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Lab D > Lab 4 Haemostasis > Flashcards

Lab 4 Haemostasis Flashcards

1
Q

What is hemostasis?

A

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

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2
Q

What are the requirements for hemostasis tests?

A

They must be quick so they can be performed by the side of the animal, easy to perform and give good estimation

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3
Q

Describe the three phases of hemostasis

A

Phase 1: vessel reaction, platelet aggregation
Phase 2: thrombus formation
Phase 3: fibrinolysis

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4
Q

Give the three major groups of hemostasis disorders

A

Vasculopathy
Thrombocytopathy
Coagulopathy

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5
Q

What is vasculopathy

A

Decreased ability of vasoconstriction in case of blood vessel injury

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6
Q

What is thrombocytopathy

A

Decreased ability of platelets to aggregate and adhere to the site of injury, thrombocytopenia

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7
Q

What is coagulopathy

A

Problems with the extrinsic, intrinsic or common pathway for the coagulation cascade, which ends with the formation of a polymerized fibrin network

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8
Q

Give 5 hemostasis tests that can be performed by the side of the animal

A
  1. Capillary resistance (mainly humans)
  2. BMBTT
  3. Clotting time (first fibrin strand)
  4. Appearance of clot (different surfaces)
  5. Clot retraction time
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9
Q

Explain capillary resistance test

A

Ligature on arm, 3-5 mins: 3 petechie should appear

If more: fragile capillaries: vasculitis

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10
Q

Explain BMBTT

A

Buccal mucosal bleeding time
Make sharp incision in buccal mucosa/inside of ext ear
Wipe blood flowing under wound every 30 secs
Measure time from appearance of blood until bleeding ceases
Normal BT: 3 ish minutes
For vasculopathy and thrombocytopathies

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11
Q

Give the 5 CT tests

A
  1. Appearance of first fibrin strand
  2. CT on watch glass
  3. CT in plastic syringe
  4. CT in glass tube
  5. CT in ACT
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12
Q
  1. Appearance of first fibrin strand
A

Drops of blood on watch slide
Move needle back and forth through blood slowly
First fibrin strand: 1-2 mins

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13
Q
  1. CT on watch glass
A

Fresh blood sample on watch glass treated with paraffin/wax

Time for the blood to completely clot: 7-15 min

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14
Q
  1. CT in plastic syringe
A

Complete coagulation

10-12 min

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15
Q
  1. CT in glass tube
A

Glass test tube
Complete coagulation
4-5 min

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16
Q
  1. CT in ACT
A 
Intrinsic pathway
SiO2 (neg charged)
Activates factor XII - contact factor
XII activates IX and kallikreinogen, kininogen
Normal: 3 mins
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17
Q

What 3 tests can be done to evaluate platelet count?

A
  1. Bürker chamber
  2. Blood smear in light microscope
  3. Automatic cell counter
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18
Q

What sample is used for platelet counts?

A

Na/K EDTA anticoagulated blood

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19
Q

Platelet count Bürker chamber

A

1:9 blood: saline solution
Count platelets in rectangles, and divide: average
Multiply by 10^9 = one litre of blood

20
Q

Platelet count blood smear in light microscope

A

1000x magnification

one platelet in one view = 20x10^9/l

21
Q

Platelet count automatic cell counter

A

5-30 fl size = platelets

22
Q

ACC platelet errors giving false results

A 
Young platelets (Cats, Spaniels): large: RBCs
Small RBCs: can be mistaken for platelets
23
Q

General platelet count

A

200-800 x10^9/l

24
Q

5 major causes of thrombocytopenia

A
  1. Decreased production in BM: parvovirus, mycotoxins
  2. Increased utilization: DIC
  3. Increased destruction: autoimmune thrombocytopenia
  4. Increased sequestration: splenomegaly
  5. Increased loss: subacute bleeding
25
Q

What tests are used to check thrombocytic function?

A

BMBT
Platelet count
Clot retraction test
Platelet aggregation test

26
Q

Clot retraction test

A

Blood clot left in tube for hours: clot retracts, serum appears
Platelets contain a contractile protein thrombostenin
Within one hour: serum 25% of whole volume of initial clut

27
Q

Platelet aggregation test

A

CITRATED blood sample, upper layer (platelet rich plasma)
Put sample in cuvette, add aggregating causing drugs (ADP, epinephrine)
Aggregated platelets: clear sample
Spectrophotometry

28
Q

Thrombocytic morphology

A

1-2 um diameter, granulomer center and hyalomer edge

Cats have the biggest platelets

29
Q

3 major causes of thrombocytopathy

A
  1. Improper development
  2. von Willebrand diesease
  3. Uraemia, liver failure, NSAIDS etc
30
Q

If coagulation is normal, what can we expect in case of thrombocytopenia, thrombocytopathy and vasopathies?

