Multicenter Study of Change in Dialysis Therapy-Maintenance Hemodialysis to Continuous Ambulatory Peritoneal Dialysis

Multicenter Study of Change in Dialysis Therapy-Maintenance Hemodialysis to Continuous Ambulatory Peritoneal Dialysis Satwant Singh, MD, FACP, Jackson Yium, MD, Edward Macon, MD, Eugene Clark, MD, David Schaffer, and Paul Teschan, MD (Editor's Note: Editorial review was performed by Dr John Curtis in Birmingham) • Serial prospective observations were made on 40 patients with end-stage renal failure who transferred voluntarily from long-term maintenance hemodialysis (MHO) to continuous ambulatory peritoneal dialysis (CAPO). Adequate data were available through 6 months on CAPO in 26 participants, whereas 20 completed the study (1 year on CAPO). There were 12 (30%) treatment failures, including two deaths. Standard CAPO (four 2-L exchanges per day) proved to be inadequate therapy in large, young males with low total urea clearances (Ktu) on MHO. There was a large variation in Ktu within MHO and CAPO therapies that employed apparently similar or identical dialysis prescriptions; this underscores the need to quantify dialysis by a measure such as Ktu. Hematocrit, white blood cell (WBe) and platelet counts, and serum bicarbonate levels were significantly higher, whereas blood urea nitrogen (BUN) and serum potassium levels were significantly lower on CAPO than on MHO. While body weight, blood pressure, bone disease, parathyroid hormone (PTH) levels, and lipid profile did not change significantly, nutritional indices tended to decline with time on CAPO. Urea generation rate (Gu) decreased significantly after transfer to CAPO and correlated with Ktu regardless of treatment modality. Central nervous system (CNS) function reflecting uremic symptomatology and as indexed by average quantified electroencephalogram (EEG) discriminant scores did not change significantly. Hospitalization rates and stays were similar during equal time intervals on both therapies. Sufficiently diverse responses followed the MHO to CAPO therapy change to warrant more extended observations on larger numbers of patients. © 1992 by the National Kidney Foundation, Inc. INDEX WORDS: Anthropometrics; continuous ambulatory peritoneal dialysis; comparison; electroencephalographyquantitative; hemodialysis; hospitalization; peritoneal dialysis; nutrition; urea kinetics.

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ONTINUOUS AMBULATORY peritoneal dialysis (CAPO) has gained considerable popularity and has been proclaimed as a viable alternative to maintenance hemodialysis (MHO) for the management of end-stage renal disease (ESRO).1,2 However, these claims have largely been based on uncontrolled subjective clinical observations and laboratory measurements. Recently, some of our patients transferred voluntarily from MHO to CAPO. We used this opportunity to measure several outcomes prospec-

From the Department ofMedicine, University ofCincinnati Medica/Center and Veterans Administration Medical Center, Cincinnati, OH; Dialysis Clinics, Inc., Chattanooga, TN, Atlanta, GA, Albany, GA, and Nashville, TN; and the Department ofMedicine Vanderbilt University, School ofMedicine, Nashville, TN. Supported in part by Dialysis Clinics, Inc, Nashville, TN. Presented in part at the IV Congress of the International Society for Peritoneal Dialysis, Venice, Italy, June 29-July 2, 1987. Address reprint requests to Satwant Singh, MD, FACP, VA Medical Center, Nephrology Section 111/H, 3200 Vine St, Cincinnati, OH 45220. © 1992 by the National Kidney Foundation, Inc. 0272-6386/92/1903-0005$3.00/0 246

