Haemostasis

Question 1

Define haemostasis

Answer 1

Process which causes bleeding to stop = first stage of wound healing

Question 2

What are the stages of normal haemostasis?

Answer 2

1) vascular spasm (vasocontriction)
2) platelet plug
3) coagulation of blood

Question 3

What are the stages of platelet plug formation?

Answer 3

1) adhesion = to damaged vessel wall to collagen via vWF.
2) activation = platelets secrete ADP + thromboxane to activate, activation of clotting cascade.
3) aggregation = cross-linking platelets form plug

Question 4

What is the role of the clotting cascade and its critical steps?

Answer 4

Initiating event = tissue factor exposure activates FVII = prothrombin = thrombin (burst) that converts soluble fibrinogen to insoluble fibrin = enmeshes in platelet plug = stable clot

Question 5

Outline the role of the fibrinolytic system and plasmin

Answer 5

process that prevents blood clots from growing and becoming problematic.

plasmin cuts the fibrin mesh at various places = prod of circulating fragments, cleared by other proteases or by the kidney and liver

Question 6

Name some natural anti-coagulants

Answer 6

protein C,

protein S,

anti-thrombin

Question 7

Discuss the function of Von Willebrands Factor

Answer 7

vWF = prod by vessel walls platelets adhere to collagen via vWF, carrier/protector of F8

Question 8

Discuss haemophilia A

Answer 8

x-linked recessive, congenital lack of F8, treated with recombinant F8 or DDAVP (= release of F8)

pres = bleeding into muscles/joints and post-op

lab = low F8, partial thromboplastin time (aPTT) is prolonged,

Question 9

Discuss haemophilia B

Answer 9

congenital reduction in FIX

pres = bleeding into muscles/joints, easy bruising, urinary tract bleed and nosebleeds

lab = low FIX, partial thromboplastin time (aPTT) is prolonged,

Question 10

Outline Von Willebrands disease

Answer 10

autosomal dominant,
reduced vWF = reduced F8 amount/activity,

pres = skin/mucous membrane bleeding, prolonged bleeding after trauma/periods/post-op/dental extraction

lab = measuring amount of vWF in a vWF antigen assay and functionality of vWF with a glycoprotein (GP)Ib binding assay

Question 11

Describe thrombocytopenia causes

Answer 11

Quantitative platelet disorder = reduced count.

Immune thrombocytopenic purpura = Ab against GP IIb/IIIa and GPIb/IX, treated with immunosuppression.

DIC = reduced platelet level by systemic clotting.

B12/folate def = reduced prod.

Infiltration of bone marrow = cancer or fibrosis.

Question 12

What are the consequences of thrombocytopenia?

Answer 12

Pt not symptomatic until platelet count <30,

easy bruising petechial (small freckled bleeding),

purpura ( larger areas of bleeding), mucosal bleeding

Question 13

Briefly outline a hereditary disorder of platelet function

Answer 13

Bernard Soulier

Def Gplb = the receptor for vWf

Question 14

Briefly outline an acquired disorder of platelet function

Answer 14

Drugs = aspirin/NSAIDs/clopidogrel

Uraemia

Hyper gammaglobulinaemia

Question 15

Discuss DIC

Answer 15

Type of microangiopathic haemolytic anaemia - pathological activation of coag = microthrombi = consumption of clotting factors/platelets

treat = platelet transfusion

Question 16

What lab results would be seen in DIC?

Answer 16

raised PT/INR/APTT/D-dimer/fibrin products,

low fibrinogen

Question 17

What causes DIC?

Answer 17

malignancy, severe burns, infections, massive haemorrhage and transfusion, ABO transfusion reaction

Question 18

What is Immune thrombocytopenic purpura?

Answer 18

Ab against platelets = GP IIb/IIIa and GPIb/IX, treated with immunosuppression

pres = bruises (purpura) and petechiae (tiny bruises), bleeding

lab = prolonged bleeding time, bone marrow examination

Question 19

Discuss thrombophilia

Answer 19

Not a condition - a term for increased risk of clotting

types = congenital (protein C/S def), acquired, idiopathic

pathophysiology = combination of abnormal blood vessel wall, abnormal blood flow, abnormal consistency of the blood

pres = DVT, PE