A

No signs of severe bleeding disorder

Prevented by formation of fibrin thrombus

31
Q

If platelet function and count is normal, and no vasopathies are present, what can we expect in case of coagulopathies?

A

Really severe bleeding disorders (suffusion, hematoma, hemothoax, hemoperitoneum
Thrombocytic thrombi are not stable without fibrin network

32
Q

What test can be done to test the extrinsic+common coagulation cascade?

A

Prothrombin time

33
Q

Explain PT, what sample is used

A

Na-Citrate 1:9
Decalcinated plasma + TF3 + CaCl2
Normal PT: 10-15 sec

Extrinsic coagulation cascade is triggered by tissue factor and Ca2+

34
Q

What test can be done to test the intrinsic+common coagulation cascade?

A

Activated Partial Thromboplastin Time
Decalcinated plasma + PF3 + Micronised silica
Normal APTT: 20-30 sec

Intrinsic coagulation cascade is triggered by surface activation (which appears on inner surface of blood vessels), PF3 + Ca2+ activates factor X (common)

35
Q

Explain thrombin time

A

Decalcinated plasma mixed with thrombin only

Coagulation time depends on conc of fibrinogen and factor XIII in plasma (fibrin stabilizing)

36
Q

Intrinsic pathway problem
APTT, PT
What can cause it?

A

APTT increased
PT normal

Hemophilia A (Factor VIII deficiency)
Hemophilia B (Factor IX deficiency)
von Willebrand disease
37
Q

Extrinsic pathway problem
APTT, PT
What can cause it?

A

APTT normal
PT increased

Factor VII deficiency
First stage of dicumarol/warfarin toxicosis

38
Q

Common pathway problem
APTT, PT
What can cause it?

A

Both increased

Liver disease
DIC
Second stage of dicumarol toxicosis (vit K def)
1, 2, 5, 10, 13 factor deficiency
Protein deficiency (cachexia)
39
Q

Dicumarol toxicosis

A

Competitive vit K antagonist
Vit K: gamma carboxylation of factor 7, 9, 10, 2 (Ca2+ dependent factors)
Deficiency: factors cannot bind to Ca2+
Factor 7 has shortest half life: deficient first
= increased PT
then after a while = increased APTT too

40
Q

FDP

D-dimer

A

Fibrin degradation products
Both from fibrin and fibrinogen

D-dimer: from fibrin only!

41
Q

Clot inhibitors

Function

A

Antithrombin III
Alpha-2 macroglobulin
Alpha-1 antitrypsin
Heparin

Responsible for keeping the clot formation within normal limits
Bind to thrombin and neutralizes it

42
Q

How are fibrinolytic enzymes activated?

A

Free collagen fibers, kallikrein and kininogen activates factor XII

Factor XII activates kallikrein which forms bradikinin (activated form of kininogen)
Bradikinin: potent mediator of pain
Kallikrein also activates plasminogen
Plasmin: endopeptidase: cleaves fibrin

43
Q

What principles are FDP and D-dimer tests based on?

What sample?

A

Latex agglutination
Fresh citrated plasma
Contains antibodies against D-dimers/FDP = bound
Macroscopic agglutination can be seen if enough D-dimers/FDP are in the plasma

44
Q

DIC

A

Disseminated intravascular coagulopathy
FDP/D-dimer test= early diagnosis
Usually secondary to diseases:
Septicaemia, pancreatitis, burn injuries, necrosis, shock
Microthrombus and fibrinolysis is present many places in the body simultaneously

Quick consumption of platelets and coag factors

45
Q

Lab parameters of DIC

A 
CT inc
BT inc
Platelet count dec
PT, APTT, TT inc
FDP/D-dimer inc
Damaged RBCs
46
Q

Diagnosis of von Willebrand

A

Deficiency of factor VIII
BT inc
Clot retraction dec

47
Q

3 parts of factor VIII

A

von Willebrand: platelet adhesion and aggregation
VIIIc: antihemophilic factor
VIII related antigen: hapten bound to vW

Lab D (8 decks)

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