Coags- ChatGPT's Version (Exam IV, Mordecai) Flashcards
What are the goals of hemostasis?
Limit blood loss, maintain blood flow, promote vessel repair.
What are the 2 stages of hemostasis?
Primary: Platelet plug
Secondary: Clotting factor activation → fibrin clot
What roles do endothelial cells play in clot prevention?
Repel platelets (negative charge)
Release prostacyclin & nitric oxide
Degrade ADP
Produce TFPI & tPA
Activate Protein C
What are the 3 phases of platelet response to injury?
Adhesion
Activation
Aggregation
What do platelet alpha granules and dense bodies contain?
Alpha: Fibrinogen, vWF, factor V/VIII
Dense bodies: ADP, calcium, serotonin, histamine
What are the 4 components needed for clotting complexes?
Substrate (inactive factor)
Enzyme (active factor)
Cofactor
Calcium
What triggers the extrinsic pathway?
Tissue Factor (TF) is exposed to blood stream
TF + VIIa → activates X and IX.
What is the main purpose of the intrinsic pathway?
Amplification of thrombin generation (not initiation).
What activates the intrinsic pathway?
Contact with negatively charged surfaces, such as:
- Exposed collagen in a damaged vessel wall
- Glass, dextran, or kaolin in lab tests (like aPTT)
- Platelet phospholipid membranes during in vivo coagulation
→ XIIa → XIa → IXa + VIIIa → Xa
What happens in the common pathway?
Xa + Va = prothrombinase → converts prothrombin (II) to thrombin (IIa) → converts fibrinogen (I) to fibrin (Ia) → XIIIa crosslinks fibrin
What is the most important step in regulating hemostasis?
Thrombin generation
What are the 4 major anticoagulant systems?
Fibrinolysis: TPA/urokinase → plasmin → breaks down fibrin.
TFPI: Inhibits TF–VIIa and Xa (extrinsic pathway)
Protein C system: Inhibits factors IIa, Va, VIIIa (common pathway)
SERPINs: Antithrombin inhibits IIa, IXa, Xa, XIa, XIIa (enhanced by heparin).
How does heparin work?
Binds antithrombin → accelerates inhibition of thrombin and factor Xa.
What does PT measure?
Extrinsic + common pathways (factors I, II, V, VII, X); used for warfarin monitoring.
Especially sensitive to which 2 factors?
What does aPTT measure?
Intrinsic + common pathways, especially sensitive to factors VIII & IX; used for heparin monitoring.
What does the Anti-Xa assay measure?
Functional effect of heparin, LMWH, or Xa inhibitors.
What is the ACT used for?
Point-of-care test for heparin responsiveness; used intraoperatively.
What tests assess global clot function?
TEG and ROTEM (viscoelastic testing).
What is the most common inherited bleeding disorder?
Von Willebrand disease (vWF deficiency).
What labs are abnormal in vWD?
aPTT may be prolonged (due to low factor VIII), PT and platelet count are usually normal.
What is the first-line treatment for mild vWD?
DDAVP (desmopressin) → increases vWF release.
What factor is deficient in Hemophilia A?
Factor VIII.
What factor is deficient in Hemophilia B?
Factor IX.
What is normal?
What lab is prolonged in hemophilia?
aPTT is prolonged; PT and platelet count are normal.