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.

Dialysis Dose Required for a Minimal Acceptable Level

Objectives

To identify the most advantageous formula for estimating creatinine clearance (CCr) and to establish a dose of dialysis that will ensure minimal acceptable levels of creatinine clearance in patients on continuous peritoneal dialysis (CPD).

Design

Analysis of all CCr studies performed in CPD patients over 40 months.

Setting

All four dialysis units following CPD patients in one city. One dialysis unit is government-owned, one is university-affiliated, and two are community-based.

Participants

One hundred and ninety-four patients representing almost the entire CPD population in Albuquerque.

Interventions

Creatinine and urea clearance studies were performed in 24-hour urine and drained dialysate samples. Creatinine clearance (peritoneal plus urinary) was normalized to either 1.73 m2 body surface area (CCr) or body water estimated by the Watson formulas (KT/V Cr). CCr and KT/Vcr were either corrected by averaging urinary creatinine and urea clearances or were not corrected. Two dialysis units were designated as the training set (92 patients, 143 clearance studies) and the other two units as the validation set (102 patients, 181 clearance studies).

Main Outcome Measures

Minimal acceptable creatinine clearance levels were determined in the training set by computing the creatinine clearance value corresponding to 1.70 weekly KTN urea by linear regression. Logistic regression models predicting low creatinine clearance were developed in the training set and were tested in the validation set.

Results

The following weekly creatinine clearance values corresponded to 1.70 KTN urea: corrected CCr 52.0 L/1. 73 m2, uncorrected CCr 54.4 L/1.73 m2, corrected KT/Vcr 1.46, uncorrected KT/Vcr 1.53. Logistic regression identified as predictors of low creatinine clearance low daily urine volume (UV) and low daily dialysate drain volume/body water (DV/V) for all four creatinine clearance formulas, plus low/low-average peritoneal solute transport (only for uncorrected CCr) and serum creatinine (for both KT/Vcr formulas). In the validation set, the predictive models produced an area under the receiver operating characteristic (ROC) curve between 0.835 and 0.919 indicating very good predictive accuracy. For corrected CCr and anuria, the regression model produced a minimal normalized drain volume (DV/V) value consistent with minimal acceptable CCr equal to 0.305 L/L per 24 hours. This DV/V cutoff detected low corrected CCr in validation set anuric subjects (n = 55) with a sensitivity of 85% and a specificity of 71 %. For uncorrected CCr and anuria, DV/V cutoffs were 0.273 L/L per 24 hours (high/ high-average peritoneal solute transport) and 0.420 L/L per 24 hours (low/low-average transport). Sensitivity and specificity of these cutoffs in validation set anuric subjects were 87% and 85%, plus 86% and 33%, respectively.

Conclusions

The uncorrected CCr appears to be the most advantageous creatinine clearance formula in CPD, because it allows the use of peritoneal solute transport type in the calculation of the minimal required normalized drain volume. The minimal acceptable uncorrected CCr is 54.4 L/1. 73 m2weekly. To achieve this uncorrected CCr in anuria, the required minimal normalized drain volume is 0.273 L per liter of body water daily if peritoneal solute transport is high or high-average and around 0.420 L per liter of body water daily if peritoneal solute transport is low or low-average. The required total daily drain volume is computed by multiplying the required normalized drain volume by body water.

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.

Body Surface Area Limitations in Achieving Adequate Therapy in Peritoneal Dialysis Patients

Objective

To estimate the maximal body surface area (BSA) at which an uric chronic peritoneal dialysis patients can achieve adequate peritoneal dialysis using a variety of continuous ambulatory peritoneal dialysis (CAPD) and cycler regimens. Adequate dialysis was defined as a creatinine clearance of either 60 L/week/1.73 m2 or 70 L/ week/1.73 m2.

Design

Calculation of daily peritoneal creatinine clearances using standard formulas. For CAPD patients, creatinine clearance was calculated using published values for dialysate-to-plasma ratios for creatinine (DIP cr) measured over a 24-hour period and assuming a daily ultrafiltration rate of 1.5 to 2.0 L/day. For cycler patients, creatinine clearance was calculated for both one and two-hour dwell volumes, using published values for DIP cr from the peritoneal equilibration test and assuming a daily ultrafiltration rate of 2.0 L/day. All clearances were corrected to a normalized body surface area of 1.73 m2.

