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Part 3: Clinical Experiences |
Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor–UCLA, Torrance, and David Geffen School of Medicine at UCLA, Los Angeles, California, U.S.A.
Correspondence to: R. Mehrotra, 1124 W. Carson Street, Torrance, California 90502 U.S.A. rmehrotra{at}labiomed.org
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ABSTRACT |
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 TOP ABSTRACT RESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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In many parts of the world, a progressively larger proportion of chronic
peritoneal dialysis (PD) patients are being treated with automated PD (APD).
Increasingly, the decision to use APD is being dictated by patient and
physician preference rather than being based on medical considerations. It is
important to determine if the PD modality has any effect on long-term patient
outcomes. Studies examining the effects of APD on residual renal function have
been inconsistent, and the effect of cycler use on native renal clearances, if
any, is small and probably not clinically significant. The preponderance of
the evidence suggests that peritonitis rates are somewhat lower in APD
patients than in patients treated with continuous ambulatory PD (CAPD). Two of
three recent studies indicated that the risk for transfer to maintenance
hemodialysis may be lower in APD patients, particularly in the early period
after starting chronic PD. However, the risk for death in patients treated
with CAPD and APD appears to be similar in most of the studies that have
looked at that question. In summary, the long-term outcomes of CAPD and APD
appear to be similar, and patient and physician preference are likely to
increase the utilization of APD in many parts of the world.
KEY WORDS: CAPD; automated peritoneal dialysis; end-stage renal disease; residual renal function; peritonitis; mortality.
Since the introduction of volumetric cyclers, automated peritoneal dialysis (APD) is increasingly being used in many parts of the world (1). In the United States, estimates suggest that almost two thirds of prevalent chronic peritoneal dialysis (PD) patients are now being treated with APD. The greater use of APD has not been driven by medical considerations, but rather largely by the flexibility offered by the use of the cyclers in designing prescriptions that match a patient's lifestyle. In light of these changes in the use of various PD modalities, it is important to understand whether APD offers at least similar, if not better, outcomes than those seen with continuous ambulatory PD (CAPD).
The comparison of outcomes between the two PD modalities is complicated by the fact that APD prescriptions are substantially more variable than are CAPD prescriptions. In most parts of the world, a patient treated with CAPD performs 4 exchanges daily with a fill volume ranging from 1.5 L to 3.0 L. However, the flexibility in designing prescriptions with APD means that, in published studies, subjects treated with the APD modality are receiving significantly more heterogeneous therapy. In addition to fill volume, prescriptions can vary in the number of hours of cycling, the number of nighttime exchanges, and the length of time that patient carries dialysate during the day (from "dry" to "partially dry" to "wet"). Most of the published studies have necessarily assumed that this heterogeneity in APD prescriptions and also in the peritoneal transport rates of the subjects do not affect the relative merits or demerits of the APD therapy as compared with CAPD. This situation should be kept in mind when evaluating the outcomes discussed in the remainder of this review. Also, discussion here will be limited to studies that have compared two intermediate outcomes—residual renal function (RRF) and peritonitis rate—and two hard outcomes—technique survival and mortality—in CAPD and APD patients.
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RESIDUAL RENAL FUNCTION |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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Although no definitive conclusions can be drawn, the current data veer us toward the null hypothesis: that there is probably no difference in the rate of loss of RRF between CAPD and APD patients. Put differently, the data are insufficient to deny patients the choice of APD based simply on concerns related to RRF. Furthermore, RRF should be closely monitored and, provided no contraindications are present, all patients should be treated with blockers of the angiotensin–aldosterone system.
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PERITONITIS RATES |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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However, care should be exercised in extrapolating these findings to current-day PD practice. The substantial advances made in connectology have been such that many CAPD patients are now treated with twin-bag systems. However, if the center does not use connection-assist devices, many APD patients have to manually spike their dialysate bags. Indeed, a recent analysis from the United States Renal Data System showed that the risk for peritonitis was slightly higher in APD than in CAPD patients (15).
The published body of data therefore seems to suggest that APD patients may experience lower peritonitis rates than CAPD patients do; however, the magnitude of the advantage may depend on local practices. Use of connection-assist devices to spike the cycler bags is probably important to maintain this advantage in favor of APD. Nevertheless, use of CAPD twin-bag systems and of exit-site antibiotic prophylaxis are far more important in lowering peritonitis rates in a PD program than is a greater use of APD.
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TECHNIQUE SUCCESS |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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Three observational studies have compared the technique success of CAPD and APD patients. Two of these (one each from the United States and Mexico) have shown that patients treated with APD are less likely to transfer to maintenance hemodialysis than are patients treated with CAPD (17,18). However, an analysis from the Australia and New Zealand registry was unable to demonstrate any difference in technique success between CAPD and APD patients (19).
The largest study to date on this subject examined 40 869 patients who used supplies from Baxter Healthcare in the United States during 2000–2003 (17). In this cohort, patients treated with APD had a lower incidence of transfer to maintenance hemodialysis for a variety of reasons: As compared with patients treated with CAPD, they had a lower chance of transfer secondary to infection, catheter problems, adequacy considerations, other medical reasons, or psychosocial causes (17). However, the advantage of higher technique success with APD was limited to the first year of therapy; in the second year, no difference was observed in the rates of transfer to maintenance hemodialysis from among either CAPD or APD patients.
Thus, the evidence to date suggests that a greater use of APD may lower the number of PD patients that transfer to maintenance hemodialysis early during the course of renal replacement therapy.
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MORTALITY |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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To date, four observational studies have examined the differences in survival among patients treated with CAPD and APD. The three largest studies have been unable to show any difference in the risk for death among patients treated with these two PD modalities (17–20). However, the results of these studies may have been complicated by the heterogeneity of the patients enrolled. A meta-analysis of studies that have looked at the relationship between peritoneal transport rate and the risk for death among PD patients indicates that APD abrogates the higher risk for death seen among high transporters (21). Thus, the studies do not exclude the fact that APD, as compared with CAPD, may be associated with a survival advantage in high transporters.
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SUMMARY |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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TOPABSTRACTRESIDUAL RENAL FUNCTIONPERITONITIS RATESTECHNIQUE SUCCESSMORTALITYSUMMARYREFERENCES |
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This article has been cited by other articles:
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  D. W. Johnson, C. M. Hawley, S. P. McDonald, F. G. Brown, J. B. Rosman, K. J. Wiggins, K. M. Bannister, and S. V. Badve Superior survival of high transporters treated with automated versus continuous ambulatory peritoneal dialysis Nephrol. Dial. Transplant., February 1, 2010; (2010): gfp780v3 - gfp780. [Abstract] [Full Text] [PDF]
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