a comparability between the formulation

a comparison between the formulas
April 20, 2021 0 Comments



Calculation of Kt/V in haemodialysis: a comparability between the formulation



Guilherme BreitsameterI; Ana Elizabeth FigueiredoII; Daiana Saute KochhannIII

IUnidade de Hemodiálise do Hospital São Lucas da Pontifícia Universidade católica do rio Grande do Sul – HSL-PUC/RS; Unidade de Hemodiálise do Hospital de Clínicas de Porto Alegre
IIUnidade de Hemodiálise do HSL-PUC/RS; Faculdade de Enfermagem, Nutrição e Fisioterapia – FAENFI- PUC/RS
IIIClinirim – Clínica de Doenças Renais de Porto Alegre, Brasil

Correspondence to




INTRODUCTION: The standard of delivered dialysis might be measured by the Kt/V ratio, which might be calculated in varied methods.
OBJECTIVE: To match the Kt/V ratio obtained with the formulation of Lowrie (L) and Daugirdas (D) with the outcomes measured by an On-line Clearance Monitor (OCM). Technique: Observational, cross-sectional research of 59 sufferers on hemodialysis (HD). Information had been collected in the identical dialysis session (predialysis and postdialysis urea) and Kt/V was calculated by the OCM of the Fresenius 4008S machine (Fresenius Medical Care AG, Dangerous Homburg, Germany).
RESULTS: A complete of 95 periods had been assessed, with a predominance of males 56% (33), and a pattern imply age of 57 + 14 years. Hypertension (42%; n = 25), diabetes (12%; n = 7) and glomerulonephritides (8%; n = 5) had been probably the most frequent causes of power kidney illness (CKD). Imply Kt/V values obtained with the L and D formulation and the OCM had been 1.31, 1.41 and 1.32, respectively. Comparability between the L and D formulation confirmed a statistically important distinction (p = 0.008), with a Pearson’s correlation of 0.950. The distinction between the D formulation and the OCM was additionally important (p = 0.011 and r = 0.346), most likely on account of convective loss, estimated by the D formulation however not by the OCM and L formulation. The distinction between the L formulation and the OCM was not important (p = 0.999 and r = 0.577).
CONCLUSION: These knowledge recommend that the OCM can be utilized as a information to the real-time adjustment of the dialysis dose.

Key phrases: Dialysis. Renal Insufficiency, Continual. High quality Management.




The incidence and prevalence of power kidney illness (CKD) have elevated at an alarming charge.1

As a result of a number of research have demonstrated a correlation between hemodialysis (HD) dose and morbidity and mortality, the previous should be measured to be able to estimate whether or not CKD sufferers on HD are being adequately handled. Though signs and indicators are necessary indicators, they don’t seem to be delicate or particular sufficient to exactly monitor the HD dose.2

The next formulation have been used to quantify the dose of dialysis: urea discount ratio (URR), Kt/V single pool (spKt/V) and equilibrated Kt/V (eKt/V). Within the Kt/V ratio, the dialyzer urea clearance (Okay) is multiplied by dialysis time (t), the product being then divided by the affected person’s urea distribution quantity (V). Okay is determined by dialyzer dimension, blood move charge and dialysate move. Though t usually ranges between 3 and 4 hours (180-240 minutes per dialysis session), it may be adjusted. The affected person’s urea distribution quantity (V) corresponds to roughly 50% of physique weight, and could also be extra exactly estimated with an anthropometric equation which considers gender, age, peak and weight (Watson’s equation, for instance).3,4

The enough normal HD dose is estimated for sufferers present process three periods every week. Dialysis adequacy is ready by the Nationwide Kidney Basis Illness Outcomes High quality Initiative (NKF-DOQI) pointers, which suggest that spKt/V ought to be stored over 1.2.2

A DOQI-approved methodology for Kt/V calculation is Daugirdas’s formulation (1996): spKt/V = – ln(R – 0.008 x t) + ( 4 – 3.5x R) 0.55 x UF/V, wherein R is predialysis urea/postdialysis urea, t is dialysis time in hours, – ln is the destructive pure logarithm, UF is weight reduction in kilograms and V is the anthropometric urea distribution quantity in liters, which can be calculated with Watson’s equation or just estimated as 0.55 X postdialysis weight.3,4 An alternative choice is to make use of Lowrie’s formulation (1983): Kt/V = ln predialysis urea/postdialysis urea.5

