Lack of correlation between urea kinetic indices and clinical outcomes in CAPD patients

Is Total Creatinine Clearance a Good Predictor of Clinical Outcomes in Continuous Ambulatory Peritoneal Dialysis?

The measurement of the adequacy of dialysis in continuous ambulatory peritoneal dialysis (CAPD) is controversial. The use of weekly total creatinine clearance (TCC) has been recommended, but not validated. We analyzed data from our recent urea kinetics in a CAPD study to investigate TCC and its relationship to patient outcomes. TCC was measured over 24 hours by adding residual renal and peritoneal creatinine clearance, correcting for 1.73 m2 surface area and converting to a weekly value. Seventy-six patients had 218 measurements, on starting CAPD and then at 6–month intervals, with mean follow-up of 20 months (range 1–57 months). The mean TCC was 73.62±32.11 L/week. Due mainly to the loss of residual renal function, the TCC decreased with time (r=-0.40, p<0.0001), from 88.65 L/week initially to 66.11 at one year, 59.84 at two years, and 50.47 at three years. Dialysate-to-plasma creatinine concentration ratios (DIP Cr) increased with time (r=0.28, p<0.0001) from 0.62 initially to 0.66 at one year and 0.73 at two years. The TCC correlated significantly with serum levels of creatinine (r=-0.46, p<0.0001), urea (r=-0.21, p<0.001), potassium (r=-0.14, p<0.05), phosphate (r=-0.25, p<0.001), and hemoglobin (r=0.16, p<0.01), but not with serum albumin or with clinical outcomes including technique failure, hospital days, transfusions, peritonitis rate, nerve conduction velocity, or subjective indices of well-being, except for a weak correlation with the fatigue index (r=0.19, p<0.05). However, of 13 deaths 6 occurred in patients with TCC under 48 L/week (p<0.05). There is little evidence of a proportionality relationship between TCC and clinical outcomes in CAPD, but a TCC of 48 L/week may usefully define a lower limit below which excess mortality occurs.

Urea Kinetics and Clinical Features of Long Term Continuous Ambulatory Peritoneal Dialysis Patients

The purpose of this study was to assess urea kinetic modeling (UKM) as a marker for adequate dialysis in continuous ambulatory peritoneal dialysis (CAPD) patients. UKM was conducted on 19 anuric patients on CAPD for more than 2 years. Serum β2-microglobulin (β2M) was also measured as a marker of large molecular weight substances. Patient clinical conditions were evaluated by the doctors and patients as well. The patients were thus asked to complete a questionnaire on uremic symptoms an d daily activities. A comparison was made in urea kinetics and biochemical parameters based on clinical assessment scores. Patient and doctor scores showed a close correlation (r=0.69) and were correlated to days of hospitalization. The peritonitis rate was significantly higher in the “not doing well” group. No correlation could be found between indexes of UKM or β2M plasma level and clinical assessment scores. A signlficant correlation was noted between serum albumin concentration and doctor scores (r=0.52). It was thus concluded that UKM was not a good indicator of the adequacy of dialysis for CAPD, but serum albumin was. However, clinical symptoms and signs are more important than biochemical parameters for assessing adequacy.

Estimation of Total Creatinine Clearance is Unreliable in Children on Peritoneal Dialysis

Objective

To test the reliability of creatinine clearance in children on peritoneal dialysis (PD).

Design

Longitudinal, case-controlled.

Setting

Routine clinic visits at the pediatric dialysis unit of the Universitätskinderklinik of Vienna. Patients: Eleven children (2 -13 years, 10 -55 kg) with end-stage renal disease on PD.

Interventions

Creatinine clearance (CCr) was determined by measuring creatinine excretion (ECr) over 24 hours in both dialysate and urine. Each child had three to five separate measurements of their CCr. At the same time we also calculated the schwartz formula clearance from the patient's height and serum creatinine, using a modified correlate.

Main Outcome Measures

Reliability of CCr was assessed by two approaches. First, we compared each serial measurement with the mean value for each patient and thereby assessed the “intramethodical” variability. Second, we compared each CCr with the simultaneous formula clearance and assessed the “intermethodical” disagreement.

Results

Twenty-seven percent of the measurements of CCr were classified as unreliable based on a comparison with the mean value for each patient. Reliability was closely correlated with residual renal function (p < 0.01); only 12% of the measurements in the an uric patients were classified as unreliable (vs 31% in the patients with residual renal function). The simultaneous formula clearance was less variable than the CCr. The formula clearance had a sensitivity of 93% and a specificity of 60% for detecting unreliable values of CCr.

Conclusion

Estimation of total CCr is unreliable in pediatric patients on PD. A simultaneous formula clearance can be used to detect which values are unreliable.

