What is the appropriate dose of heparin (unfractionated heparin) for a patient with Acute Coronary Syndrome (ACS) and severe renal impairment, with an estimated Glomerular Filtration Rate (eGFR) of 17?

Heparin Dosing in ACS with eGFR 17

Use unfractionated heparin (UFH) with continuous infusion adjusted to aPTT for this patient with severe renal impairment (eGFR 17 mL/min/1.73 m²), as low-molecular-weight heparins accumulate dangerously at this level of kidney function. 1

Primary Anticoagulation Strategy

UFH is the mandatory anticoagulant choice when eGFR is <30 mL/min/1.73 m² because it does not require renal dose adjustment and allows predictable monitoring through aPTT. 1, 2

UFH Dosing Protocol

• Initial IV bolus: 60 units/kg (maximum 4000 units) 2
• Continuous infusion: 12 units/kg/hour (maximum 1000 units/hour) 2
• Target aPTT: 1.5-2.0 times control (60-80 seconds) 1, 2
• Monitoring: Adjust infusion rate based on aPTT measurements 1

Why Other Anticoagulants Are Contraindicated

Enoxaparin (LMWH)

• Absolutely avoid at eGFR 17—enoxaparin clearance is reduced by 44% in severe renal impairment, leading to dangerous drug accumulation 3
• Even with dose reduction to 1 mg/kg once daily (recommended for eGFR <30), bleeding risk increases nearly 4-fold (8.3% vs 2.4%) 3
• Patients with eGFR <30 have 2.25 times higher odds of major bleeding (OR 2.25,95% CI 1.19-4.27) with LMWH 3

Fondaparinux

• Absolutely contraindicated when eGFR <20 mL/min/1.73 m² 1, 2
• At eGFR 17, this patient is below the safety threshold—fondaparinux should never be used 2, 4

Critical Safety Considerations

Bleeding Risk Factors

• Severe renal impairment (eGFR 17) is an independent predictor of in-hospital major bleeding 5
• Uremic platelet dysfunction compounds bleeding risk beyond drug accumulation 2
• Monitor closely for bleeding complications throughout hospitalization 2

Renal Function Assessment

• Calculate eGFR in all ACS patients, with special attention to elderly, women, and low body weight patients where near-normal serum creatinine may mask severe renal impairment 1
• Use Cockcroft-Gault formula for clinical practice, as it better identifies patients requiring dose adjustments compared to MDRD 6

Antiplatelet Therapy

Dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) does not require dose adjustment for renal function and should be administered as standard first-line treatment. 2, 4

• Aspirin and oral P2Y12 inhibitors undergo hepatic metabolism, not renal clearance 2
• However, insufficient safety data exist for P2Y12 inhibitors in stage 5 CKD (eGFR <15), so monitor closely 4

Invasive Strategy Considerations

Coronary Angiography Decision

• Coronary angiography and revascularization remain recommended after careful risk-benefit assessment, even at eGFR 17 1, 4
• However, mortality benefit of invasive strategy is lost in patients with eGFR <15 mL/min/1.73 m²—at eGFR 17, the patient is just above this threshold where benefit becomes uncertain 4

Contrast-Induced Nephropathy Prevention

• Mandatory hydration: Isotonic saline 12 hours before and 24 hours after angiography 2, 4
• Use low- or iso-osmolar contrast media at lowest possible volume (<4 mL/kg) 1, 2, 4
• Monitor renal function for 2-3 days post-procedure 2

Common Pitfalls to Avoid

1. Never use standard-dose enoxaparin—even "adjusted" dosing carries excessive bleeding risk at eGFR 17 3
2. Never switch between UFH and enoxaparin during the same hospitalization—this increases bleeding risk 3
3. Never assume normal renal function based on serum creatinine alone—calculate eGFR in all patients 1, 6
4. Never use fondaparinux—it is absolutely contraindicated at this eGFR level 2, 4

Additional Medical Therapy

• Beta-blockers, ACE inhibitors/ARBs, and statins should be used with adjusted dosing regimens appropriate for severe renal impairment 2
• High-dose statins are recommended for secondary prevention regardless of renal function 4
• Proton pump inhibitors should be considered given elevated bleeding risk with dual antiplatelet therapy 4