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Technique survival in continuous ambulatory peritoneal dialysis (CAPD) depends mostly on clearances in relation to body size and residual renal function (RRF). Our clinical impression has been that when RRF fails, larger patients leave CAPD sooner than smaller patients do. Peritoneal equilibration tests (PETs) and 24-hour adequacy evaluations performed in 277 patients in a single center from 1986 through 2009 were abstracted from the existing peritoneal dialysis adequacy database. A PET (using 2 L of 2.5% dextrose dialysis solution) was performed in 272 patients during the first 4 months of dialysis. Every 3 months, the patients brought their 24-hour urine and dialysate collections for adequacy evaluations and had height and weight recorded. Body surface area (BSA), body mass index (BMI), and total body water (TBW) were calculated. There were 1372 adequacy evaluations abstracted. The number of patients gradually declined over time because of death (28%) or transfer to other peritoneal regimens (25%) or to hemodialysis (23%). A small number of patients received a kidney graft (6%) or left CAPD for other reasons (12%); only 6% of patients remained on CAPD after 80 months of treatment. The mean (+/- standard deviation) PET 4-hour values were 0.652 +/- 0.128 for dialysate-to-plasma (D/P) ratio of creatinine (Cr), 0.403 +/- 0.0969 for 4-hour dialysate-to-initial dialysate (D/D0) glucose concentration ratio, and 2336 +/- 211 mL for the drain volume. There was no correlation between PET D/P Cr and BSA (r = 0.0051, p = 0.934), PET D/D0 glucose and BSA (r = 0.0042, p = 0.945), or PET drain volume and TBW. The correlations with other size indicators were very poor. None of the large patients (BSA > 1.9 m2, weight > 75 kg, BMI > 25 kg/m2) remained on CAPD for more than 80 months once they lost RRF. These results confirm our impression that, with declining RRF, larger patients do not continue CAPD as long as smaller patients do.

In the original peritoneal equilibration test (PET), which established standard values for membrane categorization in 1987, the dwell time of the preceding exchange was approximately 8 hours. Basing the test on an 8-hour prior exchange was convenient when almost all patients were on continuous ambulatory peritoneal dialysis (CAPD); however, many patients are now on some form of automated peritoneal dialysis (PD), and an 8-hour exchange before the PET requires a change in the dialysis schedule. Our goal in the present study was to determine whether the dialysate-to-plasma ratio (D/P) of solutes and the final dialysate to initial dialysate ratio (D/D0) of glucose in the short PET (2-hour equilibration time) are similar whether a 3-hour exchange or an 8-hour exchange precedes the test. The PETs were performed in 9 stable PD patients using 2 L of 2.5% dextrose dialysis solution (Baxter Healthcare, Deerfield, IL, U.S.A.). Before the equilibration exchange, the patients were on a randomly selected long (approximately 8-hour) or short (3-hour) dwell. During the equilibration exchange, dialysate samples were collected at 0.30, and 60 minutes of dwell time and from the drain bag (120-minute sample). Within a week, the PET was repeated in each patient after the alternate-length exchange. The values for D/P creatinine and urea and for D/D0 glucose were almost identical throughout the 2-hour PET after either the long or the short exchange. The D/P protein values tended to be higher in the PET after the long exchange. The short PET can be used for clinical purposes, and the creatinine and glucose results can be used for membrane categorization. Any dwell time between 3 and 12 hours is acceptable for the preceding exchange, and the equilibration test may be performed with either a 2-hour or a 4-hour dwell. The protein values obtained after a 3-hour prior dwell differ from those obtained after a long prior dwell. Protein values must therefore be standardized in a larger number of patients.

Objectives: Since the introduction of the peritoneal equilibration test (PET), the 4-hour dialysate/plasma creatinine (D/P Cr) has been used by several authors for determining continuous ambulatory peritoneal dialysis (CAPD) prescriptions. However, the results have been unsatisfactory because the 4-hr D/P Cr does not accurately reflect the D/P Cr in 24-hr collections. The PET and the 24-hr dialysate collections differ in the duration of dwell and the tonicity and volume of dialysate, all of which influence the equilibrated D/P Cr. It can be assumed that the D/P Cr in 24-hr collections in these patients is closer to a 6-hr D/P Cr. Because a 6-hr PET is inconvenient, we developed a mathematical model to calculate the 5- and 6-hr D/P using the results of a standard PET., Design: In a retrospective analysis, D/P Cr ratios in 24-hr collections and D/P Cr ratios calculated from a mathematical formula were correlated. Using a mathematical model, the data collected fit an exponential relation of the type D/P = a(1-e-t/tau). The values of a and tau are unique for a given patient and were determined using a nonlinear regression technique. The formula performed well on our published data-the true and predicted 6-hr D/P Cr being 0.696 and 0.71, respectively., Setting: The University Hospital and Clinics, Dalton Cardiovascular Research Center and Dialysis Clinic, Inc., Columbia, Missouri., Patients: All CAPD patients on four 2-L exchanges/day at the time of the 24-hr collections were included., Interventions: None., Main Outcome Measures: Closeness of 4-hr and 6-hr D/P Cr values to those of 24-hr ratios., Results: The study group comprised 74 patients (age, mean +/- SEM: 56.4 +/- 1.8 yr) with 80 PETs and 145 (24-hr) collections. The interval between the two tests was 8.3 +/- 0.9 months (0-48.7 months). The median 24-hr D/P Cr of 0.760 did not differ significantly from the predicted median 6-hr D/P Cr of 0.755. A subgroup analysis, based on transport type, showed that this relationship was most precise in the high-average transporters. The predicted 6-hr D/P Cr was within 10% of the 24-hr D/P Cr in 48% of patients and within 20% in 77% of patients. The margin of error was greatest in the low transporters., Conclusions: To conclude, the 4-hr D/P Cr from a PET cannot be used interchangeably with the D/P Cr in the 24-hr dialysate collections, hence, the clearances calculated thereof will be inaccurate. Using the proposed model, it is feasible to use the 4-hr PET results to obtain 5- and 6-hr D/P Cr values. In our study, using this model, the extrapolated 6-hr D/P Cr is similar to the D/P Cr in 24-hr dialysate collections only in the high-average transporters. Hence, the best way to determine clearances in peritoneal dialysis patients is still by collecting 24-hr dialysates.

