Advances in Peritoneal Dialysis, Vol. 13, 1997

PART FIVE

Pediatrics

Advances in Peritoneal Dialysis, Vol. 13, 1997

Variability of Peritoneal Equilibration Test in Children on Continuous Peritoneal Dialysis By Repeated Testing With Solutions of Different Osmolarity

Christiane Laux, Klaus-Eugen Bonzel, Friederike Rubbert-Lauterbach, Rainer Biischer, Anne-Margret Wingen

To evaluate (1) differences in the peritoneal equilibration test (PET) achieved using continuous peritoneal dialysis (CPD) solutions containing d~ ferent amounts of glucose and (2) intra individual reproducibility of PEn performed twice within an interval of 8 months on CPD, we investigated 39 PETs in 13 children aged 2.4-19.0years (median 10.6 years) on stable CPD regimens. The fill volume was 1 L/ml body surface area. We used a standard CPD solution (Fresenius) with a 2.3% glucose content (groups 2.3a and 2.3b) two times within an interval of 1 -8 months. A third test was done between the two with a CPDsolution ofl.5%glucose (group 1.5). Equilibration quotients, that is, substrate concentration in dialysis fluid divided by substrate concentration in plasma (D/P), did not show any statistically significant differences between groups 1.5 and 2.3a or between groups 2.3a and 2.3b. A significant d~ ference was seen in the decline of glucose content of dialysate between groups 1.5 and 2.3 but not between groups 2.3a and 2.3b. Ultrafiltration was higher in groups 2.3a and 2.3b compared with group 1.5. Inter and intraindividual variability between solute transfer was small during follow-up in stable CPD patients. Different glucose contents of 1.5 and 2.3 g/dL dialysis fluid had no measurable influence on PET results of stable CPD patients. For standard PETs, reducing the glucose content of dialysis fluid to isoosmolarity is not necessary.

From: Department of Pediatric Nephrology, Universitiitskinderklinik Essen, Germany.

Key words

Peritoneal dialysis in children, peritoneal equilibration test, dialysis fluid, glucose content in dialysis fluid

Introduction

A standardized peritoneal equilibration test (PET) has been used in continuous peritoneal dialysis (CPD) patients since 1986 to evaluate peritoneal transport kinetics (1,2). Later, the PET was adapted for study in children (3-5), and reference values for children were developed (6).

Subjects

Thirteen children (8 boys, 5 girls) on stable CPO were studied. The patients' age ranged between 2.4 and 19.0 years (median 10.6 years). Underlying renal diseases were congenital in 5 patients (dysplasia in 2, prunebelly syndrome in 1, nephrotic syndrome in I, and nephrocalcinosis in I) and acquired in 8 cases (different kinds of glomerulonephritis in 6, hemolytic uremic syndrome in 1, and shock in I ). Total number of PETs was 39; 15 were performed on patients on continuous ambulatory peritoneal dialysis (CAPD) and 24 on patients on continuous cyclic peritoneal dialysis (CCPD). Mean time on CPO was 22.4 months at the first, 24.0 at the second, and 28.5 months at the third PET. At time of testing all patients were free from peritonitis (at least 4 weeks after termination of antibiotic treatment). Three patients suffered from peritonitis during follow-up.

Methods

The PET was performed in the morning after an overnight dwell by CAPO or a usual nighttime exchange

264

regimen in CCPD patients. After a complete drainage, the peritoneal cavity was filled with I Llm2 body surface area of solution. We used a commercially available CPD solution (Fresenius) containing 1.5% (group 1.5) and 2.3% (group 2.3) glucose. The first and the third PETs were done with standard CPD solution containing 2.3% (groups 2.3a and 2.3b) within an interval of I -8 months, and the second PET was performed with CPD solution containing 1.5% glucose (group 1.5) between the others. Glucose, volume, potassium, urea, creatinine, and phosphorus were measured in dialysate (D) six times during a 6-hour dwell by a complete drainage technique and in plasma (P) two times (dwell time 0 and 4). The concentrations of glucose, urea, and phosphorus (enzymatic reactions), creatinine (modified Jaffe reaction, corrected for glucose concentration in dialysate ), and potassium (ion-selective electrode method) were determined in each dialysate and plasma sample (6). For each patient at each dwell time DIP was calculated for urea, phosphorus, creatinine, and potassium, D t ID o for glucose, and V t N o for ultrafiltration. All data are given as mean:1:SD. Student's t-test for paired data was used for statistical evaluation. The results are considered statistically significant for p < 0.01.

