The question about optimising solute clearance usually presents the candidate with a clinical scenario where a patient is full of some sort of noxious solute; the candidate is then invited to assist that solute in its timely exit from the patient's body fluids.
Such questions include:
Surprisingly, it is very hard to find a good single resource for this online.
This is cheating - the efficiency of per-hour solute removal is unaffected, but the circuit lasts longer, allowing a larger amount of solute to be removed per session.
Strategies to improve circuit lifespan are discussed elsewhere.
Again, this does nothing to improve the hourly solute removal rate, but it increases the total solute removal over the long term. Is that CT scan really that urgent?
If the patient's vas cath is in some profoundly stupid position, their dialysis will run poorly. The machine will alarm constantly and need to be fiddled with; interruptions and poor flow rates will result in degraded performance.
It would be slightly silly to define the dose of dialysis in the classical terms of marker solute clearance; it would be as if one says "to increase the clearance of solute, prescribe an increased rate of solute clearance". Fortunately, dialysis dose is usually prescribed in terms of effluent rate, or ultrafiltrate+dialysate rate in CVVHDF. This consists of several components, each of which contribute slightly differently to the clearance of different solutes:
Increasing the dialysate flow rate
Increasing the ultrafiltration rate
Increasing the replacement fluid rate
One can influence the concentration of the dialysate to improve the countercurrent removal of some solute of interest. This applies to electrolytes. For instance, one would not use a dialysate or replacement fluid with 5mmol/L of potassium in a patient with a 7.5mmo/L hyperkalemia - the concentration gradient would only be 2.5mmol/L. With less potassium in the dialysate, a greater concentration gradient will favour the removal of potassium from the blood; and potassium-poor replacement fluid will contribute to the clearance effect.
Chapter (pp. 540) 48 Renal replacement therapy, also by Rinaldo Bellomo
John, Stefan, and Kai-Uwe Eckardt. "Renal replacement strategies in the ICU."CHEST Journal 132.4 (2007): 1379-1388.
Clark, William R., and Claudio Ronco. "CRRT efficiency and efficacy in relation to solute size." Kidney International 56 (1999): S3-S7.
Bellomo, R., and C. Ronco. "Renal replacement therapy in the intensive care unit." Intensive Care Med (1999) 25: 781±789
Ricci, Zaccaria, et al. "Solute removal during continuous renal replacement therapy in critically ill patients: convection versus diffusion." Critical Care 10.2 (2006): R67.
Wizemann, V., et al. "Efficacy of haemodiafiltration." Nephrology Dialysis Transplantation 16.suppl 4 (2001): 27-30.
Brunet, Sylvain, et al. "Diffusive and convective solute clearances during continuous renal replacement therapy at various dialysate and ultrafiltration flow rates." American journal of kidney diseases 34.3 (1999): 486-492.
Relton, Sudhakar, ARTHUR GREENBERC, and Paul M. Palevsky. "Dialysate and blood flow dependence of diffusive solute clearance during CVVHD."ASAIO journal 38.3 (1992): M691-M696.
Baldwin, Ian, Rinaldo Bellomo, and Bill Koch. "Blood flow reductions during continuous renal replacement therapy and circuit life." Intensive care medicine30.11 (2004): 2074-2079.
Gilbert, Roger W. "Blood flow rate effects in continuous venovenous hemodiafiltration on blood urea nitrogen and creatinine reduction." Nephrology nursing journal: journal of the American Nephrology Nurses' Association 27.5 (2000): 503-6.