Survival of Capd Patients in a Center Using Three Two-Liter Exchanges as Standard Regime

Our objectives were to study long-term patient survival and dialysis adequacy of continuous ambulatory peritoneal dialysis (CAPD) patients treated with a standard regime of three 2-L daily exchanges. It was a retrospective analysis of patient survival and cross-sectional analysis of adequacy of dialysis. The setting was a dialysis unit in a tertiary referral center of a teaching hospital. All patients (n = 507) accepted into the CAPD program from 1983 to June 1994, were analyzed for survival. Adequacy of dialysis was analyzed in all existing patients in 1993 to 1994. The overall patient survival was 93%, 71%, and 57% at one, three, and five years, respectively. The three-year survival rate was 40% for diabetics and 78% for nondiabetics. It was 86%, 85%, 64%, and 43% for patients aged <35, 35 -50, 50 -65, and over 65 years, respectively. The mean weekly KT/V of 201 existing CAPD patients was 1.76, and creatinine clearance was 57 Uweek/1.73 m2. KT/V by dialysis was only 1.57. The age and disease-adjusted survival in our center was comparable to centers that used standard four 2-L exchange regimes, despite a substantially lower mean KT/V and creatinine clearance (CrCI).

Relationships between Dialysis Quantification and Normalized Protein Catabolic Rate in Peritoneal Dialysis

Normalized protein catabolic rates (NPCR) and urea clearances (Kt/V urea) correlate significantly in peritoneal dialysis suggesting that the adequacy of dietary protein Intake and dialysis dose are Interrelated. However, both of these calculated parameters are mathematical functions of the normalized urea appearance rate (GN). NPCR, GN, Kt/V urea, total creatinine clearance, residual renal clearance, and peritoneal urea and creatinine clearances were determined In 29 stable peritoneal dialysis patients with no history of recent peritonitis or other catabolic illness. Multiple linear regression analysis showed that NPCR correlated closely with both GN (r=0.96; p<0.0001) and Kt/V urea (r=0.77; p<0.0001), whereas GN also correlated with Kt/V urea (r=0.66; p<0.0001). Total weekly creatinine clearances rather than Kt/V urea should be utilized in peritoneal dialysis to permit independent estimations of dialysis dose and NPCR, since both Kt/V and NPCR are related closely to GN. Total weekly creatinine clearances correlated with NPCR (r=0.59; p<0.0002), which supports the hypothesis that dietary protein Intake is dependent on the delivered dialysis dose.

Ysis Prescription and Peritoneal Membrane Transport Characteristics on Nutritional Status

These data suggest that dialysis dose is one of the major determinants of protein and energy intake in PD patients and that higher doses of dialysis tend to improve outcome. The data also suggest that with a long time on PD the peritoneal membrane probably has some underlying histological changes that preclude it from optimally responding to injury and may predispose it to irreversible damage. A possible early finding in this case is an increase in peritoneal transport in patients whose transport was initially stable. Peritoneal membrane transport properties are an important determinant of not only dialysis dose, but also nutritional status via both direct and indirect means. It is therefore important to identify the individual patient's peritoneal membrane transport characteristics. These transport characteristics may change over time. High transporters on CAPD represent a unique challenge. They have ultrafiltration problems and a tendency toward protein malnutrition presumably due to increased dialysate protein losses while on CAPD. One must consider that malnutrition in a rapid transporter may be due to the fact that the patient is on the wrong PD therapy. A change to NIPD may rectify some of the biochemical parameters, but these patients may not always improve. Reasons for this occasional lack of improvement are multifactorial, but emphasize our need to look at each patient as an individual and not focus only on laboratory parameters.

Answers to All Your Questions about Peritoneal Urea Clearance and Nutrit Ion in Capd Patients

In summary, SA and a number of other indices related to nutritional status have been identified as being strongly predictive of outcome in CAPD patients. Evidence connecting these indices to KTN urea, or even to protein intake, remains limited, however. Increased dialytic dose may well increase protein intake, but neither of these parameters have been shown prospectively to raise SA, total body nitrogen, or SGA status on a consistent basis. Studies addressing this issue, however, have been few and small, and more data are required. For now, we will likely continue to deal with malnutrition by attempting to raise small solute clearance and protein intake, but we should be aware that such measures will frequently be unsuccessful, and we must pay attention to other factors, particularly comorbidity.

It is clear from this review that there are many unanswered questions relating to this topic and that, in particular, the effect of prospective increases in the dialytic dose needs to be further elucidated.

Albumin and Amino Acid Levels as Markers of Adequacy in Continuous Ambulatory Peritoneal Dialysis

Similar to previous findings in HD patients, a markedly decreased serum albumin level has been found to be a strong predictor of morbidity and mortality in CAPD patients. However, a slight decrease in serum albumin levels (to about 30 g/L if measured with nephelometry or the bromcresol purple method) does not always seem to reflect impaired nutritional status or to be associated with an increased morbidity or mortality in CAPD patients. A low serum albumin level among CAPD patients is related to dialysate albumin loss, comorbidity, age, and a low dietary protein intake. The possible relation between the dialysis dose (as assessed by small solute clearances) and serum albumin levels among CAPD patients is much less established and needs further study, although serum albumin tends to increase in prospective studies of increased peritoneal dialysis dose.

