Clinical meaning
The coagulation cascade involves intrinsic and extrinsic pathways converging on the common pathway to generate thrombin, which converts fibrinogen to fibrin. Unfractionated heparin (UFH) potentiates antithrombin III, inactivating thrombin (factor IIa) and factor Xa, monitored by aPTT. Low-molecular-weight heparins (LMWH) have greater factor Xa selectivity and more predictable pharmacokinetics, monitored by anti-Xa levels in specific populations. Warfarin depletes vitamin K-dependent factors (II, VII, IX, X, protein C and S), monitored by PT/INR with a narrow therapeutic index. Direct oral anticoagulants (DOACs) directly inhibit either thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban, edoxaban) with predictable pharmacokinetics requiring minimal monitoring. The nurse manages anticoagulation protocols, interprets coagulation labs, implements bridging therapy, and recognizes life-threatening bleeding.
Exam relevance
Risk factors: - Atrial fibrillation with CHA2DS2-VASc score ≥2 - Acute DVT or PE - Mechanical prosthetic heart valves - Post-orthopedic surgery thromboprophylaxis - Antiphospholipid syndrome - Cancer-associated thrombosis - Recurrent thromboembolism - Cerebrovascular disease