Chapter 140 Disorders of Platelets and Vessel Wall

Question 1

Cutoff for thrombocytopenia?

Answer 1

Platelet <150,000/uL

Normal 150,000-450,000

Question 2

Major regulator of platelet production

Answer 2

Thrombopoietin (TPO)

Synthesized in the liver
Increased in inflammation, by IL-6

Question 3

Life span of platelets?

Answer 3

7-10 days

1/3 of platelets reside in the spleen

Question 4

Next step in the algorithm if thrombocytopenia is accompanied by abnormal Hgb and WBC?

Answer 4

Bone marrow examination

Exception: Isolated thrombocytopenia in patients >60 years, also do bone marrow studies to rule out myelodysplasia

Question 5

Pinpoint non blanching hemorrhages that are usually the sign of decreased platelet NUMBER and not platelet dysfunction?

Where are these hemorrhages usually seen?

Answer 5

Petechiae

Appear in areas of increased venous pressure - ankles and feet

Question 6

Common bacterial or viral infections that cause infection induced thrombocytopenia?

Answer 6

Gram negative bacteria
Infectious mononucleosis
HIV

Question 7

Mainstay work up for diagnosis of IIT?

Answer 7

Bone marrow examination

Blood cultures

Question 8

When does thrombocytopenia occur when exposed to platelet IIB/IIIA inhibitory drugs?
Examples of these drugs?

Answer 8

Within 24 hours of initial exposure

Abciximab

Question 9

When does thrombocytopenia occur in drug induced thrombocytopenia?

Answer 9

After initial exposure, median of 21 days
Or upon reexposure

Resolves 7-10 days after drug withdrawal

Question 10

Two main differences of HIT from other drug induces thrombocytopenia?

Answer 10

Thrombocytopenia not severe

HIT is not associated with bleeding, it actually markedly increases risk for thrombosis

Question 11

Pathogenesis of HIT?

Answer 11

Development of antibodies to heparin/PF4 complex

Question 12

HIT is more common after exposure to: UFH or LMWH?

Answer 12

More common in UFH exposure

After 5-14 days of exposure

Question 13

Diagnostic algorithm for HIT (4T’s)

Answer 13

Thrombocytopenia
Timing of platelet count drop
Thrombosis
Localized skin reactions

Question 14

How long do heparin/PF4 complexes stay in circulation before disappearing?

Answer 14

~100 days following a prior exposure

Question 15

Rare type of HIT that occurs after all heparin has been stopped, beyond 14 days since last exposure

Answer 15

Delayed onset HIT

Heparin/PF4 antibody testing is markedly positive

Question 16

Diagnostic test for HIT that has high specificity but low sensitivity, may be falsely high in patients who have undergone cardiopulmonary bypass surgery?

Answer 16

IgG specific ELISA to PF4 complex

Question 17

Diagnostic test for HIT which measures the ability of the patient’s serum to activate platelets in the presence of heparin?

Answer 17

Serotonin release assay (a platelet activation assay)

Lower sensitivity, higher specificity than ELISA

Question 18

Most common complication of HIT even after discontinuation of heparin?

Answer 18

Thrombosis, venous and arterial

Question 19

What imaging modality is recommended to evaluate patients suspected of having HIT?

Answer 19

Duplex scan of the lower extremities to work up for thrombosis

Question 20

Which direct thrombin inhibitors (DTI) can be used as alternative for heparin in HITT?

Answer 20

Argatroban
Lepirudin

Others not approved by FDA:
Fondaparinux
Bivalirudin

Question 21

Alternative treatment for HIT which is a mixture of glycosaminoglycans with anti Xa activity?

Answer 21

Danaparoid

Question 22

If anticoagulation is needed due to high risk of thrombosis in HIT, what drug can be given in place of heparin?

Answer 22

Warfarin, usually for 3-6 months

Introduction of warfarin alone may precipitate thrombosis due to clotting activation and reduced protein C and S
Should be overlapped with DTI to lessen prothrombotic state

Question 23

What underlying disorders can cause secondary ITP?

Answer 23

Autoimmune disorders such as SLE

Infections such as HIV and Hepatitis C

Question 24

Expected results of platelet count and blood smear in ITP?