A previous study showed that silver-coating peritoneal catheters tended to decrease the incidence of early exit-site infections in rats. This study was designed to further evaluate the healing, biocompatability, and external tunnel morphology of standard and silver-coated catheters. Catheters were coated with silver by an ion beam-assisted process. Fourteen male Sprague-Dawley rats underwent implantation of either a standard or silver-coated double-cuff peritoneal catheter. Weekly observation and photographs documented exit-site characteristics. Erythema, exudate, loose fit, and poor hair growth were evidence of an inflamed exit. Overt infection was indicated by the presence of three or more of the following: erythema, purulent exudate, exuberant granulation tissue, loose fit, and poor hair growth. Animals were sacrificed at six weeks, and catheters were removed and processed for histology of the external tunnel. Multiple measurements were taken using a Filar eyepiece, and data were expressed as a mean of several readings. Inflammation, vascularity, and fibrosis were judged semiquantitatively. At the end of six weeks, six of the seven exits of the silver catheters showed excellent healing, while one exit site had signs of excessive inflammation. Four of the exit sites of the standard catheters healed well, two were inflamed, and one was overtly infected. The sinus tract of the standard and silver catheters had similar characteristics: keratinized and nonkeratinized epithelium lined the external part of the sinus tract and merged into granulation tissue. A fibrous sheath was noted in some sinus tracts between the granulation tissue and the cuff. The cuff evoked a foreign body reaction, with fibrosis, multiple giant cells, and vascularization. Poorly healing or infected sinus tracts had highly vascular granulation tissue with overlying exudate. The cuff of these catheters had marked inflammation and scanty giant cells, although collagen bundle thickness was similar to the well-healing catheters. In conclusion, silver-coating potentially enhances healing of the exit sites of peritoneal catheters. Additionally, the similarity of the tunnel histomorphology of standard and silver catheters confirms the favorable biocompatibility of silver.

A study was undertaken to evaluate the short-term reproducibility of peritoneal equilibration test (PET) results. Nine patients with end-stage renal disease undergoing continuous ambulatory peritoneal dialysis underwent PETs under similar conditions on 2 consecutive days. Dialysate samples were obtained at 0 hours, midcycle, and at the end of exchange. There were no significant differences between the mean ratios at 4 hours for creatine, urea nitrogen, potassium and protein, and glucose between PET 1 and PET 2. A standard PET is highly reproducible when repeated under similar conditions. Reproducibility is better for ratios of creatinine, glucose, urea nitrogen, and potassium than for protein.

Fifty-five patients on chronic peritoneal dialysis with two or more peritoneal equilibration tests (PET) performed between 1983 and 1992 with a mean interval of 21.9 +/- 22.7 months were studied retrospectively. Repeated PET were performed when transport changes were suspected rather than routinely. According to the initial PET, there were 16 high (HI), 17 high-average (HA), 15 low-average (LA), and 7 low (LO) transporters. There was a significant decrease in the mean creatinine dialysate to plasma ratio (D/P creatinine) in the HI transporters and an increase in the LA and LO transporters. The mean dialysate to instilled glucose ratio (D/Do) significantly increased in the HI transporters. The change in both the D/P creatinine and the D/Do of an individual strongly and inversely correlated to their respective initial values. The change in D/P creatinine and D/Do were significantly and inversely correlated to each other, indicating an actual transport change. No correlation was found between the change in transport with peritonitis episodes or frequencies. The centripetal [corrected] change of transport toward average described here may explain why low clearances or low ultrafiltration rates due to rapid transport are infrequent causes of peritoneal dialysis technique failure, and why patients who have been dialyzed for a long period are usually HA transporters.