Hemostasis + Disorders

Question 1

What are the 4 steps in primary hemostasis and how are they mediated? What does vWF bind? Which receptors? Where is vWF stored/made? Where is ADP released from? What does it do? What does TXA2 do and how is it made? What does fibrinogen bind? How is primary hemostasis stabilized?

Answer 1

Transient Vasoconstriction-neural reflex and endothelin

Platelet adhesion to disrupted vessel
vWF binds exposed SEC. It also binds platelets at the GPIb receptor
VWF is made in weibel palade bodies of endothelial cells and alpha granules of platelets

Platelet degranulation-adhesion causes a shape change leading to degranulation
ADP is released from dense granules on platelets and it causes GPIIb/IIIa to be promoted
TXA2 is synth by COX and causes platelet aggregation

Platelet aggregation
GPIIb/IIIa binds to fibrinogen forming a weak plug that is eventually stabilized by secondary hemostasis

Question 2

What are the clinical features of primary hemostasis? What are some useful lab studies?

Answer 2

Mucosal bleeding: epistaxis, hemoptysis, GI bleeding, hematuria, and menorrhagia

skin bleeding: petechiae (quantitative only), purpura, ecchymoses

Platelet count
Bleeding time-increased in both quant and qual.
Blood smear-number and size of platelets
Bone marrow biopsy-assesses megakaryocytes
Ristocetin test-causes primary hemostasis to occur by causing GPIb to bind vWF. Will not cause clotting if either of those are defective or absent.

Question 3

What is ITP? Pathophys? What is the acute form like? What is the chronic form like? Cause of each? What lab findings are there in ITP? What is the first line treatment? How do people lrespond? What is done if taht doesn’t work?

Answer 3

Immune thrombocytopenic purpura

IgG against platelet antigens. antibodies produced by plasma cells in spleen. Platelets then destroyed by splenic macrophages (thrombocytopenia)

Acute form: Children after viral illness or immunization, usually self limited

Chronic form: Women of child bearing age, primary or secondary

Decr. platelet count

Question 4

What is MAHA? What is the pathophys? What diseases is it associated with? Clinical findings? Lab findings? Treatment?

Answer 4

formation of platelet microthrombi in small vessels which uses up platelets and shears RBCs (schistocytes)

TTP and HUS

Skin and mucosal bleeding
MAHA
Fever
Renal insufficiency (moreso in HUS)
CNS abnormalities (moreso in TTP)

Thrombocytopenia with incr. bleeding time
Normal Pt/Ptt
Anemia with schistocytes
Incr.megakaryocytes

Plasmapheresis and corticosteroids (mainly for TTP)

Question 5

What is the pathophys of TTP? Pathophys of HUS?

Answer 5

Autoantibody against ADAMTS13 (usually in women) causes it be decreased.
It is unable to cleave some of the multimers of vWF which results in abnormal platelet adhesion leading to microthrombi.

Endothelial damage by drugs on infection
E coli O157:H7 (undercooked beeef)
Verotoxin damages endothelial cells resulting in microthrombi

Question 6

What is the pathophys of Bernard-soulier? What is seen on blood smear? What is the pathophys of glanzmann thrombastenia? How does aspirin impair platelet aggregation? How is primary hemostasis impaired in uremia?

Answer 6

Genetic GPIb deficiency
Blood smear shows mild thrombocytopenia with enlarged platelets

GPIIb/IIIa deficiency

Inactivates COX-no TXA2

Adhesion and aggregation impaired.

Question 7

What does erythrocytosis mean? Anisocytosis? Poilocytosis? What is a reticulocyte? What does it reflect?

Answer 7

Incr. hematocrit, polycythemia

Varying sizes

Varying shapes

Immature rBC=reflects erythroid proliferation.

Question 8

Waht is the lifespan of thrombocytes? What is contained in dense granules? alpha granules? Where are 1/3 of platelets stored?

