Classic intrinsic, extrinsic, and common coagulation pathway chart with PT/INR, aPTT, ACT, and anticoagulant anchors used in anesthesia review.
Review the core table first, then launch practice to convert recognition into faster recall.
This is the classic laboratory cascade model used for board review and test interpretation. Real in-vivo coagulation is better described by cell-based hemostasis, but these pathway buckets remain useful for PT/INR, aPTT, ACT, and drug-target recall.
| Pathway | Factors involved | Monitoring test | Key anticoagulant / pearl |
|---|---|---|---|
| Intrinsic | XII, XI, IX, VIII | aPTT | Unfractionated heparin often prolongs aPTT via antithrombin effects |
| Extrinsic | III (tissue factor), VII | PT/INR | Warfarin is often detected here first because Factor VII falls quickly |
| Common | X, V, II, I, XIII | PT and aPTT both prolong when the common pathway is impaired | Direct Xa inhibitors and direct thrombin inhibitors act here, though routine PT/aPTT are imperfect monitoring tools |
| Whole-blood heparin effect | Contact activation + common pathway in whole blood | ACT | High-dose unfractionated heparin during bypass or structural heart procedures |
This tool is for educational purposes only. Always verify clinical values against current authoritative sources before patient care.