How can filter life be increased on Continuous Renal Replacement Therapy (CRRT)?

Increasing Filter Life on CRRT

Regional citrate anticoagulation is the preferred strategy to maximize filter life in CRRT, providing superior circuit longevity (median 42-48 hours) compared to heparin (24-30 hours) or no anticoagulation (17-27 hours), while avoiding life-threatening bleeding complications. 1, 2

Primary Anticoagulation Strategy

Use regional citrate anticoagulation as first-line when no contraindications exist, as it significantly extends filter life without increasing bleeding risk compared to heparin or no anticoagulation. 1, 2

• Citrate provides median filter survival of 42-48 hours versus 24-30 hours with heparin and 17-27 hours without anticoagulation. 1, 2
• Filter clotting rates are similar between citrate (27%) and heparin (25%), but both are superior to no anticoagulation (50%). 1
• Life-threatening bleeding complications occur with heparin but are absent with citrate anticoagulation. 1

Citrate Monitoring Requirements

Implement strict monitoring protocols to prevent citrate-related complications while maintaining filter longevity. 3

• Measure post-filter and serum-ionized calcium frequently to titrate citrate and calcium replacement appropriately. 4, 3
• Target post-filter ionized calcium between 0.25-0.40 mmol/L; increasing from 0.25-0.35 to 0.30-0.40 mmol/L does not reduce filter life and may decrease unnecessary citrate exposure. 5
• Monitor systemic acid-base balance, particularly in patients at high risk for citrate accumulation (liver failure, shock). 4, 3
• Track serum sodium levels to prevent hypernatremia associated with citrate use. 3

Alternative Strategies When Citrate Contraindicated

Use systemic heparin anticoagulation when citrate is contraindicated or unavailable, with appropriate safety monitoring. 4, 6

Heparin Administration

Administer heparin prefilter to optimize anticoagulant effect throughout the entire extracorporeal circuit. 6

• Monitor activated clotting times (ACT) or systemic partial thromboplastin time (PTT) to minimize bleeding risk. 4, 6
• Measure platelet counts routinely to detect heparin-induced thrombocytopenia. 4, 6
• In patients with heparin-induced thrombocytopenia, switch immediately to direct thrombin inhibitors (argatroban) or Factor Xa inhibitors. 7, 3

Adjunctive Measures to Reduce Filter Clotting

Use pre-dilution fluid administration in patients with frequent filter clotting or when performing high-volume hemofiltration. 4, 7

• Pre-dilution dilutes blood before entering the hemofilter, enhancing ultrafiltration rates and reducing clotting risk. 4, 7
• Combine pre-dilution with post-dilution when extracorporeal clearance is limited by achievable blood flow. 4, 7
• Use replacement fluids with physiologic electrolyte concentrations; avoid supra-physiologic glucose concentrations that cause hyperglycemia. 4, 7

Buffer Selection

Use bicarbonate-based fluids rather than lactate in specific high-risk populations. 4, 7

• Bicarbonate is preferred over lactate in patients with lactic acidosis, liver failure, or during high-volume hemofiltration. 4, 7
• Lactate-based fluids can worsen acidosis in patients with lactic acidosis or liver failure. 4

Vascular Access Optimization

Avoid subclavian vein access when possible due to thrombosis risk and late stenosis, which can compromise circuit function. 4

• Use internal jugular or femoral vein access sites based on individual patient factors. 4
• Ensure adequate catheter function to maintain prescribed blood flow rates. 4

No Anticoagulation Approach

Reserve no anticoagulation strategy for patients with active bleeding or extreme bleeding risk, accepting reduced filter life (17-27 hours). 4, 1

• CRRT can be performed successfully without anticoagulation, though circuit life is typically less than 24 hours. 4
• This approach has significantly higher clotting rates (50%) compared to anticoagulated circuits (25-27%). 1

Key Pitfalls to Avoid

• Do not use regional heparin-protamine anticoagulation due to risk of protamine accumulation in acute kidney injury without adequate safety data. 4
• Avoid lactate-based replacement fluids in patients with liver failure or lactic acidosis as they can worsen metabolic acidosis. 4
• Do not use low-molecular-weight heparins or synthetic heparinoids without regular anti-factor Xa monitoring. 4
• Ensure adequate staff education on citrate protocols to prevent prescription errors and citrate toxicity. 3