Frequency and causes of discrepancy between Kt/V and creatinine clearance.

This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy. DESIGN: Nonrandomized, retrospective data analysis. SETTING: Single PD unit of a university teaching hospital. PATIENTS: All adult patients receiving PD at our center from January 1995 to December 1996. METHODS: Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height. RESULTS: Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V > or = 2.0/wk and Ccr > or = 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used. CONCLUSIONS: Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.     

Nutrition indices in obese continuous peritoneal dialysis patients with inadequate and adequate urea clearance.

OBJECTIVE: To test whether better nutrition is associated more with adequate urea clearance than with inadequate urea clearance in obese patients on continuous peritoneal dialysis (CPD). DESIGN: Retrospective analysis of clearance and nutrition indices in obese CPD patients. Only obese patients were analyzed. Obesity was defined as a ratio of actual weight to desired weight (W/DW) > or = 1.2. The dose of dialysis was considered adequate at weekly Kt/V urea > or = 2.0. Small solute clearances and nutrition indices were compared between patients with weekly Kt/V urea < 2.0 and patients with weekly Kt/V urea > or = 2.0 at the first clearance study. SETTING: Four university-affiliated and two private dialysis units in Canada and the United States. PATIENTS: A total of 270 CPD patients with W/DW > or = 1.2 at the first clearance study. RESULTS: Among the 270 obese CPD patients, 157 (58.1%) were underdialyzed (weekly Kt/V urea 1.66 +/- 0.22) and 113 (41.9%) had adequate dialysis (weekly Kt/V urea 2.51 +/- 0.47) at the first clearance study. Creatinine clearance values also differed between the underdialyzed and adequately dialyzed obese groups (55.6 +/- 15.2 vs 87.6 +/- 29.8 L/1.73 m2 weekly, respectively, p < 0.001). The underdialyzed group contained fewer women (39.5% vs 60.2%, p < 0.001) and more patients with anuria (35.0% vs 8.8%, p < 0.001), and had higher serum urea (20.7 +/- 6.9 vs 18.2 +/- 5.3 mmol/L, p = 0.001) and serum creatinine (974 +/- 283 vs 734 +/- 275 micromol/L, p < 0.001), marginally lower serum albumin (35.8 +/- 5.2 vs 37.2 +/- 6.4 g/L, p = 0.082), lower urea nitrogen excretion (5778 +/- 2290 vs 7085 +/- 2238 mg/24 hr, p < 0.001) and indices derived from urea nitrogen excretion (protein nitrogen appearance and normalized protein nitrogen appearance), and lower creatinine excretion (1034 +/- 349 vs 1217 +/- 432 mg/24 hr, p < 0.001) and indices derived from creatinine excretion (lean body mass normalized to actual or desired weight) than the adequately dialyzed group. CONCLUSION: Nutrition indices derived from urea nitrogen and creatinine excretion are worse in underdialyzed than in adequately dialyzed obese CPD patients. This finding may have clinical importance, despite the mathematical coupling between small solute clearances and excretion rates in cross-sectional studies, because of evidence from other studies that small solute excretion rate in cross-sectional studies is a robust Independent predictor of outcome in CPD.     

The relationship between Kt/V(urea) and nPNA in anuric peritoneal dialysis patients: a comparison with predialysis patients.

