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Clinical pathology > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

Define haemostasis.

A

Maintenance of vascular integrity and blood fluidity.Involves:

  • Blood vessel endothelium
  • Platelets
  • Coagulation cascade - Ca2+, coagulation factors, fibrinogen
  • Fibrinolytic mechanisms
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2
Q

Outline primary haemostasis.

A

Formation of the platelet plug

  • Vascular endothelial damage
  • Exposed subendothelial collagen damage
  • vWf binds collagen and platelets
  • Platelets activated, attracted and loosely aggregated
  • Local vasoconstriction (transient)
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3
Q

Outline secondary haemostasis.

A

Formation of the definitive clot

  • Exposure of subendothelial structures and platelet activation initiate thrombin generation
  • Activation of the coagulation cascade
  • Irreversible platelet aggregation
  • Fibrin clot forms - fibrinogen to insoluble fibrin
  • Fibrin forms a mesh via cross-linking
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4
Q

Describe the clotting cascade.

A

Instrinsic - activated by contact with collagen (sustaining)Extrinsic - activated by tissue factor, extravascular(initiation)

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5
Q

Outline tertiary haemostasis.

A

Fibrinolytic pathway.

  • Lysis of platelet-fibrin network Plasmin mediated
  • Activated plasminogen
  • Balanced by inhibitors
  • Fibrin degraded to FDPs (D-dimers)
  • Vascular endothelium repair
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6
Q

Which screening assays are used to assess the common and intrinsic pathways?Describe them

A
  • ACT - Activated coagulation time - whole blood, platelets and calcium
  • APTT - Activated partial prothrombin time
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7
Q

Which screening assay(s) are used to assess the extrinsic and common pathways?

A

PT - prothrombin time

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8
Q

Which screening assay(s) are used to assess the common pathway?

A

Thrombin clot time - prolonged suggests deficient or abnormal fibrinogen

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9
Q

What clinical signs would be associated with a disorder of primary haemostasis?

A
  • Oozing from small wounds
  • Petechial and ecchymotic haemorrhage
  • Mucous membrane bleeds - epistaxis and melaena
  • Underlying disease signs
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10
Q

Name some differentials for thrombocytopenia.

A
  • Immune-mediated - primary and secondary
  • Neoplasia
  • DIC
  • Infectious disease
  • Breed related - CKCS, grey hound, shiba inu
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11
Q

IMTP is associated with which agents/ conditions?

A
  • Evan’s syndrome - IMHA
  • Drug reactions - Abs
  • Neoplasia
  • Viral - FeLV
  • Ehrlichia
  • Vaccination
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12
Q

What clinical signs are associated with IMTP?

A
  • Petechia - ecchymotic haemorrhage
  • Bruising
  • Epistaxis, melaena
  • Haematuria
  • Hyphaema - eye
  • Splenomegaly
  • +/- pyrexia/ pallor
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13
Q

At which platelet counts would a dog/cat be at risk of spontaneous haemorrhage?

A
  • Dog

* Cat

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14
Q

If you are investigating thrombocytopenia what platelet featurewould you make sure to check on a blood smear?

A

Platelet clumps - an automated blood count may miss this.

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15
Q

What treatment can be used for animals with IMTP?

A

Immunosuppresives - reducing dose

  • Corticosteroids/ cyclosporin/ azathioprine
  • Vincristine
  • Blood transfusion - platelet rich plasma/ whole blood - need to control IMTP w/ others
  • Splenectomy
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16
Q

In which clinical situations may you see reduced platelet function?

A

Excessive bleeding despite normal clotting profile.

  • Azotaemia
  • vWb disease
  • Hyperproteinaemia
  • BM disease
  • hepatic disease
  • Drug therapy - NSAIDs
  • DIC
17
Q

Which screening assay(s) is used to assess platelet function?

A
  • BMBT - Buccal mucosal bleeding time

* Clot retraction - crude (affected by thrombocytopenia)

18
Q

von Willebrand factor is vital for which stage of blood clotting?

A

Platlet adherence

19
Q

Describe the three types of vW disease.

A

1 - most common, autosomal recessive, partial quantitative

  • Mucosal bleeding and bruising
  • Excessive haemorrhage in surgery
  • 2 - qualitative
  • 3 - severe quantitative
20
Q

Outline four tests which are used for diagnosis of vW disease.

A
  • BMBT increased Antigenic test
  • Remember citrated plasma for test
  • vWf function assays - type 2
  • Genetic testing - AHT
21
Q

What treatment could be used for vW disease?

A
  • Cryoprecipitate - factor 8, fibrinogen , vWf multimers
  • Whole blood/ citrated plasma
  • DDAVP - t1 - increases vWf release
22
Q
  • Normal platelet count
  • Prolonded APTT
  • Normal PT
  • Normal FDPs
    A pattern like this would suggest a problem in which pathway?
A

Intrinsic secondary

23
Q
  • Normal platelet count
  • Normal APTT
  • Prolonged PT
  • Normal FDPs
    A pattern like this would suggest problems in which pathway.
A

Extrinsic

24
Q

Which clotting factors are affected by vitamin K antagonists such as Warfarin?Which has the shortest half-life?

A

2, 7, 9, 107 - less than 5 hrs (acute decrease in production)

25
Q
  • Normal platelets
  • Prolonged PT and APTT
  • Normal FDPs
    A pattern like this would suggest problems with which clotting pathway?
A

Intrinsic and extrinsic pathwaysX, V, II

26
Q

A consumption of a vit K antagonist would be suggested by what change in screening assays over time?Why?

A
  • First prolonged PT
  • Then prolonged PT and APTT
    Since factor 7 has the shortest half life the extrinsic pathway is affected first.
27
Q

Breakdown of cross linked fibrin is characterised is characterised by an increase in which substance?

A

D-dimers

28
Q

Hypercoagulable states are associated with which conditions?

A
  • IMHA
  • Pancreatitis
  • Nephrotic syndrome - antithrombin lost in urine
  • Hyperadrenocorticism
  • DM
  • Cardiac disease
29
Q

Which tests allows you to rule out a defect of primary haemostasis?

  • PLT count
  • BMBT
  • vWf genetic test
  • Clotting time
  • Clot retraction
A

BMBT

30
Q

Predict bone marrow findings in a case of IMTP.

  • Increased thrombopoiesis
  • Decreased thrombopoiesis
  • No change
  • Generalised hypoplasia
A

Increased thrombopoiesis

31
Q

All of the following can cause increased thrombopoiesis except..

  • Hypoxia
  • Decreased PLT cound
  • Inflammation
  • Iron deficiency
  • Increased PLT loss
A

Hypoxia

32
Q

Which inherited coagulation defect causes prolonged PT without prolonged APTT?

  • Hereditary 11 deficiency
  • Hereditary thrombin (2) deficiency
  • Hereditary 7 deficiency
  • Hereditary 12 deficiency
A

Hereditary 7 deficiency

33
Q

What is the other name for an inherited deficiency of factor 8?

  • Haemophilia A
  • Hereditary thrombin deficiency
  • Haemophilia B
  • Hereditary afibrinogenemia
A

Haemophilia A

34
Q

What factors are affected by rodenticide poisoning?

  • 2, 3, 4, 5
  • 4, 7, 8, 9
  • 2, 7, 9, 10
  • 1, 5, 8, 13
A

2, 7, 9, 10Vitamin K dependent factors

35
Q 
Which type of erythrocyte abnormality is often seen in animals with DIC?	
* Spherocyte	
* Schistocyte	
* Target cell - codocyte	
* Elliptocyte
A

Schistocyte

Clinical pathology (7 decks)

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