Bleeding Disorders 1

Question 1

what are the standard screening tests for primary vs secondary hemostasis?

Answer 1

primary: platelet count + peripheral smear

secondary: aPTT (intrinsic pathway), PT (extrinsic pathway)

Question 2

thrombocythemia

Answer 2

platelet count too high

Question 3

petechial hemorrhage is a sign of what kind of disorder?

Answer 3

petechial hemorrhage: asymptomatic, non-tender, non-palpable rashes

indicative of platelet disorder (primary hemostasis issue) - low platelets (<20K)

Question 4

describe how thrombopoiesis will impact MPV

Answer 4

young platelets are larger, so MPV will increase

Question 5

what is thrombocytopenia usually associated with?

Answer 5

thrombocytopenia rarely occurs on its own - usually all cells are decreased due to bone marrow failure/injury/infiltration

radiation, chemo, chemical, leukemia, fibrosis, etc

*if it is just platelets —> problem with platelet destruction

Question 6

most causes of increased platelet destruction thrombocytopenia are:
a. immune
b. non-immune

Answer 6

usually immune:
- immune thrombocytopenic purpura (idiopathic, diagnosis of exclusion)
- drug-induced
- heparin-mediated

Question 7

how do you diagnose immune/idiopathic thrombocytopenic purpura? how does it look in children vs adults?

Answer 7

diagnosis of exclusion (no confirmatory test)

likely due to antibody-mediated destruction, patient is otherwise healthy besides purpura rash and low platelet count

resolves on its own in ~6mo in children

more severe in adults, often chronic —> immunosuppressive therapy, possibly splenectomy (removes largest volume of platelets)

Question 8

what is so important about asking a patient with thrombocytopenia if they are taking any medication?

Answer 8

almost any drug can cause drug-induced thrombocytopenia!

drop in platelets can be severe, usually occurs in 7-10 days

Question 9

Abciximab is a GPIIb/IIIa platelet receptor (binds fibrinogen for cross-linking) antagonist used to treat coronary interventions (patients having a stent placed). What is different about this drug regarding drug-induced thrombocytopenia?

Answer 9

most drug-induced thrombocytopenia has lag period of 7-10 days

however, some patients have pre-existing antibody to mouse portion of this drug (if they have been around mice) —> thrombocytopenia occurs within hours following first time use of this drug

Question 10

what is the mechanism of heparin-induced thrombocytopenia? how does it present?

Answer 10

heparin increases antithrombin activity

mechanism: heparin (-) binds platelet factor 4 (+) —> sometimes, antibodies form against PF4::heparin complex

—> PF4::heparin::IgG complex binds to platelets and causes aggregation

platelet count drops because they are begin consumed in thrombi, usually 5-14d after heparin exposure

thrombosis in venous and arterial systems - can be life-threatening