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Lab D > Lab 4 Haemostasis > Flashcards

Lab 4 Haemostasis Flashcards

(47 cards)

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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

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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

Study These Flashcards
A

1000x magnification

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

21
Q

Platelet count automatic cell counter

Study These Flashcards
A

5-30 fl size = platelets

22
Q

ACC platelet errors giving false results

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

General platelet count

Study These Flashcards
A

200-800 x10^9/l

24
Q

5 major causes of thrombocytopenia

Study These Flashcards
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
What tests are used to check thrombocytic function?
BMBT Platelet count Clot retraction test Platelet aggregation test
26
Clot retraction test
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
Platelet aggregation test
CITRATED blood sample, upper layer (platelet rich plasma) Put sample in cuvette, add aggregating causing drugs (ADP, epinephrine) Aggregated platelets: clear sample Spectrophotometry
28
Thrombocytic morphology
1-2 um diameter, granulomer center and hyalomer edge | Cats have the biggest platelets
29
3 major causes of thrombocytopathy
1. Improper development 2. von Willebrand diesease 3. Uraemia, liver failure, NSAIDS etc
30
If coagulation is normal, what can we expect in case of thrombocytopenia, thrombocytopathy and vasopathies?
No signs of severe bleeding disorder | Prevented by formation of fibrin thrombus
31
If platelet function and count is normal, and no vasopathies are present, what can we expect in case of coagulopathies?
Really severe bleeding disorders (suffusion, hematoma, hemothoax, hemoperitoneum Thrombocytic thrombi are not stable without fibrin network
32
What test can be done to test the extrinsic+common coagulation cascade?
Prothrombin time
33
Explain PT, what sample is used
Na-Citrate 1:9 Decalcinated plasma + TF3 + CaCl2 Normal PT: 10-15 sec Extrinsic coagulation cascade is triggered by tissue factor and Ca2+
34
What test can be done to test the intrinsic+common coagulation cascade?
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
Explain thrombin time
Decalcinated plasma mixed with thrombin only | Coagulation time depends on conc of fibrinogen and factor XIII in plasma (fibrin stabilizing)
36
Intrinsic pathway problem APTT, PT What can cause it?
APTT increased PT normal ``` Hemophilia A (Factor VIII deficiency) Hemophilia B (Factor IX deficiency) von Willebrand disease ```
37
Extrinsic pathway problem APTT, PT What can cause it?
APTT normal PT increased Factor VII deficiency First stage of dicumarol/warfarin toxicosis
38
Common pathway problem APTT, PT What can cause it?
Both increased ``` Liver disease DIC Second stage of dicumarol toxicosis (vit K def) 1, 2, 5, 10, 13 factor deficiency Protein deficiency (cachexia) ```
39
Dicumarol toxicosis
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
FDP | D-dimer
Fibrin degradation products Both from fibrin and fibrinogen D-dimer: from fibrin only!
41
Clot inhibitors | Function
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
How are fibrinolytic enzymes activated?
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
What principles are FDP and D-dimer tests based on? | What sample?
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
DIC
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
Lab parameters of DIC
``` CT inc BT inc Platelet count dec PT, APTT, TT inc FDP/D-dimer inc Damaged RBCs ```
46
Diagnosis of von Willebrand
Deficiency of factor VIII BT inc Clot retraction dec
47
3 parts of factor VIII
von Willebrand: platelet adhesion and aggregation VIIIc: antihemophilic factor VIII related antigen: hapten bound to vW

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