Hemostasis Flashcards
Four steps of hemostasis
- Vasoconstriction
- Primary hemostasis: Formation of platelet plug
- Secondary hemostasis: Formation of blood clot
- Fibrous organization
Petechiae
Small red/purple/brown ‘pinpoint’ spots that appear due to bleeding into the skin.
Purpura
Petechiae that is 3 - 10 mm, do not blanch upon applying pressure
Vasculitis
Inflammation of the blood vessels–can occur due to infection, medicine, or disease
Hematoma
Collection of blood (usually clotted) outside of the damaged vessel, into surrounding tissue
Ecchymosis
Superficial bleeding under the skin/mucous membrane–a bruise
Thrombosis
Formation/presence of a blood clot inside a blood vessel
Embolism
obstruction in a blood vessel (blood clot, fat globule, gas bubble, etc)
Thromboembolism
obstruction of a blood vessel by a blood clot dislodged from another site in the circulation.
Infarction
Necrosis of tissue from lack of oxygen due to obstruction of the tissue’s blood supply
Primary hemostasis: platelet plug formation
- Adhesion (vWF, collagen receptors)
2. Aggregation (fibrinogen)
Secondary hemostasis: blood clot formation
Extrinsic + intrinsic -> activate Factor X
Prothrombin -> thrombin
Fibrinogen -> fibrin
Fibrinolytic system
Plasminogen -> plasmin (breaks up clot)
Thrombin (triggers thrombin-activatable fibrinolysis inhibitor, which also cleaves the fibrin clot)
Vitamin K in clotting
Vitamin K is responsible for the formation of 4 important clotting factors in the Extrinsic, Intrinsic, and Common clotting pathways:
Extrinsic- Factor VII
Intrinsic- Factor IX
Common- Factor II (prothrombin -> thrombin),
Factor X (where they meet up)
Hemophilia
chromosomal disorder where blood can’t clot b/c lack Factor VIII from mutation of X chromosome. Very few are cases are from Factor IX deficiency
DVT
blood clot (thrombus) usually in leg, can cause swelling. Occur when don’t move (accident, airplane, bedrest), dangerous= can lead to pulmonary embolism
Thrombocytopenia
low platelet count, easily bleed, skin has purple blotches
PE
blockage of pulmonary arteries from a traveling blood clot (thrombus); emergency!
disseminated intravascular coagulation
usually a complication from another disease; cascade of unnecessary formation of blood clots in small blood vessels, compromise blood flow and lead to organ damage. Normal clotting disrupted and severe bleeding can occur
Bleeding time
crude test, making small cut on forearm. Measures platelet function. 2-9 minutes is normal. Not specific nor sensitive, and influenced by external factors like medications & thrombocythemia
Platelet count
number/concentration of platelets in a blood sample. 150k-450k/microliter is normal. Clinically notable when falls below 100k. Below 20k - mild spontaneous bleeding. Higher platelet count = great coagulation status = less bleeding time
Partial thromboplastin time (pTT)
screens for deficiencies and inhibitors of the intrinsic pathway (factors 8, 9, 11, 12) and factors in the final common pathway (factors 2, 5, 10). (Per our lecture, we can think of PTT & aPTT as the same)
Prothrombin time (PT
time it takes for clot to form after calcium and thromboplastin (Ca activator) are added. Also, assesses extrinsic (factor 7) and common pathways (2, 5, 7, 10)
D-dimer
a neoantigen formed & released into the blood when blood clots (fibrin) degrades. less than 0.5 mcg/mL or less than 200 ng/mL is normal. Quick, easy test used to determine if abnormal clotting is present; diagnoses/rules out thrombosis in patients. Does not specify location of abnormal clotting → do further testing
Platelet function test
measures ability for platelets to aggregate. Gold standard: LTA (light transmittance aggregometry) which measures light transmittance through a sample of platelets in suspension. More light is transmitted when a platelet-aggregated agonist is added to the sample. Very expensive