Although the plasma levels of amino acids seem to be lower in CAPD patients compared to HD patients, this does not reflect the intracellular amino acid pattern in muscle which is less abnormal in CAPD patients, possibly because of the sustained hyperinsulinemia during CAPD, resulting in an in creased intracellular to extracellular gradient. It is at present not established to what extent the amino acid abnormalities are related to the dialysis dose.

Malnourished and hypoalbuminemic CAPD patients should be recommended to increase the protein intake, and if this is not effective, the dialysis dose should be increased. Furthermore, the use of amino acid-based peritoneal dialysis solutions is a promising new tool for the treatment of malnourished CAPD patients and may become an important component of CAPD therapy in the future. On the other hand, if the nutritional status deteriorates in spite of these efforts, the patient should be transferred to hemodialysis if possible.

Solute Clearance Approach to Adequacy of Peritoneal Dialysis

To investigate the effect of dialysis prescription on patient outcome for peritoneal dialysis patients, the relationship between total solute clearance and the relative risk of death has been investigated. Preliminary studies have suggested that more clearance is better and that patient outcome is predicted by total solute clearance. The recently published Canada-U.S.A. (CANUSA) multicenter study, evaluating adequacy of dialysis and nutrition in peritoneal dialysis patients, has further defined this relationship. Although these publications allow us to establish guidelines for the treatment of peritoneal dialysis patients, they also define the limitations of our knowledge and raise new questions.

In this article we review our current knowledge regarding the predicted value of total solute clearance with patient outcome and nutritional status. Furthermore, we attempt to outline a practical approach for optimizing total solute clearance in peritoneal dialysis patients.

Based on a review of the published literature and clinical recommendations, we feel that the minimal target total solute clearance for continuous forms of peritoneal dialysis is a weekly total KTN > 2.0 and/or a weekly total creatinine clearance >60 L/week/1.73 m2. For intermittent therapies, a weekly total KTN > 2.2 and/or a weekly total creatinine clearance >70 L/week/1.73 m2 is recommended.

Quantification of Adequacy of Peritoneal Dialysis

Nineteen patients treated by continuous ambulatory peritoneal dialysis (CAPD) were studied according to clinical outcome parameters: insomnia, asthenia, pruritus, arterial hypertension, anorexia, nausea and/or vomiting, anemia, and rate of hospitalization. Using clinical scores, three groups were defined: poor clinical outcome (P), intermediate (I), and good (G). The quantity of treatment by PD was evaluated monthly with urea kinetic tests (weekly Kt/V, weekly urea clearance/1.73 m2 of body surface area (BSA), index of dialysis by Teehan), and with the weekly creatinine clearance/1.73 m2 of BSA. The metabolic index was analyzed: normalized protein catabolic rate (NPCR), serum albumin (Alb) and prealbumin, and reabsorption of glucose.

There was good correlation between clinical scores and quantity of dialysis. The Alb was lower in group P. Group G was differentiated from group I and from group P by quantification tests and NPCR, with lower levels as follows: weekly Kt/V=2.06, urea clearance 70 L/week/1.73 m2, index of dialysis = 0.87, and creatinine clearance = 60 L/week/1.73 m2.

We conclude that the qualitative clinical approach is not sufficient to predict deleterious signs, and the quantitative approach is predictive of the good clinical outcome and good nutritional status. We think that levels proposed to now are insufficient, and we suggest the following: weekly urea clearance >70 L, weekly Kt/V >2, weekly creatinine clearance >60 L, and index of dialysis >0.85.

Capd Viability: A Long-Term Comparison with Hemodialysis

Objective

To compare the long-term viability of continuous ambulatory peritoneal dialysis (CAPD) to that of hemodialysis (HD).

Design

Retrospective study of patients of our institution starting dialysis between January 1,1981, and December 31, 1993, and surviving for at least 2 months.

Patients

Five hundred and seventy-eight new patients (51.3% on CAPD and 48.6% on HD).

Main Outcomes Studied

Cox -adjusted assessment of patient and technique survival, and of technique success. Differences in results for two successive periods of time.

Results

Patient survival did not differ between CAPD and HD after adjusting for age and comorbidity, and significantly improved in the second part of the follow-up (1987 -1993). Technique failure was significantly higher on CAPD, in which it was inversely related to age. The probability of a patient continuing on the first method of dialysis (“technique success”) was significantly lower on CAPD than on HD, but the difference decreased progressively with age and disappeared in patients ≥75 years.

