Continuous Cycler Therapy, Manual Peritoneal Dialysis Therapy, and Peritonitis

Laura K. Troidle, Nancy GorbanBrennan, Alan S. Kliger, Frederic O. Finkelstein

An increasing number of patients are prescribed a continuous-cycling regimen because standard manual peritoneal-dialysis exchanges alone are not sufficient in achieving adequate dialysis as defined by the Dialysis Outcome Quality Initiative. Consequently, the number of patients on continuous-cycler therapy is increasing. There is controversy as to whether there are differences in the development of peritonitis between patients maintained on manual therapy and those on continuous cycling therapy. As a result, we retrospectively reviewed the charts of all cycler peritoneal dialysis (CPD) patients maintained on either manual peritoneal dialysis (Baxter UltraBag™; Group I) or continuous cycler peritoneal dialysis (Baxter HomeChoice Cycler™; Group II) between 1 June 1994 and 31 December 1996. A total of 239 patients were in Group I and 106 in Group II. Both groups were similar in age, race, gender, and presence of diabetes mellitus, coronary artery disease, peripheral vascular disease, and gastrointestinal disease. There was no difference in the overall rate of peritonitis between the two groups of patients [1 episode in 10.4 patient-months (Group I) vs. 1 in 10.0 patient-months (Group II); 0.01843 to 0.02619]. The rates of Staphylococcus aureus peritonitis [1 episode in 48.5 patient-months (Group I) vs. 1 in 141.8 patient months (Group II); 0.06152 to 1.1689]; polymicrobial peritonitis [1 episode in 278.8 patient-months (Group I) vs. 1 in 1134 patient months (Group II): 0.0079 to 0.0478], and fungal peritonitis (1 episode in 202.7 patient-months (Group I) vs. no episodes (Group II); 0.00202 to 0.00785] were significantly lower among patients maintained on the Baxter HomeChoice Cycler™. The rate of gram-negative peritonitis was higher among patients maintained on the Baxter HomeChoice Cycler™, but this difference was not statistically significant [1 episode in 82.6 patient-months (Group I) vs. 1 episode in 45.4 patient months (Group II); 0.4723 to 0.0248].

We conclude that individual rates of peritonitis were different for patients maintained on either manual or continuous CPD therapy, while the overall rate of peritonitis was found to be similar for both groups of patients. The finding that there may be a difference with the gram-negative peritonitis rate is important since gram-negative peritonitis has been shown to have a more severe outcome in terms of morbidity, mortality, and patient dropout from CPD therapy. A larger, randomized, multicenter study comparing the rates of gram-positive, gram-negative, fungal, and polymicrobial peritonitis is warranted.

Key words

Peritonitis, cycler therapy, manual therapy

From:

Renal Research Institute, New Haven, Connecticut, USA.

Introduction

Peritonitis is the leading cause of patient dropout from cycler peritoneal dialysis (CPD) therapy. However, inadequate dialysis has been accounting for an increased percentage of episodes of patient dropout from CPD therapy. The Dialysis Outcome Quality Initiative (DOQI) has recommended specific Kt/V and creatinine clearance goals for CPD patients in order to maintain adequate dialysis (1). For many CPD patients standard manual peritoneal dialysis exchanges alone are not sufficient to permit patients to achieve these goals. Thus, many CPD patients are prescribed a continuous-cycling peritoneal-dialysis regimen to attain adequate dialysis. The number of patients on continuous-cycling therapy is increasing (2).

There is controversy as to whether overall peritonitis rates differ between patients maintained on manual peritoneal dialysis regimens and those on continuous-cycling peritoneal-dialysis regimens (3-5). The Baxter UltraBag™ has been shown to significantly reduce peritonitis rates (6). Furthermore, there are differences in the functional operation of individual cycling units; some continuous cycling units drain by gravity while some drain by simulating gravity. The cycling machine that simulates gravity is more widely used.

We therefore decided to examine the peritonitis rates and the spectrum of organisms causing peritonitis in our CPD patients by comparing patients using the Baxter UltraBag™ to those using the Baxter HomeChoice Cycler™.

Material and methods

We retrospectively reviewed the charts of the CPD patients maintained on either a manual exchange peritoneal dialysis system (Baxter UltraBag™; Group I) or a continuous-cycling peritoneal-dialysis system which drains via simulation of gravity (Baxter HomeChoice™; Group II), between 1 June 1994 and 31 December 1996.

The organization and structure of our unit has previously been described (7). All patients had double-cuff silastic Tenckhoff catheters inserted by standard surgical techniques (7).

Peritonitis was defined by the presence of a cloudy dialysis effluent with greater than 100 white blood cells/mm3 and a white blood cell differential count of greater than 50% polymorphonuclear cells (7). The peritoneal effluent was cultured by standard microbiological technique (7).

Patients in Group I were maintained on the Baxter UltraBag™ for CPD therapy. The description and operation of this system has been previously described (6). Briefly, patients administer and drain a prescribed volume of sterile peritoneal-dialysis fluid. The entire system is a closed system once the patient makes the connection to the peritoneal catheter, as the patient does not need to spike the dialysis fluid bag or reconnect in order to drain.

Patients in Group II were maintained on the Baxter HomeChoice Cycler™. Briefly, the HomeChoice Cycler™ therapy involves a series of connections to several bags of sterile peritoneal-dialysis solution via manual spiking. Once each bag is connected, the patient starts the cycler, and sterile fluid is infused and drained based on the preprogrammed cycler regimen. The HomeChoice Cycler™ pulses fluid into the patient and drains the peritoneal fluid from the patient in the same pulsating manner by simulating gravity.

