Hemopath 3 Bleeding Flashcards
(15 cards)
What are the primary and secondary stages of hemostasis, and how do they differ in terms of mechanism and clinical presentation?
Primary hemostasis involves platelet adhesion, activation, and aggregation to form a temporary platelet plug. Secondary hemostasis stabilizes the plug with fibrin via the coagulation cascade. Clinical difference: Primary = mucosal bleeding, petechiae; Secondary = deep bleeding (joints, muscles), large ecchymoses.
How do platelets contribute to hemostasis, and what happens when platelet count is severely decreased?
Platelets adhere to exposed subendothelial collagen via vWF, activate, release granules, and recruit other platelets to form a plug. Severe thrombocytopenia (<20,000/μL) causes spontaneous bleeding (petechiae, mucosal hemorrhage).
What clinical signs help you distinguish between a platelet disorder and a coagulation factor deficiency?
Platelet disorders: Petechiae, epistaxis, gum bleeding, heavy periods. Factor deficiencies: Hemarthroses, deep muscle bleeds, delayed bleeding after trauma or surgery.
What is von Willebrand factor, and how does it link primary and secondary hemostasis?
vWF is a glycoprotein that helps platelets adhere to damaged endothelium (primary) and binds/stabilizes factor VIII in plasma (secondary).
What are the types and basic pathophysiology of von Willebrand disease?
Type 1: Partial quantitative vWF deficiency. Type 2: Qualitative defect (abnormal vWF function). Type 3: Severe deficiency. All types lead to impaired platelet adhesion and reduced factor VIII levels.
What lab findings would you expect in von Willebrand disease and why?
Prolonged bleeding time (platelet dysfunction). Mildly prolonged aPTT (due to ↓ factor VIII). Abnormal ristocetin cofactor test. Normal platelet count (usually).
What is Hemophilia A vs. Hemophilia B, and how do they differ in pathogenesis and lab results?
Hemophilia A: Factor VIII deficiency. Hemophilia B (Christmas disease): Factor IX deficiency. Both show: Normal PT, Prolonged aPTT, Normal bleeding time, Deep tissue bleeding.
What type of bleeding is common in hemophilia, and why are petechiae typically absent?
Hemarthroses, deep muscle bleeds, and prolonged bleeding after surgery. Petechiae are absent because platelet function is normal.
How are Hemophilia A and B inherited, and why does this pattern affect mostly males?
They are X-linked recessive. Males (XY) with one defective X show disease; females (XX) must inherit two defective copies to be affected.
How is the activated partial thromboplastin time (aPTT) used diagnostically in bleeding disorders?
aPTT measures the intrinsic and common coagulation pathways. It’s prolonged in deficiencies of factors VIII, IX, XI, or XII (e.g., hemophilia).
Why does von Willebrand disease sometimes present similarly to Hemophilia A?
Because vWF stabilizes factor VIII. In vWD, low vWF leads to decreased VIII, prolonging aPTT and causing mild hemophilia-like symptoms.
How can a patient with hemophilia develop complications from treatment, and what is the term for this?
Patients can develop inhibitors (antibodies) against infused clotting factors, making treatment less effective and increasing bleeding risk.
Why is the ristocetin cofactor assay useful in diagnosing bleeding disorders?
It assesses vWF-mediated platelet aggregation. It is abnormal in von Willebrand disease but normal in hemophilia.
What would you expect on lab results in a patient with isolated platelet dysfunction but normal coagulation factors?
Prolonged bleeding time. Normal PT and aPTT. Seen in conditions like uremia, aspirin use, or congenital platelet disorders.
How does the coagulation cascade pathway help you localize a clotting factor deficiency based on PT vs. aPTT results?
Prolonged PT = extrinsic pathway issue (e.g., factor VII). Prolonged aPTT = intrinsic pathway (e.g., VIII, IX, XI). Both prolonged = common pathway defect (e.g., X, II, fibrinogen).
