Unfractionated Heparin Dosing for Therapeutic Anticoagulation

Initial Dosing Regimen

• The American College of Cardiology recommends administering UFH as an 80 units/kg IV bolus (maximum 4000 units) followed by 18 units/kg/hour continuous infusion (maximum 1000 units/hour), adjusted to maintain aPTT at 1.5-2.0 times control 1
• For patients weighing over 50 kg, the maximum bolus should be capped at 4000 units 2
• For patients weighing over 55 kg, the maximum infusion rate should be capped at 1000 units/hour 2

Context-Specific Dosing

• For STEMI patients receiving fibrinolytic therapy, a lower dose of 60 units/kg bolus (maximum 4000 units) followed by 12 units/kg/hour infusion (maximum 1000 units/hour) is recommended to minimize bleeding risk 3
• The American College of Cardiology suggests that this reduced dosing regimen minimizes bleeding risk when combined with fibrinolytics 3

Monitoring Protocol

• The first aPTT measurement should be taken at 6 hours after bolus, then every 4-6 hours until stable in therapeutic range 1
• The target aPTT should be 1.5-2.5 times control (approximately 50-70 seconds) 3
• Once stable, aPTT should be checked daily 1
• Platelet counts should be monitored daily throughout therapy 3

Special Populations

• For patients with severe renal insufficiency (CrCl <30 mL/min), UFH is the preferred anticoagulant as it undergoes hepatic metabolism 4
• The American College of Cardiology recommends using UFH in severe renal insufficiency due to its hepatic metabolism 4

Critical Pitfalls to Avoid

• Excessive dosing errors that increase bleeding risk should be avoided, and the maximum bolus should not exceed 70 units/kg or 4000 units total 2
• The maximum infusion rate should not exceed 15 units/kg/hour or 1000 units/hour total 2
• Absolute contraindication in active heparin-induced thrombocytopenia (HIT) 4
• Use extreme caution in patients with history of HIT; consider direct thrombin inhibitors or fondaparinux instead 4