NKF-DOQI and Brazilian pointers have beneficial that the dialysis dose ought to be managed, with blood samples, not less than as soon as a month.2 Nevertheless, there are actually dialysis machines that present on-line real-time monitoring of dialysis effectivity, by displaying Kt/V on the display. On-line clearance screens (OCMs) measure the distinction of conductivity between the dialysis fluid coming into and leaving the dialyzer, by the distinction of electrolyte focus. This measurement is used to calculate the ionic dialysant, which could be very near efficient urea clearance, so long as dialysant move, blood move and blood electrolyte composition are stored fixed throughout measurement time. This methodology, which is straightforward to make use of and has low value, is predicated on the idea that sodium clearance equals urea clearance.2,6

This non-invasive methodology for Kt/V dedication is unlikely to substitute for routine blood sampling, though OCMs present a possibility for monitoring unstable sufferers, mainly in relation to dialysis high quality, by verification of the Kt/V on the finish of every dialysis session, with immediate downside identification and early decision.7

Due to this fact, the aim of this research was to check Kt/V outcomes obtained with Lowrie’s formulation (L Kt/V) with these obtained with Daugirdas’s formulation (D Kt/V), and the latter with OCM-measured outcomes (OCM Kt/V).



This was an observational, quantitative research undertaken on the Hemodialysis Unit of the Hospital São Lucas of the Pontifícia Universidade Católica do Rio Grande do Sul (HSL-PUC/RS), Brazil.

The pattern was composed of all CKD sufferers on HD on the unit. Sufferers below 18 years of age had been excluded from the research.

Information had been collected from laboratory exams and Kt/V outcomes obtained from the Fresenius 4008S HD machines (Fresenius Medical Care AG, Dangerous Homburg, Germany) outfitted with an OCM, on the identical day blood sampling occurred. The usual dialysate move, in all machines, was 500 ml/min. Every affected person underwent two blood samplings, which had been carried out on the second dialysis session of the primary week of the month, for 2 weeks.

Blood sampling occurred at two time-points: within the first minute of dialysis a blood pattern was obtained from the arterial line of the extracorporeal system (predialysis pattern); the second pattern was obtained quickly after the prescribed dialysis time was accomplished. Blood pump move was diminished to lower than 100 ml/min, for 2 minutes, accoding to the unit’s protocol. Solely then was the pattern obtained from the arterial line (postdialysis pattern).

With a purpose to calculte the Kt/V, the next knowledge had been collected: dry weight, weight achieve between periods, peak, age, intercourse, blood move and hematocrit.

We used descriptive statistics and categorical knowledge, described as frequencies and percentages. Steady variables had been described as means and normal deviations when there was a standard distribution. Comparability between the formulation was made by variance evaluation (ANOVA), with identification of the variations by Bonferroni’s check, with significance set at p < 0.05. The Statistical Package deal for the Social Sciences model 17.0 (SPSS) program was used for the statistical calculations.

The research was authorised by the Ethics Committe of the HSL-PUC/RS (protocol 10/05098).



We assessed 95 HD periods of a complete of 59 sufferers, 95% of the periods lasting 4 hours.

The cnincal and demographic variables of the pattern are offered in Desk 1. Desk 2 exhibits the distribution of the sufferers in response to their underlying illness.





ANOVA between the formulation confirmed a statistically important distinction (p = 0.003). Imply L Kt/V, obtained by blood samples, was 1.31 (± 0.24). Imply second-generation D Kt/V was 1.41 (± 0.26). Though there was a major distinction between these outcomes (p = 0.008), the formulation had an excellent Pearson’s correlation of 0.950 (p < 0.000).

