- Binds antithrombin III → heparin-antithrombin III complex → inhibits
multiple steps (IXa, Xa, XIa, XIIa and thrombin) in intrinsic and
- Low-molecular-weight heparins (LMWH) are obtained from heparin, but
have a longer half-life, greater bioavailability, and greater activity
against factor Xa.
- Bleeding may be spontaneous or related to trauma.
- Warfarin, other "warfain-like" anticoagulants, ingestion of brodifacoum (rat poison)
- Usually clear from patient's history and exam
- Elevation of PT/INR and aPTT
- Stop heparin.
- Protamine sulfate: 1-1.5 mg IV per 100 units heparin,
MAX: 50 mg/dose, rate: 5 mg/min.
- Indicated for severe bleeding complications only (risk of
serious anaphylaxis with administration)
- Reverses the effect of heparin and partially inactivates LMWH
- Dose is calculated from the dose of heparin given.
- Onset of action is 30-60 seconds with a duration lasting 2
- Heparin-induced thrombocytopenia (HIT): May occur 5-8 days
after initiating therapy or as late as 3 weeks after stopping therapy.
Antibodies cause significant drop in platelets (>50%) and skin changes
at injection sites. Systemic venous and arterial thrombotic events
can cause a wide variety of end organ damage. This is more common with
heparin versus LMWH.