hemostasis Flashcards
What are the steps of hemostasis?
primary hemostasis
secondary hemostasis
fibrinolysis
What are the phases that occur during primary hemostasis?
PHASE I
- vasoconstriction: decrease in local blood flow
PHASE II
- platelet plug (Vin Willebrand factor): thromboplastin -> adherence of platelets to sub-endothelial tissue
PHASE III
- tamponade: surrounding tissue tension acts as a tamponade for bleeding
- interstitial hemorrhage is less profuse than external or internal hemorrhage
When is vasoconstriction less effective?
- in partially injured vessels
- in stiff atherosclerotic vessels
- in large veins (poor muscle coat)
What occurs during secondary hemostasis?
ACTIVATION OF COAGULATION CASCADE
- includes the intrinsic & extrinsic pathways
What are the factors activated in the intrinsic pathways & what test is used to measure their function?
factor XII
factor XI
factor IX
factor VIII
PTT
Which factor is activated in the extrinsic pathway & what test is used to assess its function?
factor XII
PT
What factor is activated in the common pathway?
factor X
which activates the conversion of thrombin to fibrinogen
What initiates the extrinsic pathway?
tissue lipoprotein
How does fibrinolysis occur?
tissue plasminogen activator converts plasminogen to plasmin which breaks down fibrin
What test will be affected incase of deficiency of factors VIII & IX and what is the disease that causes this deficiency?
HEMOPHILIA A for factor VIII & B for factor IX
PTT is affected
What are the manifestations of hemophilia?
- spontaneous bleeding in childhood (severe form)
- bleeding after mild trauma or surgery
How should hemophilia be treated?
infusion of factor concentrate 1 hour before surgery & 10 days after
What are the manifestations of Von Willebrand disease & how should it be treated?
- purpuric eruptions, ecchymosis or bleeding per orfices
- infusion of Von Willebrand factor
What are the hemostatic disorders associated with liver disease?
- decreased concentration of factors 1972 (effected by vitamin K)
- thrombocytopenia due to hypersplenism
How should hemostatic disorders due to hepatic diseases be treated?
- Vit K administration
- Fresh frozen plasma
Vitamin K is a co-factor in the synthesis of which clotting factors?
1972
X, IX, VII, II
increase in traumatic bleeding
What are the causes of vit K deficiency?
- inadequate diet or TPN
- obstructive jaundice
- prolonged broad antibiotic
- malabsorption
How should vit. K deficiency be treated?
- daily vit. K injection (SLOW IV)
- FFP in emergencies
What are the causes of DIC?
- septicemia
- severe shock, trauma, & burns (SIRS)
- ABO incompatible transfusion
What occurs during DIC?
- widespread activation of coagulation within circulation leading to dilution of clotting factors
How should DIC be treated?
- treat underlying cause
- FFP to replace coagulation factors
- platelet transfusion
What are the platelet disorders?
THROMBOCYTOPENIA
THROMBASTHENIA
What is the normal platelet count?
150 000 to 400 000
What are the causes of thrombocytopenia?
PRIMARY: ITP
SECONDARY: Bone marrow suppression OR increase destruction in hypersplenism
What are the causes of thrombasthenia?
disorders of platelet function due to drugs like ASPRIN & NSAIDS
How can we differentiate between the 2 secondary causes of thrombocytopenia?
Bone marrow aspiration to search for megakaryocites (platelet precursors)
- decreases in megakaryocites -> bone suppression
- increase megakaryocites -> hypersplenism
What are the characters of bleeding if the defect is of primary hemostasis?
- superficial bleeding (patichae, purpura, & easy bruisability)
- early onset following trauma
- controlled by local pressure
What are the characters of bleeding if the defect is of secondary hemostasis?
- bleeding is deep (hematoma inside muscle)
- delayed onset following trauma
- local pressure is ineffective
What disorder has a decreased number of platelets < 100 000?
thrombocytopenia
What is the normal bleeding time & what diseases increase it?
normal = < 8 minutes
- thrombocytopenia
- abnormal platelet function
- deficiency of Von Willbrand disease
- Vascular abnormality
What is the normal PT time & what factors affect it?
normal = 12 - 15 seconds
- deficiency in factor VII or X
What is the normal PTT time & what factors affect it?
normal = 30 - 40 seconds
- factor XII, XI, X, IX, VIII, V, II
What is the normal INR and what effects it?
normal = 1
- patients taking oral anticoagulants (2-3)
- patients with prosthesis (2.5-3.5)
an increase in FDPs (fibrinogen degradation products) is an indication of?
DVT
