What is the recommended heparin (unfractionated heparin) dosing for patients with acute coronary syndrome (ACS)?

Recommended Unfractionated Heparin Dosing for Acute Coronary Syndrome

For patients with acute coronary syndrome, the recommended unfractionated heparin (UFH) dosing is an initial loading dose of 60 IU/kg (maximum 4000 IU), followed by an infusion of 12 IU/kg per hour (maximum 1000 IU/h) adjusted to maintain an activated partial thromboplastin time (aPTT) of 60-80 seconds. 1

Initial Therapy Dosing

• For NSTE-ACS (Non-ST-Elevation ACS):

  • Loading dose: 60-70 IU/kg (maximum 4000 IU) 1
  • Initial infusion: 12 IU/kg/h (maximum 1000 IU/h) 1
  • Target aPTT: 60-80 seconds (approximately 1.5-2 times normal) 1, 2

• For STEMI with fibrinolytic therapy:

  • Loading dose: 60 IU/kg (maximum 4000 IU) 1
  • Initial infusion: 12 IU/kg/h (maximum 1000 IU/h) 1
  • Adjust to therapeutic aPTT range 1

PCI Support Dosing

• For patients who have received prior anticoagulant therapy:

  • Additional UFH as needed to achieve an activated clotting time (ACT) of 250-300 seconds 1

• For patients who have not received prior anticoagulant therapy:

  • 70-100 U/kg initial bolus to achieve target ACT of 250-300 seconds 1

Monitoring and Adjustment

• Monitor aPTT approximately every 4-6 hours during initial treatment 2
• Adjust dose to maintain aPTT at 1.5-2 times normal (60-80 seconds) 2
• Periodically monitor platelet counts and check for signs of bleeding 2

Duration of Therapy

• Continue parenteral anticoagulation until revascularization (PCI or CABG) is performed 1
• For patients not undergoing an invasive approach, continue for the duration of hospital stay (maximum 8 days) 1

Alternative Anticoagulants

• Bivalirudin is a useful alternative to UFH in patients with STEMI undergoing PCI to reduce mortality and bleeding 1
• Enoxaparin is recommended for patients with NSTE-ACS in whom an early invasive approach is not anticipated 1
• Fondaparinux should NOT be used to support PCI due to risk of catheter thrombosis 1

Common Pitfalls and Caveats

• Avoid excessive anticoagulation, as the risk of bleeding increases with higher heparin doses 1
• The lowest mortality rate appears with a heparin dose of approximately 14 U/kg/h or an aPTT of approximately 70 seconds 3
• Bleeding risk is increased with concomitant administration of fibrinolytic agents or glycoprotein IIb/IIIa inhibitors 1
• Reduce dose in patients with renal impairment 1
• Avoid intramuscular injections due to risk of hematoma formation 2
• Discontinue parenteral anticoagulation immediately after the invasive procedure unless there is a compelling reason to continue 1

UFH remains a cornerstone therapy for ACS management, with specific dosing regimens established to balance efficacy in reducing ischemic events against the risk of bleeding complications.