Source / episode info
- **Episode:**8
- **Title:**Divine Intervention Episode 8 – Comprehensive Heme Pharmacology.
- **Published:**2018-03-20
- Source:Episode page
One-liner
This episode comprehensively reviews hemostasis from the subendothelial collagen adhesion step through primary platelet aggregation, detailing the intrinsic and extrinsic coagulation cascades, and covering pharmacology of antiplatelet agents (aspirin, P2Y12 inhibitors), NSAIDs/COX-2 selective inhibitors, and anticoagulants (heparin, warfarin, C5 blockade).
High-yield summary
- Primary Hemostasis Defects: Bernard-Soulier syndrome involves defective GP1b/IX receptor (adhesion defect); Glanzmann thrombasthenia involves defective GPIIb/IIIa receptor (aggregation defect); vWF deficiency impairs adhesion and prolongs bleeding time.
- Antiplatelet Agents: Aspirin irreversibly inhibits COX-1/COX-2, leading to reduced Thromboxane A2 ({TXA}_2) synthesis; selective COX-2 inhibitors (e.g., Celecoxib) reduce GI risk by sparing COX-1 function in the stomach.
- Anticoagulation Monitoring: Unfractionated Heparin is monitored via aPTT (both PTT and aPTT are elevated); Low Molecular Weight Heparin (LMWH) is monitored via Anti-Xa activity.
- PNH Pathophysiology: Deficiency of the GPI anchor leads to loss of complement inhibitors (CD55, CD59) on red blood cells, resulting in intravascular hemolysis. Treatment involves C5 blockade with Eculizumab.
- HIT Management: This is a Type II hypersensitivity reaction (IgG against Heparin-PF4 complex). Treatment requires direct thrombin inhibitors (e.g., Argatroban) or Factor Xa inhibitors (e.g., Rivaroxaban), never LMWH.
Learning objectives
- Differentiate between primary hemostasis defects (adhesion vs aggregation).
- Describe the molecular mechanism and clinical implications of various antiplatelet drugs (aspirin, COX inhibitors, P2Y12 blockers).
- Compare the monitoring, mechanisms, and contraindications of different anticoagulants (Heparin, Warfarin, DOACs).
- Identify the pathophysiology and management of acquired thrombotic/hemorrhagic states (HIT, PNH, VWD).
- Understand the role of GPI anchors in cell surface proteins and complement regulation.
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