Answer 24

Very low platelet count

Normal peripheral blood smear

Question 25

What PE findings herald life threatening bleeding in ITP?

Answer 25

Wet purpura (blood blisters in the mouth) and Retinal hemorrhages

Question 26

When is lab testing recommended for ITP?

Answer 26

To evaluate for secondary causes: tests for HIV Hep C H pylori
Protein electrophoresis for SLE HIV

Question 27

What test should be performed in ITP with accompanying anemia to rule out combined autoimmune HA (Evans Syndrome)?

Answer 27

Direct Coombs test

Question 28

Outpatient treatment of ITP include:

Answer 28

Prednisone is 1mg/kg - first line treatment, 90% will relapse, remission in 1-3 weeks

IVIgG > Anti RhO - given at the 1-2g/kg over 1-5 days, used for acute bleeding risk

Question 29

Which set of ITP patients warrant admission?

Answer 29

Severe thrombocytopenia <5,000

Signs of impending bleeding such as retinal hemorrhage or large oral mucosal hemorrhage

Question 30

What anti CD20 B cell antibody has shown efficacy in treatment of refractory ITP?

Answer 30

Rituximab

Question 31

What type of vaccination is recommended prior to splenectomy?

Answer 31

Vaccination against encapsulated organisms (pneumococcus, meningococcus, haemophilus)

Question 32

Pentad of findings in TTP

Answer 32

1. Microangiopathic hemolytic anemia
2. Thrombocytopenia
3. Renal failure
4. Neurologic findings
5. Fever

Question 33

Pathogenesis of TTP is due to deficiency of:

Answer 33

ADAMTS13 (deficiency or antibodies against this metalloproteinase)

• cleaves vWF
  Show symptoms of TTP if assay activity level is <10%

Question 34

Expected finding in peripheral smear of TTP?

Answer 34

Presence of schistocyte

Also with polychromasia

Question 35

Mainstay treatment for TTP?

Answer 35

Plasma exchange using FFP

Continued until platelet count is normal and hemolysis is resolved for 2 days

Question 36

Triad of symptoms of HUS?

Answer 36

1. Acute renal failure
2. Microangiopathic hemolytic anemia
3. Thrombocytopenia

Question 37

Most frequent etiologic serotype of HUS?

Answer 37

E coli O157:H7

Question 38

Presenting symptom of HUS in children?

Answer 38

Episodes of diarrhea usually hemorrhagic in nature

Question 39

Treatment of HUS?

Answer 39

Supportive, symptom relief of diarrhea
May also do plasma exchange
Hemodialysis for AKI if needed

Treatment from atypical HUS - Eculizumab

Question 40

Most common type of VWD?

Answer 40

Type 1 Disease - decrease in VWF protein/function and Factor VIII

Question 41

Common manifestation of VWD in childhood and in young women?

Answer 41

Children - excessive bruising and epistaxis
Young women - menorrhagia

Can also present as excessive post op bleeding after dental extraction

Question 42

Mainstay of treatment for patients with VWD?

Answer 42

DDVAP (Desmopressin)

Given IV or via intranasal spray results in release of VWD and Factor VIII from endothelial stores

Question 43

Major side effect of DDVAP?

Answer 43

Hyponatremia
Due to decreased free water clearance
Should advise fluid restriction

Question 44

Drug that can be given to patients with VWD as prophylaxis for dental procedures, tonsillectomy, prostate procedures? But should be used in caution in upper urinary tract bleeding (may cause obstruction)

Answer 44

Tranexamic acid

Antifibrinolytic drugs

Question 45

Screening test for hemophilia?

Answer 45

Prolonged aPTT

Playelets and other bleeding parameters are usually normal

Question 46

Transfusion of what blood product is CONTRAINDICATED for TTP/HUS (unless with active bleeding)?

Answer 46

Transfusion of platelet concentrate

Question 47

Erythromelalgia is characterized as

Answer 47

Erythema, burning, pain in the extremities

Question 48

Thrombosis of what vessel should warrant suspicion of PV

Answer 48

Hepatic vein thrombosis

Question 49

To distinguish PV vs true erythrocytosis

Answer 49

PV - expansion of plasma volume

True erythrocytosis - plasma volume contraction