Improving KT/V

What can patients do to improve their Kt/V?

If a patient’s average Kt/V—usually the average of three measurements—is consistently below 1.2, the patient and the nephrologist need to discuss ways to improve it. Since the V value is fixed, Kt/V can be improved either by increasing K or t.

Increase Blood Flow through the Dialyzer

Increasing K depends primarily on the rate of blood flow through the dialyzer. No matter how good a dialyzer is, how well it works depends primarily on moving blood through it. In many patients, a good rate is difficult to achieve because of vascular access problems.

If a patient’s blood flow rate is good, further improvements in clearance can be obtained by using a big dialyzer (High Flux Dialyzer) or, in some cases, by increasing the flow rate for dialysis solution from the usual 500 mL/min to 600 or 800 mL/min. A good flow rate for adult patients is 350 mL/min and higher. A few centres are even using two dialyzers at the same time to increase K in larger than average patients.

However, the rate of blood flow through the dialyzer is key, and a good vascular access is crucial to make sure a patient is getting good clearance.

Increase Time on Dialysis

The other way to improve the Kt in Kt/V is to increase t by increasing the haemodialysis session.

For example, if the Kt/V is 0.9 and the goal is 1.2,
Then 1.2/0.9 = 1.33, So 1.33 times more Kt is needed.

If K is not changed, this means the length of the session needs to increase by 33 percent. If the inadequate sessions lasted 3 hours, they should be increased to 4 hours.

Identify and Eliminate Circulation Problems

If during any given month a patient’s Kt/V is extremely low, the measurement should be repeated, unless a reason for the low Kt/V is obvious. The actual reasons include treatment interruption for any reason, delivered (dose) less than the prescribed: Low blood flow; Inadequate dialyzer performance; Low dialysate flow; Hemodialysis ended prematurely; Access recirculation , problems with blood or solution flow, and a problem in sampling either the pre- or post-dialysis blood, should be suspected.

Are there other uremic toxins that are present in patients with end-stage renal disease?

Yes. There are literally hundreds of toxins that accumulate in renal failure. Some of them are middle or large molecules, some are charged particles, and others are protein bound. Many of these compounds are not well removed by conventional haemodialysis. Urea is thus a surrogate marker for uremic toxins, although the removal of urea on dialysis is often dissimilar to that of most other uremic toxins. Additional research is needed in this area to determine the extent and effects of these other uremic toxins on morbidity and mortality of patients with ESRD.

Points to Remember

• The two methods generally used to assess dialysis adequacy are URR and Kt/V
• A patient’s average URR should exceed 65 percent
• A patient’s average Kt/V should be at least 1.2
• A patient’s URR or Kt/V can be increased either by increasing time on dialysis or increasing blood flow through the dialyzer

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