tively. The aim of the study was to make an objective comparison between MHO and CAPO. MATERIAL AND METHODS This study population was drawn from five dialysis clinics located in the midwestern and southern United States. All patients with ESRD of either sex, ages 16 or above, who were clinically stable on MHD for 3 months or more were eligible for inclusion. Exclusion criteria included disseminated or advancing malignancy, pregnancy, sufficiently limited intelligence to preclude cooperation in the study, seizure disorder, known intracranial disease, or any significant symptomatic illness. The protocol was approved by the respective institutional review boards and informed consent was obtained from all participants. The study design consisted of baseline measurements and definition of clinical status during the final 3 months of treatment by means of home or in-center MHD (therapy I), followed by periodic repetition of the same measurements for 12 months after transfer to CAPD (therapy II). Hemodialysis therapy was administered for 12 to 15 hours per week (total urea clearance [Ktu], 1,980 to 4,820; mean, 3,321 mL/wk/ L). The actual amount of dialysis and dialyzers were prescribed according to the preference of the individual nephrologists and were held constant for the duration of the MHD treatment period. During the CAPD phase (therapy II), four daily exchanges of 2 Leach (Ktu, 860 to 2,440; mean, 1,689 mL/wk/ L) were used. The dialysate dextrose content was determined by the needs of individual patients for bulk fluid removal. The weekly Ktu was calculated monthly, as previously described/ as the sum ofresidual renal clearance (mL/wk) and

American Journal of Kidney Diseases, Vol XIX, No 3 (March), 1992: pp 246-251

247

COMPARATIVE EVALUATiON OF MHO AND CAPO

of estimated dialyzer urea clearance (kdu , mL/min X minutes per dialysis session X sessions per week), the sum divided by the patient's urea distribution volume (body water) in liters. The latter was estimated by standard formulae using each patient's body height, weight, and gender. Peritoneal "Kdu" during CAPO was calculated monthly from the sum of urea nitrogen recovered (concentration X volume) of the dialysate bags measured separately. The study population was carefully monitored by such observations as complete physical examinations and repeated, usually monthly, measurements of anthropometrics, rehabilitation class, 4 standard conventional laboratory determinations (predialysis on MHO), urea kinetics, 3 serum immune reactive parathyroid hormone (iPTH) levels, lipid profiles, and serum transferrin levels. The quantitative electroencephalogram (EEG) power spectrum was used as an index of dialysis-responsive encephalopathy as described previously. 5 Increased EEG slowing (deterioration) is indicated by more positive discriminant scores. Protein intake on hemodialysis was prescribed at I g/kg ideal body weight per day, and was increased to 1.2 g/kg/d on CAPO. The results were analyzed using repeated measures analysis of variance adjusted for missing data, post-hoc contrasts, and trends within treatments according to Kirk. 6 If more than 50% of assessments were missing for any period, the data from that period were not analyzed.

RESULTS

Forty patients met initial inclusion-exclusion criteria and were enrolled in the study. The duration on MHD ranged between 3 and 132 months (mean, 47; median, 38 months). Fourteen patients dropped out before 6 months on CAPD and did not contribute to analyzable data. The reasons for withdrawal are detailed in Fig 1. Table 1. Demographic Data

No. of patients Mean age Males Females Diagnosis Glomerulonephritis Nephrosclerosis Other Baseline parameters (on MHO) GFR (mL/min) Ktu (mL/wk/L) BSA(m2) TBW(L)

Entered Study

Included in Analysis

40 49.6 31 9

26 51.5 19 7

14 46.1 12 2

17

11 12

8 8 10

9 3 2

0.57 3,200 1.86 40.5

0.33 3,321 1.81 38.9

1.02 2,976 1.96 43.4

Not Analyzed'

Abbreviations: GFR, glomerular filtration rate; BSA, body surface area; TBW, total body water. • See Fig 1 for reasons for dropping these patients from analysis.

r.;o.

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Fig 1. Outcome in 40 patients admitted to study. "Data not analyzed for MHD-CAPD comparison; ""therapy I data only.

Another six patients dropped out between 6 and 12 months. These included 12 (30%) treatment failures: three catheter failures, seven "inadequate dialysis," and two deaths. Inadequate dialysis was defined by such symptoms as weakness, tiredness, anorexia, nausea, and in one patient, pericarditis; these symptoms were relieved promptly upon return to MHD. The baseline data obtained on MHD were similar in the group that completed at least 6 months on CAPD (n = 26) and the dropouts who did not contribute to analyzable data (n = 14, Table 1). However, as shown in Table 2, significant differences were observed between the paTable 2. Mean Baseline Data Obtained While on MHO in Patients Who Completed 6 or More Months on CAPO and Those Withdrawn From CAPD Due to "Inadequate DialysiS"