The charts of the CPD patients in Groups I and II were retrospectively reviewed for (1) basic demographic data including age, race, and gender; (2) total patient-months on the prescribed CPD system; (3) total patient-months on all types of CPD therapy; (4) presence of diabetes mellitus, cardiovascular disease, peripheral vascular disease, and gastrointestinal disease; and (5) peritonitis history, including organism identification while each patient was on the respective system only.

The peritonitis rate was calculated by dividing the total patient-months by the total number of peritonitis episodes occurring during the time period when each patient was on the respective system, and reported as episodes per patient-months. For each group an overall peritonitis rate was calculated, as well as rates for gram-positive, gram-negative, fungal, culture-negative, polymicrobial, Staphylococcus aureus, and other staphylococcal peritonitis episodes.

The rates of peritonitis were compared statistically by using the fixed Poisson method as previously described by Vonesh (8).

Results

A total of 345 CPD patients' charts were retrospectively reviewed in this analysis. There were 239 patients in Group I and 106 patients in Group II.

The demographic features and incidence of comorbid disease states for both groups of patients are outlined in Table I. Both groups were similar in age, race, gender, presence of diabetes mellitus, coronary artery disease, peripheral vascular disease, and gastrointestinal disease.

Patients in Group I and Group II were maintained on CPD therapy for similar lengths of time (19.81 patient-months versus 20.88 patient-months, P = NS). The time on all types of CPD therapy, including the total patient-months of CPD therapy the patient was performing in the study period, was the same for the two groups of patients. Group I patients experienced a total of 2230 patient-months on the UltraBag™ while Group II patients experienced a total of 1134 patient-months on the HomeChoice Cycler™.

The spectrum of organisms responsible for the episodes of peritonitis in both Group I and Group II are outlined in Tables IIa and IIb. Gram-positive organisms predominated, with staphylococcal organisms accounting for 78% of all gram-positive organisms in both groups of patients.

Table III demonstrates the overall rate of peritonitis and the rate of gram-positive, gram-negative, fungal, polymicrobial, and culture-negative peritonitis for both Group I and Group II. There was no significant difference in the overall rate of peritonitis for both groups of patients. The rates of Staphylococcus aureus, polymicrobial, and fungal peritonitis were significantly different for both groups of patients. There was a difference noted among the rates of gram-negative peritonitis between both groups of patients, but this difference did not reach statistical significance (0.4723 to 0.0248).

Discussion

Inadequate dialysis accounts for an increased percentage of patient dropout from CPD therapy. Because of the specific Kt/V and creatinine clearance goals suggested by DOQI, more patients are prescribed a continuous CPD regimen (2).

There has been controversy as to whether overall peritonitis rates differ between CPD patients dialyzed via manual regimens and those dialyzed via continuous cycling regimens (3-5). Furthermore, previous studies have not examined differences in the rate of gram-positive, gram-negative, fungal, or polymicrobial peritonitis for patients using manual or cycler therapy. In this review we found the overall rate of peritonitis to be similar for patients maintained on manual regiment and those continuous-cycling regimens. However, significant differences were noted when individual peritonitis rates were examined. Patients using the Baxter HomeChoice Cycler™ system had a significantly lower rate of Staphylococcus aureus, fungal, and polymicrobial peritonitis than patients using the Baxter UltraBag™. The rate of gram-negative peritonitis was higher in the patients maintained on the Baxter HomeChoice Cycler™ system, but this did not differ statistically from the rate of gram-negative peritonitis for patients using the Baxter UltraBag™. This finding is of particular importance because gram-negative peritonitis has been shown to have a more severe outcome in terms of morbidity, mortality, and patient dropout from CPD therapy (9,10).

The reasons for these differences in infection rates are not clear. Both groups of patients in this review were similar in age, race, gender, presence of diabetes, and other comorbid disease. Both groups of patients were maintained on the Baxter HomeChoice Cycler™ and the Baxter UltraBag™ for similar lengths of time.

The Baxter UltraBag™ has been shown in one study to significantly decrease the rate of peritonitis when compared to continuous-cycling peritoneal dialysis (6). This difference occurred chiefly because of a reduction in staphylococcal infections (6). Some have argued that the improved rate was a result of the elimination of the spiking procedure with the Baxter UltraBag™ and a consequent decrease in touch contamination. Yet, the operation of the Baxter HomeChoice Cycler™ system involves patients manually spiking the dialysis solution bags.

We regard these results as preliminary. Clearly, a larger, prospective, multicenter study comparing peritonitis rates of patients using manual or cycler peritoneal dialysis therapy is warranted. Particular attention needs to be paid to the different rates of gram-positive, gram-negative, fungal, and polymicrobial peritonitis.

References

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  7. Troidle L, Kliger AS, Gorban-Brennan N, et al. Nine episodes of CPD-associated peritonitis with vancomycin resistant enterococci. Kidney Int 1996; 50:136872.
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  9. Troidle L, GorbanBrennan N, Kliger AS, et al. Outcomes of gram-positive and gram-negative peritonitis. Perit Dial Int 1997; 17(Suppl 1):S40.
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Corresponding author:
Laura K. Troidle, New Haven CPD Partnership, Renal Research Institute, 136 Sherman Avenue, New Haven, CT 06511, USA.