BLOOD Flashcards
-df: Coagulation is a biological system that preserves the liquid state of the blood, prevents or inhibits blood loss by maintaining the integrity of the vascular wall and the formation of blood clots in places of blood vessels damage.
-In coagulation system there are 3 parts:
I. Morphological part includes:
1) vascular endothelium;
2) platelets;
3) red blood cells, white blood cells.
II. Biochemical part includes:
1) coagulation system:
- plasma coagulation factors;
- plate coagulation factors;
2) anti-coagulation system:
- anticoagulant system;
- fibrinolytic system.
III. A physiological part includes neurohumoral mechanisms of regulation of the relationship of the I and II parts of the system.
From the perspective of pathophysiology and clinic it is preferable to distinguish between 1-primary and 2-secondary coagulation.
Explain the primary and secondary coagulation
-Primary (vascular and platelet) hemostasis or primary coagulation :
It is provided by a vascular wall, platelets and partly erythrocytes. It has a leading role in the initial stop of bleeding in the area of microcirculation. The final result of primary coagulation is a white blood clot
-The mechanism of primary clot formation:
In case of damage to the walls of the blood vessel, platelets come into contact with the endothelium, in particular, with the main stimulator of adhesion – collagen. Platelets swell, form processes and are glued to the site of damage. In parallel, the adhesion is in the process of platelet aggregation, swelling and
bonding among themselves with the formation processes and blending of aggregates for a defect of the vessel, resulting in a hemostatic plug, or clot, is growing rapidly. The primary stimulus to aggregation is given by collagen, catecholamines and serotonin, released from the vascular wall in case of damage.
-From platelets subjected to adhesion and aggregation, granules containing substances that enhance the aggregation process and form a second wave of aggregation are actively secreted. In the cytoplasm of a
platelet there are 4 types of granules that contain the catecholamines, calcium, thromboxane, thrombotonin and 12 endogenous factors are included.
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-Secondary clot formation :Blood clotting is a complex multi-stage enzyme process involving a number of enzyme proteins, as well as non-enzymatic proteins, which provide the interaction of coagulation factors on phospholipid matrices.
-Blood clotting can be represented as four successive phases :
1) formation of active prothrombinase;
2) formation of thrombin from inactive prothrombin under the influence of prothrombinase;
3) formation of soluble fibrin (soluble);
4) formation of insoluble fibrin (insoluble).
-mechanism :
It is known that there are two main mechanisms to start the process of coagulation - extrinsic and
intrinsic. In the extrinsic mechanism, coagulation is stimulated by the entry of tissue thromboplastin
(factor III) into the plasma. The trigger factor of the intrinsic mechanism of blood coagulation is factor
XII, which is activated either by contact of blood with an alien surface (glass, metal, kaolin, etc.), or by
contact of blood with collagen and other components of connective tissue, which is observed with
damage to the walls of blood vessels. In addition, the activation of factor XII can be carried out by its
enzymatic cleavage (kallikrein, plasmin, etc.).
Consequently, there are two types of activation of factor XII:
- contact (with the formation of factor XIIa);
- enzyme (with the formation of the active fragment of factor XIIf).
There are certain qualitative differences between the action of factor XIIa (more affects clotting) and
factor XIIf (it has an activating effect on the kallikrein-kinin system and fibrinolysis). In general, factor XII
is a universal activator of all plasma proteolytic systems - coagulation, kallikrein-kinin, fibrinolytic and
complement systems.
Both with the external and with the internal mechanism of coagulation, interaction and activation of
factors is carried out on phospholipid membranes playing the role of matrices, on which coagulation
factors are fixed, change their structure and intensively react with each other. The role of such matrices
is performed by membranes of cells and platelet granules (platelet factor 3) and similar components
from the membranes of other cells (erythrocytes, etc.). Therefore, thrombocytopenia (with a lack of
phospholipid membranes) can lead to an increase in clotting time, and hemolysis (the release of a large
number of erythrocyte membranes) - to accelerate blood coagulation.
explain ANTICOAGULANT SYSTEM , Df , groups, formation ,
-df:Physiological anticoagulants are needed to maintain blood in the liquid state and to limit the process of blood coagu;ation. They can be divided into two main groups:
1) primary, they are synthesized in the liver independently, their concentration in the blood is constant;
2) secondary, they are formed in the process of proteolysis during blood coagulation and fibrinolysis.
