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Hemostasis and Related disorders Flashcards

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1
Q

Hemostatis 2 stages:

A

Primary: forms weak platelet pug (platelets and vessel wall)

Secondary - coagulation cascade stabilizes platelet plug

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2
Q

Primary hemostasis (4 steps)

A
  1. transient vasoconstriction of damaged vessel
  2. Platelet adhesion to surface of disrupted vessel
  3. Platelet degranulation
  4. Platelet aggregation
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3
Q

Vasoconstriction of damaged wall mediated by

A

reflex neural stimulation and endothelin release

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4
Q

Platelet adhesion to surface of disrupted vessel

A

vWF binds exposed subendothelial collagen (BM & CT underneath exposed)

Platelets bind vWF using GP1b Receptor

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5
Q

What is vWF derived from

A

Weibel-Palade bodies of endothelial cells and alpha granules of platelets

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6
Q

Platelet degranulation

A

Adhesion induces shape change in platelets and degranulation

ADP release: GP2B/3A receptor expression
TXA2: promotes platelet aggregation

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7
Q

Platelet aggregation

A

Aggregate via GP2B/3A using fibrinogen - forming weak platelet plug

Stablize platelet plug using secondary hemostasis

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8
Q

Disorders of primary hemostasis d/t?

A

abnormalities of in platelets

quantitative or qualitative

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9
Q

Clinical features of primary hemostasis

A

mucosal and skin bleeding

epistaxis, hemoptysis, GI bleeding, hematuria, mehorrhagia

intracranial bleeding w/ severe thrombocytopenia

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10
Q

Skin bleeding symptoms

A

Petechiae, purpura, ecchymoses

Petechiae sign of thrombocytopenia (NOT QUALITATIVE disorders)

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11
Q

normal platelet count

A

150-400K

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12
Q

normal bleeding time

A

2-7 minutes

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13
Q

Immune Thrombocytopenia Purpura

A

AI - IgG against platelet antigens (GP2B/3A)

most common thrombocytopenia of children and adults

Ab produced by plasma cell in spleen - ab bound platelets are consumed by splenic macrophages

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14
Q

Acute Immune Thrombocytopenia Purpura

A

children
after viral infection/immunization

Self limted

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15
Q

Chronic Immune Thrombocytopenia Purpura

A

Adults
Women of child bearing age

Primary/Secondary
Secondary associated with lupus

May cause short-lived thrombocytopenia in offspring - IgG crosses placenta

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16
Q

Lab findings in Immune Thrombocytopenia Purpura

A

Decrease platelet count

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17
Q

Treatment of Immune Thrombocytopenia Purpura

A

Corticosteroids

Adults may relapse

IVIG: when symptomatic bleeding to raise platelet count

Splenectomy (in refractory cases)

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18
Q

Microangiopathic hemolytic anemia cause

A

pathologic formation of platelet microthrombi in small vessels

RBC shear when passing thrombus - lyse and become schistocyte

Platelets are consumed

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19
Q

What are two disorders you seee Microangiopathic hemolytic anemia

A

TPP (thrombocytopenic pupura) - platelet microthrombi - skin bleeding - decrease in ADAMSTS13 which normally cleaves vWF multimers

HUS (Hemolytic uremic syndrome)

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20
Q

TTP d/t decrease in what enzyme?

A

ADAMTS13 - cleaves vWF multimer into smaller monomers for eventual degredation

Large multimers lead to abn platelet adhesion = microthrombi

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21
Q

Who is decreased ADAMTS13 seen in most?

A

adult females (acquired autonantibody)

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22
Q

HUS d/t?