Imply second-generation D Kt/V, obtained by blood samples, was 1.41 (± 0.26). Imply non-invasive OCM Kt/V was 1.32 (± 0.30). Comparability between D Kt/V and OCM Kt/V confirmed a statistically related significance (p = 0.011) and a low Pearson’s correlation of 0.346 (p < 0.001).

Comparability between L Kt/V and OCM Kt/V dis not present statistical significance (p = 0.999) and had an enough Pearson’s correlation of 0.577.



On this research there was a predominance of males (56% of the pattern), a outcome which, alongside the imply age, is much like that of different research.8 Our outcomes are in settlement with the 2010 census undertaken by the Brazilian Nephrology Society, which confirmed that 57% of the Brazilian inhabitants on HD consists of males, the male intercourse being a danger issue for CKD. As well as, 35.2% of the dialysis inhabitants have hypertension as their principal underlying illness, adopted by diabetes mellitus in 27.5% of the circumstances.1,9

Our research additionally confirmed hypertension as the primary underlying illness (42%), adopted by diabetes mellitus (12%), glomerulonephritides (8%) and polycystic kidney illness (7%). A earlier research undertaken within the south of Brazil discovered hypertension because the underlying illness in 36.7% of all CKD circumstances, with diabetic nephropathy accounting for 31.4%.8

On this research, imply hematocrit was 32.9%, which is equal to a hemoglobin focus of 11g/dl, slightly below what’s beneficial within the literature. One other research undertaken in Porto Alegre, at one other dialysis unit, confirmed hematocrit values very near ours (imply 33.5%).10 However, the UK Renal Affiliation pointers suggest that hemoglobin ought to be stored between 10 and 12 g/dL in CKD sufferers phases 4 and 5, with the usage of stimulants of erythropoiesis.11

Analysis has demonstrated that weight achieve over 2.5 kg was related to will increase of each systolic and diastolic predialysis blood strain.12 Our sufferers had a imply interdialytic weight achieve of two.4 kg (± 1.03).

Dialysis dose is an effective marker of dialysis high quality. It’s thus important to know the precise dialysis dose that’s being delivered at every session.2 In line with the DOQI pointers, the minimal worth beneficial for 3 periods every week is a Kt/V over 1.2.2

Our Kt/V outcomes are, on common, in accordance with what is suggested, being 1.31 (± 0.24) for Lowrie, 1.41 (± 0.35) for Daugirdas and 1.32 (± 0.29) for OCM. There was a major distinction between the D Kt/V and L Kt/V and OCM Kt/V.

A Spanish research noticed that concordance between D Kt/V and Kt/V obtained with different formulation varies. As a result of Daugirdas formulation overestimates Kt/V as compared with Lowrie’s, the authors proposed a 1997 Okay/DOQI criterion, in response to which dialysis is taken into account enough when D Kt/V is 1.2 or above and L Kt/V is 1.0 or above.6

This most likely happens as a result of Daugirdas’s formulation contains convective loss, that’s the weight distinction divided by the distribution quantity.3 On the opposite handn Lowrie’s formulation and the OCM assess diffusive loss solely. The weak correlation between the OCM and Daugirdas’s formulation could also be accounted for by the several types of transport. OCM Kt/V is diffusive whereas D Kt/V is convective. Lowrie’s formulation and OCM have good correlation, probably because of the similar transport mechanism (diffusive) they assess.

One other Spanish research in contrast OCM Kt/V and D Kt/V (second era), however in hemodiafiltration periods of power sufferers. There was good correlation (r = 0,952), with imply OCM Kt/V of 1.49 + 0.54/session and D Kt/V of 1.74 + 0.58/session.13 The distinction we discovered, as compared with the Spanish research, could also be attributed to hemofiltration, which has larger convective loss, partially decided by dialysate move (800 ml/min), ultrafiltrate, blood move and process time.13 In our research, the dialysate move was 500 ml/min, and solely hemodialysis periods had been assessed.

Kt/V is essential for the evaluation of dialysis high quality and adequacy. Every formulation has its personal related traits, Lowrie’s formulation being easy, simply understood and readily acceptable. Though extra complicated, Daugirdas’s formulation is broadly used, because it contains individualized data reminiscent of peak, weight and blood move. These knowledge are additionally included within the OCM measurements, however with the added bonus of offering real-time Kt/V values, which permit immediate interventions to extend Kt/V ought to the necessity come up.