Results

For CAPD patients, 2– L dwell volumes can provide a weekly creatinine clearance of 60 L/week/1.73 m2 in patients with BSA < 1.45 m2 in the high transporter group and with BSA < 1.2 m2 in the low-average transporter group. Increasing dwell volume from 2.0 to 2.5 L increases these BSA limits in the four transport groups by 0.2 0.3 m2. Cycler therapy is not a viable option for patients in the low transporter group, and this therapy can achieve adequate creatinine clearances in patients in the low-average transport group only with large dwell volumes and in patients with BSA < 1.55 m2. However, in the high-average and high transporter groups, cycler therapy provides for superior creatinine clearances compared to CAPD patients using similar dwell volumes.

Conclusions

Adequate creatinine clearances in anuric patients are most likely to be achieved in patients with BSA > 2.0 m2 if they have high-average or high transport characteristics and are receiving cycler therapy with large dwell volumes and at least one daytime dwell. However, adequate creatinine clearances may be difficult to achieve in an uric patients who have a large BSA an d a low or low-average transport type, regardless of peritoneal dialysis modality. These patients should be considered for either high-dose peritoneal dialysis (multiple daytime and nighttime exchanges) or hemodialysis therapy.

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.

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.

Peritoneal Dialysis Kinetic Modeling: Validation in a Multicenter Clinical Study

Objective

To clinically validate the use of a computer-based kinetic model for peritoneal dialysis (PD) by assessing the level of agreement between measured and modeled values of urea and creatinine clearances and ultrafiltration (UF).

Design

An open multicenter observational study.

Patients

There were 111 adult continuous ambulatory peritoneal dialysis (CAPD) patients (47 female, 64 male) in four centers. All patients underwent a four-hour peritoneal equilibration test (PET) using 2.5% dextrose but with variable fill volumes (range: 1 -3 L). Patients with a residual renal function greater than 10 mL/min were excluded.

Main Outcome Measures

Correlations and limits of agreement between measured and modeled values of total weekly urea KTN, total weekly normalized creatinine clearance (L/week/1.73 m2), daily drain volume (L), net ultrafiltration (L), daily peritoneal urea clearance (L/day), and daily peritoneal creatinine clearance (L/day). Measured values were obtained from 24-hour urine and dialysate collections while modeled values were based on results from the PET in combination with the PD ADEQUEST® kinetic program.

Results

The results show there is excellent agreement between measured and modeled urea KTN and creatinine clearances, with concordance correlations of 0.94 and 0.92, respectively. Given the excessive variation and limited range in ultrafiltration values, the concordance correlation between measured and modeled UF was only 0.50. In terms of daily peritoneal clearances and ultrafiltration, the level of precision (i.e., standard deviation) in the differences between modeled and measured values is ±1.05 L/ day for urea clearance, ±1.03 L/day for creatinine clearance, and ±0.919 L/day for ultrafiltration. By contrast, the level of precision (i.e., standard deviation) in the differences between two measured values is estimated to be ±0.979 L/day for urea clearance, ±0.802 L/day for creatinine clearance, and ±0.707 L/day for ultrafiltration. Defining the limits of clinical agreement to be ±2 standard deviations of the differences between two clinically measured 24-hour clearances (or ultrafiltration), we find that 94% of the modeled urea clearances, 87% of the modeled creatinine clearances, and 86% of the modeled ultrafiltration values fall within the limits of clinical agreement.

Conclusion

Data from a carefully performed PET and overnight exchange can, in combination with a scientifically validated kinetic model, provide clinicians with a powerful mathematical tool for use in CAPD dialysis prescription management. Although not intended to replace actual measurements, kinetic modeling can prove useful as a means for predicting clearances for various alternative prescriptions and perhaps also as a means for checking certain types of noncompliance.

Comparison of Measured and Predicted Creatinine Excretion is An Unreliable Index of Compliance in Pd Patients

Objective

To evaluate the use of the ratio of measured to predicted creatinine excretion as an index of compliance in peritoneal dialysis (PD) patients.

Design

A prospective analysis.

Setting

Academic teaching hospital dialysis unit.

Patients

Forty-three patients on PD.