Conclusion

CAPD is as effective as HD in preserving life in uremic patients in the long-term, and gives better results in the older elderly. In adults, the lower technique success rate may not be a problem for patients with access to a good transplantation program; for others, this drawback must be weighed against the advantages of home treatment.

Prescription and Assessment of Tidal Peritoneal Dialysis Delivery with a Specific Equilibration Test

Objective

To propose a simplified equilibration test specific for tidal peritoneal dialysis (TPD) that will overcome the inconveniences of the measurement of TPD peritoneal solute clearances through whole dialysate collection. This will enable the prediction of peritoneal creatinine and urea clearances, the suitability of patients for TPD, and routine assessment of TPD delivery.

Design

In a prospective study, patients had a standardized TPD run, and dialysate-to-plasma (DIP) ratios for creatinine and urea were calculated at various TPD and peritoneal equilibration test (PET) time points and on total TPD dialysate. Solute clearances were estimated and measured, and correlation coefficients were obtained among all these variables.

Setting

Dialysis unit of a pediatric nephrology department and patients’ homes.

Patients

Eleven pediatric patients with end-stage renal disease in stable clinical conditions treated with TPD.

Interventions

Dialysate and blood sample collections.

Main Outcome Measures

DIP ratios for creatinine and urea at the fifth and seventh TPD exchanges, at 15–,30–,60, and 120-minute PETtimes, and on total TPD dialysate and TPD peritoneal creatinine and urea clearances.

Results

Correlation coefficients between PET -derived and total TPD dialysate-derived DIP ratios, and those between PET -derived and measured creatinine and urea clearances were more significant at the 120-minute PET time point compared with the other PET time points. Best correlations were obtained at the fifth and seventh TPD exchanges. DIP ratios for creatinine and urea of the fifth and seventh TPD exchanges correlated significantly with the DIP ratios calculated from total TPD dialysate. A significant correlation was also found between peritoneal creatinine and urea clearances on total dialysate volume (measured clearances) and those derived from the dialysate collection of the fifth and seventh TPD exchanges (estimated clearances) -that based on the seventh exchange being slightly more significant. Moreover, the estimated clearances derived from the seventh exchange were within 10% of the measured value in 90.9% of patients both for creatinine and urea.

Conclusion

The significant correlation between measured and estimated peritoneal creatinine and urea clearances and the low percentage of underestimates of measured clearances obtained using the seventh TPD exchange-derived indices confirm the accuracy of the DIP ratios for creatinine and urea derived from any exchange after the fifth (preferably the seventh) of a standardized TPD run in estimating peritoneal creatinine and urea clearances. This method could represent a simple and accurate means for prescribing TPD and routinely assessing TPD delivery.

Determining Peritoneal Dialysis Prescriptions by Employing a Patient -Specific Protocol

Objective

To develop a formula that would permit a rapid and simple calculation of required dialysate volume needed to provide a predetermined daily creatinine clearance.

Design

Prospective study of peritoneal dialysis patients followed for 6 months.

Setting

A primary care teaching hospital in New York.

Patients

Twenty-six patients beginning peritoneal dialysis entered and completed the study.

Intervention

By employing each patient's measured peritoneal equilibration test (PET) and a standard clearance formula, a patient-specific treatment protocol (PSP) was calculated. The PET 2-hour DIP croat was used for continuous cycling peritoneal dialysis (CCPD) and the 4hour DIP patients on continuous ambulatory peritcornoeal dialysis (CAPD) to determine a PSP that would provide a minimum of 6 L of creatinine clearance daily.

Main Outcome Measures

Patients were followed for 6 months to assess the ability of this approach of maintaining acceptable levels of blood urea nitrogen, creatinine, albumin, and hematocrit over the 6–month period of observation.

Results

Our study of 26 patients revealed that only 6 patients (23%) could be treated with the standard prescription of 8 L/day on CAPD. The remaining 77% of our patients required 9–13 L/day for CAPD and 12–21 L/day for CCPD. All patients were free of uremic symptoms and demonstrated acceptable biochemical parameters over a 3–6 month period of observation.

Conclusions

A patient-specific protocol utilizing individually derived PET data provides an acceptable and easy to calculate initial treatment prescription for each patient that avoids the necessity for trial and error that has heretofore been employed.

The Removal Index for Evaluation of Dialysis

Objectives

To find an index of adequacy that takes into consideration the effect of the decreasing concentration of urea nitrogen in hemodialysis (HD) and can be used before treatments to quantitate the prescriptions with the same criterion for both HD and continuous ambulatory peritoneal dialysis (CAPD).

Design

The removal index was obtained through mathematical theories and then compared with the urea index (KT/V) values of the sample patients.

Patients

Thirty-two HD and 21 CAPD patients were included. All patients were dialyzed with optimal urea index values and had been stable for at least one year.

