Compare Continuous Venovenous Haemofiltration (CVVHF) , Sustained Low Efficiency Dialysis (SLED) and Intermittent hemodialysis (IHD) with respect to
a) mechanism of solute clearance
b) advantages and
c) disadvantages
|
CVVH |
SLED |
IHD |
|
|
Mechanism of solute clearance |
Solvent removal occurs as a consequence of a pressure gradient across a semi permeable membrane. Solute removal occurs only by convection (solvent drag). |
Solute removal occurs predominantly by diffusion down a concentration gradient created by dialysate fluid on the other side of the semi permeable membrane. |
Solute clearance by diffusion |
|
Advantages |
Achieves better clearance of middle molecules (< 15 Kd) than CVVHD/IHD, fluid management easier and flexible, lesser hemodynamic instability as compared to IHD. |
Can be done at night so patient can be mobilized during the day. Period of anticoagulation reduced. Possible cost savings by using online water and ability for one |
shortest treatment time, anticoagulation often not required, cost savings by using online water |
|
Limitations |
Patient immobilized , need for continuous anticoagulation , higher nursing requirement |
inferior clearance of middle molecules, reduced fluid management flexibility. Higher risk of disequilibrium syndrome |
least clearance of middle molecules, least flexible fluid management, highest risk of disequilibrium syndrome. Possible greater |
CVVHDF, IHD and SCUF are discussed in this fashion in Question 10 from the first paper of 2011.
Thus, the same table can be reproduced here, mutatis mutandis.
An even more expansive table of comparison between all conceivable RRT modalities is available in the Required reading section.
| Modality | CVVHF | SLED | IHD |
| Access | Vas cath | Vas cath | Vas cath or fistula |
| Flow rate | Low flow rate | Low flow rate | High flow rate |
| Anticoagulation | Continuous | May be continuous or intermittent | Intermittent boluses |
| Fluid removal | Slow | Medium | Rapid |
| Electrolyte removal | Slow; by convection (mainly) and diffusion |
Medium rate | Rapid; by convection and diffusion |
| Efficiency of solute clearance | Low However, good solute clearance is ultimately achieved over a prolonged course |
Medium clearance efficacy | High efficiency; however the short couse of treatment and the intermittent nature of the treatment results in less solute clearance than CVVHDF |
| Hemodynamic impact | Well tolerated | Tolerated by most patients | Unsuitable for hemodynamically unstable patients |
| Cost | Expensive | Cheap | Cheapest |
| Advantages |
Good clearance of middle molecules Well tolerated hemodynamically Good control over fluid removal and solute exchange |
Intermittent, thus less labour intensive; Anticoagulation may not be required; Intermittent, allowing periods of mobility for the patient Well tolerated unless very unstable |
Less labour intensive; Anticoagulation may not be required; Intermittent, allowing periods of mobility for the patient |
| Disadvantages |
Expensive Requires anticoagulation Prolonged immobilization |
Poorly tolerated by very hemodynamically unstable patients; Requires reverse osmosis facilities; |
Poor fluid management Limited clearance of middle molecules Poorly tolerated by hemodynamically unstable patients; and then there is the risk of disequilibrium syndrome. |
D'Intini, Vincent, et al. "Renal replacement therapy in acute renal failure." Best Practice & research clinical anaesthesiology 18.1 (2004): 145-157.
O'Reilly, Philip, and Ashita Tolwani. "Renal Replacement Therapy III: IHD, CRRT, SLED." Critical care clinics 21.2 (2005): 367-378.
Wei, S. S., W. T. Lee, and K. T. Woo. "Slow continuous ultrafiltration (SCUF)--the safe and efficient treatment for patients with cardiac failure and fluid overload." Singapore medical journal 36.3 (1995): 276-277.
Kanno, Yoshihiko, and Hiromichi Suzuki. "Selection of modality in continuous renal replacement therapy." (2010): 167-172. -This seems to be an entire issue of Contributions to Nephrology (Vol. 166) by Claudio Ronco.