Which parameter is used to monitor intravenous heparin therapy in most institutions?

Which parameter is used to monitor intravenous heparin therapy in most institutions?

• A. Partial thromboplastin time (aPTT)
• B. White blood cell count
• C. Serum calcium
• D. Blood glucose

Answer: (A)

The key idea is that unfractionated heparin works by enhancing antithrombin III, which slows the intrinsic and common pathways of coagulation. The test that most accurately reflects this anticoagulant effect in real time is the activated partial thromboplastin time (aPTT). By measuring how long it takes plasma to form a clot after adding phospholipid and calcium, aPTT assesses the activity of factors II (thrombin), V, VIII, IX, and XI in the presence of heparin. Clinicians aim for a therapeutic range that corresponds to adequate anticoagulation without excessive bleeding risk, often a multiple of the normal aPTT value defined by the lab’s reference range. Because of variability in reagents and patient factors, the dose is adjusted based on this test result. Other parameters listed don’t monitor heparin therapy: white blood cell count tracks infection or inflammation, not coagulation; serum calcium affects various processes including coagulation but is not used to gauge heparin effect; blood glucose is unrelated to anticoagulation control.

The key idea is that unfractionated heparin works by enhancing antithrombin III, which slows the intrinsic and common pathways of coagulation. The test that most accurately reflects this anticoagulant effect in real time is the activated partial thromboplastin time (aPTT). By measuring how long it takes plasma to form a clot after adding phospholipid and calcium, aPTT assesses the activity of factors II (thrombin), V, VIII, IX, and XI in the presence of heparin. Clinicians aim for a therapeutic range that corresponds to adequate anticoagulation without excessive bleeding risk, often a multiple of the normal aPTT value defined by the lab’s reference range. Because of variability in reagents and patient factors, the dose is adjusted based on this test result.

Other parameters listed don’t monitor heparin therapy: white blood cell count tracks infection or inflammation, not coagulation; serum calcium affects various processes including coagulation but is not used to gauge heparin effect; blood glucose is unrelated to anticoagulation control.