The info recommend a statistically important distinction between the outcomes obtained with Daugirdas’s formulation and people obtained with Lowrie’s formulation and the OCM.

Our research demonstrated that though these formulation might result in deifferent outcomes, there’s good correlation between them. The necessary purpose is to not evaluate outcomes from completely different formulation or establish one of the best one, however set a typical for the formulation in use. We confirmed that OCM is a sensible instrument for every day use, to enhance the opposite formulation, serving to to enough the dialysis dose delivered to succeed in glorious affected person’s profit. It ought to be highlighted, nonetheless, that the affected person’s scientific image is above any formulation and ought to be the final word information to dialysis adequacy.



1. Barros E, et al. Nefrologia: rotinas, diagnóstico e tratamento. 3a ed. Porto Alegre: Artmed; 2006.         [ Links ]

2. Nationwide Kidney Basis NKF/DOQI. Scientific follow pointers and scientific follow suggestions, 2006 updates hemodialysis adequacy, peritoneal dialysis adequacy, vascular entry. Am J Kidney Dis 2006;48(Suppl):S1.         [ Links ]

3. Daugirdas JT, et al. Prescrição de hemodiálise crônica: uma abordagem da cinética da uréia. In: Daugirdas JT, Ing TS. Handbook de diálise. 3a ed. Rio de Janeiro: Medsi; 2003. Cap. 9.         [ Links ]

4. Watson PE, et al. Complete physique water volumes for grownup women and men estimated from easy anthropometric measurements. Am J of Clin Nutr 1980;33:27-39.         [ Links ]

5. Lowrie EG, et al. Rules of prescribing dialysis remedy: implementing suggestions from the Nationwide Cooperative Dialysis Examine. Kidney Int 1983;23(Suppl):113-22.         [ Links ]

6. Teruel JL, et al. Utilidad de la dialisancia iônica para management de la dosis de diálisis. Experiência de um ano. Nefrologia 2003;23:444-50.         [ Links ]

7. Uhlin F, et al. Dialysis dose (Kt/V) and clearance variation sensitivity utilizing measurement of ultraviolet-absorbance, blood urea, dialysate urea and ionic dialysance. Nephrol Dial Transplant 2006;21:2225-31        [ Links ]

8. Morsch C, et al. Avaliação de indicadores assistenciais de pacientes em hemodiálise no sul do Brasil. J Bras Nefrol 2008;30:120-5.         [ Links ]

9. Sociedade Brasileira de Nefrologia (SBN). Censos. Censo Brasileiro de Diálise 2010. [cited 2011 Oct 17]. Accessible from: http://www.sbn.org.br/index.php?censoAdmAtual&menu=24.         [ Links ]

10. Morsch C. Avaliação da qualidade de vida e de indicadores assistenciais de pacientes renais crônicos em tratamento hemodialítico [master’s thesis]. Porto Alegre: Faculdade de Medicina, Universidade Federal do rio Grande do Sul; 2002.         [ Links ]

11. RA Scientific Apply Pointers – Anemia CKD, The Renal Affiliation UK. [cited 25 Mar 2011] Accessible from: http://www.renal.org/Scientific/GuidelinesSection/AnaemiaInCKD.aspx.         [ Links ]

12. Pinheiro ME, et al. Hipertensão arterial na diálise e no transplante renal. J Bras Nefrol 2003;25:142-8.         [ Links ]

13. Maduell F, et al. Monitoring hemodialysis dose with ionic dialysance in on-line hemodiafiltration. Nefrologia 2005;25:521-6.         [ Links ]



Correspondence to:
Guilherme Breitsameter
Avenida João Carlos Bertussi da Silva, 115 – Jardim Itu Sabará
Porto Alegre – RS – Brazil
Zip code 91220-270
E-mail: [email protected]

Submitted on: 04/04/2011
Accepted on: 10/20/2011



This research was undertaken on the HSL–PUC/RS.
The authors report no battle of curiosity.

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