haemostasis Flashcards
what is haemostasis?
the arrest of bleeding and maintenance of vascular patency
what are the 4 stages?
platelet plug formation (primary)
fibrin clot formation (secondary)
fibrinolysis
anticoagulant defences
what is primary haemostasis?
platelet plug formation
damage to endothelium = collagen + VWF -> platelet adhesion at site of injury
secretion of various chemicals -> platelet aggregation at site of injury
what is secondary haemostasis?
formation of fibrin clot
platelets are negatively charged
platelets release calcium when activated (positive charge)
blood clotting factors (negatively charged) are attracted to sit on phospholipid surface sue to positive calcium
what is fibrinolysis?
fibrin clot broken down by plasmin
what are the anticoagulant defences?
anti-thrombin, protein C and protein S
what factors are involved in the intrinsic pathway?
8, 9, 11, 12
what does the intrinsic pathway increase?
activated partial thromboplastin time (APTT)
what clotting factors are involved in extrinsic pathway?
7 (activated)
what increases in the extrinsic pathway?
partial thrombin time (PTT)
what factors are involved in the common pathway?
5, 10, 2, 1
what is increased in the common pathway?
APTT and PTT
what factors are affected by heparin?
2, 9, 10, 11
what clotting factors are affected by warfarin?
2, 7, 9, 10 (1972)
what clotting factors are affected in DIC?
1, 2, 5, 8, 11
what factors are affected in liver disease?
1, 2, 5, 7, 9, 10, 11
what factor is affected in von willebrands?
8
what does VWF increase?
APTT
what is increased in haemophilia?
APTT
what is increases in von willebrands?
APTT and bleeding time
what is increased in vitamin K deficiency?
APTT and PTT
what type of drug is heparin?
anticoagulant
what is unfractionated heparin MOA?
antithrombin agonist leading to inhibition of factor 2a and 10a
when in UFH used over LMWH and why?
in patients with higher risk of bleeding or renal impairment
due to shorter half-life