Measurement Males(%) Mean age (yr) BSA(m") TBW(L) Ktu (mL/wk/L) Serum potassium (mrnol/L) Serum phosphorus (mrnol/L) (mg/dL)

Completed 6 or More Months (n = 26)

Inadequate Dialysis (n = 7)

P

90 52 1.81 38.9 3,321

73 43.5 2.05 46.6 2,641

0.036 0.007 0.021 <0.022 0.027

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1.77 5.5

2.42 7.5

0.009

SINGH ET AL

248

Table 3. Comparative Data on MHO and on CAPO (Mean ± SE) Measurement

MHO (n = 26)

170 ± 3.6 Kdu, mL/min 3,321 ± 121 Ktu, mL/wk/L 5.1 ± 0.35 Gu, mg/min 0.92 ± 0.08 Gcr, mg/min 1.15 ± 0.24 PCR, g/kg/d 40 ± 0.7 Albumin, gIL 0.24 ± .007 Hematocrit 24 ± 0.7 (vol%) 5.9 ± 0.23 WBC x 10·/L 5.9 ± 0.23 (X 10"/mm") 209 ± 12.6 Platelets X 1O'/L 209 ± 12.6 (X 103/mm3 ) 138 ± 0.7 Sodium, mmolfL 4.9 ± 0.1 Potassium, mmolfL 20 ± 1 Total CO2 , mmolfL 26.4 ± 1 BUN, mmol/L 74 ± 3 (mg/dL) Total cholesterol, mmol/L 4.94 ± 0.23 191 ± 9 (mg/dL) 2.7 ± 0.23 LOL-cholesterol, mmol/L 106 ± 9 (mg/dL)

CAPO (n = 26) 6.14 ± 1,689 ± 4.2 ± 0.77 ± 0.8 ± 36.6 ± 0.27 ± 27 ± 6.8 ± 6.8 ± 249 ± 249 ± 140 ± 4.2 ± 23.4 ± 23.4 ± 66 ± 5.6 ± 218 ± 3.82 ± 148 ±

0.16 57 0.2 0.05 0.22 0.6 0.012 1.2 0.33 0.33 20 20 0.4 0.1 0.6 0.8 2.4 0.19 7 0.47 18

p <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.007 <0.001 0.017

NOTE. MHO values represent the mean of two to three values on hemodialysis; CAPO values are the mean of all values on CAPO. Abbreviation: LOL, low-density lipoprotein.

tients who completed 6 or more months on CAPO (n = 26) and those withdrawn from study for inadequate dialysis (n = 7). As expected, dialyzer (Kdu)* and total urea clearance (Ktu) decreased markedly after transfer from MHO to CAPO (Table 3, Fig 2). A noteworthy finding was the large variation in Ktu within MHO (range, 1,980 to 4,820 mL/wk/L) and CAPO (range, 860 to 2,440 mL/wk/L) therapies, which used apparently similar "prescribed amounts" of dialysis in therapy I (MHO) and identical prescriptions in all patients in therapy II (ie, CAPO using four daily 2-L exchanges). Protein intake by dietetic history on two therapies was not different. However, protein catabolic rate (PCR) calculated from urea kinetics decreased significantly after transfer to CAPO. Urea (Gu) and creatinine (Gcr) generation rates also decreased significantly following institution of CAPO. Serum transferrin did not change, whereas serum albumin decreased significantly, but within its normal limits after transfer to

* The designation "Kdu" in therapy II is understood to refer to peritoneal urea clearance.

CAPO. Mean anthropometric measurements were not different between the two therapies, but did manifest a significant downtrend as time progressed on CAPO. Hematocrit, hemoglobin, white blood cell (WBC) counts, and platelet counts were significantly higher on CAPO than on MHO and also showed a significant uptrend during CAPO therapy. Average blood urea nitrogen (BUN) concentrations decreased significantly after change of therapy, but increased progressively with time on CAPO. Serum creatinine, on the other hand, did not change significantly across two therapies, but like the BUN did show a significant uptrend during CAPO. Serum bicarbonate levels increased, whereas potassium decreased significantly after change of dialytic modality. Among the objective measures of the central nervous system (CNS) functions that index symptomatic responses to renal failure and dialysis, the mean discriminant EEG scores for resting and arousal states as scored by computer, as well as visually, did not register statistically significant differences between the two therapies;

KTU

ml/wk/L

6000

5000

00 I 2 3 I 2 3 4 5 6 9 LTherapyII Therapy 1I------' Months Fig 2. Range and individual values of weekly Ktu in therapies I and II.

