What is the current status of SLED (Sustained Low-Efficiency Dialysis) versus Hemofiltration in the treatment of acute kidney injury?

SLED vs Hemofiltration: Current Status

SLED and continuous hemofiltration (CVVHF) demonstrate equivalent mortality outcomes in critically ill patients with acute kidney injury, with no survival benefit of one modality over the other, allowing selection based on practical considerations including hemodynamic tolerance, resource availability, and institutional expertise. 1, 2

Mortality and Clinical Outcomes

The evidence consistently shows no survival advantage between modalities:

• The Canadian Society of Nephrology's commentary on KDIGO guidelines explicitly states that CRRT (including hemofiltration) has not been shown to confer superior short-term outcomes compared to intermittent therapies, with no survival benefit over intermittent hemodialysis despite theoretical advantages. 1

• SLED has been shown to offer comparable results to CRRT in terms of hemodynamic stability in hemodynamically unstable patients, challenging the notion that CRRT should be the standard of care for this population. 1

• The totality of evidence does not support an advantage of CRRT over intermittent modalities with respect to patient-relevant outcomes, including survival. 1

• A 2012 systematic review and meta-analysis found no effect of hemofiltration on mortality (RR 0.96,95% CI 0.73-1.25) or other clinical outcomes including RRT dependence, vasopressor use, or organ dysfunction compared to hemodialysis. 3

Practical Advantages and Disadvantages

SLED Advantages:

• Significantly lower cost: $1,431 per week for SLED versus $2,607-$3,089 per week for CRRT. 4

• Can be performed without anticoagulation in 65% of treatments, with filter clotting rates of 18% with heparin and 29% without heparin (not statistically different). 4

• Provides equivalent solute removal to CRRT with weekly Kt/V of 8.4±1.8 and equivalent renal clearance (EKR) of 29±6 ml/min. 4

• Allows unrestricted daytime access to patients when performed nocturnally for procedures and tests. 5

• Enables RRT delivery in centers with dialysis capability but without CRRT infrastructure, potentially avoiding patient transfers. 1

• Increased citrate removal by the treatment itself (100-300 kcal/day energy gain) compared to CRRT. 1

CVVHF Advantages:

• More efficient for middle and large molecular weight solute removal, including inflammatory cytokines, though clinical significance remains unclear. 3, 2

• Provides continuous therapy with slower, more gradual fluid and solute shifts. 2

• May be preferred when 24-hour continuous clearance is specifically required. 2

CVVHF Disadvantages:

• Higher protein requirements (1.5-1.7 g/kg/day) due to continuous amino acid and peptide/protein losses (up to 15-20 g/day and 5-10 g/day respectively) compared to SLED (1.3-1.5 g/kg/day). 1, 2

• Substantial energy gain from citrate, lactate, and glucose in replacement fluids (115-1,300 kcal/day depending on protocol), requiring careful calculation to avoid overfeeding. 1

• Target effluent dose of 20-25 mL/kg/hour, though delivered dose often falls short (68-85% of prescribed) due to treatment interruptions and filter efficiency decline. 1, 2

• Shorter time to filter failure compared to hemodialysis modalities (mean difference -5 to -7 hours). 3

Hemodynamic Considerations

The assertion that CRRT is superior for hemodynamically unstable patients lacks robust evidence:

• SLED has replaced CRRT in some Canadian centers specifically for hemodynamically unstable patients with comparable hemodynamic stability results. 1

• Both modalities may exacerbate hypotension through fluid/solute shifts and electrolyte fluxes, particularly when net ultrafiltration is required. 1

• For patients not requiring net ultrafiltration, it remains uncertain whether CRRT/SLED would be better tolerated than intermittent hemodialysis. 1

• Hemodynamic stability during SLED allows achievement of prescribed ultrafiltration goals in most cases with mean shortfall of only 240 mL per treatment. 5

Practical Implementation Algorithm

When both modalities are available:

1. For hemodynamically unstable patients: Either SLED or CVVHF is acceptable, with choice based on local expertise and resource availability rather than presumed superiority. 1, 2

2. When cost is a consideration: SLED offers equivalent outcomes at approximately half the cost of CRRT. 4

3. When anticoagulation is contraindicated or high bleeding risk: SLED can be performed without anticoagulation in majority of cases. 4

4. When daytime procedures/testing are frequent: SLED performed nocturnally provides unrestricted daytime access. 5

5. When CRRT is unavailable: SLED should not be viewed as an inferior alternative but rather as an interchangeable option. 1

Critical Caveats

• It is inappropriate to characterize SLED as an inferior alternative to CRRT given the lack of survival benefit for any single modality. 1

• ESPEN guidelines indicate no clear advantage for CRRT over prolonged intermittent kidney replacement therapy (PIKRT, including SLED) in hemodynamically unstable patients. 2

• When intermittent hemodialysis is available and efficient poison removal is needed (e.g., atenolol, sotalol), it should be preferred over SLED or CRRT for maximal clearance. 1

• Nutritional management differs significantly: patients on CVVHF require higher protein intake and careful energy accounting from dialysis solutions. 1, 2

• The perception that SLED is "technically more complex" than CRRT is center-specific, with some citing relative ease of delivery as a SLED advantage. 1