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Lab D > 3. Haemostasis > Flashcards

3. Haemostasis Flashcards

1
Q

What is haemostasis?

A

The name of a group of processes initiated in the body in order to stop bleeding in case of tissue and/or blood vessel injuries

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2
Q

Major groups of hemostasis disorders

A
  1. Vasculopathy (decr ability of vasoconstriction in case of blood vessel injury, first step of haemostasis proc)
  2. -Thrombocytopathy (decr ability of platelets to aggregate and adhere to the site of injury, and form of primary thrombocyte-thrombus, second step)
    - Thrombocytopenia (decr amount of thrombocytes in blood)
  3. Coagulopathy (problems with extrinsic-, intrinsic-, or common pathway of coagulation cascade, which ends w. form of a polymerised fibrin network, which keeps thrombocyte thrombi at the site of injury, third and final step)
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3
Q

Tests performed by side of the animals

A
  1. Signs of incr bleeding tendency:
    * On skin and mucous membr: anemia, petechia, ecchymosis, suffusion
    * In thoracic cavity: haemothorax
    * In abd cavity: haemoperotoneum
    * In GI-tract: haematemesis, melena
  2. Capillary resistance (human medicine)
  3. Bleeding time (buccal mucosal bleeding time test, BMBTT)
  4. Appearance of the first fibrin strand (clotting time)
  5. Appearance of the clot (clotting time on different surfaces)
  6. Clot retraction time
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4
Q

Capillary resistance test

A
  • The test is usually used in the human medicine, also called Rumpel-Leed-test.
  • Performed by putting a ligature on the arm, above the elbow and checking the palmar side of the lower arm for petechie.
  • Norm: After 3-5 min. of ligature 3 small petechie should appear
  • If not proper, more petechia appear.
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5
Q

Bleeding time

A

Bleeding time (BT)/Buccal mucosal bleeding time (BMBT): test for thrombocytopenias, thrombocythopathies and vasopathies.

  • 0.1-0.2 mm deep, 0.5 cm long incision on skin of inner part of the external ear or on buccal mucosal surface. Vipe the blood drop flowing UNDER the wound carefully with a cotton wool tissue, or paper towel in 20-30 sec. intervals. Measure the time from the appearance of the first drop of blood until the ceasing of bleeding.
  • Dependent on the thrombocytic function, the platelet count, and the capillary function.
  • Normal BMBT: 3-5 min.
  • No danger of clinical bleeding until platelet count is above 50 x 109/l.
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6
Q

Coagulation time (CT)

A
  • Test for coagulopathies
  • Fresh, native, whole blood samples, immediately after taking them
  • ”two syringe method”
  • Tests:
    1. Appearance of the first fibrin strand
    2. Clotting time (CT) on watch glass
    3. CT in plastic syringe
    4. CT in glass tube
    5. CT in ACT (activated clotting time) tube
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7
Q

Appearance of the first fibrin strand

A

put some drops of blood sample onto a glass slide and sink the tip of a needle into it and move the needle forward and back while carefully and slowly pulling the tip out of the blood sample.
-The first fibrin strand should appear within 1-2 min

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8
Q

Clotting time (CT) on watch glass: normal time

A

-Normal is 7-15 min

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9
Q

CT in plastic syringe: normal time

A

-Normal is 10-12 min.

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10
Q

CT in glass tube: normal time

A

-Normal is 4-5 min.

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11
Q

CT in ACT (activated clotting time) tube

A

-The tube contains SiO2
-SiO2 activates Factor XII (Hagemann-factor, contact factor). -> activated Factor XII activates Factor IX and
kallikreinogen, kinigogen.
-Normal is 3 min.

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12
Q

Platelet (thrombocytic) count

A
  • Important especially when BT, BMBT is incr, or petechie are visible on the skin or mucous membranes.
  • Anticoagulated blood; Na2-, or K2 EDTA should be used
  • Method 1: Bürker chamber
  • Method 2: Blood smear
  • Method 3: Cell counters
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13
Q

General Platelet Count

A

200-800 x10^9/l

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14
Q

Major causes of thrombocytopenia:

A
  1. Decr prod of thrombocytes in bone marrow
  2. Incr utilisation of thrombocytes: DIC (disseminated intravascular coagulopathy)
  3. Incr destruction of thrombocytes : autoimmune thrombocytopenia (AITP)
  4. Incr sequestration of thrombocytes: in case of (chronic) splenomegaly
  5. Incr loss of thrombocytes: subacute/chronic bleeding
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15
Q

