Hemostasis

Question 1

Hemostasis

Answer 1

Physiologic coagulation of blood in injured vessels to prevent bleeding.

Question 2

Describe steps in hemostasis

Answer 2

1. Vascular constriction
2. Formation of platelet plug
3. Formation of blood clot
4. Fibrous organization

Question 3

Cold water step 1 of hemostasis

Answer 3

Injured vessels produce thromboxane A2. Vasoconstrict smooth muscles of vessel.

Question 4

Cold water step 2 of hemostasis

Answer 4

Platelets adhere to exposed subendothelial collagen. Recruit other platelets; fibrinogen assists platelet-platelet adhesion.

Question 5

Cold water step 3 of hemostasis

Answer 5

Intrinsic, extrinsic, and combined pathway form blood clot.

Question 6

Cold water step 4 of hemostasis

Answer 6

Fibroblasts complete organization of clot into fibrous tissue in 1-2wks.

Question 7

Petechiae

Answer 7

Small, purplish, hemorrhagic spots on skin (thrombocytopenia, febrile illnesses).

Question 8

Purpura

Answer 8

Rash where blood cells leak into skin or mucous membranes (disorders of coagulation/thrombosis).

Question 9

Vasculitis

Answer 9

Inflammation of blood vessels

Question 10

Hematoma

Answer 10

Swollen mass of extravasated (us. clotted) blood.

Question 11

Ecchymosis

Answer 11

Superficial bleeding under skin or mucous membrane.

Question 12

Thrombosis

Answer 12

Formation or presence of blood clot within vascular system.

Question 13

Embolism

Answer 13

Sudden obstruction of blood vessel by debris (clot, choloesterol plaque, injected substances).

Question 14

Infarction

Answer 14

Death of tissue from blood supply deprivation.

Question 15

Describe conversion of prothrombin to thrombin

Answer 15

Factor Xa; where intrinsic and extrinsic pathways meet.

Question 16

Describe conversion of fibrinogen to fibrin

Answer 16

Thrombin catalyzes. Fibrin stabilized and solidifies aggregates to final thrombus.

Question 17

Describe lysis of blood clot

Answer 17

Fibrinolytic system: plasminogen converted to plasmin - breaks up clot; thrombin triggers thromin-activatable fibrinolysis inhibitor - cleaves fibrin clot.

Question 18

Desribe role of vitamin K in formation of blood clots

Answer 18

Required by 5 important clotting factors: prothrombin, Factor VII, IX, X, protein C. Insufficiency can lead to serious bleeding.

Question 19

Hemophilia

Answer 19

Bleeding disease of varying severity seen with mild to severe trauma. Treated with Factor VIII or IX (depending on type, but expensive). X-linked; males only.

Question 20

DVT

Answer 20

Endothelial surface roughened (arteriosclerosis, infection, trauma) initiating clotting process. Flow of blood is slowed (treated with t-Pa or anticoags).

Question 21

Thrombocytopenia

Answer 21

Low platelet count. Purpura on skin. Tx include whole blood transfusion or splenectomy.

Question 22

Pulmonary embolism

Answer 22

Part of thrombus breaks off (embolus) and travels through right side of heart blocking pulmonary arteries. Tx t-Pa or anticoags.

Question 23

Disseminated intravascular coagulation

Answer 23

Dying tissue or trauma causes release of tissue factor initiating widespread clotting mechanism. Can occlude peripheral vessels. Caused by septicemia.

Question 24

Bleeding test

Answer 24

Cuts made on forearm and time to stop bleeding measured. Not sensitive nor specific, can be influenced by meds and thrombocythemia; not commonly used.

Question 25

Platelet count

Answer 25

Determine concentration of platelets in blood. Normal range 150-450,000/ul. Below 20,000 = mild spontaneous bleeding.

Question 26

Thrombocythemia

Answer 26

Elevated platelet count

Question 27

Thrombocytopenia

Answer 27

Decreased platelet count

Question 28

Partial thromboplastin time (pTT)

Answer 28

Used to screen for deficiencies and inhibitions of factors in intrinsic and common pathway. Used to assess pts response to heparin therapy.

Question 29

Prothrombin time

Answer 29

Time clot takes to form after addition of calcium and thromboplastin (Ca activator). Assess extrinsic and common pathway.

Question 30

D-dimer

Answer 30

Antigen formed with fibrin degradation. Used to diagnose or rule out thrombosis in pts. Positive test rules in, but no infor on location. Neg test rules out.

Question 31

Platelet function test

Answer 31

Measures ability of platelets to aggregate. (Not worrying about warm water shizz)

Question 32

Mechanisms which prevent excessive thrombosis

Answer 32

Fibrolytic system dissolves and remodels fibrin clot. Natural inhibitors: Antithrombin and vitamin K dependent proteins C and S (inhibit thrombin). Heparin and antithrombin medication: Inhibit coagulation cascades by speeding up process and inactivating Factors, respectively. Tissue factor pathway inhibitor: Inhibits extrinsic pathway PG2 and NO: Generated by endothelial wall prevent thrombosis. Plasminogen activators: Limit platelet aggregation.

Question 33

Describe hereditary causes of thrombosis

Answer 33

Factor V Leiden, Prothrombin mutation, anticoagulation deficiencies, fibrinolytic defects (rare).

Question 34

Describe acquired causes of thrombosis

Answer 34

Trauma, medications (OCs), malignancy, orthopedic surgery, infection (rare), thrombocytosis and myeloproliferation, antiphospholipid antibodies.