| Abstract|| |
The adequacy of peritoneal dialysis is generally dependant on the choice of peritoneal fluid, the intraperitoneal fill volume and the contact time. Moreover, the peritoneal surface area acts as a major factor in the exchange dynamics of a peritoneal membrane. We designed a mechanism to increase the membrane surface contact area by using an abdominal belt in order to exert enough pressure on the fill volume, to effectively recruit more area in contact for exchange. We studied 12 patients on regular continuous ambulatory peritoneal dialysis (CAPD) at our center from January to October 2008. The age of patients ranged from 44 to 75 years, with a median of 55 years. All the patients were maintained on the same prescription four months before and during the study. Dialysis solutions were 1.36% Deaneal® , two liters, three exchanges and the last fill volume was two liters 7.5% Extraneal® . The belt was applied to all the patients most of the day and all night. We then observed its effect on dialysis adequacy, reflected by various parameters over a period of eight months. The average Kt/V before wearing the belt was 1.89 and improved after applying the belt to 2.3 (P <0.05). Our study suggests that increasing the abdominal pressure by wearing an abdominal belt rendered the filling volume of the PD dialysate to have a better contact with the peritoneal membrane and improved the dialysis adequacy. Studies with larger sample size are required to confirm the results.
|How to cite this article:|
Alhwiesh A, Esam S, Saeed I, Ahmmed M, Almohana F. The influence of increased peritoneal membrane surface area on dialysis adequacy. Saudi J Kidney Dis Transpl 2011;22:717-22
|How to cite this URL:|
Alhwiesh A, Esam S, Saeed I, Ahmmed M, Almohana F. The influence of increased peritoneal membrane surface area on dialysis adequacy. Saudi J Kidney Dis Transpl [serial online] 2011 [cited 2021 Mar 6];22:717-22. Available from: https://www.sjkdt.org/text.asp?2011/22/4/717/82650
| Introduction|| |
Since the beginning of peritoneal dialysis (PD), there have been numerous trials on modifying the adequacy of PD by changing the number and duration of cycles, the volume of dialysis fluid applied, and the choice of dialysis solution. ,,,
Looking from another perspective, the adequacy can be altered by making use of peritoneal membrane anatomic dynamics. The membrane can be viewed as being composed of three exchange entities: the anatomic, the contact, and the vascular areas. First, the anatomic area appears to be constant for every individual when expressed as per square meter body surface area (BSA). The fluid volume can be selected based on this surface area. , However, 30-60% of this area, the contact area, is utilized for exchange. ,, The extent of its recruitment depends on factors such as posture, filling volume, and intra-abdominal pressure (IAP).  Finally, the vascular area is represented by the mesenteric blood flow and the number of perfusing capillaries. This area is also changeable and is affected by the composition of filling volume and the production of inflammatory agents as well as growth factors. ,
Out of the above-mentioned three exchange areas, the contact area can be worked upon easily and most efficiently to improve the adequacy of PD. Theoretically, the IAP, and hence the recruited contact area, can be increased externally by making the patient wear a special belt around his/her waist. This belt is to exert enough pressure, while not compromising patient's daily lifestyle and comfort.
The aim of our study was to evaluate the effect of increasing peritoneal surface area on the parameters that reflect dialysis adequacy and peritoneal membrane function by making the patient wear an abdominal belt that covers most of his/her abdomen.
| Patients and Methods|| |
We studied 12 patients on continuous ambulatory peritoneal dialysis (CAPD) from January to October 2008 at King Fahd Hospital of the University, Al-Khobar, Saudi Arabia. All the patients were stable on CAPD, six months prior to the study. Their age ranged from 44 to 75 years, with a median of 55 years. The patients' characteristics are shown in [Table 1].
Patients with one or more of the following conditions were excluded from the study: those who had peritonitis or exit-site infection during the last 6 months prior to the study, those with recent abdominal surgery, those with abdominal or inguinal hernias, and pregnant women.
All the patients were maintained on the same dialysis prescription for six months before and during the study period in the form of 1.36% Dianeal® (Baxter Company, Deerfield, USA), filling volume of two liters, three exchanges per day, and the last filling volume was two liters 7.5% Extraneal® (Baxter Company-USA). Complete blood count, renal function tests, liver function tests, calcium, phosphorus, uric acid, serum albumin, bicarbonate level, KT/V and peritoneal creatinine clearance were measured monthly. The patients were routinely evaluated by PD nurses and nephrologists.
The abdominal belt [Figure 1], [Figure 2] and [Figure 3] designed at our hospital was worn by all the study patients most of the day and all night. The belt is made of a combination of elastic and soft nylon pile bonded to 1/4 foam for comfort with special elastic panel construction that provides even support and prevents roll over. In addition, there is a special hole in the center through which the external part of the catheter passes with the transfer set. There is also a special rubber hook at the side of the belt to fix the transfer set. The belt's width is fixed (23 cm), but its length varies according to the patient's size.
|Figure 2: Diagrammatic illustration of the peritoneal dialysate before applying the belt.|
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|Figure 3: Diagrammatic illustration of the peritoneal dialysate after applying the belt.|
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Urea Kt/V and peritoneal creatinine clearance were calculated weekly based on 24-hour urine and dialysate collections prior to the scheduled visit to the PD unit. Serum, urine, and dialysate urea and creatinine levels were analyzed using Hitachi 917 equipment (Roche Diagnostics, Division of Hoffmann-La Roche, Basel, Switzerland). Calculations of Kt/V and creatinine clearance were performed using original Polish software, Nephron 97 for Windows (DDPS, Kraków, Poland).