OBJECTIVE: It is unknown whether a given level of urea clearance by the native kidneys provides better or similar control of uremia than the same level of urea clearance by continuous peritoneal dialysis (PD). More insight into possible differences between renal and peritoneal urea clearances is warranted. Therefore, we investigated the relationship between Kt/V(urea) and protein equivalent of total nitrogen appearance normalized to body weight (nPNA), the relationship between urea clearance and creatinine appearance, and other nutritional parameters in PD patients without residual renal function, and in predialysis end-stage renal disease patients. PATIENTS: All patients participated in the Netherlands Cooperative Study on the Adequacy of Dialysis. This is a prospective cohort study of incident dialysis patients, in whom regular assessments of renal function are done. A group of 75 PD patients was identified at the first follow-up assessment in which their urine production was less than 100 mL/day. These patients were considered the anuric group. This group was compared with a control group of 97 predialysis patients studied 0-4 weeks before the start of dialysis treatment. RESULTS: Linear relationships were present between Kt/V(urea) and nPNA, in both the predialysis patients and the anuric PD patients. A significant difference was present between the slopes of the two regression lines (0.40 vs 0.18, p = 0.007). When Kt/V(urea) exceeded 1.3/week, a given level of Kt/V(urea) was associated with a higher nPNA in predialysis than in anuric PD patients. Similar relationships were found between Kt(urea) and PNA. Kt(urea) was also significantly related to urine or dialysate creatinine appearance. A significant difference existed between the slopes of the regression lines in the two groups of patients (p < 0.001). A weekly Kt(urea) of 70 L was associated with a urine creatinine appearance of 11.0 mmol/day and a dialysate creatinine appearance of 8.4 mmol/day. Nutritional status measured with creatinine appearance and Subjective Global Assessment was better in the predialysis population, despite much lower values for Kt/V(urea) in these patients. CONCLUSIONS: The relationship between Kt/V(urea) and nPNA in anuric PD patients is different from that in a predialysis population. It follows from our results that, when Kt/V(urea) is above 1.3/week, a given level of Kt/V(urea) is associated with a higher nPNA in predialysis than in anuric PD patients.This challenges the concept of equivalency between renal and peritoneal Kt/V(urea) with respect to control of uremic morbidity.     

Risk factors for early mortality in U.S. peritoneal dialysis patients: impact of residual renal function.

BACKGROUND: Potential risk factors for 1-year mortality, including the peritoneal component of dialysis dose, residual renal function, demographic data, hematocrit, serum albumin, dialysate-to-plasma creatinine ratio, and blood pressure, were examined in a national cohort of peritoneal dialysis patients randomly selected for the Centers for Medicare and Medicaid Services End-Stage Renal Disease (ESRD) Core Indicators Project. METHODS: The study involved retrospective analysis of a cohort of 1,219 patients receiving chronic peritoneal dialysis who were alive on December 31, 1996. RESULTS: During the 1-year follow-up period, 275 patients were censored and 200 non censored patients died. Among the 763 patients who had at least one calculable adequacy measure, the mean [+/- standard deviation (SD)] weekly Kt/V urea was 2.16 +/- 0.61 and the mean weekly creatinine clearance was 66.1 +/- 24.4 L/1.73 m2. Excluding the 365 patients who were anuric, the mean (+/- SD) urinary weekly Kt/V urea was 0.64 +/- 0.52 (median: 0.51) and the mean (+/- SD) urinary weekly creatinine clearance was 31.0 +/- 23.3 L/1.73 m2 (median: 26.3 L/1.73 m2). By Cox proportional hazard modeling, lower quartiles of renal Kt/V urea were predictive of 1-year mortality; lower quartiles of renal creatinine clearance were of borderline significance for predicting 1-year mortality. The dialysate component of neither the weekly creatinine clearance nor the weekly Kt/V urea were predictive of 1-year mortality. Other predictors of 1-year mortality (p < 0.01) included lower serum albumin level, older age, and the presence of diabetes mellitus as the cause of ESRD, and, for the creatinine clearance model only, lower diastolic blood pressure. CONCLUSION: Residual renal function is an important predictor of 1-year mortality in chronic peritoneal dialysis patients.     

Residual renal function in a large cohort of peritoneal dialysis patients: change over time, impact on mortality and nutrition.

