For an ICU patient with acute kidney injury and limited cardiovascular reserve, what is sustained low‑efficiency dialysis (SLED), how is it performed, and when is it indicated versus continuous renal replacement therapy or intermittent hemodialysis?

Sustained Low-Efficiency Dialysis (SLED) for ICU Patients with AKI

SLED is a practical, cost-effective hybrid renal replacement modality that delivers comparable hemodynamic stability and clinical outcomes to CRRT and should be used interchangeably with CRRT for hemodynamically unstable ICU patients with acute kidney injury, particularly when CRRT resources are limited. 1

What is SLED?

SLED is a hybrid dialysis technique that bridges intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT) by using:

• Extended treatment duration: 8–12 hours per session (typically 6 days per week), compared to 3–4 hours for standard IHD 2
• Lower blood flow rates: 200 mL/min (versus 300–500 mL/min for IHD) 2
• Lower dialysate flow rates: 300–350 mL/min (versus 500–800 mL/min for IHD) 2
• Standard hemodialysis machines: Uses conventional dialysis equipment rather than specialized CRRT machines 3

How SLED is Performed

Technical Setup

• Use standard hemodialysis machines or batch dialysis systems with conventional dialyzers 3
• Insert an uncuffed nontunneled dialysis catheter, preferably via right internal jugular vein, then femoral, then left internal jugular (avoid subclavian) 4, 5
• Always use ultrasound guidance for catheter insertion 4
• Obtain chest radiograph after internal jugular or subclavian placement before first use 4

Treatment Parameters

• Session duration: 8 hours per session, 6 days per week 2
• Blood flow rate: 200 mL/min 2
• Dialysate flow rate: 300–350 mL/min 2
• Hemofiltration component: May add 1 liter saline/hour for enhanced clearance 2
• Target clearance: Weekly Kt/V of approximately 8.4, providing equivalent renal clearance (EKRjc) of 29 mL/min, comparable to CRRT 2

Anticoagulation Strategy

• 65% of SLED treatments can be performed heparin-free with saline flushes alone 2
• Filter clotting occurs in 18% of heparin treatments versus 29% of heparin-free treatments (not statistically different) 2
• Regional citrate anticoagulation is first-line if anticoagulation is needed 4
• Use unfractionated or low-molecular-weight heparin if citrate is contraindicated 4

Fluid and Buffer Selection

• Use bicarbonate-buffered dialysate rather than lactate-buffered solutions, especially for patients with circulatory shock, liver failure, or lactic acidemia 4, 6
• Ensure dialysis fluids comply with AAMI standards for bacterial and endotoxin contamination 4

When SLED is Indicated

Primary Indications (Equivalent to CRRT)

SLED should be used interchangeably with CRRT for hemodynamically unstable patients because no survival benefit has been demonstrated for CRRT over other modalities. 1

• Hemodynamic instability: SLED provides comparable hemodynamic control to CRRT, with hemodynamic instability occurring in 56.4% of SLED sessions versus 50.0% of CRRT sessions (not statistically different) 7
• Septic shock requiring vasopressors: SLED facilitates fluid balance management similar to CRRT 5
• Severe fluid overload: Extended treatment time allows gradual fluid removal 5

Practical Advantages Over CRRT

• Cost-effectiveness: Weekly costs are $1,431 for SLED versus $2,607 for CRRT with heparin and $3,089 for CRRT with citrate 2
• Resource availability: SLED can be delivered in centers with standard dialysis capability but without CRRT infrastructure 1
• Nursing efficiency: Does not require continuous ICU nurse presence at bedside for 24 hours 3
• Reduced anticoagulation requirements: Majority of treatments can be performed without systemic anticoagulation 2

When CRRT Remains Preferred Over SLED

• Acute brain injury with elevated intracranial pressure: CRRT provides slower, more continuous solute shifts that minimize ICP fluctuations 4, 5
• Severe cerebral edema: Continuous therapy avoids osmotic shifts 5
• Extreme hemodynamic instability requiring minute-to-minute fluid adjustment: CRRT allows continuous fine-tuning 5

SLED Versus Intermittent Hemodialysis

SLED is superior to standard IHD for hemodynamically unstable patients because:

• Session interruption occurs in 28.2% of SLED treatments versus 16.3% of IHD treatments, but SLED provides better hemodynamic tolerance than IHD in unstable patients 7
• Extended treatment time allows gradual fluid and solute shifts, reducing hypotension risk 3
• Lower blood and dialysate flow rates minimize cardiovascular stress 2

Clinical Outcomes

Mortality

• 30-day mortality is 54% for SLED versus 61% for CRRT (adjusted OR 1.07,95% CI 0.56–2.03; not statistically different) 8
• Overall ICU mortality ranges from 43.1% to 56.9% for SLED-treated patients 9

Renal Recovery

• Risk of persistent RRT dependence at 30 days is similar between SLED and CRRT (adjusted OR 1.36,95% CI 0.51–3.57) 8
• Renal recovery rates are comparable between SLED and CRRT 3

Hemodynamic Stability

• Hemodynamic instability occurs in 56.4% of SLED sessions versus 50.0% of CRRT sessions (p = 0.51) 7
• Multivariable analysis shows odds ratio for hemodynamic instability with SLED is 1.20 (95% CI 0.58–2.47) compared to CRRT—not statistically different 7

Monitoring and Dose Adjustment

• Target delivered dose: Equivalent to CRRT effluent volume of 20–25 mL/kg/hour when calculated as continuous equivalent 4, 5
• Solute clearance: Weekly Kt/V should be approximately 8.4 2
• Monitor actual delivered dose frequently and adjust prescription to achieve electrolyte balance, acid-base balance, and fluid balance goals 4
• Assess for filter performance and circuit integrity throughout each session 4

Common Pitfalls and How to Avoid Them

• Inadequate delivered dose: Prescribed dose often exceeds delivered dose due to treatment interruptions; monitor actual effluent volume and adjust prescription upward by 20–25% if needed 1
• Inappropriate buffer selection: Never use lactate-buffered solutions in patients with liver failure or lactic acidosis; always use bicarbonate 4, 6
• Subclavian vein access: Avoid due to thrombosis risk and late stenosis; use right internal jugular as first choice 4, 5
• Electrolyte depletion: SLED causes continuous losses of potassium, phosphate, magnesium, and amino acids; monitor every 2–6 hours initially and supplement as needed 6
• Antibiotic underdosing: Therapeutic drug monitoring is essential for beta-lactams and other dialyzable medications 4

Special Considerations

Resource-Limited Settings

• SLED is particularly valuable in centers without CRRT capability or during equipment shortages (e.g., COVID-19 pandemic) 3
• Standard hemodialysis machines can be used, making SLED widely accessible 3
• Feasibility may be limited by availability of hemodialysis personnel for extended treatment hours 1

Nutritional Support

• Provide 1.5–1.7 g/kg/day protein once hemodynamically stable, as SLED causes continuous amino acid losses of 10–15 g/day 6
• Target total energy intake of 20–30 kcal/kg/day 6
• Supplement water-soluble vitamins (thiamine, folate, vitamin C) due to dialytic losses 6