Answer 8

8-10 days

Ca, ADP

vWF, fibrinogen

spleen

Question 9

Describe the steps of secondary hemostasis (both pathways) including the various factors? Where are the factors produced? What are the 3 things required to activate them (both pathways) ?

Answer 9

Activated after exposure to an activating substance (SEC activates FXII in the intrinsic pathway and Tissue thromboplastin activates factor VII in extrinsic pathway)
Phospholipid surface of platlets
Calcium (from dense granules)

XII to XI to IX to X to II to I
VII to X to II to I

FII (thrombin) also activates FVIII which works with FIX to make it more efficient at converting X
activates V which makes X more efficient at converting II
Activates XIII which crosslinks fibrin forming mesh.

Question 10

What are some clnical features of secondary hemostasis? Lab studies used?

Answer 10

deep tissue bleeding into muscles and joints nd rebleeding after surgical procedures.

PT=Extrinsic
PTT=Intrinsic

Question 11

What is hemophilia A pathophys? Presentation? Lab findings? Treatment? What hemophilia B? Same questions? What is a coag factor inhibitor? Same questions? How can it be differentiated from hemo A?

Answer 11

FVIII defic.

Deep tissue, joint bleeding and rebleeding

Incr. PTT, normal PT
Decr. FVIII
Normal platelet count and bleeding time

Recomb. FVIII

FIX defic, otherwise very similar to A.

Antibody against a coag factor, usually FVIII.
clinically looks like Hemo A
PTT Not corrected by mixing plasma with normal plasma

Question 12

What is the pathophys of Von willebrand disease? How does it present? Lab findings? What is the treatment? Mechanism?

Answer 12

vWF defic, can cause quant. or qual. disorders.
Impaired vWF prevents platelet adhesion.
Normally, vWF stabilizes FVIII, but it can’t do that when impaired.

Mild mucosal and skin bleeding (no deep tissue)

Incr. bleeding time
Incr. PTT, normal PT
Abnormal ristocetin

Desmoressin-incr. vWF release from WP podies

Question 13

How and where is vitamin K activated? What is the function of vit. k in coag? When does defic occur?

Answer 13

Epoxide reductase in liver

gamma carboxylates factors II, VII, IX, X, protein C/S.

Newborns, long term antibiotic therapy, malabsorption

Question 14

How does liver failure lead to abnormal secondary hemostasis? Large volume transfusion?

Answer 14

Liver=Decr. production of coag factors and decr. activation of vit. K. Followed using PT

Large volume transfusion dilutes coag factors.

Question 15

What is heparin induced thrombocytopenia?

Answer 15

platelet destruction secondary to heparin therapy

Fragments of destroyed platelets may activate other platelets leading to thrombosis

Question 16

What is DIC? Clinical results? 5 causes? 5 lab findings? Treatment?

Answer 16

pathogic activation of coag cascade leads to widespread microthrombi w/ ischemia and infarction.
The microthrombri use up platelets and factors resuling in bleeding from IV sites a nd mucosal surfaces

Obstetric omplications (tissue thromboplastin in amnio
Sepsis (E. coli and N menin)=endotoxins from bacterial wall and cytokines (TNF and IL-1) induced endothelial cells to amke tissue factor
Adenocarcinoma=mucin
acute promyelocytic leukemia=primary granules
rattlesnake bite=venom

decr. platelets
Incr. PT/PTT
Decr.fibrinogen
MAHA
Elevated fibrin split products (D Dimer=not produced in slitting of fibrinogen)

Address underling cause; give blood products, cryoprecipitate

Question 17

How does normal fibrinolysis function? What causes disorders of fibrinolysis? Examples? How do they present? Lab findings? Treatment? Mechanism?