Results

Different glucose contents of dialysis fluid of 2.3% and 1.5% glucose do not influence PET results in stable CPD patients (Table I). This is even more important when realizing the small inter and intraindividual variance ofPET results. Also, repeated testing of all patients after I -8 months showed intraindividually stable equilibration curves even after a cured intercurrent peritonitis episode (Figure I ). In 2 of the 3 patients who developed peritonitis between the tests, PETs after one month showed steeper equilibration curves for potassium and phosphorus, which reversed later on (Figure 2). DIP of urea always showed the steepest curves and was never influenced by peritonitis.

Discussion

CPD is an extensively used dialysis method in children. Peritoneal membrane mass transfer is both diffusive and convective. The considerable individual variability in the handling of different solutes is well known (6). The experience with pediatric PET curves differed from those in adults by showing many more

Laux et al.

high and high-average transporters up to 70% (5). This is in agreement with our findings (not shown here). But the variability ofPET results in the literature is rather large. By selecting patients strictly according to stable clinical conditions without signs of active peritonitis, we found an interindividual variance much smaller than shown before (5,6). In contrast to our previous data, intra individual variance was also small, if short time influences near a preceding episode of peritonitis were excluded. Glucose resorption profiles of our follow-up only hint at increasing permeability of the peritoneal membrane by time. But loss of ultrafiltration was not detectable in the absence of peritonitis. Unlike others (7), we did not observe a decrease in DIP creatinine following peritonitis, albeit 6 of our 13 patients had between one and four episodes of peritonitis before the tests, and 3 patients each had one episode during the test. We know that our follow-up time was somewhat short. We think that even repeated episodes of peritonitis will not necessarily influence peritoneal function in a negative way, if the intervals between episodes of peritonitis are long enough and healing is complete. Two of the 3 patients with peritonitis between the tests and who underwent PETs one month after peritonitis was cured showed a reversible increase in DIP values for potassium and phosphorus. Variability of PETs seems to be much smaller than expected and not detectable by changing the osmolarity of dialysis fluid. Therefore, the PET can be

Variability of PET

265

266

performed with reasonable accuracy, without reducing the glucose content of dialysis fluid to isoosmolarity. The reason for this might be that measuring the DIP ratio is only an approximate method of testing peritoneal function. We need more refined methods to really detect membrane dysfunction in a predictive sense.

References

1 Verger C, Larpent L, Dumontet M. Prognostic value

of peritoneal equilibration curves in CAPD patients.

In: Maher JF, Winchester JF, eds. Frontiers in

peritoneal dialysis. New York: Field, Rich and Associates, 1986:88~93.

2 Twardowski ZJ, Nolph KD, Khanna R, et al. Peritoneal equilibration test. Perit Dial Bull 1987 ; 7: 138--47.

3 Fischbach M, Mengus J, Birmele B, Hamel a, Simeioni U, Geisert J. Solute equilibration curves, crossing time for urea and glucose during peritoneal dialysis: A function of age in children. In: Khanna R, Nolph KD, Prowant BF, Twardowski ZJ, Oreopoulos Do, eds. Advances in peritoneal

Laux et at.

dialysis. Toronto: Peritoneal Dialysis Bulletin, 1991; 7:262-5.

4 Hanna ill, Foreman JW, Gehr TWB, Chan JCM, Worfrum J, Ruddley J. The peritoneal equilibration test in children. Pediatr Nephrol1993; 7:731--4.

5 Geary DF, Harvey EA, MacMillan JH, Goodman Y, Scott M, Balfe JW. The peritoneal equilibration test in children. Kidney Int 1992; 42:102~5.

6 Schaefer F, Langenbeck D, Heckert, KH, Schiirer K, Mehls 0. Evaluation of peritoneal solute transfer by the peritoneal equilibration test in children. In: Khanna R, Nolph KD, Prowant BF, Twardowski ZJ, Oreopoulos Do, eds. Advances in peritoneal dialysis. Toronto: Peritoneal Dialysis Bulletin, 1992; 8:410-15.

7 Nishi A, Ito Y, Amamoto Y, Aida K, Kato H. Longitudinal changes in peritoneal equilibration test with or without peritonitis in children. Pediatr Nephrol1995; 9:562-5.

Corresponding author:

Klaus-Eugen Bonzel, MD, Pediatric Nephrology, Universitiitskinderklinik Essen, Hufelandstr. 55, 45122 Essen, Germany.