| Abstract|| |
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 2021 Aug 4];25:788-92. Available from: https://www.sjkdt.org/text.asp?2014/25/4/788/135004
| Introduction|| |
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. , 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. , 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. ,,,, 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. ,
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|| |
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. 
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. 
| Statistical Analysis|| |
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|| |
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.
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.
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].
| Discussion|| |
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. ,, 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. , 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. ,
Several studies have shown that T-Kt/V of 1.7 or more reduced the mortality in patients on PD. , 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.  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.  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. ,, A lower weekly T-Kt/V was associated with increased patient mortality. ,,
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. 
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Hassan A Al-Malki
Nephrology Section, Internal Medicine, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha
[Table 1], [Table 2], [Table 3]