What is the optimal maximal fluid removal rate per day for pediatric Continuous Renal Replacement Therapy (CRRT) patients who are volume overloaded?

Optimal Fluid Removal Rate in Pediatric CRRT for Volume Overloaded Patients

For pediatric patients who are volume overloaded and receiving CRRT, the optimal maximal fluid removal rate should be individualized to gradually reduce fluid overload without causing hemodynamic instability, targeting removal of no more than 10% of the patient's fluid overload per day.

Assessment of Fluid Overload Status

• Fluid overload should be quantified using the formula: (fluid in [L] - fluid out [L])/(ICU admit weight [kg]) x 100% 1
• Patients with ≥20% fluid overload have significantly higher mortality (65.6%) compared to those with 10-20% (43.1%) or <10% fluid overload (29.4%) 1
• Each 1% increase in fluid overload severity is associated with a 3% increase in mortality risk 1

Optimal Fluid Removal Approach

• After shock resuscitation, high-flux CRRT should be used for patients who are ≥10% fluid overloaded and unable to maintain fluid balance with native urine output/extrarenal losses 2
• Target a gradual reduction in fluid overload status, especially in hemodynamically unstable patients 3
• For critically ill children, fluid removal should be guided by:
  • Clinical endpoints including perfusion 2
  • Central venous pressure 2
  • Echocardiographic determination of end-diastolic volume 2
  • Maintenance of normal perfusion pressure for age 2

Monitoring Parameters During Fluid Removal

• Monitor the following parameters to ensure safe fluid removal:
  • Hemodynamic stability with maintenance of normal perfusion and blood pressure 2
  • Urine output >1 mL/kg/h 2
  • Normal mental status 2
  • Cardiac index >3.3 and <6.0 L/min/m² 2
  • ScvO₂ >70% 2
  • Capillary refill ≤2 seconds 2
  • Normal pulses with no differential between peripheral and central pulses 2

Fluid Removal Rate Considerations

• Fluid removal should be adjusted based on hemodynamic tolerance, with close monitoring for signs of decreased perfusion 2
• For patients with septic shock, consider initiating CRRT within 48 hours of admission, as earlier initiation (within 48h) has been associated with better survival (61% vs 33%) 2
• Patients with multi-organ dysfunction syndrome have higher mortality rates during CRRT compared to those with isolated acute kidney injury 4

Special Considerations

• For neonates and very small children, ensure an instilled volume of at least 1,100 mL/m² 3
• In pediatric cardiac patients on ECMO requiring fluid removal, progression from ultrafiltration to CRRT is associated with worse outcomes 5
• Patients with oncologic or hematologic diseases have higher mortality risk during CRRT (OR 11.7) and may require more cautious fluid removal approaches 6

Pitfalls to Avoid

• Avoid rapid fluid removal that could precipitate hemodynamic instability, particularly in patients with cardiac dysfunction or vasopressor dependence 2
• Different methods of calculating fluid overload can yield significantly different results (varying from 14% to 48% of patients identified as having >10% fluid overload), so use a consistent calculation method 7
• Do not delay CRRT initiation in patients with significant fluid overload (≥20%), as this is associated with an adjusted mortality odds ratio of 8.5 compared to those with <20% fluid overload 1
• Avoid high-volume hemofiltration (>35 mL/kg/hr) as it has not shown mortality benefit over standard hemofiltration rates and may increase the risk of complications such as hyperglycemia 2