OBJECTIVE: Residual renal function contributes importantly to total solute clearance in peritoneal dialysis (PD) patients. This study was designed to examine the progression of residual renal function over time and its impact on nutrition and mortality in PD patients in the six New England states (ME, NH, VT, CT, MA, RI) comprising End Stage Renal Disease (ESRD) Network 1. DESIGN: As part of the ESRD Clinical Indicators Project, data on 990 PD patients in Network 1 were abstracted from data supplied by dialysis units in the fourth quarter of 1997. This included demographic information; dose of PD in L/day; weekly renal, dialysis, and total Kt/V urea; weekly renal, dialysis, and total creatinine clearance (CCr); serum albumin level; and mortality and transplantation information. Data collection was repeated in the second and fourth quarters of 1998 and in the second quarter of 1999. PATIENTS: 990 PD patients in Network 1. OUTCOME MEASURES: The change in total and renal solute clearances over time, the relationship between renal clearance and mortality, and the relationship between renal clearance and nutritional status, as represented by serum albumin. RESULTS: Over the 2-year period, mean weekly renal Kt/V urea and weekly renal CCr dropped significantly. To examine the effect of residual renal function on mortality, patients were divided into high and low (above and below the median) weekly renal Kt/V urea and weekly renal CCr groups. Patients above the median levels of both weekly renal Kt/V urea and weekly renal CCr had a significantly decreased risk of dying during the observation period, after controlling for age, gender, serum albumin level, and diabetic status [OR for high vs low renal Kt/V urea 0.54 (CI 0.34 - 0.84), OR for high vs low renal CCr 0.61 (CI 0.40 - 0.94)]. The mean weekly renal Kt/V urea was significantly and directly correlated with the mean serum albumin level by Spearman rank correlation (R = 0.133, p < 0.001), as was the mean weekly renal CCr (R = 0.115, p < 0.001). CONCLUSIONS: Residual renal function is an important contributor to total solute clearance in PD patients. Even at low levels it is linked to decreased mortality and better nutritional status.     

Suitable dialytic indicators for pediatric peritoneal dialysis patients: the alternative to creatinine clearance.

OBJECTIVE: Owing to the discord between body weight and body surface area (BSA), creatinine clearance (CCr) is predisposed to be small in pediatric patients on peritoneal dialysis (PD). Alternatively, Kt/V creatinine (Kt/V creat), which is normalized to total body water (TBW) rather than BSA, could be a better dialytic indicator. In this study, the efficiency of dialysis and the nutritional status of pediatric patients on chronic PD were examined, and the utility of dialytic indicators was evaluated. PATIENTS AND METHODS: 49 patients under 20 years old, in stable condition, and on PD were analyzed. Weekly total Kt/V of urea (Kt/V urea), CCr, Kt/V creat, and normalized protein equivalent of nitrogen appearance (nPNA) were measured for all patients and for patients under 6 years old. The target value was 2.0/week for Kt/V urea and 60 L/ week/1.73 m2 for CCr, as recommended by the Kidney Disease Outcomes Quality Initiative guidelines. The target value for Kt/V creat was set as 1.52/week, using a male model with a height of 170 cm and a body weight of 65 kg. RESULTS: The mean values of delivered Kt/V urea, CCr, Kt/V creat, and nPNA (and proportion of patients that achieved each target value) for all patients were 2.25 +/- 0.57/ week (67.4%), 53.8 +/- 19.3 L/week1/.73 m2 (26.5%), 1.83 +/- 0.73/ week (65.3%), and 1.11 +/- 0.42 g/day, respectively. The values for patients under 6 years old were 2.38 +/- 0.26/week (90.0%), 45.9 +/- 12.8 L/week/1.73 m2 (10.0%), 1.94 +/- 0.51/week (90.0%), and 1.52 +/- 0.67 g/day, respectively. Stepwise multiple regression analyses revealed that the relationship between CCr and Kt/V urea was affected by the patient's age. CONCLUSIONS: Our pediatric patients achieved the recommended target value of Kt/V urea. At the same time, the nPNA results reflected the patient's status well. However, CCr appeared to be inappropriate as an indicator for patients under 6 years old. Kt/V creat is suggested to be a better dialytic indicator for these patients.     

