Anticoagulant monitoring

Anticoagulant monitoring

Anticoagulant monitoring	See also Thrombolytic therapy .
Heparin (standard, unfractionated)
Prior to commencing therapy	FBC , platelet count ; baseline APTT , INR if patient on warfarin; PT if warfarin treatment planned.
During therapy	Platelet counts 2-3 times weekly are recommended.
Continuous IV infusion	APTT ; check therapeutic interval with laboratory. In the first 24 hours, frequent assessment may be required, but the APTT should not be performed <4 hours after any change in dose. Subsequently, a daily APTT usually suffices.
Intermittent IV injection	Monitoring not of value.
Prophylactic SC injection (low dose heparin)	Monitoring not of value.
If bleeding occurs	APTT ; FBC , platelet count . Check other medications with patient and/or from records. Concomitant aspirin or other NSAID increase the risk of bleeding; their effect on platelet function is predictable and testing is not indicated. The possibility of a pre-existent acquired or inherited bleeding disorder should also be considered.
If progression of thrombosis, or thrombosis in other site(s)
Inadequate anticoagulation	APTT .
Heparin-induced thrombocytopenia (HIT type II)	FBC , platelet count ; heparin-dependent platelet antibodies if significant thrombocytopenia is documented.
Antithrombin III deficiency	Antithrombin III assay: should be deferred until heparin has been ceased. See under Thrombosis - venous.
Low Molecular Weight Heparin (LMWH) and heparinoids	The standard dose protocol is based on body weight; monitoring is not usually required except in renal failure or other high risk bleeding situations. Heparin-induced thrombocytopenia is less common than with standard, unfractionated heparin, but may occur: see above.
Prophylactic SC injection	Monitoring is not cost-effective and is not indicated.
Continuous IV infusion (full dose, therapeutic LMWH)	Anti Xa assay is the appropriate test, if testing is required; for therapeutic interval, consult pathologist.
Oral anticoagulants	INR .
If bleeding occurs
Excessive anticoagulation	INR .
Alcohol
Diet
Intercurrent illness
Cardiac failure
Diarrhoea
Other drugs esp	Consult pathologist/pharmacist about drug interactions; consider possibility of recent change in dose, introduction of new, or non-prescribed, medications.
Analgesics
Antibiotics
Aspirin, other NSAID	Predictable effect on platelet function; bleeding time does not predict the risk of bleeding and is not indicated.
Dose error
Concomitant bleeding disorder	See Bleeding .