Results

The removal index in HD (ξHD) for each dialysis was 0.62±0.07, and the normalized removal index in CAPD (ξCAPD) was 0.59±0.11. There was no statistical significance. This result is consistent with the fact that no difference of morbidity or mortality exists between these two modalities.

Conclusion

After mathematical manipulation, the removal index in HD can be presented in the form of the urea reduction ratio, which is a retrospective measure to estimate the performance of hemodialysis. This study implies that the removal index is able to facilitate the prescriptions for adequate dialysis. The removal index can also be used to explain the reason why the urea index values are always larger in HD than in CAPD.

Volume of Distribution and Fractional Clearance of Urea in Amputees on Continuous Ambulatory Peritoneal Dialysis

Objectives

To demonstrate the effects of amputation on the estimates of urea volume of distribution (V) and KTN urea in continuous ambulatory peritoneal dialysis (CAPD) patients and to present a method for correcting the errors created by the uncorrected anthropometric formulas estimating V.

Design

(1) A mathematical analysis of the error and the correction proposed was performed. (2) Urea kinetic modeling with uncorrected and corrected estimates utilizing both the Watson and the Hume anthropometric formulas was performed in amputees on CAPD.

Setting

Subjects were recruited from four dialysis units in one city: one Veterans Affairs unit, one university-affiliated unit, and two community units.

Patients

Fourteen amputees on CAPD: 12 with unilateralleg amputation and 2 with bilateral leg amputation, at the same length of the leg, were studied.

Interventions

Urea kinetic studies were performed in 24-hour drained dialysate and urine specimens.

Main Outcome Measures

Uncorrected and corrected estimates of V and KTN urea were compared to each other and to the predictions of the mathematical model. Body weights corresponding to uncorrected and correct ed V estimates were compared to the actual body weights.

Results

(1) The mathematical model predicts that uncorrected estimates by the anthropometric formulas will falsely characterize unilateral amputees as leaner than they are and bilateral amputees as more obese than they are. (2) In unilateral amputees studied with the Watson formulas, uncorrected V was 0.546±0.023 L/kg and corrected V was 0.520±0.023 L/kg (p < 0.001). Corresponding weekly KTN urea values were 1.97±0.14 and 2.07±0.14, respectively (p < 0.001). Similar results were obtained with the Humeformulas. In bilateral leg amputees studied with the Watson formulas, uncorrected V was 0.479±0.022 L/kg and corrected V was 0.514±0.023 L/kg. Corresponding KT N estimates were 2.11 ±0.45 and 1.96±0. 14, respectively. The differences were even greater with the Hume formulas. Estimates of body weight calculated from corrected V values were equal to actual weight measurements, whereas those calculated from uncorrected V values were lower than actual body weight measurements in unilateral amputees, and much higher than actual body weight measurements in bilateral amputees.

Conclusion

Uncorrected anthropometric estimates falsely characterize unilateral amputees as leaner than they actually are and bilateral amputees, amputated at the same leg length, as more obese than they actually are. Uncorrected KTN estimates are, therefore, falsely low in unilateral amputees, and falsely high in bilateral amputees. The proposed correction of the anthropometric formulas provides estimates agreeing closely with dietary estimates of body composition. Further studies are needed to define the accuracy of the corrected formulas.

Outcome Studies in Adequacy of Dialysis

The theoretical constructs indicate that, for a 70kg high transport anephric patient, adequate dialysis requires a weekly KtN of 2.0 2.25 (1–5). The prospective cohort studies, with one exception, suggest that better survival requires a weekly KtN >1.89 (7–11). Multivariate analyses confirm the statistical association of patient survival with higher Kt/V(14–17) and with higher CCr (16,17). The use of initial values in one study (15), mean values in two studies (14,16), and time -dependent values in another (17) makes comparison difficult. In general, higher values are associated with better survival and are consistent with the values suggested by theoretical constructs (i.e., KtN 2.0 2.25).

Assessment of Dialysis Dose by Measured Clearance versus Extrapolated Data

Objective

To determine whether estimates of daily dialysis clearance of creatinine and urea, based on data from the 4-hour peritoneal equilibration test, correlate well with daily dialysis clearance measured by 24-hour dialysate collection in chronic ambulatory peritoneal dialysis patients.

Design

Prospective study in which each subject collected all dialysate from a 24-hour period and then immediately thereafter underwent a standard peritoneal equilibration test (PET). Daily clearances of creatinine and urea were calculated from 24-hour dialysate collections by standard methods and then were compared with several estimates of 24-hour clearance based on PET data.

Setting

Single peritoneal dialysis unit of a university teaching hospital.

Patients

Thirty-six stable patients on continuous ambulatory peritoneal dialysis (CAPD).