-The first group:
1-antitrypsin,:Their action extends only to activated coagulation factors, without
affecting the profactors. The primary anticoagulants include also antithrombin III, heparin, protein C and S
2-Antithrombin III (AT-III) is a universal inhibitor of many clotting factors, which accounts for more than
75% of all plasma anticoagulant activity. It is the main cofactor of heparin. Synthesized in the liver and vascular endothelium. The main inhibitory effect of AT-III is directed to factors IIa and Xa. In addition,
AT-III inhibits factors IXa, XIa, VIIa, XIIa, as well as plasmin and kallikrein.
3-Heparin is a sulfated polysaccharide, synthesized in mast cells, is found in large quantities in the liver and lungs.
4-Proteins C and S are synthesized in hepatocytes in the presence of vitamin K.
-2nd group :
1-macroglobulin accounts for about 25% of the antithrombin potential. 2-macroglobulin develops
gradually. It has the ability to bind activated components of blood coagulation and fibrinolysis, turn
them off from the interaction with other factors. 2-Macroglobulin (AT-IV) is the main inhibitor of
plasmin. 2-macroglobulin develops graduallyInhibition of thrombin activity under the action of The group of secondary physiological anticoagulants includes, first of all, “spent” coagulation factors and their fragments. So, a powerful anticoagulant is fibrin (antithrombin I), which adsorbs and inactivates large amounts of thrombin.
explain the FIBRINOLYTIC SYSTEM
-df :The enzyme system that provides lysis of fibrin in the bloodstream, called fibrinolytic (or plasmin)
system. She plays the main role in removing the fibrin formed in physiological and pathological conditions. The main component of this system is the enzyme plasmin (fibrinolysin), contained in the plasma in the form of pro-enzyme (plasminogen).
-Plasminogen activators share:
1) in plasma; 2) tissual; 3) bacterial.
Tests for primary coagulation research
1-Duke bleeding time
The earlobe, after warming and treatment with alcohol, is pierced with a sterile lancet at the bottom outer edge to a depth of 3 mm. Immediately after the puncture include a stopwatch. Drops of blood blot with filter paper, without touching the wound, every 30 seconds. Normally, bleeding time is 2-4 minutes.
2-Platelet count
The platelet count is an integral component in assessing coagulation abnormalities, a first test in evaluating primary haemostasis. It only reflects the quantity of platelets in numbers and provides no information about their function. The normal range is between 150,000-440,000/mm3 (150-440109/l). Count less than 150,000/mm3 is categorised as thrombocytopenia. Spontaneous bleeding is less likely with counts >10,000-20,000/mm3. Surgical bleeding may be severe with counts from 40,000 to 70,000/mm3
3-Study of platelet aggregation function
The process of platelet aggregation is studied in platelet-rich blood plasma with the addition of aggregation inducers - adenosine diphosphate (ADP), adrenaline, collagen, thrombin, ristomycin, and some others. The test can be carried out on glass or using an aggregometer. Visual method for determining platelet aggregation by Shitikova. Platelet-rich plasma is applied to a glass slide and mixed with an aggregating agent. On a dark background, the time of appearance of the aggregates in the form of a “snow storm” is recorded.
4-Determination of von Willebrand factor according to Weiss
The method is based on determining the effect of von Willebrand factor contained in the plasma under study on platelet aggregation of healthy people (in the presence of the von Willebrand factor platelets retain the ability to ristomycin aggregation, but cannot aggregate spontaneously and under the action of other aggregation inducers). Willebrand factor activity is expressed as a percentage relative to normal plasma (normally, 80–120%).
Tests for secondary coagulation research
A. Tests characterizing the internal mechanism of coagulation
1. Clotting time by Lee-White
The blood coagulation time is the simplest common coagulation test, which reveals the most serious disturbances in the blood coagulation system (normally, 8–10 minutes).
Increasing in the clotting time may be associated with severe deficiency of one or more clotting factors, an excess of anticoagulants in the blood (heparin), hypocoagulation stage of DIC. To the greatest extent, the test indicators are reflected in the lack of factors involved in the internal mechanism of formation of prothrombinase (XII, XI, IX, VIII), prothrombin and
fibrinogen. This test reveals the most severe forms of pathology.
