What are the indications for using heparin?

Indications for Heparin Use

Heparin is indicated for the treatment and prevention of venous thromboembolism (deep vein thrombosis and pulmonary embolism), unstable angina and acute myocardial infarction, prevention of mural thrombosis after MI, atrial fibrillation with embolization, arterial and cardiac surgery anticoagulation, and prevention of clotting in extracorporeal circuits. 1

Venous Thromboembolic Disease

For acute deep vein thrombosis and pulmonary embolism, heparin is the initial anticoagulant of choice because it achieves therapeutic anticoagulation within minutes and can be rapidly reversed if bleeding occurs. 2

• Treatment of established DVT/PE: Heparin prevents extension of existing thrombi and reduces recurrent thromboembolism from 25% to approximately 2% when therapeutic anticoagulation is achieved within 24 hours. 3, 2

• Prophylaxis in surgical patients: Low-dose subcutaneous heparin (5,000 units every 8-12 hours) effectively prevents postoperative DVT and PE in patients undergoing major abdominothoracic surgery or those at risk for thromboembolic disease. 3, 1

• High-risk surgical patients (such as total hip replacement): Adjusted-dose subcutaneous heparin should be used to prolong the aPTT by 4-5 seconds into the upper normal range. 4

Acute Coronary Syndromes

In unstable angina and non-ST-segment elevation myocardial infarction, adding IV heparin to aspirin reduces cardiovascular death and subsequent MI by approximately 30% compared with aspirin alone. 2

• Unstable angina or acute MI without thrombolytic therapy: Administer 5,000 U IV bolus followed by 32,000 U per 24 hours by continuous IV infusion, adjusted to maintain aPTT in the therapeutic range. 3

• Acute MI after thrombolytic therapy: Use lower doses—60 U/kg bolus (maximum 4,000 units) followed by 12 U/kg/h infusion (maximum 1,000 U/h)—to reduce bleeding risk when combined with fibrinolytic agents. 3, 2

• Prevention of mural thrombosis after anterior MI: Moderate-dose subcutaneous heparin reduces mural thrombosis incidence by 58-72%. 2

Atrial Fibrillation and Arterial Thromboembolism

• Atrial fibrillation with embolization: Heparin prevents systemic embolization in patients with atrial fibrillation at high risk for stroke. 1

• Peripheral arterial embolism: Both prophylaxis and treatment of acute arterial thromboembolism are established indications. 1, 5

Procedural and Device-Related Indications

• Arterial and cardiac surgery: Heparin prevents clotting during cardiovascular procedures. 1

• Percutaneous coronary intervention: Loading dose of 100-175 U/kg targeting ACT >300-350 seconds (or 70 U/kg with GP IIb/IIIa inhibitors targeting ACT >200 seconds). 2

• Extracorporeal circulation: Heparin is used as an anticoagulant in blood transfusions, dialysis procedures, and cardiopulmonary bypass. 1

• Arterial line maintenance: While heparinized saline was historically used, normal saline flush alone maintains adequate arterial waveform quality and eliminates HIT risk. 6

Consumptive Coagulopathies

• Disseminated intravascular coagulation (DIC): Heparin is indicated for acute and chronic consumptive coagulopathies, particularly when symptomatic thrombotic complications occur. 1, 5

Critical Dosing Considerations

Weight-based dosing (80 U/kg bolus followed by 18 U/kg/h infusion) is essential for VTE treatment, as fixed-dose regimens produce subtherapeutic anticoagulation in the first 24 hours and are associated with a 25% recurrence rate. 3, 2

• The therapeutic aPTT target is 1.5-2.5 times control, equivalent to heparin levels of 0.2-0.4 U/mL or anti-factor Xa levels of 0.30-0.7 U/mL. 3

• Patients who achieve therapeutic aPTT within 24 hours have markedly lower recurrence rates (2% vs 25%) and reduced mortality compared with delayed therapeutic levels. 3, 2

Common Pitfalls

Avoid fixed-dose heparin regimens for acute VTE treatment—they consistently fail to achieve therapeutic anticoagulation early and increase recurrent thromboembolism risk. 3, 2

Monitor platelet counts daily to detect heparin-induced thrombocytopenia, which occurs in up to 5% of patients receiving unfractionated heparin. 3, 6

Do not use heparinized saline for arterial line maintenance—it increases HIT risk without improving catheter patency compared to normal saline. 6