Anticoagulants: Heparin
38,904views

00:00 / 00:00
Flashcards
Anticoagulants: Heparin
0 of 15 complete
Questions
USMLE® Step 1 style questions USMLE
0 of 2 complete
USMLE® Step 2 style questions USMLE
0 of 4 complete
Laboratory Value | Results |
Hemoglobin | 11.0 g/dL |
Hematocrit | 33% |
Leukocyte Count | 8,700/mm3 |
Platelet Count | 170,000/mm3 |
Partial thromboplastin time (activated) | 105 seconds |
Prothrombin time | 14 seconds |
Memory Anchors and Partner Content
External References
First Aid
2024
2023
2022
2021
Acute coronary syndrome
heparin for p. 440
Bleeding
heparin p. 440
Deep venous thrombosis (DVT) p. 691
heparin for p. 440
Factor Xa
heparin effect on p. 441
Heparin p. 440
acute coronary syndromes p. 314
for anticoagulation p. 419
in basophils p. 414
in coagulation cascade p. 418
deep venous thrombosis p. 690
mast cells and p. 409
osteoporosis p. 249
thrombocytopenia p. 249
toxicity treatment p. 247
warfarin vs p. 441
Intrinsic pathway p. 204
heparin and p. 441
Myocardial infarction (MI) p. 308
heparin for p. 440
Osteoporosis p. 467
heparin p. 440
Pregnancy p. 651
heparin in p. 440
Pulmonary embolism p. 691
heparin for p. 440
Thrombocytes (platelets) p. 413
heparin adverse effects p. 440
Thrombocytopenia p. 413
heparin adverse effects p. 440
Venous thrombosis p. 415
heparin for p. 440
Warfarin p. 441
heparin vs p. 441
Transcript
Anticoagulant medications are used to prevent blood clots from forming. These medications work by interfering with the normal function of plasma proteins called coagulation factors, which take part in secondary hemostasis-- where hemo refers to blood, and stasis meaning to halt or stop. In this video we’re going to focus on heparin, which works by indirectly inhibiting two clotting factors called thrombin and factor Xa by binding to and enhancing the activity of an anticoagulant protein called antithrombin III.
Now, before we discuss heparin in detail, we need to talk about the coagulation cascade, which is where heparin exerts its effect. The coagulation cascade begins via two pathways --the extrinsic and intrinsic pathways. The intrinsic pathway starts when circulating factor XII comes into contact with the surface of activated platelets or collagen. Activated factor XII, then activates factor XI, which activates factor IX which activates factor X. Factor Xa starts the common pathway where it activates factor II, or thrombin, which activates factor I that builds the fibrin mesh. When factor II gets activated it also activates 4 other factors: V, VIII, IX, and XIII. Factor V gets activated and acts as a cofactor for X, factor VIII acts as a cofactor for factor IX, and factor XIII helps factor I, or fibrin, form crosslinks. In the extrinsic pathway, exposed tissue factor activates factor VII, which activates factor X and starts the common pathway.
Now, the most important point of clot regulation is when a coagulation factor called thrombin is produced. Thrombin, or activated factor II, is a very important clotting factor, because it has multiple pro-coagulative functions. Think of thrombin as the accelerator on a car--the pedal that takes secondary hemostasis from 20 miles per hour to 100 miles per hour! First, thrombin binds to receptors on platelets causing them to activate. Activated platelets change their shape to form tentacle-like arms that allow them to stick to other platelets. Second, thrombin activates two cofactors; factor V used in the common pathway, and factor VIII used in the intrinsic pathway. Third, thrombin proteolytically cleaves fibrinogen or factor I, into fibrin or factor Ia which binds with other fibrin proteins to form a fibrin mesh. And finally, thrombin proteolytically cleaves stabilizing factor or factor XIII into factor XIIIa. Factor XIIIa combines with a calcium ion cofactor to form cross links between the fibrin chains, further reinforcing the fibrin mesh.
Sources
- "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
- "Rang and Dale's Pharmacology" Elsevier (2019)
- "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
- "Overview of hemostasis" J.C. Aster, H. Bunn (Eds.), Pathophysiology of Blood Disorders, 2e. McGraw-Hill (2016)
- "Critical Issues and Recent Advances in Anticoagulant Therapy: A Review" Neurology India (2019)
- "Heparinoid Complex-Based Heparin-Binding Cytokines and Cell Delivery Carriers" Molecules (2019)