A 60-year-old man on ICU is receiving continuous venovenous haemofiltration (CVVH) for sepsis-associated AKI. The prescribed effluent dose is 25 mL/kg/hr. His weight is 80 kg. The nurse notes that the filter is clotting frequently, requiring filter changes every 8 hours. What is the recommended anticoagulation strategy for the CVVH circuit in this patient without systemic bleeding risk?