Main Outcome

The estimated values for daily dialysis clearance both overestimated and underestimated the measured 24-hour clearance. The correlation coefficient between the extrapolations and the actual 24-hour clearances ranged from 0.63–0.68. The range of discordance for daily creatinine clearance was from -2530 mL/dayto +2199 mL/day. For daily urea clearance, the range of discordance was from -21 03 mL/ day to +1940 mL/day. The peritoneal membrane transport characteristics of the individual patient did not predict whether the extrapolation overestimated orunder estimated the measured daily clearance.

Conclusion

Extrapolation of PET data is not a reliable method to estimate the dose of dialysis delivered to the patient. A 24-hour collection of dialysis is necessary for this determination.

Neither Size Nor Weight Predicts Survival in Peritoneal Dialysis Patients

Objective

To determine if patient size or weight at the start of PO influences patient or technique survival.

Design

A prospective cohort study of adult PO patients.

Setting

A university and a Veterans Administration outpatient dialysis unit.

Patients

343 adults patients with 660 years on PO enrolled from 1979 to 1995.

Main Outcome Measures

Patient survival (censoring for transplant, 60 days post -transfer to hemodialysis, and end of study) and technique survival (censoring for death, transplant, or end of the study) for patients as grouped by weight (≤ 64 kg vs. >64 kg or ≤82.7 kg vs. > 82.7 kg) or BSA (≤2.0 m2 vs >2.0 m2).

Results

Patient survival was 86.3% at one year, 77.0% at two years, 65.2% at three years, and 56.9% at 4 years. Technique survival was 84.9% at one year, 77.5% at two years, 63.5% at three years, and 58.3% at four years. The patient and technique survival curves were not significantly different for patients as grouped by weight or BSA. Using Cox proportional hazards model, age, diabetes, peritonitis rate, and albumin at the start of PO were independent predictors of patient survival, but BSA and weight were not. The only predictor of technique survival was the peritonitis rate. Larger patients had higher initial albumins, which may indicate better nutritional status that may offset the risk of underdialysis.

Conclusions

Large patients do as well as smaller patients on PO. Size alone should not preclude patients from PO.

Growth Hormone and Malnutrition in Dialysis Patients

Objective

To review the normal function of the growth hormone (GH) insulin-like growth factor (IGF) axis, how it is altered in end-stage renal failure, how this may contribute to malnutrition in dialysis patients, and how therapy with recombinant human growth hormone (rHuGH) and recombinant human IGF-I (rHuIGF-1)might be used to treat malnutrition in these patients.

Data Sources

Studies in the literature dealing with the GH-IGF endocrine axis and its role in uremic malnutrition.

Study Selection

Eight studies in which uremic adults were treated with either rHuGH or rHuIGF-I.

Data Extraction

Data were abstracted from all of these studies.

Results

The review shows that there are marked abnormalities of the GH-IGF axis in uremic patients and that these lead to a state of GH resistance, which can be overcome by pharmacological doses of rHuGH. A small number of clinical studies in uremic adults suggests that both rHuGH and rHuIGF-I have dramatic beneficial effects on nutritional status in these patients.

Conclusions

rHuGH and rHuIGF-I have both been shown to have a beneficial effect on nutritional status in shortterm studies on small numbers of patients. Further studies need to be done for longer periods in larger groups of patients. Areas for additional research are suggested.

The Effect of Small Solute Clearances on Survival of Anuric Peritoneal Dialysis Patients

Objective

Primarily, to determine whether peritoneal small solute clearance is related to patient and technique survival among anuric peritoneal dialysis [continuous ambulatory (CAPD) and automated peritoneal dialysis (APD)] patients. A secondary goal was to describe the ability to attain Dialysis Outcomes Quality Initiative (DOQI) targets among anuric patients on peritoneal dialysis.

Design

Retrospective cohort study via chart reviews.

Setting

Peritoneal Dialysis Unit of Toronto Hospital (Western Division).

Patients

The study included 122 CAPD and APD patients between January 1992 and September 1997, with 24-hour urine volume less than 100 mL, or renal creatinine clearance (CCr) less than 1 mL/minute. Adequacy data were available for 115 patients.

Outcome Measures

Mortality and technique failure (TF). Regression analysis was used to estimate the mortality and TF rate ratios (RR) for peritoneal Kt/V urea (pKt/V) and pCCr, adjusting for age, gender, diabetes, months of follow-up prior to anuria, albumin, transport status, coronary artery disease, cardiovascular disease, and peripheral vascular disease.

Results

Fifty seven per cent (51/89) of patients on CAPD and 81% (21/26) on APD had a weekly pKt/V ≥ 2 and ≥ 2.2, respectively (DOQI targets); whereas only 35% on CAPD (31/89) and 35% (9/26) on APD had a weekly pCCr ≥ 60 L/1.73 m2 and 66 L/1.73 m2, respectively. Median follow-up times among patients were 16.5 and 19.5 months pre- and postanuria, respectively. Patients with pKt/V ≥ 1.85 experienced a strong decrease in patient mortality (RR = 0.54, p = 0.10); the effect was less pronounced for pCCr ≥ 50 L/1.73 m2 (RR = 0.63, p = 0.25). No relationship was observed between pKt/V or pCCr and TF.