Measurements

Creatinine excretion in daily dialysate and urine collections was measured on one occasion in 10 patients and on two occasions in 33 patients, and, after adding an estimate for extrarenal creatinine degradation, was divided by predicted creatinine excretion to give a creatinine excretion ratio, which has been proposed as an index of compliance with exchanges in PD patients. Values above 1.24 have been suggested to indicate non-compliance. Lean body mass was also estimated from creatinine excretion.

Results

The mean creatinine excretion ratio was 1.12, and 30% of patients had a value above 1.3. Only one patient admitted noncompliance. Studies on four consecutive days of guaranteed compliance in 7 patients with high ratios showed that creatinine excretion remained constant, suggesting that the patients were high creatinine producers rather than noncompliant. Creatinine excretion was stable when measured at intervals of days, but over months it tended to change markedly in many patients. Lean body mass estimations using creatinine excretion were low in most patients.

Conclusion

Comparison of measured and predicted creatinine excretion is not a reliable indicator of noncompliance because many compliant patients consistently excrete more creatinine than predicted. The standard formulas were not validated in dialysis patients and underestimate creatinine excretion significantly in many PD patients. Existing estimates in the literature of non-compliance, using this methodology, may not be accurate. Better methods of detecting this problem are required.

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).

A Multinational Clinical Validation Study of Pd Adequest 2.0

Objective

To clinically validate the use of the newly released kinetic modeling program, PD ADEQUEST 2.0 for Windows (Baxter Healthcare Corporation, Deerfield, IL, U.S.A.), by assessing the level of agreement between measured and modeled values of urea and creatinine clearances (CCr), glucose absorption, total drain volumes, and net ultrafiltration for all forms of peritoneal dialysis.

Design

A nonrandomized, multinational, prospective longitudinal study.

Patients

The study involved 104 adult patients [41 on continuous ambulatory peritoneal dialysis (CAPD), 63 on automated peritoneal dialysis (APD)] from 16 centers in 7 countries. All patients underwent a 4-hour peritoneal equilibration test (PET) but with varying percentage dextrose concentrations (1.5% or 2.5% dextrose) and varying fill volumes (range 1.5 – 2.5 L). Patients with a residual renal function greater than 10 mL/min were excluded, as were patients who had peritonitis within 6 weeks prior to baseline.

Main Outcome Measures

Correlation coefficients and Bland–Altman limits of agreement were used to assess the level of agreement between measured and modeled values of weekly peritoneal urea Kt/V (pKt/V) and total Kt/V, weekly peritoneal creatinine clearance (pCCr, L/week/ 1.73 m2) and total CCr (L/week/1.73 m2), daily drain volume (L/day), net ultrafiltration (UF, L/day), daily peritoneal urea and creatinine mass removal (g/day), and daily peritoneal glucose absorption (g/day). Measured values were obtained from three repeat 24-hour urine and dialysate collections per patient, while modeled values were calculated using the Baxter PD ADEQUEST 2.0 program in conjunction with kinetic parameters estimated from a 4-hour PET and long-dwell exchange independent of the 24-hour collections.

Results

The results show there is excellent agreement between measured and modeled urea Kt/V and CCr with concordance correlation coefficients ranging from 0.83 to 0.97 among CAPD and APD patients. There was also excellent agreement between measured and modeled values of glucose absorption and total drain volumes (concordance correlations of 0.90 and 0.98, respectively). This level of agreement was further supported by a Bland– Altman analysis of individual differences, including differences between measured and modeled net UF (coefficient of clinical agreement ranged from 0.66 to 0.92).

Conclusions

Data from a carefully performed PET and overnight exchange can, in combination with a scientifically and clinically validated kinetic model, provide clinicians with a powerful mathematical tool for use in CAPD and APD prescription management. Although not intended to replace actual measurements, kinetic modeling can prove useful as a means for quickly estimating approximate levels of clearance for a wide variety of alternative prescriptions. This, in turn, should speed up the process by which a physician can optimize the dose of dialysis suitable for a given patient and his/her lifestyle.

The Impact of Peritoneal Permeability and Residual Renal Function on Pd Prescription

Our objective was to evaluate the impact of peritoneal transport characteristics and residual renal function on peritoneal clearance and to determine the dialysis volume required to achieve targets for KT/V and weekly creatinine clearance (WCC) in patients with differing weights, renal function, and transport status.

