What are the differences between Sustained Low-Efficiency Dialysis (SLED) and normal Hemodialysis (HD) for critically ill patients with Impaired renal function?

SLED versus Normal Hemodialysis for Critically Ill Patients

Sustained Low-Efficiency Dialysis (SLED) is a practical and cost-effective alternative to Continuous Renal Replacement Therapy (CRRT) for hemodynamically unstable critically ill patients with impaired renal function, offering comparable hemodynamic stability without evidence of inferior outcomes compared to CRRT. 1

Key Differences Between SLED and Normal Hemodialysis

Duration and Intensity

• Normal HD (Intermittent Hemodialysis):

  • Short duration (3-4 hours)
  • Higher blood flow rates (300-400 mL/min)
  • Higher dialysate flow rates (500-800 mL/min)
  • Typically performed 3 times per week

• SLED:

  • Extended duration (8-12 hours)
  • Lower blood flow rates (approximately 200 mL/min)
  • Lower dialysate flow rates (approximately 350 mL/min)
  • Can be performed daily or 6 days per week 2

Hemodynamic Stability

• Normal HD: More likely to cause hemodynamic instability due to rapid fluid and solute shifts
• SLED: Better hemodynamic stability due to slower fluid removal and solute clearance, making it suitable for critically ill patients 3

Clinical Applications

• Normal HD: Best suited for hemodynamically stable patients
• SLED: Particularly valuable for:
  • Hemodynamically unstable patients
  • Patients with fluid overload requiring gradual ultrafiltration
  • Patients in whom conventional HD has failed or been withheld 3

Advantages of SLED

1. Hemodynamic Stability: SLED provides comparable hemodynamic stability to CRRT for critically ill patients 1

2. Cost-Effectiveness: SLED is significantly less expensive than CRRT

   • Weekly costs: $1,431 for SLED vs. $2,607-$3,089 for CRRT 2
   • Uses standard hemodialysis equipment rather than specialized machines

3. Anticoagulation Requirements:

   • 65% of SLED treatments can be performed without anticoagulation
   • Regional citrate anticoagulation can be safely used with SLED when needed 4

4. Solute Clearance:

   • Provides adequate solute removal with weekly Kt/V of approximately 8.4±1.8
   • Equivalent renal clearance (EKRjc) of 29±6 mL/min, similar to CRRT 2

5. Operational Flexibility:

   • Can be performed nocturnally, allowing unrestricted access to patients during daytime for procedures and tests
   • Uses existing dialysis systems and infrastructure 5

Considerations for Implementation

Patient Selection

• SLED is particularly beneficial for:
  • Critically ill patients with hemodynamic instability
  • Patients with impaired renal function requiring RRT in ICU settings
  • Patients with contraindications to systemic anticoagulation 6

Potential Challenges

• Filter clotting may occur (18% with heparin, 29% with heparin-free treatments) 2
• May require specialized nursing staff familiar with both critical care and dialysis
• Availability of hemodialysis personnel for extended hours may be a limiting factor 1

Monitoring During SLED

• Regular monitoring of:
  • Hemodynamic parameters
  • Electrolytes (particularly phosphate and potassium)
  • Acid-base status
  • Ultrafiltration goals 3

Clinical Outcomes

• Mortality rates with SLED appear comparable to expected mortality based on illness severity scores 3
• Recent evidence suggests SLED can be considered as an alternative to CRRT for selected hemodynamically unstable patients requiring renal replacement therapy 6
• The Canadian Society of Nephrology notes that SLED has replaced CRRT in some Canadian centers for hemodynamically unstable patients 1

Practical Implementation

• SLED treatments typically run for 8-12 hours, often overnight
• Blood flow rates around 200 mL/min and dialysate flow rates around 350 mL/min
• Can be performed with or without anticoagulation based on patient needs
• May be combined with hemofiltration (adding 1L saline/hour) for enhanced middle molecule clearance 2

In conclusion, SLED represents a viable middle ground between conventional intermittent hemodialysis and CRRT, combining the advantages of both approaches for critically ill patients with impaired renal function.