What is the ideal duration for Continuous Renal Replacement Therapy (CRRT) in patients with acute kidney injury (AKI)?

Optimal Duration for CRRT in Acute Kidney Injury

CRRT should be continued until there is evidence of renal recovery, typically assessed by urine output ≥400-500 mL/24h without diuretics, and discontinued when patients remain dialysis-free for at least 48 hours after stopping, with most mortality outcomes determined by 60 days. 1, 2

Duration of CRRT Therapy

The duration of CRRT is not predetermined by a fixed time period but rather guided by recovery markers and clinical stability:

• Continue CRRT until renal recovery is evident, as indicated by improving urine output, stabilizing or declining serum creatinine, and resolution of metabolic derangements requiring dialysis support 1
• Minimum 48 hours off RRT is necessary to confirm sustained reversal and separate distinct AKI episodes, as rapid reversal within 48-72 hours of AKI onset is associated with better outcomes 1
• Most deaths occur within 60 days of CRRT initiation (54.6% of all mortalities), making this the critical follow-up window rather than extending therapy indefinitely 2

Criteria for CRRT Discontinuation

Urine output is the most robust predictor of successful RRT discontinuation, though optimal thresholds vary widely across studies (191-1720 mL/24h) 1:

• Target urine output ≥400-500 mL/24h measured without diuretic augmentation provides moderate predictive accuracy for successful liberation 1
• Avoid relying on diuretic-augmented urine output as studies show conflicting results—some suggest improved prediction while larger studies found decreased reliability 1
• Monitor serum creatinine trends alongside urine output, as combined parameters improve prediction of successful discontinuation 1

Assessment Timeline for Discontinuation

• Assess readiness for discontinuation daily once hemodynamic stability is achieved and the precipitating cause of AKI is resolving 1
• If dialysis continues beyond 14 days, perform weekly assessments of renal recovery with pre-dialysis creatinine and residual kidney function measurements 3
• Confirm sustained recovery for minimum 48 hours after stopping CRRT before considering the patient successfully liberated from RRT 1

Modality Considerations Affecting Duration

• CRRT as first modality offers no survival advantage over intermittent hemodialysis and may be associated with worse outcomes in less severely ill patients 4
• For hemodynamically unstable patients requiring vasopressors, CRRT remains the preferred modality and should be continued until hemodynamic stability allows transition to intermittent therapy 3, 5
• Consider transitioning to intermittent hemodialysis once hemodynamically stable, as this may improve outcomes while maintaining adequate solute clearance 4

Common Pitfalls to Avoid

• Do not discontinue CRRT based solely on a single urine output measurement, as this has poor predictive accuracy without considering trends and clinical context 1
• Avoid premature discontinuation before 48 hours of sustained improvement, as this increases risk of requiring RRT reinitiation 1
• Do not continue CRRT indefinitely in patients with persistent anuria beyond 14-21 days without reassessing for irreversible kidney injury and transition to chronic dialysis planning 3
• Beware of using diuretic-augmented urine output as the primary discontinuation criterion, as this may overestimate true renal recovery 1

Monitoring During CRRT

While on CRRT, perform the following assessments to guide duration decisions:

• Monitor urine output hourly if any residual function exists, targeting trends rather than isolated values 3
• Check electrolytes and acid-base status every 2-4 hours initially, then less frequently as stability improves 3
• Assess for resolution of the original indication for CRRT (hyperkalemia, acidosis, volume overload, uremia) 3, 6