Retrospective analysis and mathematical model simulation of urea and creatinine clearance were used.

This review demonstrates the important contribution of both residual renal function and peritoneal transport in attaining target values for KT/V and WCC. The limitations of a standard 4 x 2 L dialysis prescription are highlighted in anuric patients and those with low peritoneal transport. In addition, the limitations of short dwell, rapid exchange dialysis modalities are emphasized, especially in patients with low and low average peritoneal transport where daily clearance is demonstrated to be considerably less than conventional continuous ambulatory peritoneal dialysis (CAPD).

Attainment of proposed targets for KT/V (1.7) and WCC (50 L) is greatly dependent on residual renal function. In CAPD, peritoneal transport characteristics determine urea clearance through an effect on ultrafiltrate. Thus low transporters of identical weight will have greater values for peritoneal dialysis KT/V. Creatinine clearance is considerably influenced by transport status. The majority of low and low average groups will need some degree of renal function to achieve currently proposed targets. In these patients, conversion to high volume, short dwell modalities will further compromise small solute clearance unless daytime long dwells or tidal dialysis is instigated.

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.

Estimated versus Predicted Creatinine Generation as an Indicator of Compliance with the Prescribed Dose of Continuous Peritoneal Dialysis

The expression (Estimated - Predicted)/Predicted creatinine generation {(E-P)IP} has been proposed as an index of compliance in continuous peritoneal dialysis (CPD). We attempted to define an (E-P)IP value that can be used as a cut-off for non-compliance and to characterize the relation of (E-P)IP to serum albumin. In 324 clearance studies, (E-P)/P had a normal distribution with a mean of +0.094 and an SD of 0.357. In these studies, there was a weak correlation between (E-P)/P and serum albumin (r=0.12, P<0.05), but (E-P)/P was not a predictor of serum albumin by logistic regression. In 34 CPD patients, who had an increase in the dose of CPD resulting in an increase in measured creatinine clearance from 43.8 ± 14.0 to 66.1 ± 17.6 L/1.73 m2 weekly (P<0.001), (E-P)/P increased correspondingly from +0.018 ± 0.284 to +0.153 ± 0.369 (P = 0.018), although all subjects should be in a steady state of creatinine excretion in the second study. The rise in (E-P)/P was statistically significant in the subgroup of 17 subjects who had a decrease in serum albumin, but not in the subgroup of 14 subjects who had an increase in serum albumin from the first to the second clearance study. The (E-P)/P cut-off for a definitive diagnosis of CPD non-compliance may be around +0.400 or +0.500. The findings of this study suggest that non-compliance, as indicated by (E-P)/P, has an adverse effect on serum albumin and that non-compliance increases after a prescribed increase in the dose of CPD.

Multicenter cross-sectional study for dialysis dose and physician's subjective judgment in Japanese peritoneal dialysis patients. Group for the Water and Electrocyte Balance Study in CAPD

The purpose of this study was to investigate the state of dialysis and nutrition among Japanese peritoneal dialysis (PD) patients. Two hundred thirty-nine Japanese PD patients from 21 centers, 79 female and 160 male, were evaluated to determine their status of dialysis and nutrition. Mean age of the patients was 50 years; mean duration on PD, 4.2 years; mean body weight, 58 kg; and body surface area (BSA), 1.61 m(2). Sixty-three percent of the patients had no residual renal function. Mean daily delivered volume was 6.9 L for female continuous ambulatory peritoneal dialysis (CAPD), 8.1 L for male CAPD, 10.5 L for female automated peritoneal dialysis (APD), and 10.7 L for male APD. Total (dialysis and kidney) mean weekly values for creatinine clearance (Ccr), Kt/V, and beta2 microglobulin (beta2MG) clearance were 56 L/1.75 m(2), 1.80, and 11 L/1.73 m(2), respectively. Fifty percent of the patients who had no residual renal function (RRF) and 17% of the patients with RRF did not achieve 50 L/wk/1.73 m(2) of Ccr. With regard to nutritional parameters, mean values for plasma total protein, serum albumin, and normalized protein catabolic rate (nPCR) were 6.5 g/dL, 3.6 g/dL, and 0.97 g/kg BW/d. Mean daily protein loss was 5.8 g. Although a significant number of patients did not achieve 50 or 60 L/wk/1.73 m(2) of Ccr, the physicians determined that 72% of the patients received adequate dialysis and 71% were well nourished according to clinical and laboratory features. In conclusion, the daily prescribed volume and the delivered dialysis dose were lower than expected. The discrepancy between the actual delivered dialysis dose and the physicians' evaluation should be explored in the future.

