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Factor VII (proconvertin)
Last reviewed: 23.04.2024
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The reference values (norm) of factor VII activity in blood plasma are 65-135%.
Factor VII (proconvertin, or convertin) refers to α 2 -globulins and is synthesized in the liver with the participation of vitamin K. It is mainly involved in the formation of tissue prothrombinase and the transformation of prothrombin into thrombin. Its half-life is 4-6 hours (the shortest half-life among the coagulation factors).
Congenital deficiency of proconvertin
Congenital deficiency of factor VII causes the development of Alexander's disease - an autosomal recessive disease associated with a defect in the synthesis of proconvertin.
For this pathology is characterized by hemorrhagic syndrome of mixed type - hematoma-microcirculatory. Leading clinical signs: melena, ecchymosis and petechiae, bleeding from the umbilical wound, cephalothorem. These typical manifestations occur only when the content of proconvertin in the blood is less than 5% of the norm, which is rarely observed in clinical practice.
In laboratory studies, an increase in the time of blood clotting (with normal bleeding time and platelet count) is found, an increase in PV and APTT. For the final confirmation of the diagnosis, it is necessary to establish the content of proconvertin in the blood serum (in the norm of 65-135%).
Treatment
Bolus administration of a concentrated preparation of the prothrombin complex, which includes factor VII, 15-30 units / kg intravenously.
For newborn doses of factor VII administration are not worked out, but should not exceed 70 units. If necessary, intravenous administration can be repeated. More efficiently with this coagulopathy intravenous infusion of anti-inhibitory coagulant complex (Feiba T1M 4 Immuno) in a dose of 50 to 100 units 2 times a day or NovoSeven (INN: Eptakog alpha activated) at a dose of 20 to 70 μg / kg at 3-hour intervals .
Acquired Proconvertin Deficiency
Acquired forms of hypoproconvertinemia are possible in patients with liver damage, as well as as a result of the action of indirect anticoagulants. Reduction of the activity of proconvertin in blood plasma is noted in patients with viral hepatitis, liver cirrhosis, acute alcoholic hepatitis, chronic persistent hepatitis. In patients with cirrhosis of the liver, there is a distinct relationship between the decrease in the level of proconvertin and the severity of the process. Because of the short half-life, a decrease in the activity of proconvertin is the best marker of the development of liver failure, the onset of which can be monitored literally by the hour, examining the activity of proconvertin in the blood.
The minimum hemostatic level of factor VII activity in the blood for operations is 10-20%, with a lower content the risk of postoperative bleeding is extremely high. The minimum hemostatic level of factor VII activity in the blood to stop bleeding is 5-10%, with a lower content of bleeding stopping without the introduction of a factor VII patient is impossible.
With ICE-syndrome, beginning with the II stage, there is a distinct decrease in the activity of factor VII due to consumption coagulopathy.
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