A

Drugs or infection -

children: E coli O157:H7 dysentery (verotoxin damages endothelial cells resulting in platelet microthrombi)

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23
Q

Clinical findings of HUS/TTP

A 
Skin/mucosal bleeding
Microagniopathic hemolytic anemia
Fever
Renal insufficiency (HUS) 
CNS abnromalities (TTP)
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24
Q

HUS/TTP lab findings

A

Thrombocytopenia w/ increased bleeding time
Normal PT/PTT
Anemia w/ schistocytes
Increased megakaryocytes on bone marrow biopsy

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25
TX: HUS/TTP
plasmapheresis | Corticosteroids
26
Qualitative problems of platelets
1. Bernard Soullier syndrome | 2. Glanzmann thrombasthenia
27
Bernard Soulier Syndrome
Genetic defect GP1b deficiency Platelet adhesion impaired Blood smear; Mild thrombocytopenia and enlarged platelets (immature)
28
Glanzmann Thrombasthenia
Genetic GP2b/3A deficiency Platelet aggregation impaired
29
How does aspirin cause qualitative defect in platelets?
Irreversibly inhibits COX - so lack of TXA2 impairs platelet aggregation
30
Uremia disrupts platelet function
both adhesion and aggregation impaired
31
Secondary hemostasis for:
stabilizing weak platelet plug Thrombin converts fibrinogen to fibrin in platelet plug - crosslinked stablizing platelet-fibrin thrombus
32
Where are coagulation cascade factors produced?
Liver in inactive form
33
Coagulation cascade factors activated by?
Exposure to activation factors Phospholipid surface (of platelets) Calcium - from platelet granules
34
Disorders of secondary hemostasis usually d/t
factor abnormalities
35
Clinical features of secondary hemostasis disorders
Deep bleeding into muscles/joints Rebleeding after surgical procedures
36
PT measures:
extrinsic (VII) and common (II, V, X + fibrinogen) Prothrombin time
37
PTT measures
Intrinisc factors (XII, XI, IX, VIII) and common (II, V, X + fibrinogen) Partial thromboplasin time
38
Hemophilia A
VIII males - x linked Can be from new mutation w/o family hx deep tissue, joint, post surgical bleeding
39
Lab findings in Hemophilia A
Increase PTT Normal PT Decrease Factor VIII Normal platelet ct, bleeding time
40
Hemophilia B
``` IX ncrease PTT Normal PT Decrease Factor IX Normal platelet ct, bleeding time ```
41
Coagulation factor inhibitor disorder
Acquired ab against coagulation factor - impaired factor function Anti-F VIII most common Distinction by mixing study: Mix with normal plasma - if hemophilia A - PTT will correct Mix with normal study - inhibitor - PTT will not correct
42
vWB dz
Most common inherited coagulation disorder*** most common is AD - decreased vWF levels Platelet adhesion can't occur Mild mucosal and skin bleeding
43
vWB dz lab findings
Increased bleeding time Increase PTT normal PT abnormal ristocetin test
44
vWF tx
desmopressin - increases vWF release from Weibel Palade bodies
45
why is PTT elevated in vWF?
need to stabilze factor 8
46
RIstocetin test***
Introduce restocetin - normally causes platelets to aggregate - but in vWF - they don't
47
VIT K deficiency
Vit K gamma carboxylates factors II, VII, IX, X and S
48
VIT K deficiency occurs in?
Newborns Long term antibiotic therapy Malabsorption
49
Why does liver failure cause abnormal secondary hemostasis
decreased production of coagulation factors, decreased activation of VIT K by epoxide reductase
50
Heparin induced thrombocytopenia (HIA
platelet destruction secondary to heparin therapy Fragments of destroyed platelets activate remaining platelets, leading to thrombosis Heparin forms complex with PF-4 Don't give coumdin
51
DIC
Pathologic activation of coagulation cascade Widespread microthrombi in ischemia/infarction Consumption of platelets and factors resulting in bleeding - IV sites and mucosal surface
52
Common causes of DIC
``` obstetric complications (amniotic fluid) Sepsis - endotoxins and cytokines Adenocarcinoma Acute promyelocytic leukemia Rattlesnake bite ```
53
Lab findings of DIC
``` decreased platelet count Increased PT/PTT decreased fibrinogen Microangiopathic hemolytic anemia Elevated fibrin split products (D-dimer) ```