COMPARATIVE EVALUATION OF MHO AND CAPO

nor did any significant trends develop with time on CAPO. However, resting EEG scores deteriorated (increased) nearly twice as often as they improved following change in therapy in the 20 patients in whom resting EEG scores were available in both therapies. There was no correlation between absolute Ktu and EEG scores, either within or across the two therapies; nor was a correlation noted between the degree of change in Ktu and EEG scores after therapy change. Morbidity as measured by the number ofhospitalizations and total inpatient days was similar on the two treatment modalities (Table 4). Peritonitis accounted for 29% of total hospital stay, but only 0.78% of total days on CAPO. Altogether, there were 29 episodes of peritonitis or one episode every 10.27 patient-months. Ten patients (38%) remained free of peritonitis during the study period. Only three patients had more than two episodes, but between them, they accounted for 38% of all peritonitis episodes. DISCUSSION

Forty patients enrolled in the present study; half of them were able to finish the protocol. Those failing to complete the study included 12 (30%) treatment failures over 1 year. In the only other prospective comparison of two modalities, Rubin et al? reported a 39% failure rate in 56 patients on CAPO for an average follow-up of 0.7 years, as compared with 16% in 37 patients on home MHO for an average of 1.2 years. In retrospective comparisons of CAPO and MHO I-year modality failure rates for CAPO were 12.5%8 and 29%.9 It is noteworthy that none of the treatment failures in the present series were attributable to recurrent peritonitis, which figures heavily in other reports. lO,ll As compared with 26 patients who completed at least 6 months on CAPO, the failed group was younger, all but one were males, and they had a greater body surface area and total body water and therefore a lower Ktu on therapy I (MHO). Thus, it appears that "standard" CAPO (four 2L daily exchanges) represents suboptimal therapy for large, young males. Lower Ktu values on therapy I in the failed group suggest that these patients were possibly receiving barely adequate amounts of hemodialysis. A further decline in Ktu after transfer to CAPO led to clinical and chemical decompensation.

249 Table 4. Hospitalization Data on MHO and CAPO in 26 P~tients Who Completed 6 or More Months on CAPO MHO

CAPO

Days at risk' 9,090 8,940 No. of hospitalizations 30 31 Average stay per hospitalization (d) 6.8 7.9 Total inpatient days 205 245 2.74 Inpatient days as % of days at risk 2.25 Dialysis-related inpatient days 133 (65) 133 (54) 51 (25) Vascular access-related inpatient 13 (5) days Peritoneal access-related inpatient 12 (5) days Peritonitis-related inpatient days 70 (29) Note. Number in parentheses are percent of total inpatient days. , Observation period was less than 1 year for some of the partiCipants.

The lower Kdu and Ktu on CAPO of course reflect the lower rates of urea clearance across the peritoneum. We observed large variations in Ktu in patients receiving apparently similar (MHO) or identical (CAPO) dialysis prescriptions. This underscores the heterogeniety of apparently similar dialysis prescriptions and the desirability of tailoring dialysis to individual needs. Furthermore, it highlights the difficulties in interpreting the studies that fail to quantify dialysis by a measure like Ktu. KTIV, liters of dialyzer urea clearance per liter of total body water per hemodialysis session, is an alternate measure to quantify dialysis. However, while KTIV expresses the normalized, within-session dialyzer urea clearance, it ignores the urea removal by residual renal function. 3 Thus, Ktu is a more comprehensive measure of urea removal than KT/V. PCR, which should correlate well with the dietary protein intake (OPI) estimated by patients and dietitian in steady-state conditions, decreased significantly after transfer to CAPO. This is consistent with the declining trend in anthropometric measurements and serum albumin levels and provides, in part, an explanation for the lower BUN levels on CAPO. In tum, these findings do not indicate a non-steady, anabolic state that is otherwise implied by OPI > PCR. Instead, the decreased protein consumption may represent adaptation to the significant decline in Ktu that occurred after transfer to CAPO, a relationship that has been reported by others. 12- 15