Clot retraction test

A
  • Ieave blood clot in a tube for some hours->will become smaller+serum around the clot.
  • Normally volume of serum released by clot within one hour is approx. 25% of the whole volume of the initial clot..
  • Thrombocytic function can be estimated by performing this test. If the clot retraction is slower, or does not happen at all, we can suspect thrombocytopathy.
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16
Q

Platelet aggregation test

A
  • When we suspect thrombocytopathy , ie. von Willebrand disease.
  • Use aggregometers to estimate the aggregating ability of platelets correctly.
  • Citrated blood sample and the upper layer should be used for this analysis.
  • Then we put this sample into a cuvette and add some drugs which causes exaggerated aggregation. These drugs will induce platelet aggregation which will cause the clearing up of the fluid in the cuvette.
  • The speed and the rate of the clearing can be analysed by a spectrophotometer.
  • The device gives numerical values to this process
17
Q

Thrombocytic morphology

A
  • 1-2 µm diameter.
  • Their centre is the granulomer and the edge is the hyalomer part
  • Horses, sheep, cattles, have the smallest platelets (3-5 fl)
  • dogs and swine have bigger (7-8fl)
  • cats have the biggest (10-15fl) thrombocytes
18
Q

Major causes of thrombocytopathies

A
  1. improper development of platelets, for example because of hereditary glucoprotein deficiencies, etc.
  2. von Willebrand’s disease
  3. uraemia, liver failure, myelo-, and/or lymphoproliferative diseases, NSAID treatment, etc.
19
Q 
Major alterations of the basic tests in different haemostasis disorders:
BT? / CT? / PC? / Platelet morphology?
1. Coagulopathy: 
2. Thrombocytopenia
3. Thrombocytopathy
4. Vasculopathy
A
  1. Coagulopathy: incr CT
  2. Thrombocytopenia: incr BT, decr PC, altered or not
  3. Thrombocytopathy: incr BT, altered
  4. Vasculopathy: incr BT
20
Q

Exam. of Coagulopathies

A
  • by using more specific “global “tests, so that we can evaluate, which group(s) of factors are not functioning properly.
  • Citrated blood should be used, which means, 3,8 % Na-citrate:blood = 1:9
21
Q

Prothrombin time (PT)

A

-within 1 hour after sampling.
-Blood samples should be mixed with 3.8% sodium
citrate in 9:1 dilution. Then centrifuge it, and separate the plasma from sediment
-reagent (Simplastin) for PT evaluation contains rat uterus tissue homogenate as tissue thromboplastin (Factor
III.), and CaCl2.
-The evaluation can be performed by using coagulometer or in test-tube.
-Normal PT: 10-15 sec.
-gives info about the function of extrinsic pathway
-Factors involved: VII., X., V., II., I., XIII.

22
Q

Activated partial thromboplastin time (APTT)

A
  • decalcinated plasma
  • reagent (Silimat) contains rabbit brain homogenate as PF3 (platelet factor 3)
  • micronised silica as contact activator
  • Normal APTT: 20-30 sec.
  • gives info on the function of intrinsic pathway
  • Factors involved: XI., IX., VIII., X., V., II., I., XIII.
23
Q

Thrombin time (TT)

A
  • decalcinated plasma should be simply mixed with a reagent containing thrombin only
  • coagulation time depends on the conc of fibrinogen and Factor XIII. in the plasma.
  • can also be used for the estimation of fibrinogen conc
24
Q 
What is the problems with... 
and how is APTT / PT in...
1. Intrinsic pathway problem
2. Extrinsic pathway problem
3. Common pathway problem
A
  1. (haemophilia A-factor VIII. deficiency; haemophilia B-factor IX. deficiency; von Willebrands disease) - APTT incr
  2. (Factor VII deficiency, dicumarol toxicosis - first stage) - PT incr
  3. (liver disease-decr. prod. of coag. factors, DIC, dicumarol toxicosis - second stage, Factor X. and/or V. and/or II. and/or I. and/or XIII. deficiency) - Both incr
25
Q

What is dicumarol?

A

Dicumarol is a competitive antagonist of vitamin K.

26
Q

What is vit.K responsible for, and what happens from vit.K. def.?