Influence of residual renal function on dietary protein and caloric intake in patients on incremental peritoneal dialysis.

OBJECTIVE: To evaluate protein and caloric intake in peritoneal dialysis (PD) patients on an incremental dialysis schedule, in an attempt to discriminate the influence of residual renal function (RRF) on these nutritional parameters. DESIGN: Prospective observational study. PATIENTS: Nine patients who had significant RRF at the beginning of PD therapy, which permitted a schedule of incremental PD (i.e., the number of peritoneal exchanges was increased as the RRF fell) in order to maintain the sum of renal and peritoneal clearance (weekly Kt/V urea) at approximately 2. METHODS: The mean adequacy parameters (urine and peritoneal Kt/V urea and creatinine clearance) along with the mean dietary energy (DEI) and protein intake (DPI) estimated by 3-day diet histories, were determined 6 and 9 months after the beginning of PD, when patients had RRF (period 1), and 6 and 9 months after the loss of RRF (period 2). The mean data obtained in both periods were compared. The best determinants for the changes in DEI and DPI after the loss of RRF were also investigated. RESULTS: Mean total Kt/V urea was very similar in both periods (2.16+/-0.32 vs 2.15+/-0.18), although creatinine clearance decreased significantly after the loss of RRF (74.41+/-12.28 L/week/1.73 m2 vs 56.78+/-11.77 L/week/1.73 m2, p = 0.0001). Absolute and normalized DPI values for actual body weight decreased after the loss of RRF (68.21+/-11.87 g/kg vs 59.27+/-13.66 g/kg, p = 0.02; and 1.17+/-0.32 g/kg/day vs 0.97+/-0.32 g/kg/day, p = 0.01). Although the energy delivered by peritoneal glucose uptake increased significantly after the loss of RRF, the mean total energy intake (DEI plus peritoneal glucose uptake) was very similar in both periods (2141+/-339 kcal/day vs 2010+/-303 kcal/day, p = 0.13). However, the mean total energy intake normalized for actual body weight decreased significantly after the loss of RRF (37.5+/-10.1 kcal/kg/day vs 32.8+/-8.9 kcal/kg/day, p = 0.02). The changes in DEI and DPI between periods 1 and 2 correlated negatively with the difference of the energy delivered by peritoneal glucose uptake (r = 0.65, p = 0.05, and r = 0.88, p = 0.001, respectively). The magnitude of DPI changes between both periods correlated significantly with the magnitude of urinary Kt/V urea changes (r = 0.77, p = 0.01). However, there was no correlation between the changes in DPI and the changes in total Kt/V urea, total or renal creatinine clearance, or the length of time on PD. CONCLUSIONS: The loss of RRF led to a reduction in dietary caloric and protein intake. The magnitude of the reduction in the DPI was strongly correlated with the increase in the energy delivered by peritoneal glucose uptake and with the decrease in the urinary Kt/V urea, but not with the total Kt/V urea.     

Weekly clearances of urea and creatinine on CAPD and NIPD.

Weekly creatinine clearance (Ccr) and weekly Curea/v (kt/v) are popular indices for quantitating the amount of peritoneal dialysis provided. Studies were undertaken on 44 patients on continuous ambulatory peritoneal dialysis (CAPD) and 10 patients on nightly intermittent peritoneal dialysis (NIPD) to compare relationships of weekly creatinine clearance to weekly urea clearance (Curea) divided by total body water (v). With a long cycle therapy such as CAPD, the ratio of weekly Ccr to weekly kt/v is higher than with a short cycle technique, such as NIPD, in the same patient. If patients are shifted from CAPD to NIPD maintaining the same weekly kt/v, the weekly Ccr will decrease. If patients are shifted from CAPD to NIPD maintaining the same weekly Ccr, then the weekly kt/v will increase. The clinical implications of these observations are unknown, but should be kept in mind for future studies comparing CAPD and NIPD.     

