Coagulation
Anticoagulants and procoagulants
Heparin
Author: Jeremy C. Parsons, M.D.
Last author update: 1 June 2012
Last staff update: 22 September 2020
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Heparin [title]
Table of Contents
Definition / general | Pathophysiology | Diagrams / tables | Clinical features | Laboratory | TreatmentCite this page: Parsons JC. Heparin. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationheparin.html. Accessed November 28th, 2024.
Definition / general
- Also called unfractionated heparin
- Short acting anticoagulant with half life of approximately 90 minutes
Pathophysiology
- Derived from porcine intestinal mucosa or bovine lung, which contain heparin-rich mast cells
- Markedly enhances activity of antithrombin, which inhibits activated factors II, IX, X, XI, XII, kallikrein and probably VII, but doesnt cause a true decrease in factor levels
- Most heparin preparations are heterogeneous, with a molecular weight between 7 - 25K daltons
- Anticoagulant activity is variable, since only 1 / 3 of heparin molecules have the pentasaccharide sequence necessary for antithrombin mediated anticoagulant activity
Diagrams / tables
Images hosted on other servers:
Heparin 2-D structure
Function of heparin
Clinical features
- Used as initial anticoagulant therapy, to treat deep venous thrombosis, post-operatively and for other short-term indications
- Decreases morbidity and mortality from acute thrombotic disease
- Complications include hemorrhage (overcoagulation) and heparin-induced thrombocytopenia (up to 3% of patients)
- Recommended that 90% of patients should achieve therapeutic anticoagulation within 24 hours
Laboratory
- Recommended to monitor with PTT assay (that has been standardized using determination of heparin levels), activated clotting time (if high heparin levels present, as during cardiopulmonary bypass surgery, since no clotting occurs at these levels with PTT) or heparin levels assayed by measuring activity against factor Xa (therapeutic range is 0.3 to 0.7 anti-Xa units/ml) within 12 hours (Clin Lab Med 2009;29:283)
- Also monitor platelet count within 72 hours, with platelet monitoring to continue periodically for 20 days; PT is usually normal
- Note: often the cause of prolonged PTT is heparin in sample collected through indwelling line; identify by treating with heparinase
Treatment
- Protamine sulfate (for emergency reversal of heparin)