2. Determination of activated partial thromboplastin time - APTT (APTT) or kaolin-kefalin time:
The time of plasma coagulation with calcium chloride is determined under conditions of coagulation activation by phospholipids (kefalin) and by contact with an alien surface\ (kaolin). Normal indicators - 35-45 s.
APTT - highly standardized coagulation test, sensitive only to plasma coagulation defects, especially to the deficiency of factors XII, XI, IX and VIII, as well as to an excess of plasma anticoagulants. The APTT is a basic test for determining the stage of DIC and monitoring the effectiveness of therapy. Clinical Significance
3-. Autocoagulation test (ACT)
Citrate blood is centrifuged and divided into two tubes: the plasma and the blood elements
separately. Hemolysate-calcium mixture (HCM) is prepared from the blood elements by mechanical
lysis of erythrocytes and addition of calcium chloride. The blood plasma is poured into 10 test tubes.
In each tube with a plasma sequentially after 2, 4, 6, 8, 10, 20, 30, 40, 50 and 60 minutes add HCM
and note the time of the formation of a clot.
Normally, the ACT for 2 min - 17-50 s, for 4 min - 8-25 s, for 6 min - 8-14 s, for 8 min - 7-11 s, for 10
min - 7-10 s (maximum activity ), for 20 min - 7-14 s, for 30 min - 10-18 s, for 40 min - 10-22 s, for 50
min - 12-25 s, for 60 min - 12-32s.
ACT is a very informative and easy-to-do test in any laboratory, which allows to judge the state of both the coagulation and anticoagulation units of hemostasis.
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B. Tests characterizing the extrinsic coagulation mechanism
1. Prothrombin Time (PT)
The PT measures the time necessary to generate fibrin after activation of factor VII. It measures the integrity of the “extrinsic” and “common” pathways (factors VII, V, X, prothrombin, and fibrinogen).
2. Echys test
The introduction of venom Iranian Echis carinatus into the plasma causes coagulation by direct
activation of prothrombin to form abnormal thrombin. This thrombin is insensitive to heparin and ATIII, does not activate factor XIII, and does not cause retraction of the blood clot. The clotting time in
the Echys test depends on the content of prothrombin and fibrinogen in the plasma, as well as on molecular features. Normally, clotting occurs in 30 seconds.
Elongation of the specified test indicates a deficiency of prothrombin and / or fibrinogen, or of quality defects of these factors. The elongation of Echys test time of coagulation at normal thrombin time and normal fibrinogen level indicates a deficiency or anomaly of prothrombin.
The shortening of the test indicates the circulation in the blood of activated forms of prothrombin (DIC, thrombosis). With heparin therapy, this test is very convenient to use to control the basic state of hemocoagulation (heparin therapy does not affect the time of the echox test)
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C. Indicators of the final stage of blood coagulation
1. Thrombin Time
This test measures the time necessary to drive the reaction of fibrinogen to fibrin in the presence of thrombin. It measures the integrity of this reaction and isolates an abnormality to either a decrease in normal fibrinogen or an inhibitor to its activation.
-Abnormalities can be explained in one of three ways: deficient fibrinogen (< 100 mg/dl), abnormal
fibrinogen, or an inhibitor to the reaction:
- hypofibrinogenemia;
- excessive plasma FDP (DIC, thromboembolism);
- molecular abnormalities of fibrinogen;
- the presence of paraproteins in the plasma;
- pronounced hyperfibrinogenemia;
- hyperheparinemia;
- the phase of hypocoagulation of DIC
2. Test with snake venom of copperhead snake (ancystrodon test)
In contrast to thrombin, the poison of copperhead snake transforms fibrinogen into an incomplete fibrin monomer, splitting off only terminal peptides A from each molecule. It does not activate factor XIII and platelets, and therefore an unstabilized fibrin clot is formed that is not capable of retraction. The action
of the poison is also not inactivated by AT-III and heparin (at the usual therapeutic dosages of the latter).
Coagulation of blood under its action occurs normally in 30 seconds.
The ancystrodone test does not change with the patient’s heparinization and with an excess of ATIII, little depends on the FDP. In DIC, it detects a greater amount of fibrinogen than the thrombin test, and therefore is used to diagnose dysfibrinogenemia.