Dialysis Adequacy Indices and Body Composition in Male and Female Patients on Peritoneal Dialysis

♦ Objectives: Creatinine clearance scaled to body surface area (BSA) and urea KT/V normalized to total body water (TBW) are used as indices for peritoneal dialysis (PD) adequacy. We investigated relationships of indices of dialysis adequacy (including KT/V, KT, clearance, dialysate over plasma concentration ratio) and anthropometric and body composition parameters (BSA, TBW, body mass index (BMI), weight, height, fat mass (FM), and fat-free mass (FFM)) in male and female patients on continuous ambulatory peritoneal dialysis.♦ Methods: Ninety-nine stable patients (56 males) performed four 24-hr collections of drained dialysate for four dialysis schedules with three daily exchanges of glucose 1.36% and one night exchange of either: 1) glucose 1.36%, 2) glucose 2.27%, 3) glucose 3.86% or 4) icodextrin 7.5%.♦ Results: KT and dialysate over plasma concentration ratio, C_D/C_P, for urea and creatinine were similar for males and females and, in general, did not depend on body-size parameters including V (= TBW), which means that the overall capacity of the transport system in females and males is similar. However, after normalization of KT to V or 1.73/BSA yielding KT/V and creatinine clearance, Cl_(1.73/BSA), respectively, the normalized indices were substantially higher in females than in males and correlated inversely with body-size parameters, especially in males.♦ Conclusions: As KT/V depends strongly on body size, treatment target values for KT/V should take body size and therefore also gender into account. As KT is less influenced by body size, body composition and gender, KT should be considered as a potential auxiliary index in PD.     

Increasing the dialysis volume and frequency in a fixed period of time in CPD patients: the effect on Kpt/V and creatinine clearance.

BACKGROUND: The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) has evidence- and opinion-based recommendations for weekly Kt/V(urea) and weekly total creatinine clearance (CC) in chronic peritoneal dialysis (CPD) patients. Using standard continuous ambulatory peritoneal dialysis technique, it is often difficult to achieve the suggested targets in anuric patients with large body mass. Thus, the use of automated peritoneal dialysis (APD) has been increasingly utilized to achieve adequate clearances. Automated dialysis is usually performed at night over an 8- to 10-hour period. The role of increases in dialysate volume and frequency of exchanges during this time period to achieve these target K/DOQI recommendations remains uncertain. We decided to study the effects of increasing the volume and number of exchanges in a fixed period of time in CPD patients. METHODS: In the New Haven CAPD unit, 29 patients maintained on APD were considered eligible for the study and 11 agreed to participate. The patients were characterized according to standard peritoneal equilibration test criteria.The patients were placed into two groups: group 1 included high (H) and high-average (HA), and group 2 low-average (LA) transporters. The patients were dialyzed at night for 9 hours with standard cycling technique, using 2.5% Dianeal (Baxter Healthcare, Deerfield, Illinois, USA) solution, with a cycle volume of 2,500 mL, and a 2,000-mL daytime dwell. Three studies were done on each patient using a total dialysis volume of 9.5 L (3 cycles), 14.5 L (5 cycles), and 19.5 L (7 cycles). Daily Kpt/V(urea) and daily CCp (peritoneal) (L/day/1.73 m2) were obtained. RESULTS: Six patients were H or HA (group 1) and 5 were LA transporters (group 2). For the group 1 patients, mean weight was 86.6 +/- 13.5 kg; Kpt/V(urea) was 1.68 +/- 0.21 using 9.5 L, 2.03 +/- 0.28 for 14.5 L (p < 0.05 compared to 10 L), and 2.28 +/- 0.28 with 19.5 L (p < 0.05 compared to 10 L and 15 L); mean weekly CCp was 45.43 +/- 7.63 L/1.73 m2 for 9.5 L (p < 0.05 compared to 14.5 L and 19.5 L), 51.17 +/- 7.07 with 14.5 L, and 54.67 +/- 10.08 for 19.5 L; ultrafiltration rates were not different in the three studies. For the group 2 patients, mean weight was 74.3 +/- 17.7 kg; mean weekly Kpt/V(urea) was 1.68 +/- 0.35 using 9.5 L, 2.10 +/- 0.42 for 14.5 L (p < 0.05 compared to 9.5 L), and 2.31 +/- 0.56 for 19.5 L (p < 0.05 compared to 9.5 L and 14.5 L); mean weekly CCp was 42.56 +/- 10.64 L/1.73 m2 for 9.5 L (p < 0.05 compared to 14.5 L and 19.5 L), 50.89 +/- 12.66 for 14.5 L, and 51.94 +/- 11.20 for 19.5 L; ultrafiltration was lower in the 9.5-L study than in the 14.5-L and 19.5-L studies, but was not different in the 14.5-L and 19.5-L studies. CONCLUSIONS: In both H/HA and LA transporters, Kpt/V(urea) and CCp rise significantly when the frequency of exchanges and total volume of dialysate are increased. Thus, the use of larger volumes of dialysate with cycling peritoneal dialysis may result in increased clearances of urea and creatinine.     

