What is the recommended heparin dose for a patient with Acute Coronary Syndrome (ACS) and severe impaired renal function, specifically a creatinine clearance of 15ml/min?

Heparin Dosing for ACS in Severe Renal Impairment (CrCl 15 ml/min)

For a patient with Acute Coronary Syndrome (ACS) and severe renal impairment with creatinine clearance of 15 ml/min, unfractionated heparin (UFH) should be used with 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 achieve a therapeutic aPTT range of 60-80 seconds. 1

Anticoagulant Selection in Severe Renal Impairment

When managing ACS in patients with severe renal impairment (CrCl <30 ml/min), the choice of anticoagulant is critical:

• Unfractionated heparin (UFH) is the preferred agent as it:

  • Does not require dose adjustment for renal dysfunction 1
  • Has a predictable dose response 1
  • Can be monitored via aPTT and dose-adjusted accordingly

• Avoid other anticoagulants:

  • Enoxaparin: Requires dose reduction to 1 mg/kg once daily if used, but UFH is preferred 1, 2
  • Fondaparinux: Contraindicated when CrCl <30 ml/min 1
  • Bivalirudin: Requires dose reduction to 1 mg/kg/h in severe renal impairment 1

Specific UFH Dosing Protocol for ACS with CrCl 15 ml/min

1. Initial bolus: 60 IU/kg (maximum 4000 IU) 1
2. Initial infusion: 12 IU/kg/h (maximum 1000 IU/h) 1
3. Monitoring: Adjust dose to maintain aPTT in therapeutic range of 60-80 seconds 1
4. Duration: Continue during hospitalization until revascularization or clinical stabilization 1

Monitoring Recommendations

• Check aPTT 6 hours after starting therapy and after any dose adjustment
• Once stable, check aPTT daily
• Monitor for signs of bleeding (especially GI, retroperitoneal, or intracranial)
• Monitor platelet count for heparin-induced thrombocytopenia (HIT)

Special Considerations in Renal Impairment

1. Increased bleeding risk: Patients with renal dysfunction have higher bleeding risk with all anticoagulants 2

2. Weight-based dosing importance: Standard non-weight-adjusted dosing (e.g., fixed 5000 U bolus/1000 U/h infusion) increases bleeding risk, particularly in patients with lower body weight 3

3. PCI considerations: If the patient requires PCI:

   • For patients already on UFH: Additional UFH as needed to achieve ACT 250-300 seconds
   • For patients not on prior anticoagulant: 70-100 U/kg initial bolus to achieve ACT 250-300 seconds 1

Common Pitfalls to Avoid

1. Using LMWH at standard doses: Standard therapeutic doses of enoxaparin in severe renal impairment lead to drug accumulation and increased bleeding risk (8.3% vs 2.4% in normal renal function) 2

2. Fixed dosing instead of weight-based: Non-weight-adjusted UFH dosing increases bleeding risk, particularly in elderly, females, and those with lower body weight 3

3. Inadequate monitoring: Failure to monitor aPTT frequently in the initial phase of treatment can lead to subtherapeutic or supratherapeutic anticoagulation

4. Premature discontinuation: Early discontinuation of anticoagulation is associated with rebound thrombin activity and increased risk of reinfarction, with greatest risk in the first 4-8 hours after discontinuation 1

By following these specific dosing recommendations for UFH in patients with ACS and severe renal impairment, you can provide effective anticoagulation while minimizing the risk of bleeding complications.