54
DIC tx
transfuse blood products and cryoprecipitate
55
Disorders of fibrinolysis
D/t plasmin overactivity resulting in excessive cleavage of fibrinogen tPA cleave plasminogen to plasmin which cleaves fibrin and fibrinogen Destroys coagulation factors Blocks platelet aggreation
56
What inactivates plasmin?
alpha-2 antiplasmin
57
Examples of excess plamin
Radical prostatectomy - release of urokinase activates plasmin Cirrhosis of liver - reduced alpha-2 antiplasmin production
58
Increased plasmin presents as & lab findings
Increased bleeding Increased PT/PTT - destroys coagulation factors Increased bleeding time w/ normal platelet count Increased fibrinogen w/o D dimers (because fibrin thrombi abscent)
59
TX of increased plasmin
Aminocaproic acid - blocks activation of plasminogen
60
Thrombus characterized by
Lines of Zahn (alternating layers of platelets/fibrin & RBCs) And Attachemenet to vessel wall
61
Virchow triad:
``` Disruption in blood flow Endothelial cell damage Hypercoaguable state (common in cancer) ```
62
Disruption in blood flow examples
Immobilization Cardiac wall dysfunction Aneurysm
63
How to endothelial cells prevent thrombosis
1. Block exposure to subendothelial collagen & underlying tissue factor 2. Produce Prostacyclin & NO 3. Secrete heparin like molecules 4. secrete tPA 5. secrete thrombomodulin
64
Causes of endothelial damage
Atherosclerosis Vaculitis High levels of homocysteine
65
Cystathionine beta synthase (CBS) deficiency
High homocysteine levels w/ homocysteinuria Vessel thrombosis, mental retardation, lens dislocation, long slender fingers
66
Hypercoaguable state
Excessive procogaulant or defective anticoagulant proteins Recurrent DVT as young age
67
Hypercoaguable state causes
1. Protein C/S def 2. Factor V Leiden mutation 3. Prothrombin expression increased 4. ATIII def 5. oral contraceptives
68
Protein C & S inactivate which factors?
V & VIII
69
What can you see with warfarin when pt has protein C/S def?
Warfarin skin necrosis (coumidin skin necrosis) Can't produce 2, 7, 9, 10, C, S factors when given Warfarin - C& S are first to depelete Activating 2, 7, 9, 10 so give heparin If deficient in C & S - very increase risk of hypercoagulable state with 2, 7, 9, 10
70
Factor V Leiden
Mutated factor 5 - can't be cleaved by protein C & S (can't shut off FV) Most common inherited cause of hypercoagulable state
71
Prothrombin 20210A
Inherited pt mutation in prothrombin | Increased gene expression - prothrombin to thrombrin - converts fibrinogen to fibrin - leads to thrombus
72
Antithrombin III def
Decreases protective effect of heparin-like molecules produced by endothelium, increasing risk for thrombus Heparin admin - PTT in these patients doesn't rise
73
Oral contraceptives
Estrogen induces increased production of coagulation factors
74
Atherosclerotic embolus
plaque dislodges - presense of cholesterol clefts
75
Fat embolus
long bone fracture, soft tissue damage dyspnea and petechia on skin overlying chest
76
Gas emoblus
Decompression sickness Nitrogen dissolves in blood - then precipitates out during ascent Bends/Chokes
77
Chronic gas emoli
Caisson dz | Multifocal ishcmeic necrosis of bone
78
Amniotic fluid embolus
enters maternal circulation during labor or delivery - lodges in lungs SOB, neurologic symptoms, DIC Characterized by Squamous cells & Keratin debris from fetal skin in embolus
79
Pulmonary embolism
DVT - femoral, iliac, popliteal veins disoldge and get thromboembolous
80
Why are most PE's clinically silent
Lung has dual blood supply | Embolus usually small/self resolving
81
Pulmonary infarction clinical signs
SOB, hemoptysis, pleurtic chest pain, pleural effusion V/Q scan shows mismatch - perfusion abn Spiral CT shows vascular filling defect in lung (blocking blood supply) LE doppler useful to detect DVT D-dimer elevated
82
Pulm HTN is d/t what?
chronic emboli that are reorganized over time
83
Systemic emobli
D/t thromboembolus Left heart Occlude flow to organs - commonly LE

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