Target BUN After 24 Hours of CRRT Starting at 117 mg/dL
Aim for a BUN reduction to approximately 75-85 mg/dL after 24 hours, representing a 25-30% decrease from the initial value of 117 mg/dL. This controlled reduction rate prevents dialysis disequilibrium syndrome while providing adequate uremia control 1, 2.
Recommended Rate of BUN Reduction
The optimal approach is gradual correction over 3-4 days rather than rapid normalization within 24 hours 1, 2. Specifically:
- Target a 25-30% reduction in BUN per 24-hour period during the initial phase of CRRT 1
- For a starting BUN of 117 mg/dL, this translates to a target of 75-85 mg/dL at 24 hours 1
- The ultimate goal is achieving a steady-state BUN of 40-80 mg/dL over 3-4 days through exponential decline 2
CRRT Prescription to Achieve Target
Deliver an effluent volume of 20-25 mL/kg/hr to control uremia adequately while avoiding excessive solute removal 3, 2:
- This intensity is based on large randomized trials showing no benefit from higher doses (35-40 mL/kg/hr) 2
- Prescribe 20-25% higher than the target dose (approximately 25-30 mL/kg/hr) to account for treatment interruptions, filter clotting, and declining membrane efficiency 2
- In practice, patients receive only 68-85% of prescribed dose due to circuit issues and treatment interruptions 2
Monitoring Strategy During Initial 24 Hours
Check BUN and creatinine every 4-6 hours during the adjustment period to ensure the decline rate does not exceed 25-30% per 24 hours 1:
- Monitor for neurological symptoms including altered mental status, headache, nausea, or seizures that may indicate dialysis disequilibrium syndrome 1
- Check electrolytes every 4-6 hours as rapid BUN correction can unmask hypophosphatemia, hypokalemia, and hypomagnesemia 1
Clinical Evidence Supporting Gradual Reduction
Research data demonstrates the safety and efficacy of controlled BUN reduction:
- In neonates with non-metabolic acute kidney injury on CRRT, BUN reduction averaged 33.7% at 24 hours, which was associated with acceptable outcomes 4
- A comparative study showed CRRT provided better azotemia control with lower BUN levels compared to intermittent dialysis, while maintaining hemodynamic stability 5
Critical Pitfalls to Avoid
Do not aim for rapid BUN normalization to <40 mg/dL within 24 hours 1, 2:
- Excessively rapid solute removal precipitates cerebral edema due to osmotic gradients between blood and brain tissue, particularly in severe uremia 1
- A precipitous drop from 117 mg/dL to normal range within 24 hours indicates overly aggressive CRRT dosing and requires immediate prescription adjustment 1
- Avoid using BUN levels in isolation; interpret them in context of their rate of change over time 1, 2
Special Considerations
The BUN:creatinine ratio provides additional context 6: