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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2014  |  Volume : 25  |  Issue : 4  |  Page : 788-792
Standard continuous ambulatory peritoneal dialysis therapy provides similar initial T-Kt/V regardless of the patient's peritoneal membrane transporter category: Single-center experience

Nephrology Section, Internal Medicine, Hamad General Hospital, Hamad Medical Corporation, Doha, Qatar

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Date of Web Publication24-Jun-2014


Patients on continuous ambulatory peritoneal dialysis (CAPD) are routinely eva­luated using the peritoneal equilibrium test (PET) to determine the best method for achieving target total dialysis clearance (T-Kt/V). In this study, we tested the hypothesis that standard CAPD prescription would achieve an initial T-Kt/V of more than 1.7 in all the patients regardless of their PET measurements. This is a retrospective study that included patients who started standard CAPD of four two-liter exchanges per day. The study included 118 patients; their mean age was 51.5 years with a standard deviation (SD) of 14.39 years. There were 83 males (70.3%) and 35 females (29.7%). PET and Kt/V were performed during the first four to six weeks of the study. The PET classified the patients into four categories: 24 (20.3%), high transporters; 65 (55.1%), high average; 28 (23.7%), low average; and one (0.8%), low transporter. Patients were then divided in two groups: Group 1 comprised of the high transporters while Group 2 included all the other patients. The T-Kt/V of the two groups was similar; in Group 1, it was 2.57 (±1.17) and in Group 2 it was 2.50 (±0.88) (P = 0.77). The T-Kt/V of patients with no residual renal function was also similar; in Group 1 and Group 2 it was 1.8 (±0.29) and 1.97 (±0.56), respectively (P = 0.45). All patients in our study who started on standard CAPD treatment had an adequate initial T-Kt/V. Thus, our data demonstrate that all patients with end-stage renal disease can safely begin standard CAPD without PET, which only needs to be performed if the patient encounters trouble in his/her T-Kt/V or fluid removal.

How to cite this article:
Al-Malki HA, Fawzy AA, Rashid AH, Asim M, Fituri OM. Standard continuous ambulatory peritoneal dialysis therapy provides similar initial T-Kt/V regardless of the patient's peritoneal membrane transporter category: Single-center experience. Saudi J Kidney Dis Transpl 2014;25:788-92

How to cite this URL:
Al-Malki HA, Fawzy AA, Rashid AH, Asim M, Fituri OM. Standard continuous ambulatory peritoneal dialysis therapy provides similar initial T-Kt/V regardless of the patient's peritoneal membrane transporter category: Single-center experience. Saudi J Kidney Dis Transpl [serial online] 2014 [cited 2023 Feb 4];25:788-92. Available from: https://www.sjkdt.org/text.asp?2014/25/4/788/135004

   Introduction Top

Chronic kidney disease is a common health problem that affects approximately 10% of the population. Patients who reach end-stage renal disease need to start renal replacement therapy, either dialysis or transplantation. Currently, two types of dialysis are available, hemo-dialysis and peritoneal dialysis (PD). In PD, the lining of the peritoneal cavity is used to clear the blood of waste products. [1],[2] There are two types of PD: Continuous ambulatory peritoneal dialysis (CAPD) in which the pa­tient performs manual exchange of fluid four times per day, and automated peritoneal dia­lysis (APD) in which the exchange is done by the PD machine at night.

CAPD is the usual mode of treatment chosen for patients at the beginning of PD. [1],[2] Selection of the ideal type of dialysis, to achieve the target total dialysis clearance (T-Kt/V), is usually based on the patient's body weight, residual renal function and the peritoneal equilibrium test (PET). PET is used to test the transport function of the peritoneal membrane of each patient, in which the solute (creatinine, sodium, urea, glucose) transport rates are assessed by the rate of their equilibration between the dialysate and the peritoneal capil­laries. The PET value will divide patients into four categories: High transporters, who achieve rapid equilibration of the solutes; low transporters, who achieve slower equilibration of the solutes; and high average and low average, who have intermediate values of equilibration of the solutes. The current recom­mendation is to perform the PET and T-Kt/V during the first four to six weeks of starting the PD. Patients classified as high transporters are thought to do better with APD, in which a shorter dwell time is used, leading to a better dialysis clearance and fluid removal; therefore, they are usually switched from CAPD to APD to achieve the best T-Kt/V and fluid removal. [3],[4],[5],[6],[7] PET is expensive, time consuming and tech­nologically challenging in centers with limited resources. All studies till now have not shown that PET measurements affect the outcome in patients using CAPD. [8],[9]

We tested the hypothesis that standard CAPD prescription would achieve initial T-Kt/V of more than 1.7 in all the patients regardless of their PET measurements. Therefore, routine PET is unnecessary. We compared high trans­porter patients with the other patients. If this hypothesis is supported by our data, the re­commendation to perform PET in all patients is not valid, and patients can be safely started on CAPD. Subsequently, one could perform the PET if the performance of CAPD is not satisfactory in terms of T-Kt/V or fluid removal.

   Methods Top

Study population

We performed a retrospective study of pa­tients who received PD from 2000 through 2008. The inclusion criteria were patients who were started on PD in Qatar using standard CAPD (four two-liter exchanges per day), age greater than 14 years and having full data of the T-Kt/V calculation and peritoneal mem­brane transporter type measurements by PET; the PET was measured within the first four to six weeks after initiating PD. The exclusion criterion was the development of peritonitis in the first two months after initiating PD. All patients were followed-up in the same dialysis center in Qatar.

The residual renal function was divided into two categories: (a) no residual renal function: anuric patients, with urine output less than 100 mL/day and (b) with residual renal function: patients with oliguria/normal urine output (more than 100 mL/day).

This study was conducted according to the Helsinki declaration, and the study protocol had been approved by the local institute's Committee on Human Research (our local ethics body).

The T-Kt/V and the PET were performed in our center following the first four to six weeks of initiating PD. The T-Kt/V values were cal­culated using the standard method recommen­ded in the K/DOQI guidelines. [10]

The PET measurements were performed fol­lowing a 2.5% glucose exchange overnight using the patient's standard dwell volume. The abdomen was drained over 20 min. Dextrose dialysate (2.5%, 2 L) was instilled. Following this, a 10-mL sample was removed at 4 h to measure the urea, creatinine and glucose le­vels. Serum chemistries and a full blood count were also obtained at the same time. Peritoneal membrane transport function was classified as low, low average, high average or high trans­porter, as proposed by Twardowski. [11]

   Statistical Analysis Top

Results were expressed as mean ± SD for continuous parametric data and as frequencies or percentages for categorical data. The Stu­dent's t-test was performed using unpaired analysis for the parametric data. The chi square test, with Yates correction, and the Fisher's exact test were used for two-by-two contin­gency tables when appropriate, for non-nume­rical data. Data were analyzed using the soft­ware package SPSS for Windows, release 16 (SPSS Inc.). P-values less than 0.05 were considered to be significant.

   Results Top

Patients' characteristics and peritoneal mem­brane transporter types

A total of 118 patients were included in the study. The mean age was 51.5 years (SD of 14.39), and there were 83 males (70.3%) and 35 females (29.7%). The PET demonstrated that there were 24 high transporter patients (20.3%), 65 high average transporters (55.1%), 28 low average transporters (23.7%) and one low transporter (0.8%). We divided the pa­tients into Group 1 (high transporters) and Group 2 (high average, low average and low transporters). [Table 1] shows the basic charac­teristics of the two groups; they were similar in all areas, including age, sex, body mass index (BMI) and co-morbidities.
Table 1: Baseline patient characteristics of the two study groups.

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T-Kt/V results of all patients

The T-Kt/V includes two measurements: The peritoneal clearance (P-Kt/V) and the renal clearance (R-Kt/V). The P-Kt/V measures the clearance that occurs through the peritoneal membrane. The R-Kt/V measures the clea­rance performed by the kidney (residual renal function). The P-Kt/V and R-Kt/V give a clear indication of the contribution of each in the T-Kt/V.

The T-Kt/V was performed during the first four to six weeks after initiating PD, and the results from Group 1 and Group 2 were com­pared [Table 2]. The patients in both study groups had similar P-Kt/V, R-Kt/V and T-Kt/V.
Table 2: Results of the T-Kt/V among patients in the two study groups.

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T-Kt/V results of anuric patients

Knowing that some patients start dialysis with no residual renal function (anuric), we performed a sub-group analysis by dividing the patients according to their urine output. This sub-group analysis is important as the T-Kt/V depends only on the peritoneal contri­bution (P-Kt/V) in anuric patients.

There were ten anuric patients (41.6%) in Group 1 and 17 (18%) anuric patients in Group 2. The T-Kt/V values were similar in the two groups [Table 3].
Table 3: Value of the T-Kt/V according to the residual renal function.

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   Discussion Top

To the best of our knowledge, our study is the first to examine the effect of using one stan­dard CAPD treatment on dialysis clearance in patients with different types of membrane-transport characteristics. We conducted a re­trospective study on all locally treated patients (2000-2008), in whom full data were avai­lable, and we compared the clearance in pa­tients with different types of membrane-trans­port characteristics.

There was a male predominance in our pa­tient sample, which was similar to the percen­tages reported from previous studies in other countries. [12],[13],[14] The mean BMI of the patients in this study was 26.2, and 41.7% of the patients were diabetic. Similar figures have been re­ported previously. [15],[16] The patients were clas­sified as follows: 24 high transporters (20.3%), 65 high average transporters (55.1%), 28 low average transporters (23.7%) and one low transporter (0.8%). The majority of patients were in the high average or low average cate­gory; this unequal distribution has also been described in most centers around the world. [17],[18]

Several studies have shown that T-Kt/V of 1.7 or more reduced the mortality in patients on PD. [19],[20] Ramon et al demonstrated that a T-Kt/V of 1.7 is the optimal target for impro­ving a patient's survival, and a value greater than 1.7 will not yield any additional bene-fit. [12] Wai-Kei Lo et al studied the relationship between T-Kt/V and the survival of anuric patients on PD. They found that T-Kt/V less than 1.67 was associated with increased morta­lity while T-Kt/V more than 1.8 did not im­prove survival. The authors suggested a mini­mal T-Kt/V target of 1.70 in all patients. [21] Many recent recommendations suggest the need for a minimum dialysis dose, T-Kt/V, of 1.7 per week to provide the minimally accep­table delivered small solute clearance of patients on PD. [10],[12],[22] A lower weekly T-Kt/V was associated with increased patient mortality. [23],[24],[25][26]

To answer the main question of this study, "will standard CAPD prescription achieve initial T-Kt/V of more than 1.7 in all the patients re­gardless of their type of peritoneal membrane transport function," we divided the patients into two groups. Group 1 included the high trans­porters while Group 2 included all other types (high average, low average and low transport-ters). Our data showed that both groups had similar T-Kt/V (2.5 ± 1.17 for Group 1 vs. 2.5 ± 0.88 for Group 2; P = 0.005) while on CAPD.

These results question the need for perfor­ming a routine PET four to six weeks after the initiation of CAPD. We feel that it is reason­able to continue the standard CAPD pres­cription while monitoring the T-Kt/V and the ultra filtration. If at any stage low T-Kt/V or ultrafiltration is encountered, PET can be per­formed and the PD regimen could be modified in the light of the PET results. This is likely to happen when the residual renal function is lost.

The limitations of this study include: Being a retrospective study, the confounding factors could not be controlled. The second limitation was that the BMI of this study population was 26.1 in Group 1 and 26.3 in Group 2, which makes our results less applicable to patients with higher BMIs. The third limitation is the missing data regarding the ultrafiltration (fluid removal during PD treatment) of each patient. Ultrafiltration during PD is very important as some patients with high transporter type may need to be shifted to APD because of low ultrafiltration. Repeating this study in a pros­pective manner will solve all these limitations.

In summary, our study provides evidence that using a standard CAPD (four two-liter ex­changes per day) prescription to treat patients with ESRD, regardless of their membrane transporter status or urine volume, will provide adequate T-Kt/V, as recommended by the K/DOQI guidelines. [10]

   References Top

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2.Van Biesen W, Vanholder R, Lameire N. The role of peritoneal dialysis as the first-line renal replace­ment modality. Perit Dial Int 2000;20:375-83.  Back to cited text no. 2
3.Moran J, Correa-Rotter R. Revisiting the peri­toneal dialysis dose. Semin Dial 2006;19:102-4.  Back to cited text no. 3
4.Twardowski ZJ. Clinical value of standardized equilibration tests in CAPD patients. Blood Purif 1989;7:95-108.  Back to cited text no. 4
5.Johnson DW, Mudge DW, Blizzard S, et al. A comparison of peritoneal equilibration tests performed 1 and 4 weeks after PD commence­ment. Perit Dial Int 2004;24:460-5.  Back to cited text no. 5
6.Cueto-Manzano AM, Correa-Rotter R. Is high peritoneal transport rates an independent risk factor for CAPD mortality? Kidney Int 2000; 57:314-20.  Back to cited text no. 6
7.Rabindranath KS, Adams J, Ali TZ, et al. Auto­mated vs continuous ambulatory peritoneal dia­lysis: A systematic review of randomized con­trolled trials. Nephrol Dial Transplant 2007;22: 2991-8.  Back to cited text no. 7
8.Passadakis PS, Thodis ED, Panagoutsos SA, et al. Outcome for continuous ambulatory perito­neal dialysis patients is not predicted by perito­neal permeability characteristics. Adv Perit Dial 2000;16:2-6.  Back to cited text no. 8
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10.K/DOQI Clinical Practice guidelines for perito­neal dialysis adequacy. Am J Kidney Dis 2006; 47(Suppl 4):S1.  Back to cited text no. 10
11.Twardowski ZJ, Nolph KD, Khanna R. Perito­neal equilibration test. Perit Dial Bull 1987; 7:138-47.  Back to cited text no. 11
12.Paniagua R, Amato D, Vonesh E, et al. Effects of Increased Peritoneal Clearances on Mortality Rates in Peritoneal Dialysis: ADEMEX, a Prospective, Randomized, Controlled Trial. J Am Soc Nephrol 2002;13:1307-20.  Back to cited text no. 12
13.Badve SV, Zimmerman DL, Knoll GA, et al. Peritoneal phosphate clearance is influenced by peritoneal dialysis modality, independent of peritoneal transport characteristics. Clin J Am Soc Nephrol 2008; 3:1711-7.  Back to cited text no. 13
14.Kaczmarek EE, Grzegorzewska AE. Two years on continuous ambulatory peritoneal dialysis-does it change peritoneal transport? Adv Perit Dial 2004; 20:2-7.  Back to cited text no. 14
15.Kang DH, Yoon KI, Choi KB, et al. Relation­ship of peritoneal membrane transport charac­teristics to the nutritional status in CAPD pa­tients. Nephrol Dial Transplant 1999;14:1715-22.  Back to cited text no. 15
16.Davies SJ, Phillips L, Griffiths AM, et al. Impact of peritoneal membrane function on long-term clinical outcome in peritoneal dialysis patients. Perit Dial Int 1999;19 Suppl 2:S91-4.  Back to cited text no. 16
17.Lin A, Qian J, Li X, et al. Randomized controlled trial of icodextrin versus glucose containing peri­toneal dialysis fluid. Clin J Am Soc Nephrol 2009;4:1799-804.  Back to cited text no. 17
18.Perl J, Huckvale K, Chellar M, et al. Peritoneal protein clearance and not peritoneal membrane transport status predicts survival in a contem­porary cohort of peritoneal dialysis patients. Clin J Am Soc Nephrol 2009;4:1201-6.  Back to cited text no. 18
19.Adequacy of dialysis and nutrition in continuous peritoneal dialysis: Association with clinical out­comes. Canada-USA (CANUSA) Peritoneal Dia­lysis Study Group. J Am Soc Nephrol 1996;7: 198-207.  Back to cited text no. 19
20.Churchill DN, Thorpe KE, Nolph KD, et al. Increased peritoneal membrane transport is associated with decreased patient and technique survival for continuous peritoneal dialysis pa­tients. The Canada-USA (CANUSA) Peritoneal Dialysis Study Group. J Am Soc Nephrol 1998; 9:1285-92.  Back to cited text no. 20
21.Lo WK, Lui SL, Chan TM, et al. Minimal and optimal peritoneal Kt/V targets: Results of an anuric peritoneal dialysis patient's survival ana-lysis. Kidney Int 2005;67:2032-8.  Back to cited text no. 21
22.Lo WK, Ho YW, Li CS, et al. Effect of Kt/V on survival and clinical outcome in CAPD patients in a randomized prospective study. Kidney Int 2003;64:649-56.  Back to cited text no. 22
23.Brimble KS, Walker M, Margetts PJ, et al. Meta-Analysis: Peritoneal membrane transport, morta­lity, and technique failure in peritoneal dialysis. J Am Soc Nephrol 2006;17:2591-8.  Back to cited text no. 23
24.Rodrigues AS, Martins M, Korevaar JC, et al. Evaluation of peritoneal transport and membrane status in peritoneal dialysis: Focus on incident fast transporters. Am J Nephrol 2007; 27:84-91.  Back to cited text no. 24
25.Nolph KD. Clinical implications of membrane transport characteristics on the adequacy of fluid and solute removal. Perit Dial Int 1994;14 Suppl 3:S78-81.  Back to cited text no. 25
26.Jansen MA, Termorshuizen F, Korevaar JC, Dekker FW, Boeschoten E, Krediet RT; NECOSAD Study Group. Predictors of survival in anuric peritoneal dialysis patients. Kidney Int 2005;68:1199-205.  Back to cited text no. 26

Correspondence Address:
Hassan A Al-Malki
Nephrology Section, Internal Medicine, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-2442.135004

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  [Table 1], [Table 2], [Table 3]

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