Evaluation of the PD Adequest Program in Japanese Patients on Peritoneal Dialysis

To perform adequate peritoneal dialysis, it is necessary to individualize the dialysis regimen. PD Adequest is a software program based on the three-pore model that can be used to predict solute clearance and ultrafiltration volume during peritoneal dialysis. We evaluated the ability of this program to predict the solute clearance and ultrafiltration volume in Japanese patients on peritoneal dialysis. The weekly creatinine clearance and weekly urea Kt/V were determined in 45 patients. The PD Adequest was used to simulate their current dialysis regimens and the predicted values of these parameters were calculated. Strong positive correlations were obtained between the actual and predicted weekly creatinine clearance (r=0.993) and weekly urea Kt/V (r=0.991). In conclusion, this program is potentially useful for designing peritoneal dialysis regimens in Japanese patients, even though they have a smaller body mass than Canadians and Americans for whom it was designed.

Influence of the preceding exchange on peritoneal equilibration test results: a prospective study

The standard peritoneal equilibration test (PET) should be performed after a long overnight dwell, which is easily possible in continuous ambulatory peritoneal dialysis patients. However, for such a procedure, patients undergoing automated peritoneal dialysis or daily ambulatory peritoneal dialysis have to change their regimen and, in the case of high peritoneal transport rates, run the risk for fluid absorption. We compared dialysate to plasma ratios (D/P) of creatinine, blood urea nitrogen (BUN), phosphate, sodium, total protein, and albumin measured during PET after an 8- to 11-hour dry period (PET dry), after a preceding exchange with a long dwell time (PET standard), and immediately after tidal peritoneal dialysis (PET tidal). D/P ratios of creatinine, BUN, phosphate, and sodium at 2 and 4 hours were greater during PET dry compared with both PET standard and PET tidal. The quotient of dialysate glucose at 2 hours to dialysate glucose at time point 0 was significantly less in PET dry compared with both PET tidal and PET standard. During the first 2 hours of PET, the increase of D/P curves of creatinine and BUN, as well as phosphate, was significantly steeper in PET dry than PET tidal and PET standard. D/P ratios of albumin and protein were greatest in PET dry and least in PET tidal. There was a significant difference between all three PETs at 0, 2, and 4 hours of dwell time. PET curves were significantly steeper during PET dry compared with PET tidal in case of D/P protein (during the first 2 hours of dwell time) and D/P albumin (during the entire dwell time). Similar differences between the PET curves of protein and albumin were observed between PET dry and PET standard. These data clearly indicate a dry period before PET significantly influences the D/P ratios of small solutes, protein, and albumin measured during the test.

Ethnic variability in peritoneal equilibration test and urea kinetics

The influence of ethnicity on peritoneal permeability and the adequacy of peritoneal dialysis was studied in 202 end-stage renal failure patients on peritoneal dialysis. Patients were classified into whites, Orientals, blacks, and a miscellaneous group consisting of East Indians, Persians, and others whose ethnicity was unknown. The patients were on peritoneal dialysis for a mean period of 29.1 +/- 15.8 months before the study. All patients underwent a peritoneal equilibration test with 24-hour urine and dialysate collection. The kinetic parameters were calculated using commercial software (PD Adequest; Baxter Healthcare, Round Lake, IL). The mean volume of exchange, weekly Kt/V, and weekly creatinine clearance were comparable in the different ethnic groups, but the normalized protein catabolic rate was significantly higher in the Orientals (P = 0.03). The high transporters tended to be males with a large body surface area and in the older age group. The low transporters achieved a higher Kt/V than those in the other transport groups (2.3 +/- 0.4 v 2.06 +/- 0.52; P = 0.015). The women had a significantly higher Kt/V than the men (2.16 +/- 0.43 v 1.93 +/- 0.59; P < 0.01). Repeat peritoneal equilibration test was done after a mean duration of 10.5 +/- 4.9 months in 33 patients. Although the mean exchange volume (8.37 +/- 0.83 v 9.32 +/- 1.72; P = 0.003) increased significantly, weekly creatinine clearance (62.3 +/- 25.6 L/1.73 m2 to 63.1 +/- 18.3 L/1.73 m2; P < 0.05) and other kinetic parameters did not change markedly with duration. There was a tendency for the patients to move from the extreme transport groups to the average category with duration.