250 7.0

SINGH ET AL Gu mg/min

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3000

3500

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Fig 3. Changes in net Gu with changes in Ktu in four series: 0, 33% reduction in Ktu on MHO'; 0, 50% reduction in Ktu by modality change MHO (I) to CAPO (II), present series; _, 50% increase in Ktu by modality change CAPO/IPO (I) to MHO (11)*; ., 25% reduction in Ktu on MHOt. *These represent patients who exited present study due to "inadequate dialysis" and were returned to MHO. tUnpublished observations in another cohort in this multicenter study in which MHO was reduced by 25% (mean Ktu decreased from 3,743 to 2,868 mL/wkl L) and the participants were studied on a protocol identical to that of the present study.

Decrease in Gu might be an adaptation to a reduction in Ktu and is seen consistently whether Ktu was reduced within the same therapy (ie, decreasing amount of hemodialysis) or by modality change (ie, MHO to CAPO). Interestingly, Gu increased when Ktu was increased by transferring patients from intermittent peritoneal dialysis (IPO)fCAPO to MHOt (Fig 3). Thus, Gu correlated directly with Ktu within or across the different dialytic modalities, unlike EEG power spectrum, which responded to the changes in Ktu within the same modality, but not across the modalities (Fig 4). Despite the fact that EEG discriminant scores deteriorated twice as often as they improved as Ktu was reduced with the change to CAPO, mean EEG discriminant scores during the two therapies were not different. Similarly, the National Cooperative Oialysis Study l6 failed to document a correlation between individual EEG scores and Ktu in hemodialysis patients receiving clinically adequate dialysis. The lack of significant change in the mean EEG scores is quite remarkable since t These represent patients who exited present study due to "inadequate" dialysis and were returned to MHD.

the Ktu decreased by greater than 50% after transfer from MHO to CAPO, whereas, as also shown in Fig 4, reductions in Ktu in patients on MHO have been reported to cause a significant deterioration in EEG scores. 3 •16 This response to a decrease in Ktu within the same modality (ie, MHO) is obviously different from the response to a decrease in Ktu associated with a change in modality (ie, MHO to CAPO), as in the present study (Fig 4). The reasons for this difference are not apparent, but raise speculations concerning the wider spectrum of dialyzed molecular species in the course of CAPO than may be the case in MHO. However, these EEG findings support the clinical impression of the adequacy of CAPO as a dialysis modality in most of these patients in terms of suppression and control of the clinical uremic illness. Morbidity, as measured by frequency and duration of hospitalization over a I-year period on each modality, was similar on the two therapies. Contrary to our findings, Rubin et al 7 noted longer hospital stays on CAPO (7.5 ± 0.01% of days at risk) than on home MHO (2.8 ± 0.01 %). In an uncontrolled comparison, Kurtz and Johnson 17 reported higher hospitalization rates in CAPO patients than in those on MHO, largely due to peritonitis. Technique and patient survival in the two groups were similar. Morbidity and mortality were similar for in-center MHO and CAPO in the report by Capelli et al. IS In a retrospective comparison, Frascinos noted higher hospitalization rates (2.8 v 0.75 per patient per -0,2

EEG Disc Score (resting)

n

o

"-4 Tachon,.'ol,o.oio J,I983.C·MHD-E·MHO ...... MCS.I......10- D ... HO O-~MCS. I. · .. HD-n ·CAPO

-0.2

'000

'500

2000

2500

:lOOO

3500

4000

KTU,ml/wk/L

Fig 4. Changes in mean quantitative EEG discriminant scores with changes in Ktu in three series: ., 25% reduction in Ktu on MHOtj 0, 33% reduction in Ktu on MHOS; 0, 50% reduction in Ktu by modality change MHO (I) to CAPO (II)-present series. tSee note in Fig 3 for definition of this group.

