What is Deficiency Factor V?
For the first time, a patient with a hereditary coagulation factor deficiency was described in 1947. Subsequently, this factor received the following designations: labile factor, proaccelerin, Ac-globulin, factor V.
Factor V is synthesized, like other factors of the prothrombin complex (II, VII, X), in hepatocytes (liver cells), but its formation does not depend on vitamin K. It is labile (changeable), poorly preserved in canned blood and plasma, consumed in the coagulation process differs from factors VII and X. In fresh serum, traces of factor V are determined, and after an hour of storage at 37 ° C, this factor is no longer determined. Factor V, as well as factor II, is not sorbed (drawn out) of barium sulfate from the plasma.
Factor V deficiency is inherited in an autosomal dominant type with an incomplete expressiveness of the pathological gene and in an autosomal recessive type. These data indicate the polygenicity of parahemophilia. This is also evidenced by a certain heterogeneity of hemostasis disorders in different patients, in particular, the relatively frequent combination of factor V deficiency with prolonged bleeding time and factor VIII deficiency.
Symptoms of Deficiency Factor V
The severity of hemorrhagic syndrome depends on the degree of deficiency in the plasma of factor V patients, as well as on the presence of concomitant disorders in other parts of the hemostasis system, such as lengthening the bleeding time, factor VIII deficiency. There are minor hemorrhages and bruises, nasal and gingival, uterine and menstrual bleeding. Possible bleeding from the umbilical cord, gastrointestinal bleeding. In patients with severe forms of the disease, prolonged bleeding during tooth extraction, tonsillectomy (tonsil removal) and cuts are frequent, but abdominal operations are rarely complicated by bleeding. The most severe bleeding is observed in patients with a level of factor V below 2% and when combined with a deficiency of this factor with a deficiency of factor VIII. With moderate disease, the level of factor V in plasma is 2-6%, with a mild form of the disease – 6-16%. With a higher factor V, bleeding does not occur.
Diagnosis of Defecit Factor V
Factor V deficiency, as well as Stewart-Prouwer disease, is accompanied by prolonged prothrombin time and impaired indication of activated thromboplastin time, thromboplastin generation test, and autocoagulation test.
All the above violations are combined with normal thrombin time and are eliminated by adding fresh normal plasma to the studied plasma. In contrast, the “old” normal plasma does not possess such a corrective action. To obtain an “old” plasma, it is stored in a refrigerator at 4 ° C until its prothrombin time lengthens to 60 s or more; such a plasma can be considered practically devoid of factor V, but still containing a sufficient number of factors II, VII and X. The diagnosis is clarified by quantitative determination of factor V in the patient’s blood plasma.
Defecit Factor V Treatment
Replacement therapy for factor V deficiency is performed with fresh donor blood or fresh frozen plasma. They should be harvested in plastic bags, since contact with glass accelerates the inactivation of factor V. In special cases, direct blood transfusions from a donor to a patient are possible. In this case, in no case do not use the blood of the parents and other relatives of the patient.
In case of large bleeding and preparation for surgical interventions, the level of factor V in plasma should be higher than 25-30%. This is achieved by repeated jet transfusions of fresh frozen plasma at the rate of 15 ml / kg every 12 hours. It is better to start preoperative preparation of patients 1–2 days before surgery. On the first day of treatment or preoperative preparation, plasma is administered by intravenous infusion at a dose not exceeding 40-50 ml / kg body weight. The volume of infusion of blood for an adult patient can reach 1.5-2 liters of donor plasma in 2 administrations. After that, they switch to the introduction of plasma at the rate of 15 ml / kg of body weight. For minor injuries and surgeries (tooth extraction, etc.), it is sufficient to increase the level of factor V in the patient’s plasma not to 25-30%, but only to 15-20%. With simultaneous deficiency of factor VIII, cryoprecipitate is also prescribed.