The importance of monitoring dialysis adequacy in chronic peritoneal dialysis

The case of a patient who was noted to be malnourished but improved after his dialysis dose was increased is presented. This case and the discussion that follows emphasize the importance of proactively monitoring peritoneal dialysis adequacy and nutritional intake, supporting the notion that the dose of peritoneal dialysis is a major determinant of appetite and, consequently, of nutritional status. In the clinical setting, this influence is best indicated by changes in the serum albumin level and ultimately in long-term patient survival. The case discussion reviews the major principles and supporting literature, describing how we target peritoneal dialysis delivery and optimize nutritional status in an effort to reduce morbidity and mortality.

Assessing the peritoneal dialysis capacities of individual patients

A method for measuring the peritoneal dialysis capacity (PDC) of the individual patient has been developed as an aid to treatment of patients with renal failure and peritoneal dialysis. The patient collects the data him or herself during an almost normal CAPD day using a carefully designed protocol whereby the nursing time is kept to a minimum. The three-pore model is used to describe the PDC with three physiological parameters: (1.) the 'Area' parameter (A0/delta X), which determines the diffusion of small solutes and the hydraulic conductance of the membrane (LpS); (2.) the final reabsorption rate of fluid from the abdominal cavity to blood (JVAR) when the glucose gradient has dissipated; and (3.) the large pore fluid flux (of plasma, JVL), which determines the loss of protein to the PD fluid. In the adult PD population (age 60, N = 97) the normal 'Area' parameter was 23,600 cm/1.73 m2, with an SEM of 650. The JVAR was 1.49 ml/min/1.73 m2 and JVL was 0.078 ml/min/1.73 m2. The PDC parameters were reproducible and could adequately predict the concentrations of the test solutes as well as that of beta 2-microglobulin. The results in terms of clearance, 'UF volume' and nutritional consequences were presented on easily understandable graphs, whereby patient compliance was improved. These physiological parameters are highly dynamic, as evidenced by the marked increases observed during peritonitis. It seems safe to conclude that PDC is a useful tool to achieve adequate dialysis and to enhance the understanding of PD exchange.

Assessment of adequacy in peritoneal dialysis

Adequacy of peritoneal dialysis has been less well studied than that of hemodialysis. Fractional urea removal, total creatinine removal, and various indices have been proposed to reflect or predict patient morbidity and mortality. No prospective study has been published in this regard. To evaluate this area further, in addition to reviewing selected literature, 45 continuous ambulatory peritoneal dialysis (CAPD) patients were recruited in two dialysis centers for a prospective study on treatment adequacy. Patients were well rehabilitated and had no peritonitis or hospitalization in the 6 months before the study. Urea and creatinine kinetics were analyzed, as were dietary intake and fluid balance. The weekly Kt/V, calculated to include peritoneal and residual renal clearance (KprT/V), averaged 1.77 with a Kt/V hemodialysis equivalent of 0.59. Patients with residual renal function (58% of the studied population) had an average residual renal clearance of 3.42 mL/min, and had lower steady-state concentrations of urea nitrogen and creatinine in the plasma than patients with no residual renal function. As a consequence, a lower percent excretion of urea and creatinine in the peritoneal fluid was observed in the former patients compared with the latter, where the peritoneal route was the only one for solute excretion. The concentration profiles in blood appear to be the critical factor in achieving the final target of the treatment, ie, the excretion of the overall amount of waste products derived from protein and other metabolic pathways. The constant blood levels in CAPD explain why such a low Kt/V can be adequate whereas, in hemodialysis, a higher Kt/V is required.(ABSTRACT TRUNCATED AT 250 WORDS)