It is a CVVHDF modality, with a prescribed rate of ultrafiltrate fluid removal
- Blood flow rate: ~ 100-300 ml/min
- Dialysate flow rate: ~ 100-300 ml/min… typically 150
- Runs over 6-12 hours
Those who cannot afford, or are unable to physically lift Critical Care Nephrology can find very helpful information in an older article by Mark Marshall et al (2001), or a more recent 2007 review by Tolwani et al.
Cardinal features which distinguish SLED from CRRT
Its neither IHD or CRRT; its a "hybrid" therapy.
- Employs features of both IHD and CRRT
- Runs for 6-12 hours
- Blood flow rates 100-300ml/min
- Dialysate does not come in pre-made bags: it is either generated from water that comes from a wall outlet, or it is mixed from pre-packaged electrolytes and sterile water.
- "Single-pass" machines use a dialysate generated "on-line" from reverse osmosis purified water
- "Batch" machines contain a huge tank ("batch") full of sterile water mixed with prepackaged salts.
- The dialysate flow rate is usually about 300ml/min, particularly for shorter treatments.
Advantages of SLED
From basic principles, one can establish that
- The sessions are shorter, and therefore the duration of exposure to anticoagulant is shorter.
- The patient is off-circuit for a large portion of the day. In fact, most places perform nocturnal SLED so that the patient can be mobile and active during the day.
- Haemodynamically, it is better tolerated than IHD.
Furthemore, a good pro-SLEDD review has reported several advantages of SLED over CRRT:
- Its cheaper than CRRT - up to 8 times cheaper!
- No need for any anticoagulation (much of the time saline flushes are sufficient)
- Solute removal is equivalent to CRRT.
Disadvantages of SLED
- Less efficient than IHD
- May not be tolerated by extremely unwell unstable patients.
- No difference in mortality between the different RRT modalities; thus, there is no survival advantage in using SLED - only an increased convenience and decreased cost. This was also confirmed by the SHARF study.