Question 10

Created on Sun, 05/17/2015 - 07:29
Last updated on Sun, 11/01/2015 - 04:07
Pass rate: 67%
Highest mark: 9.0

Other SAQs in this paper

Other SAQs on this topic

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

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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.