What duration on Continuous Renal Replacement Therapy (CRRT) increases the likelihood of requiring long-term renal replacement therapy?

Duration of CRRT and Risk of Long-Term Renal Replacement Therapy

There is no specific duration of CRRT that definitively predicts the need for long-term renal replacement therapy, but patients with eGFR <30 mL/min/1.73m² at hospital discharge are at significantly higher risk for requiring permanent dialysis.

Risk Factors for Long-Term RRT After CRRT

The need for long-term renal replacement therapy after CRRT depends on multiple factors rather than just the duration of CRRT treatment. Key predictors include:

Primary Predictors

• Discharge kidney function: eGFR <30 mL/min/1.73m² at hospital discharge is the strongest predictor of long-term dialysis dependence 1
• Pre-existing conditions:
  • Pre-existing hypertension increases risk (HR 8.7) 1
  • Pre-CRRT kidney function (lower baseline eGFR increases risk) 1

Secondary Factors

• Patient age: Older patients (≥75 years) have higher mortality but similar rates of dialysis dependence compared to younger patients 2, 1
• Urine output: Poor urine output before and during CRRT is associated with longer CRRT duration 3
• Illness severity markers:
  • Need for mechanical ventilation 3, 4
  • Need for ECMO 3
  • Underlying cardiac disease 4, 1

Outcomes After CRRT

The evidence shows concerning outcomes for patients requiring CRRT:

• Mortality: 35-63% in-hospital mortality for patients requiring CRRT 2, 5
• Dialysis dependence: Among non-ESRD patients who survive hospitalization requiring CRRT:
  • 47% need intermittent hemodialysis at ICU discharge
  • 28% continue to need hemodialysis at last follow-up 5
• Long-term outcomes: In cardiovascular surgery patients requiring CRRT who survived to hospital discharge:
  • 34.9% mortality during follow-up (median 1075 days)
  • 13.3% chronic dialysis rate during follow-up 1

Clinical Implications

1. Risk assessment: Patients with eGFR <30 mL/min/1.73m² at discharge should receive close nephrology follow-up due to high risk of progression to chronic dialysis 1

2. Patient counseling: Patients requiring CRRT should be informed about:

   • High in-hospital mortality risk (46-63%) 5
   • Significant risk of dialysis dependence after discharge (13-28%) 5, 1

3. Modality selection: For acute kidney injury in critically ill patients, CRRT is preferred over intermittent hemodialysis due to:

   • Better hemodynamic stability
   • Avoidance of large intravascular volume shifts
   • Management of electrolyte and acid-base disorders 2

Pitfalls and Caveats

1. Focusing only on CRRT duration: The evidence does not support using CRRT duration alone as a predictor of long-term dialysis need. Instead, focus on kidney function at discharge and pre-existing conditions.

2. Overlooking older adults: While older adults have higher mortality with CRRT, they don't necessarily have higher rates of dialysis dependence if they survive 2. Age alone should not determine CRRT decisions.

3. Neglecting follow-up: Given the high risk of dialysis dependence (13-28%), close nephrology follow-up is essential for all CRRT survivors, especially those with eGFR <30 mL/min/1.73m² at discharge 1.

4. Underestimating recovery potential: While many patients require dialysis at ICU discharge (47%), a significant proportion recover kidney function by last follow-up, with only 28% remaining dialysis-dependent 5.