COMPARATIVE EVALUATION OF MHO AND CAPO

year) and more inpatient days (23.6 v 5.7 per patient per year) on CAPO than on MHO. In contrast, in a comparison of the two modalities in diabetics, in-hospital days on MHO were twice those on CAPO. 9 The reasons for these differences are not clear, but may relate to the differences in patient populations on various treatment modalities. We conclude that "standard" CAPO (four 2L exchanges per day) provides inadequate dialysis for large, young males with low Ktu on MHO. While the remaining patients' symptomatic states were stable, as also indexed by the EEG power

251

spectrum, and while no statistically significant differences were observed in a large number of other measurements over a I-year period, the tendency of nutritional indices to decline with time on CAPO urges caution. The wide variation in Ktu in the face of apparently similar/identical hemodialysis and CAPO prescriptions suggests the need for quantification of dialysis by an index such as Ktu for optimal interpretation of dialysisrelated outcomes in this population. ACKNOWLEDGMENT We thank Ellen Starr, Jaqueline Lusk, and Ellen Blythe for secretarial assistance.

REFERENCES 1. Moncrief JW, Nolph KD, Rubin J, et al: Additional experience with continuous ambulatory peritoneal dialysis (CAPD). Trans Am Soc ArtifIntern Organs 24:476-83, 1978 2. Khanna R, Oreopoulos 00, Dombros N, et al: Continuous ambulatory peritoneal dialysis (CAPD) after three years: Still a promising treatment. Perit Dial Bull 1:24-34, 1981 3. Teschan PE, Ginn HE, Bourne JR, et al: A prospective study ofreduced dialysis. ASAIO J 6:108-122, 1983 4. Brunner FP, Brynger H, ChantlerC, et al: Combined report on regular dialysis and transplantation in Europe, IX, 1978. Proc Eur Dial Transplant Assoc 16:2-73, 1979 5. Teschan PE, Ginn HE, Bourne JR, et al: Quantitative indices of clinical uremia. Kidney Int 15:676-697, 1979 6. Kirk R: Experimental Design: Procedures for the Behavioral Sciences. Belmont, CA, Brooks/Cole, 1968 7. Rubin J, Barnes T, Burns P, et al: Comparison of home hemodialysis to continuous ambulatory peritoneal dialysis. Kidney Int 23:51-56, 1983 8. Frascino JA: A comparison of self care dialysis modalities-Home hemodialysis, continuous ambulatory peritoneal dialysis, in-center self-care hemodialysis. Dial Transplant 14: 13-16, 1985 9. Mejia G, Zimmerman SW: Comparison of continuous ambulatory peritoneal dialysis and hemodialysis for diabetics. Perit Dial Bull 5:7-11, 1985 10. Report of the National CAPD Registry of The National Institutes of Health. Bethesda, MD, NIH, January 1985

11. Williams C, University of Toronto Collaborative Dialysis Group: CAPD in Toronto-An overview. Perit Dial Bull 3:S6-8, 1983 (suppl) 12. Gotch FA: A quantitative evaluation of small and middle molecule toxicity in therapy of uremia. Dial Transplant 9:183-188, 1980 13. Ginn HE, Teschan PE, Bourne JR, et al: Neurobehavioral and clinical responses to hemodialysis. Trans Am Soc ArtifIntern Organs 24:376-380, 1978 14. Lowrie EG, Steinberg SM, Gallen MA, et al: Factors in the dialysis regimen which contribute to alterations in the abnormalities of uremia. Kidney Int 10:409-422, 1976 15. Johnson WJ, Schniepp BJ: Comparison of urea kinetic modelling with other approaches to dialysis prescription. Dial Transplant 10:280-284, 1981 16. Bourne JR, Hamel B, Giese D, et al: The EEG analysis system of the National Cooperative Dialysis Study. IEEE Trans Biomed Engr BME-27:656-664, 1980 17. Kurtz SB, Johnson WJ: A four year comparison of continuous ambulatory peritoneal dialysis and home hemodialysis: A preliminary report. Mayo Clin Proc 59:659-662, 1984 18. Capelli JP, Camiscioli TC, Vallorani RD, et al: Comparative analysis of survival on home hemodialysis, in-center hemodialysis and chronic peritoneal dialysis (CAPD-IPD) therapies. Dial Transplant 14:38-52, 1985