Question 10

Compare and contrast the use of continuous veno-venous haemodialysis (CVVHD), intermittent haemodialysis (IHD) and slow continuous ultrafiltration (SCUF) in the intensive care patient.

[Click here to toggle visibility of the answers]

College Answer

	CVVHD	SCUF	IHD
Vascular access	Good vascular access required via double lumen catheter in central vein	Good vascular access required via double lumen catheter in central vein	Double lumen catheter or A-V fistula Higher flows than with CVVHD or SCUF
Anticoagulation	Continuous anticoagulation generally required	Continuous anticoagulation generally required	Intermittent anticoagulation only while on dialysis
Fluid shifts	Slow fluid shift Least fluid removed per hour	Slow fluid shift More fluid removed than CVVHD but less than IHD	Rapid fluid shift Greatest fluid removal possible over time
Electrolyte shifts	Slow electrolyte shift all sized molecules removed	Small molecules removed much less that CVVHD and IHD	Rapid electrolyte shift all sized molecules removed but less than CRRT
Cerebral dysequilibirum	Disequilibrium uncommon	No disequilibrium	Disequilibrium syndrome more likely, but still not common
Mode of solute clearance and efficiency	Ultrafiltration Convection, diffusion, adsorption Less efficient than IHD	Ultrafiltration only not intended for solute clearance	Ultrafiltration, diffusion, convection, less adsorption Most efficient
Haemodynamic stability	Significantly reduced haemodynamic instability	Minimal haemodynamic instability	Higher incidence of Haemodynamic instability
Practical considerations	Needs expertise and equipment	Needs expertise and equipment	Expertise more widespread
Cost	Most costly	Less cost than CVVHD	Cheapest

Discussion

This tabulated college answer is an excellent model, and can be easily left unmodified as a tool of fellowship exam revision.

If one were prone to reinventing wheels, one would reorganise the table in the following manner:

Modality	CVVHD	SCUF	IHD
Access	Vas cath	Vas cath	Vas cath or fistula
Flow rate	Low flow rate	Low flow rate	High flow rate
Anticoagulation	Continuous	Continuous	Intermittent boluses
Fluid removal	Slow	Medium	Rapid
Electrolyte removal	Slow; by convection and diffusion	Slow; by convection	Rapid; by convection and diffusion
Efficiency of solute clearance	Low However, good solute clearance is ultimately achieved over a prolonged course	Very low (minimal, really) - but it is not meant for solute clearance	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	Very well tolerated	Unsuitable for hemodynamically unstable patients
Cost	Expensive	Expensive	Cheaper

An even larger, (barely readable) table comparing all previously examined RRT modalities is also available in the Required Reading section.

References

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.

[Submit a comment or correction]