The Kt/V by ionic dialysance: Interpretation limits

In advanced Chronic Kidney Disease, patients require renal replacement therapy (dialysis or transplantation) for clearance of toxins, electrolyte and acid-base balance and removal of excess fluid. Dialysis adequacy should be taken into consideration in the adjustment of the dialysis prescription. Kt/V urea is one method of measuring dialysis adequacy that is commonly used in clinical practice. Different formulae for calculating Kt/V are available. The appropriate Kt/V formula to be used depends on the clinical scenario, as well as parameters such as gender and size of patient, frequency of dialysis, mode of dialysis (ie hemodialysis vs, peritoneal dialysis), inter-dialysis weight gain, clinical symptoms, complications (fluid overload, hyperkalemia, intolerance to dialysis, etc), and residual kidney function. Nutrition parameters including serum protein and albumin levels, vitamin B12 and β2-microglobulin levels should be factored into the assessment of dialysis adequacy. In this review, we have described how Kt/V urea is calculated in hemodialysis and peritoneal dialysis with examples. We reviewed the available literature by searching for papers related to calculating Kt/V urea, single pool Kt/V, double pool Kt/V, weekly Kt/V, standard Kt/V, surface area normalized Kt/V, and various equations commonly practiced in clinical practice. We found several original articles, some review articles along with detailed information from manufacturers of different dialyzers published on their websites or as package inserts. Understanding the different equations available for calculating Kt/V urea and the application of these results in the clinical setting is important for refining patient care and for designing clinical studies.

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“…It is done by measuring ionic dialysance through conductivity measurements of dialysate using online clearance monitor. [ 46 ]…”

Section: Discussionmentioning

confidence: 99%

The nitty-gritties of Kt/V_urea calculations in hemodialysis and peritoneal dialysis

Churchill

Patri

2021

Indian J Nephrol

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“…This method does not require blood sampling and can be used with each dialysis treatment. However, more recent studies has shown that Kt/V OCM with V determined by Watson formula, leads to systematic underestimation of Kt/V by 22%–24% when comparing to Kt/V derived from urea reduction using the Daugirdas second generation equation …”

Section: Clinical Standard and Targetsmentioning

confidence: 96%

Clinical practice guidelines for the provision of renal service in Hong Kong: Haemodialysis

Cheng

Tang²,

Tong³

2019

Nephrology

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“…In practice, the ionic dialyzer clearance (Kd‐cond) obtained in this fashion has been used to estimate Kt/V, by multiplying Kd‐cond by the dialysis session length (t), and dividing by an estimate of the urea distribution volume (V), the latter usually estimated from either anthropometry (eg, the Watson volume), or from bioimpedance, given that the urea distribution volume is closely related to the total body water . However, this conductivity based Kt/V correlates only modestly with Kt/V derived from predialysis and postdialysis SUN measurement . For this reason, the use of conductivity clearance monitoring has not replaced monthly urea modeling, with its attendant complexities (staff time, safety issues, and laboratory expenses) associated with obtaining the postdialysis urea nitrogen blood sample.…”

Section: Introductionmentioning

confidence: 99%

“…6 However, this conductivity based Kt/V correlates only modestly with Kt/V derived from predialysis and postdialysis SUN measurement. [7][8][9] For this reason, the use of conductivity clearance monitoring has not replaced monthly urea modeling, with its attendant complexities (staff time, safety issues, and laboratory expenses) associated with obtaining the postdialysis urea nitrogen blood sample.…”

mentioning

confidence: 99%

Eliminating the need for routine monthly postdialysis serum urea nitrogen measurement: A method for monitoring Kt/V and normalized protein catabolic rate using conductivity determined dialyzer clearance

Daugirdas

2018

Seminars in Dialysis

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Many dialysis machines can compute dialyzer sodium clearances at multiple time points during a dialysis treatment using conductivity. For a given treatment, the average dialyzer sodium clearance (K), when combined with treatment time (t), and the estimated urea distribution volume (V, usually based on either anthropometry or bioimpedance), can be used to estimate Kt/V, an important measure of hemodialysis adequacy. While this conductivity‐derived value for Kt/V correlates moderately with Kt/V calculated from predialysis and postdialysis serum urea nitrogen (SUN) values (urea reduction ratio, URR), the ultrafiltration volume, and session length it is, unfortunately, not sufficiently accurate to replace URR‐based Kt/V. Here we underline the potential utility of an alternative method to estimate Kt/V (a variant of a technique originally proposed by Gotch and Levin and their colleagues) using conductivity‐derived sodium clearance (K) that does not require routine measurement of the postdialysis SUN but which should closely track Kt/V computed in the usual fashion. The increased accuracy with the new method is explained by the use of a patient‐specific value of V, which is an average value calculated from several dialysis sessions where both conductivity dialyzer clearance and predialysis and postdialysis SUN have been measured. Once this patient‐specific conductivity/URR‐based value for V has been determined, it can be used to calculate Kt/V for subsequent treatments in which conductivity‐based dialyzer clearances are measured, but around which predialysis and postdialysis SUN values have not been obtained. (If the predialysis SUN values for such a subsequent treatment are also measured, then a normalized protein catabolic rate that closely tracks the value from conventional urea modeling, can also be determined.) By reducing the number of postdialysis SUN measurements needed to monitor hemodialysis adequacy this new method of estimating Kt/V by conductivity should save staff time and laboratory costs, increase patient and staff safety, and decrease error rates associated with improper postdialysis blood sampling technique.

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The Kt/V by ionic dialysance: Interpretation limits

Cited by 15 publications

References 21 publications

The nitty-gritties of Kt/V_urea calculations in hemodialysis and peritoneal dialysis

The nitty-gritties of Kt/V_urea calculations in hemodialysis and peritoneal dialysis

Clinical practice guidelines for the provision of renal service in Hong Kong: Haemodialysis

Eliminating the need for routine monthly postdialysis serum urea nitrogen measurement: A method for monitoring Kt/V and normalized protein catabolic rate using conductivity determined dialyzer clearance

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The Kt/V by ionic dialysance: Interpretation limits

Cited by 15 publications

References 21 publications

The nitty-gritties of Kt/Vurea calculations in hemodialysis and peritoneal dialysis

The nitty-gritties of Kt/Vurea calculations in hemodialysis and peritoneal dialysis

Clinical practice guidelines for the provision of renal service in Hong Kong: Haemodialysis

Eliminating the need for routine monthly postdialysis serum urea nitrogen measurement: A method for monitoring Kt/V and normalized protein catabolic rate using conductivity determined dialyzer clearance

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Product

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The nitty-gritties of Kt/V_urea calculations in hemodialysis and peritoneal dialysis

The nitty-gritties of Kt/V_urea calculations in hemodialysis and peritoneal dialysis