4. Determining the amount of fibrinogen A
The normal level of blood fibrinogen is 2-4 g / l. A decrease in the concentration of fibrinogen is noted in its congenital insufficiency (a-, hypo-, dysfibrinogenemia), severe liver disease, phase III DIC, acute fibrinolysis. An increase in the concentration of fibrinogen is observed in infectious diseases, acute and chronic inflammatory processes, neoplasms, thrombosis, thromboembolism, after injuries, childbirth, operations.
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D-Paracoagulation tests
a) naphthol test. Determination of fibrinogen B. If fibrinogen B (fibrin monomers formed from
fibrinogen under the action of thrombin and plasmin) is present in the plasma, then β-naphthol in the sediment appears filaments, granules or clots. Fibrinogen B can be determined quantitatively (normally not more than 0.07 g / l) and qualitatively (normally negative). The test becomes positive with DIC
b) ethanol test. If there are blocked fibrin monomers in the plasma under study, i.e. their complexes
with fibrin degradation products (fibrinolysis products), a gel-like clot forms in the plasma under the influence of ethanol. A positive ethanol test suggests that there is DIC, accompanied by lysis of the formed fibrin. More often, the test is positive at the early stages of the process and can become negative with pronounced hypofibrinogenemia (less than 0.5 g/l), as well as after the absorption of the SFMC, the system of phagocytic macrophages. In a wave-like course of DIC in different periods of the disease, alternation of positive and negative test results may occur.
c) Protamine sulphate test. The appearance of a clot in the plasma upon the addition of protamine sulfate to it indicates the presence of SFMC in this plasma. The test can give a false positive result with severe hyperfibrinogenemia (more than 8 g / l). In DIC, the test is less likely to give a positive result than ethanol, but it is often determined positive when the latter becomes negative. Therefore, these tests complement and not replace each other
d) Ortofenanthrolin test (OFT). OFT becomes positive and reveals different contents of fibrin monomer complex with DIC, as well as thrombosis and embolism. Unlike other paracoagulation tests, OFT allows quantitative dynamic control of SFMC content in plasma, including during treatment. Normally, the level of SFMK in plasma does not exceed 0.035 g.
e) D-dimer test. D dimer is a FDP, a small protein fragment present in the blood after a clot is degraded by plasmin (fibrinolysis). It is so named because it contains two D fragments of the fibrin. D-dimer concentration may be determined to help diagnose thrombosis
Tests of Fibrinolysis and the Mechanisms That Control Hemostasis
-df :The coagulation cascade is an efficient system for generating fibrin. Equally important is the system that limits this process, neutralizes activated factors, stops propagation of the clot, and keeps the process of coagulation confined to the area of endothelial rupture.
Fibrinolysis is accomplished by the action of plasmin on fibrin polymer. Plasmin is generated from plasminogen (produced by the liver) by the action of plasminogen activators. These compounds are present in endothelial cells, and the reaction is accelerated in the presence of fibrin. Thus the generation of fibrin appears to turn on the fibrinolytic process and localize the formation of the fibrin gel.
-Fibrin Degradation Products: As a marker of fibrinolysis, fibrin degradation products (FDP), also known as fibrin split products (FSP), can be quantified by a test based on latex agglutination. The test uses antibodies to FSP which are measured using serial dilutions.
-Clinical Significance ;Increased FDP is the laboratory expression of increased fibrinolysis. This may be part of a local problem of fibrin generation such as brain trauma, chronic bleeding, vascular thrombosis, prostate surgery, uterine disorders, or malignancy, or a systemic process, usually DIC. Patients with severe liver disease can have increased fibrinolysis on the basis of poor clearance of circulating plasminogen activators.
-Determination of blood fibrinolytic activity (BFA) by plasma euglobulin lysis
The principle of the method is based on precipitation in an acidic medium and at a low temperature of the euglobulin fraction containing coagulation factors and fibrinolysis. The main component of the euglobulin fraction is plasminogen. The time from the formation of a fibrin clot to its dissolution reflects the fibrinolytic activity of the blood. Normally, BFA is 150-220 minutes. An increase in the BFA time (over 220 min) indicates a decrease in plasma fibrinolytic potential (impaired plasminogen activation due to a lack of its activators, a decrease in plasminogen, a slowdown in kallikrein-kinin activation, inhibition of factor XII). An increase in the time of BFA is observed in patients with thrombosis, thromboembolism, with stage III-IV DIC, in patients with hemorrhagic vasculitis, sepsis, and pregnancy toxicosis. Slow lysis reflects hypercoagulable state.
