💊 Unfractionated Heparin

Unfractionated Heparin (UFH) is a rapidly acting parenteral anticoagulant that interferes with the coagulation cascade at multiple points. It is a heterogeneous mixture of glycosaminoglycans.

UFH binds to antithrombin III, significantly enhancing its ability to inactivate thrombin (Factor IIa) and Factor Xa. It also inactivates other clotting factors, including IXa, XIa, and XIIa.

UFH is used for the acute treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE), particularly in unstable patients. It is also indicated for anticoagulation during cardiac surgery, percutaneous coronary intervention (PCI), and haemodialysis. UFH is preferred in situations requiring rapid onset and offset of action, or in severe renal impairment.

Absolute contraindications include active major bleeding, a history of heparin-induced thrombocytopenia (HIT), and severe uncontrolled hypertension. It is also contraindicated in patients with severe haemophilia or other haemorrhagic disorders, and recent intracranial haemorrhage. Caution is required in patients with a high risk of bleeding, such as recent surgery or peptic ulcer disease.

The most significant adverse effect is bleeding, which can be severe and life-threatening. Heparin-induced thrombocytopenia (HIT) is a serious immune-mediated complication. Other side effects include osteoporosis with long-term use, hypersensitivity reactions, and hyperkalaemia due to aldosterone suppression. Local irritation at injection sites can also occur.

UFH requires close monitoring of the activated partial thromboplastin time (APTT) to ensure therapeutic anticoagulation. Platelet counts must be monitored regularly, especially during the initial phase of treatment, to detect HIT. Renal and liver function should also be assessed.

Always check for active bleeding, a history of HIT, and severe uncontrolled hypertension. Ensure appropriate monitoring of APTT and platelet count is in place. Counsel patients (or their families) on the risks of bleeding and the need for close observation. Be aware of potential drug interactions with other antiplatelet or anticoagulant agents.

UFH has a short half-life and is rapidly reversible with protamine sulfate, making it suitable for situations requiring precise control of anticoagulation. It is metabolised by the liver and excreted renally, but its clearance is less dependent on renal function than LMWHs, making it safer in severe renal impairment. Remember the high risk of HIT and the need for frequent monitoring.

SBAs often focus on the indications for UFH, particularly in acute, unstable situations or where rapid reversal is needed. Questions may also test the monitoring requirements (APTT, platelets) and the recognition and management of HIT. Differentiating UFH from LMWH in terms of mechanism and monitoring is a common theme.