[HAP-08] Haematology, Haemostasis, Coagulation Cascade & Anaemia Pathophysiology
HAP-08 • 9. PathophysiologyLearning Objectives
Differentiate microcytic hypochromic anaemia (Iron deficiency vs Thassaemia), macrocytic megaloblastic anaemia (Vitamin B12 [10.8] vs Folate [10.7] deficiency), and normocytic anaemia of CKD ([10.11] Erythropoietin).; Trace primary platelet plug formation (vWF, GP Ib, COX-1/TXA2, ADP/P2Y12, GP IIb/IIIa) and the intrinsic, extrinsic, and common coagulation pathways.; Correlate PT/INR (Extrinsic + Common: Factor VII, X, V, II) and aPTT (Intrinsic + Common: Factors XII, XI, IX, VIII) with anticoagulant monitoring.
Chapter Overview & Core Explanation
Blood transports oxygen inside haemoglobin-packed red blood cells and seals blood vessel injuries using a two-step defence: platelets stick together to form a rapid temporary plug, and clotting factors weave a tough cross-linked fibrin mesh over it.
Key Exam & Clinical Takeaways
- Factor VII has the shortest plasma half-life (~6 hours) of the Vitamin K-dependent clotting factors (II, VII, IX, X), while Protein C also has a short half-life (~8 hours)—explaining why [3.43] Warfarin requires 4–5 days of overlap bridging with [3.44] Enoxaparin/Heparin to prevent warfarin-induced skin necrosis.
- Early intravenous [3.52] Tranexamic Acid (1 g IV over 10 min within 3 hours of birth/trauma) significantly reduces death from postpartum haemorrhage and traumatic bleeding.