In any anticoagulant therapy, the major risk is bleeding. Estimates range from 0.8% per day to about 5% overall in recent surveys. Dose seems to be the most important factor, hence the vigilance regarding the aPTT. Bleeding risk also increases with intermittent subcutaneous use, duration of therapy, and concurrent use of aspirin and thrombolytic agents.
Heparin can cause mild or severe thrombocytopenia. The mild form is due to heparin-induced platelet aggregation and occurs after 2 days to 2 weeks of full-dose heparin in about 15-25% of cases. The platelet counts usually stabilize above 100,000/|il, even with continued heparin therapy. In the severe form, immune mechanisms cause a marked fall in platelet count (50,000/|tl) and arterial thrombi can occur. Bovine-derived heparin is more commonly involved than the porcine product. Platelet counts should be checked daily; if they drop below 100,000, heparin should be discontinued. Switching from bovine to porcine heparin, adding antiplatelet drugs, or using the new low molecular weight heparin may be options.
At 5-10 days of therapy, transient abnormalities of liver function tests can occur. Rarely, anaphylaxis, skin necrosis, local urticaria, or hyperkalemia is seen. Long-term heparin use can cause osteoporosis.
Is heparin resistance real?
Massive pulmonary embolism can be associated with increased clearance of heparin, giving a picture of relative resistance. Antithrombin III, which is required for heparin’s action, can be the key to heparin resistance. Congenital antithrombin III deficiencies usually reduce antithrombin III levels to 40-60%, sufficient for anticoagulation with heparin. In acquired deficiencies from hepatic cirrhosis, nephrotic syndrome, or disseminated intravascular coagulation, antithrombin III levels can fall to lower levels (25%), where heparin activity is impaired.
1If long-term anticoagulation is anticipated, how do you combine heparin and warfarin?
Start warfarin on day 1 of heparin therapy. This allows depletion of vitamin K-dependent factors while the patient is fully anticoagulated with heparin. After 5-6 days of heparin and with at least
2 days of a therapeutic PT/INR, heparin can be discontinued. A minor decrease in PT/INR may be seen as the heparin effect wanes.
What are the complications of heparin therapy? Photo Gallery
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