A

Responsible for the gamma carboxylation of Proconvertin (Factor VII), Christmas (Factor IX), Stuart-Prower (Factor X) and the Prothrombin (Factor II), as they are Ca2+ dependent factors. Function of Vit K is to exaggerate the post-synthetic gamma carboxylation of those factors in the liver.
-So vitamin K deficiency causes the inability of these factors to bind calcium. In case of def. of any origin, improperly carboxylised prothrombin can be detected by using an ELISA (Enzyme Linked Immunosorbent Assay) test, called PIVKA II. (Proteins Induced by Vitamin K Absence)

27
Q

Coagulation cascade

  1. Extrinsic factors
  2. Intrinsic factors
A
  1. Ext: Tissue damage: III, VII*
  2. Intrinsic: Collagene (neg. charge, SiO2): XII, XI, IX, VIII, PF3 V X, II, TT I, XIII, polimerised fibrin
    (Signed factors (    ) are the Vit-K dependent factors)
28
Q

Fibrinolytic pathway

A

Responsible for keeping the clot formation within normal limits.

29
Q

Fibrin degradation products (FDP)

A

Clot inhibitors - bind to thrombin and neutralise it.
-Activator factors of XII (Hageman): free collagen fibres, kininogen and kallikrein
-XII.a: further activates extrinsic pathway, and is also able to form kallikrein from prekallikrein.
-Kallikrein activates kininogen system, also, forming
bradikinin, which is a very potent mediator of pain.
-Kallikrein: most important activator of plasminogen
-Plasmin: an endopeptidase, can cleave fibrin strands into small pieces.
-More accurate way to detect incr fibrinolysis, is the exam of D-dimer level in the blood.
-Both tests are based on latex agglutination method
-Reagent contains antibodies against FDPs or D-dimers attached to latex particles.

30
Q

DIC

A

-Disseminated intravascular coagulopathy
-Performing FDP, or rather D-dimer, is very helpful in early diagnosis of DIC
-Common acute disorder, that requires accurate and quick laboratory diagnosis.
-Usually a secondary problem, caused by primary diseases
-Microthrombus formation and fibrinolysis are present at many different places in the body simultaneously, because of severe tissue damage or necrosis, and blood vessel injury, so coagulation factors and platelets are consumpted very quickly during this process.
-can be a life threatening complication of the
aforementioned diseases.
-Early diagnosis is very important in the management of this condition.
-First laboratory sign of DIC can be a pos. FDP or D-dimer test.

31
Q

Laboratory diagnosis of DIC

A
  • Coagualtion time: incr
  • Bleeding time: incr
  • Platelet count: DECR.
  • PT: incr
  • APTT: incr
  • TT: incr
  • Fibrin degradation products (FDP), and D-dimer: incr
  • Appearance of schysocytes and/or burr-cells in blood smear (damaged RBCs)
32
Q

Diagnosis of von Willebrand disease

A
  • Humans, and Dobermann/pinchers, often accompanied by
    hypothyroidism.
  • The von Willebrand factor, or the complete Factor VIII is deficient.
  • There are 3 main part of complete Factor VIII:
    1. von Willebrand factor: responsible for platelet adhesion and aggregation
    2. VIIIc: antihaemophylic factor
    3. Factor VIII related antigen: hapten that is the determinable part, and is bound strongly to von Willebrand factor.
  • The dogs with this disease have incr BT, BMBT, decr clot retraction ability and sometimes coagulation disorders.
  • The specific diagnosis is based upon the detection of the lack of von Willebrand related antigen
33
Q

BT, BMBT / Platelet count / APTI /PI

in. ..
1. Thrombocytopenia
2. Thrombocytopathy
3. Intrinsic pathway disorder
4. Factor VII deficiency
5. Disorder of the Common pathway
6. DIC
7. von Willebrand-disease

A
  1. Thrombocytopenia: BT, BMBT incr. / Platelet count decr.
  2. Thrombocytopathy: BT, BMBT incr
  3. Intr. P disorder: APTI incr
  4. F. VII def.: PI incr
  5. Disorder of Com. P: BT, BMBT same/incr / APTI incr / PI incr
  6. DIC: BT, BMBT incr / Platelet count decr / APTI incr / PI incr
  7. von Willebrand-dis: BT, BMBT incr / APTI same/incr

Lab D (18 decks)

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