Conclusion

Mortality was noticeably less frequent among patients with a pKt/V ≥ 1.85 compared with those with a Kt/V < 1.85 ( p = 0.10). Given the magnitude of the association, the failure to observe statistical significance relates to the size of the patient cohort. Our results imply that it is, in fact, possible to achieve DOQI targets among anuric patients on peritoneal dialysis.

Nutritional Status of Capd Patients at Three Years

A nutritional assessment was carried out in 63 patients starting treatment from April 1990 up to December 1993. Anthropometric measurements were performed showing a prevalence of protein-calorie malnutrition (PCM) of 21 % in a total of 142 clinical surveys carried out in the above-mentioned sample. A steady state of albumin levels in plasma was verified during a three-year follow-up period at a lower level than that of the control group. The patients’ lymphocytic profile throughout the study was characterized by lymphopenia and decreased B and T 8 lymphocytes. During the first two years of continuous ambulatory peritoneal dialysis (CAPD), a high percentage of patients met the “adequacy” dialysis criteria as residual renal function plays an important role as regards treatment.

Variability in Creatinine Clearance (Ccr) and Ktn Due to Different Methods of Calculating Volume and Ccr

Objective

This study aimed to compare the correlations between KTN and creatinine clearance (Ccr) calculated by different methods and to determine and compare the correlations between KTN and Ccr.

Design

Nonrandomized, retrospective analysis of data.

Setting

Continuous ambulatory peritoneal dialysis (CAPD) outpatient clinic in a teaching hospital.

Patients

All patients were included for analysis if the data collection was complete for the calculations of KTN and Ccr using five different methods.

Interventions

Volume of distribution for urea (V) was estimated by four methods: Watson nomogram, ideal body weight (IBW), actual body weight, and total body surface area. Ccr was determined by five methods: Dialysate Ccr was calculated by creatinine (Cr) uncorrected and corrected for the presence of glucose; urinary Ccr was calculated using urinary Cr alone and the average urinary clearance of urea and Cr; and by the Cockcroft and Gault method.

Main Outcome Measures

Correlations between KTN and Ccr.

Results

Sixty-three data sets were collected from 52 CAPD patients. The correlations between weekly KTN and Ccr normalized to 1.73 m2 body surface area were found to be highly variable from one method to another (r2 = 0.012 -0.494). For obese patients (20% above IBW), KTN values obtained were more variable using the Watson nomogram compared to the IBW and BSA methods.

Conclusion

KT/V calculated using the Watson nomogram and the Ccr determined using average of urinary urea and creatinine clearance gave the best correlation (r2 = 0.49).

Growth Hormone and Malnutrition in Dialysis Patients

Objective

To review the normal function of the growth hormone (GH) insulin-like growth factor (IGF) axis, how it is altered in end-stage renal failure, how this may contribute to malnutrition in dialysis patients, and how therapy with recombinant human growth hormone (rHuGH) and recombinant human IGF-I (rHuIGF-1)might be used to treat malnutrition in these patients.

Data Sources

Studies in the literature dealing with the GH-IGF endocrine axis and its role in uremic malnutrition.

Study Selection

Eight studies in which uremic adults were treated with either rHuGH or rHuIGF-I.

Data Extraction

Data were abstracted from all of these studies.

Results

The review shows that there are marked abnormalities of the GH-IGF axis in uremic patients and that these lead to a state of GH resistance, which can be overcome by pharmacological doses of rHuGH. A small number of clinical studies in uremic adults suggests that both rHuGH and rHuIGF-I have dramatic beneficial effects on nutritional status in these patients.

Conclusions

rHuGH and rHuIGF-I have both been shown to have a beneficial effect on nutritional status in shortterm studies on small numbers of patients. Further studies need to be done for longer periods in larger groups of patients. Areas for additional research are suggested.

Adequacy of Continuous Ambulatory Peritoneal Dialysis

Adequacy of continuous ambulatory peritoneal dialysis (CAPD) and its variants is assessed by clinical outcomes, biochemical parameters and clearance parameters. Clinical outcomes lack specificity and probably sensitivity. Nevertheless, they constitute the “gold standard” to which any other method assessing dialysis adequacy must be compared. Biochemical parameters are both non-sensitive and non-specific and cannot be used to assess dialysis adequacy. Clearance of small molecular weight azotemic substances (urea, creatinine) presents considerable computational problems and interpretative difficulties. In preliminary studies, clearance studies have been able to differentiate between peritoneal dialysis patients having symptoms of inadequate dialysis and those clinically adequately dialyzed. Among population outcomes (morbidity, maintenance of peritoneal dialysis for long periods, hospitalization rate, mortality), only mortality sems to be associated with low clearances in retrospective studies. Prospective multicenter studies comparing clearance values to clinical outcomes are needed to evaluate clearance studies as methods of assessing peritoneal dialysis adequacy.