Answer 17

Tissue plasminogen activator (tPA) converts plasminogen to plasmin
Plasmin cleaves fibrin and serum fibrinogen;destroys coag factors and blocks platelet aggregation
Alpha 2 antiplasmin inactivates plasmin

PLasmin overactivity
Radical prostatectomy: urokinase activates plasmin
Cirrhosis of liver=decr. alpha 2 antiplasmin

Increased bleeding (like DIC)

Incr. PT/PTT
Incr. bleeding time with normal platelet count
Incr. fibrinogen split products w/o D dimers

Aminocaproic acid-blocks plasmin activation

Question 18

What are 3 things that lead to a disruption in blood flow? How do endothelial cells prevent thrombosis? What does ATIII do? What does thrombomodulin do? Protein C/S? What are some causes of endothelial cell damage?

Answer 18

Immobilization
cardiac wall dysfunction
aneurysm

Block exposure to SEC and tissue factor
Produce PGI2 and NO
Secrete heparin like molecules which augment ATIII function (inactivates FII and FX)
Secrete tPA which converts plasminogen to plasmin
Secrets thrombomodulin-redirects thrombin to activate protein C which inactivates factors V and VIII.

Atherosclerosis, vasculitis, and high levels of homocysteine

Question 19

Describe how the lack of vit. b12 or folate can lead to incr. risk of thrombosis. Describe the pathophys of cystathionine beta synthase defic. How does it present?

Answer 19

folate circulates as methyl-THF
The methyl group is transferred to vit. b12, which allows THF to be used in production of DNA precursors.
Cobalamin transfers methyl to homocystein resulting in methionine.
Lack of Vit. B9 or cobalamin results in incr. homocysteine and thus incr. thrombocytosis.

CBS converts homocystein to cystathionine; enzyme deficiency leads to homocystein buildup
Vessel thrombosis, mental retardation, lens dislocation, and long slender fingers

Question 20

What is a hypercoagulable state? How does it present? Where?

Answer 20

Excessive procoag and defic anti coags

Recurrent DVTs or DVT at young age

Usually in lower leg (maybe hepatic or cereral)

Question 21

How does protein C and S defic lead to a hypercoag state? What does it incr. risk for when using warfarin? Why? What is factor V leidn? Prothrombin 20210A? ATIII deficiency? OCPs?

Answer 21

Protein C/S inactivate factors V and VIII

Warfarin blocks Protein C/S as well as pro coag factors but C/S have shorter half lives and thus are defic. first leading to a hyper coag state, but if C/S are already defic it becomes a big problem, leading to ischemia in skin or warfarin induced necrosis

mutated factor V can’t be inactivated by Protein C/S

Mutation leads to incr. production of prothrombin

ATIII defiency makes it so heparin like molecules can’t exert as great an effect b/c ATIII can’t inactivate thrombin and factor X

Estrogen incr. coag factors

Question 22

What is a fat embolus associated with? Clinical manifestations? Pathophys of gas embolus? Clinical manifestation? Causes? Chronic form? Amniotic fluid embolus presentation? Characterization?

Answer 22

Bone fractures and soft tissue trauma
Dyspnea and petechiae on the skin over chest

Decompression sickness=rising too quickly, N2 precipitates out of blood. 
Joint and muscle pain and respiratory symptoms
Chronic form (Caisson)=multifocal ischemic necrosis of bone
May also occur in laparascopic surgery

Amniotic fluid embolus enters maternal circulation during labor or delivery
Shortness of breath, neuro sympoms, DIC
Squamous cells and keratin debris in embolus

Question 23

What causes a pulmonary embolism? Why are most clinically silent? When does a pulmonary infarction occur? How does it present? When does sudden death occur? When does pulmonary hypertension occur

Answer 23

Usually due to a DVT of lower extremity.

Usually silient b/c lung has dual blood supply and embolus is small

Pulmonary infarction occurs if large or medium sized arter is occluded in someone with preexisting cardio compromise
Shortnes of breath, hemoptysis, pleuritic chest pain, and pleural effusion
V/Q lung scan shows mismath
Spiral CT shows a vascular filling defect
Lower extremity doppler
D-dimer elevated
Hemorrhagic wedge shaped infarct

Sudden death occurs with large saddle embolus blocking left and right pulm. arteries

Pulmonary hypertension occurs with repeated PE that are reorganized over time.