What is the recommended bicarbonate-based solution composition for the prefilter in Continuous Renal Replacement Therapy (CRRT) to lower clotting?

Bicarbonate-Based Solution for Prefilter in CRRT to Reduce Clotting

Bicarbonate-based solutions are recommended as the buffer of choice for prefilter administration in CRRT to reduce clotting, particularly in patients with shock, liver failure, or lactic acidosis. 1

Rationale for Bicarbonate-Based Solutions

• Bicarbonate has replaced lactate and acetate as the dialysate buffer of choice for intermittent renal replacement therapy (RRT) and is preferred for CRRT 2
• The KDIGO guidelines specifically recommend bicarbonate over lactate as a buffer in dialysate and replacement fluid for CRRT in patients with acute kidney injury (AKI) 1
• Bicarbonate is strongly recommended (1B recommendation) for patients with AKI and circulatory shock 1
• Bicarbonate is suggested (2B recommendation) over lactate for patients with AKI and liver failure and/or lactic acidemia 1

Mechanism of Action for Reducing Filter Clotting

• Prefilter fluid administration dilutes the blood before it enters the hemofilter, enhancing the achievable ultrafiltration rate and reducing the risk of filter clotting 1
• This approach is particularly beneficial in high-volume continuous venovenous hemofiltration (CVVH) where filter clotting is more common 1
• Prefilter fluid administration can be used in combination with post-dilution when extracorporeal clearance is limited by achievable blood flow 1

Recommended Composition of Bicarbonate-Based Solution

• The bicarbonate-based solution should contain physiologic concentrations of electrolytes, except in patients with extreme imbalances 1
• A typical bicarbonate solution composition includes: sodium 144 ± 3 mEq/L, bicarbonate 37 ± 2 mEq/L, potassium 3 or 4 mEq/L, calcium 3.0 ± 0.3 mEq/L, and magnesium 1.4 ± 0.3 mg/dL 3
• Avoid fluids with supra-physiologic glucose concentrations as they can lead to excessive glucose intake and hyperglycemia 1

Anticoagulation Strategies to Further Reduce Clotting

• Use anticoagulation for patients receiving RRT who are not at increased risk of bleeding 2
• The choice of anticoagulant should be determined by patient characteristics, local expertise, nursing comfort, ease of monitoring, and pharmacy considerations 1
• For patients with heparin-induced thrombocytopenia, all heparin must be stopped, and direct thrombin inhibitors or Factor Xa inhibitors should be used instead 1
• In thrombocytopenic patients without contraindications to citrate, regional citrate anticoagulation is recommended over heparin 1

Practical Considerations for Implementation

• The recommended CRRT effluent volume is 20-25 mL/kg/h 2, 4
• Monitor filter function regularly as available evidence suggests that delivery of RRT often falls short of the prescribed dose 2
• When using regional citrate anticoagulation with bicarbonate solutions, careful monitoring of acid-base status and electrolytes is essential to prevent complications 5
• Warming the dialysate helps maintain hemodynamic stability during CRRT 4

Potential Complications and Monitoring

• Monitor for electrolyte abnormalities that commonly develop during CRRT, including hypophosphatemia, hypokalemia, and hypomagnesemia 4
• When using bicarbonate solutions with citrate anticoagulation, monitor for metabolic alkalosis 6
• Ensure proper fluid balance monitoring to avoid significant errors in fluid balance 4