Estimating Urea Clearance in Patients on Continuous Ambulatory Peritoneal Dialysis: A Multivariate Analysis

The purpose of this study was to determine if Kt/V urea in continuous ambulatory peritoneal dialysis (CAPD) could be estimated by a multivariate model based upon simple clinical observations. The study included 439 clearance studies in 301 CAPD patients followed in 8 dialysis centers. Weekly urea clearance, 24 h urine volume and 24 h drain volume were normalized to body water by the formulae of Watson (Kt/V, UV/V, and DV/V respectively). Adequate dialysis was defined as Kt/V ≥2.0 weekly. Subjects at 2 units were used to derive the models, while others were used for model validation. Stepwise multiple linear regression was performed on the derivation set (DS) to identify the clinical variables that correlated with Kt/V. The model was then used to estimate Kt/V for the validation set (VS). In the DS, 110 clearance studies were performed in subjects with residual renal function. Multiple linear regression showed that weekly Kt/V was defined by the expression: Kt/V = 1.48 + 24.1 (UV/V) + 2.92(DV/V) - 0.049 (serum creatinine) (r=0.750, p<0.001). In 204 VS studies, the correlation between estimated and measured Kt/V was 0.633. There were marked differences in the proportion of adequately dialyzed patients when Kt/V estimated from the formula shown was <2.0, between 2.0 and 2.3, and >2.3 weekly (7.9%, 54.7% and 79.7%, respectively; p<0.001). In the 33 studies done in DS anuric patients, regression analysis showed the following: Kt/V = 0.46 + 2.59 (DV/V) + 0.009(age) (r=0.562; p = 0.003). In 92 VS studies in anuric subjects, there was strong correlation between estimated and measured Kt/V (r=0.740). Again, there were marked differences in the frequency of adequate dialysis in anuric patients with estimated Kt/V <2.0, between 2.0 and 2.3, and >2.3 weekly (8.1%, 68.8%, and 100%, respectively; p<0.001). The risk of low Kt/V can be estimated by multivariate linear models requiring only simple clinical measurements.

Sleep Disorders in Peritoneal and Haemodialysis Patients as Assessed by a Self-Administered Questionnaire

Sleep disorders have been reported as a frequent problem in dialysis patients. However, only one paper has compared the prevalence and possible causes of this complication in peritoneal (PD) and haemodialysis (HD) patients.

We surveyed 84 PD and 87 HD patients about disordered sleep using a self-administered questionnaire. Forty-nine percent of PD and 56% of HD patients reported problems sleeping. These problems were rated as severe by 29 PD and 22 HD patients. Type of disturbances involved delayed sleeping (13 PD and 32 HD, p< 0.005), interrupted sleep (32 PD and 44 HD) and early morning awakening (25 PD and 37 HD). The number of hours of sleep varied widely among patients: it was 5 and 21 minutes in PD patients with sleep disorders and 7 and 37 min in PD pts without such problems. No statistically significant relationship was evidenced between sleep disorders and age, sex, body weight, obesity, duration of dialysis, dialysis dose, self-assessed sadness, anxiety, worry, pain, pruritus, dyspnoea, restless leg syndrome, use of cigarettes, caffeine, or sleeping pills. In conclusion, sleep disorders are a frequent problem in both PD and HD patients. Apparently the relationship with demographics, dialysis dose, lifestyle and personality traits is poor. The possible role of other causes should be investigated.

Epidemiology of dietary nutrient intake in ESRD

Protein-energy wasting (PEW) is one of the strongest risk factors of adverse outcomes in patients with chronic kidney disease including those with end-stage renal disease (ESRD) who undergo maintenance dialysis treatment. One important determinant of PEW in this patient population is an inadequate amount of protein and energy intake. Compounding the problem are the many qualitative nutritional deficiencies that arise because of the altered dietary habits of dialysis patients. Many of these alterations are iatrogenically induced, and albeit well intentioned, they could induce unintended harmful effects. In order to determine the best possible diet in ESRD patients, one must first understand the complex interplay between the quantity and quality of nutrient intake in these patients, and their impact on relevant clinical outcomes. We review available studies examining the association of nutritional intake with clinical outcomes in ESRD, stressing the complicated and often difficult-to-study inter-relationship between quantitative and qualitative aspects of nutrient intake in nutritional epidemiology. The currently recommended higher protein intake of 1.2 g/kg/day may be associated with a higher phosphorus and potassium burden and with worsening hyperphosphatemia and hyperkalemia, whereas dietary control of phosphorus and potassium by restricting protein intake may increase the risk of PEW. We assess the relevance of associative studies by examining the biologic plausibility of underlying mechanisms of action and emphasize areas in need of further research.