The above protocol was reviewed and approved by our local ethics committee.
| Statistical Analysis|| |
Analysis of the data was performed using statistical 5.1 software (StatSoft, Tulsa, Oklahoma, USA). All normally distributed variables were presented as mean ± SD and those with nonnormal distribution were presented as median and range. Pearson test was used for correlation between variables. We considered P values less than 0.05 as statistically significant.
| Results|| |
Of the total 8 months of follow-up, the study patients were kept off the abdominal belt for four months, followed by its application for the rest of the study period. There were no exit site infections or peritonitis. Eight patients were slow and four were fast average transporters. The 24-hour urine output ranged from 155 to 1,837 mL, with a mean of 664 mL. The body mass index ranged from 18.8 to 42.5 with a mean of 31.3 Kg/M 2 . The average Kt/V before applying the belt was 1.89 and after applying the belt was 2.3; the difference was statistically significant with a P value <0.05 [Table 2]. The difference was more significant in patients with low body mass index as compared with patients having high body mass index (3.1 vs. 2.2, P <0.01). The average peritoneal creatinine clearance before wearing the belt was 71 mL/min compared with 68.6 mL/ min after wearing the belt. The difference was not statistically significant. The average peritoneal creatinine clearance in patients with low body mass index (patients 5, 7 and 9) after applying the belt was 83.9 mL/min compared with 67.7 mL/ min in those with high body mass index (P <0.05) [Table 3]. The rest of biochemical markers including serum blood urea nitrogen (BUN), creatinine, phosphorus, albumin, bicarbonate and uric acid did not show significant differences before and after wearing the belt.
|Table 3: Creatinine clearance (peritoneal) before and after applying the belt.|
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IAP was measured with and without the belt as described by Durand et al.  The mean values during inspiration and expiration were used, and the IAP was expressed in mmHg by multiplying the result of IAP in cm H 2 O by conversion factor 0.74.
The mean IAP in supine position without and with the belt was 12.6 ± 4.7 and 12.8 ± 4.8 mmHg, respectively, (P = 088), while in the erect position without and with the belt, the values were 21.4 ± 7 and 21.6 ± 6.9 mmHg, respectively, (P = 0.9).
| Discussion|| |
Optimal treatment of ESRD involves consideration of several interrelated aspects: fluid removal, blood pressure control, nutrition, acid-base balance, mineral metabolism (calcium and phosphate), anemia and lipid control, and small-solute removal. Adequate small-solute removal is frequently, though perhaps not correctly, taken as the single parameter of dialysis adequacy.  Theoretically, patient survival and morbidity have a dose-dependent relationship with small-solute clearance.  Several prospective cohort studies found that a higher dialysis dose, in terms of total Kt/V or creatinine clearance, was associated with a better patient survival and a fewer hospitalizations. ,, Based on the results of these studies, the Dialysis Outcomes Quality Initiative (DOQI) workgroup recommended a total weekly Kt/V of 2.0 or weekly creatinine clearance of 60 L as targets for adequate PD.  The prescription of PD is based mainly on the choice of the PD fluid, the intraperitoneal filling volume based on the BSA, and the contact time. The working mode of the peritoneal membrane as a dialysis membrane is more related to a dynamic complex structure. ,,,,, Both posture and filling volume may affect the extent of recruitment of the contact area with the dialysate. ,,,, The contact area is an expandable surface and a new contact area may be recruited by different factors. , In support of this hypothesis, the PD membrane has been proven in animal studies to be impacted by mechanical factors, such as agitation, or pharmacological factors, such as surfactant. , Using computed tomography in humans, Chagnac et al  have shown that only 25-30% of the anatomic area comes into contact with the filling volume under basal conditions. In other studies, authors have clearly demonstrated that an increase in the filling volume from 2 to 3 L resulted in an increase in the contact area from 0.57 to 0.67 m 2 (18% ± 2.3%), which in turn resulted in a significant increase in the mass transfer area coffeciance (MTAC) value for creatinine from 10.6 to 13.6 mL/min (28% ± 2.4%). , When the dose of dialysis is increased to achieve higher target values, there is always a potential for an introduction of adverse effects associated with efforts to enhance the dose. This may include hernias from the increased IAP, patient dissatisfaction because of the increased time needed to perform exchanges, weight gain from glucose absorption, possible systemic toxicity from components of the dialysate that may be absorbed (glucose degradation products), and increased cost because of the additional dialysis solutions.  Discrepancy between KT/V and creatinine clearance is multifactorial and includes low transporter membrane status and a decrease of residual renal function. In our patients 2 and 12 and in patient 11, the creatinine clearance was better than the KT/V. However, up to 20% of patients may reveal a significant discrepancy between the two measurements.
We found a positive effect of wearing an abdominal belt that exerts enough abdominal pressure on the filling volume in our PD patients. The dialysis adequacy in terms of Kt/V and peritoneal creatinine clearance increases, especially in patients with low and normal body mass index. This may be explained by an increase of the contact area with pressure support obtained from wearing the belt. The limitations of our study include the small number of the study patients and short duration of follow-up. Additional studies with a large sample size are needed to confirm this conclusion.
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Nephrology Department, King Fahd University Hospital, Al-Khobar
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]