vessel, and initiates the process of tissue repair( restoration).

Vascular platelet hemostasis and its disorders

Vascular-platelet hemostasis performs stopping of bleeding in the smallest vessels( capillaries) where blood pressure is low and the lumen of the vessels is small.

In a healthy person, bleeding when injuring small vessels stops in 13 minutes( the so-called bleeding time).Vascular hemostasis is achieved by narrowing( contraction) of blood vessels and clogging them with clots of platelets - a "white thrombus".When the endothelium is damaged( cells lining the inner lumen of the vessels), primary hemostasis is triggered: special substances are released - biochemical "alarm signals" that work as a starter of the process of stopping bleeding.

Platelets floating with blood flow are in the non-activated state. By contacting the wound surface and clotting factors, they become activated and release a number of substances necessary for hemostasis.

Endothelium acts as a powerful anticoagulant surface that does not activate blood clotting proteins and does not attract platelets to itself. After injury, the endothelium becomes a powerful stimulant for clotting. If it is damaged, adhesion( adhesion) of the platelets to the superficially located collagen fibers occurs. This process is supported by a substance contained in the vascular endothelium and platelets - von Willebrand factor( PV).With VW deficiency( Willebrand disease), platelet adhesion is impaired.

Thrombosis in primary hemostasis disorder

There are factors that stimulate the formation of the primary thrombus and disturb it. The first include, for example, various inflammatory processes. When inflammation increases in the blood of biologically active substances: we can say that the body is ready to form a thrombus, it is only for local damage to the vessel. Therefore, with severe infectious diseases, clogging of blood vessels may occur. The readiness for a thrombus formation and during pregnancy, and also at some hereditary diseases( a thrombophilia) is raised or increased. Also, the abuse of table vinegar( marinades) and coffee can lead to a violation of hemostasis.

The process of formation of the primary thrombus is disrupted with a decrease in the number of platelets( thrombocytopenia) and with their qualitative inferiority( thrombocytopathy).This violation of the hemostatic system may occur when taking a number of medications. First of all, these are anti-inflammatory drugs: aspirin, analgin, brufen, some antibiotics. Thrombocytopathy also develops in kidney diseases. The full value of platelets can also reduce the consumption of spices and strong alcoholic beverages.

Violation of the formation of the primary thrombus is manifested in the tendency to bleeding, the formation of a bluish rash. To the development of thrombosis conducts excessive activity of thrombocytes. A similar violation of blood hemostasis, accompanied by clogging of the surface vessel, is accompanied by a sharp pain, a feeling of raspiraniya;When the clogged vessel is broken, hematoma( hemorrhage) occurs. If a person has also increased blood pressure, violation of hemostasis, thrombosis can lead to hemorrhage in the brain( stroke) and in the eyes.

Coagulation hemostasis and disorders in the coagulation system

Coagulation hemostasis performs stopping of bleeding in larger vessels( arteries and veins).This is achieved by coagulation( coagulation).

In the event of a wound, a thrombus is formed, which must contract, squeezing the blood serum( retraction) to bring the edges of the wound closer together in the wall of the vessel. Further, this thrombus should be kept in place all the time necessary for the wound to become overgrown with scar tissue. And only after this thrombus, like the Moor, who has done his work, must dissolve( fibrinolysis).

The blood coagulation system is actually several interrelated reactions taking place with the participation of enzymes. At each stage of this process, activation of the proenzyme( inactive form of the enzyme) takes place. The clotting system is made up of thirteen such proteins( clotting factors).They are usually designated Roman numerals( for example, VII - factor VII), and for the activated form, the index "a"( VIIa - activated factor VIII) is added. Coagulation occurs according to the type of chain reaction: the appearance of a stimulant leads to the launch of a cascade of reactions that result in the formation of fibrin, the final product of blood clotting reactions.

Plasma clotting factors include: I( fibrinogen), II( prothrombin), III( thromboplastin / thrombokinase), IV( calcium ions), V( proacceleurin), VI( acceleurin), VII( proconvertin), VIII( antihemophilicglobulin A), IX( factor Kristmasa), X( Stewart-Prower factor / thrombotropin), XI( precursor of plasma thromboplastin), XII( Hageman factor / contact factor) and XIII( fibrin-stabilizing factor).

Such a disorder in the coagulation system, as a reduction in the content or activity of clotting factors, may be accompanied by increased bleeding( eg hemophilia A, hemophilia B, von Willebrand disease).Excessive activation of coagulation hemostasis leads to the development of thrombosis( thrombophilia).

Pathologies in the system of hemostasis in pregnancy

Pathology of the hemostatic system in pregnancy among the causes of miscarriage are in second place after obstetric-gynecological problems.

During pregnancy the organism of the future mother prepares for childbirth. The system of hemostasis is also being prepared, which, as the birth approaches, is activated more and more, because labor is blood loss. And if the woman's hemostasis is initially hyperactive, during pregnancy, microthrombi in the vessels of the uterus, the placenta, can be formed, which leads to miscarriage or to a stagnant pregnancy.

Under what conditions this can happen:

  • With hereditary thrombophilia.
  • Most often when folic acid metabolism is disturbed, when the amount of homocysteine ​​increases in the blood. It damages the endothelium of the vessels, than triggers the mechanism of thrombus formation. The reasons for this may be a deficiency in the diet of folic acid and vitamin B, thyroid disease and kidneys. The level of homocysteine ​​is also able to rise in smokers, coffee lovers and on the background of taking a number of medications( theophylline, nicotinic acid).
  • When antiphospholipid syndrome( AFS) is an autoimmune disease, when the body produces antibodies to its own clotting factors, as a result of which spontaneous thrombi in the vessels are also formed.

Preventing hemostasis in pregnancy

To avoid increased hemostasis in pregnancy, all women bearing a baby should undergo laboratory tests: a clinical blood test, a coagulogram( blood clotting parameters are revealed), a homocysteine ​​level determination.

If you have a miscarriage or a frozen pregnancy, you need a complete study of the hemostatic system, a blood test for antiphospholipid antibodies. In the case of IVF( in vitro fertilization), blood coagulation parameters need to be monitored throughout the pregnancy. Correction of the hemostasis system during pregnancy is carried out jointly by two specialists - a gynecologist and a hematologist.

Ideally, a full survey should be performed not after pregnancy, but at the stage of family planning.