Effect of oral administration of losartan, prazosin, and verapamil on peritoneal solute transport in continuous ambulatory peritoneal dialysis patients.

BACKGROUND: Several intraperitoneally administered drugs have been shown to modify transport of peritoneal solute and fluid. Fewer studies, however, have evaluated the effect of orally administered drugs. The present study was performed to evaluate the effects of oral losartan, prazosin, and verapamil on peritoneal membrane transport during a peritoneal equilibration test (PET), as well as the effects on creatinine clearance (CrCl), Kt/V urea, 24-hour protein in drained dialysate, and drained volume. METHODS: This was an open, controlled, crossover clinical trial performed in 20 patients on continuous ambulatory peritoneal dialysis. All subjects used four 2-L 1.5% glucose dialysis exchanges per day. After a 7-day washout period (without antihypertensives), they had a baseline standard PET and dialysis adequacy assessment performed. Subsequently, they were randomly allocated to receive the first of three study drugs (losartan, prazosin, and verapamil), which were administered orally for a 7-day period. Immediately after each drug period, patients had a new 3-day washout and subsequently started the next drug, until they had received each of the three drugs. On the last day of administration of each drug, patients were subjected to a new PET and adequacy of dialysis evaluation. RESULTS: None of the studied drugs significantly modified the peritoneal transport of creatinine, glucose, urea, sodium, potassium, or total protein as evaluated by PET. Verapamil significantly increased peritoneal CrCl [51.3 (44.3 - 53.3) vs baseline 45.8 (41.4 - 50.5) L/week/ 1.73 m2, p < 0.05], weekly Kt/V urea [1.75 (1.60 - 1.78) vs baseline 1.59 (1.54 - 1.73), p < 0.05], and drained dialysate volume [8.80 (8.30 - 8.96) vs baseline 8.44 (8.20 - 8.50) L/day, p < 0.05]. CONCLUSIONS: Oral administration of losartan, prazosin, and verapamil did not modify the peritoneal transport of solutes during a 4-hour PET. Oral verapamil significantly increased CrCl, Kt/V urea, and 24-hour drained dialysate volume. It is most likely that verapamil increases peritoneal (hydraulic) conductivity, and then net ultrafiltration volume and convective transport of urea, creatinine, and protein. Verapamil could be considered as an alternative in patients requiring increased dialysis dose and/or ultrafiltration.     

Intermittent peritoneal dialysis: urea kinetic modeling and implications of residual kidney function

♦ Background: Intermittent peritoneal dialysis (IPD) is an old strategy that has generally been eclipsed, in the home setting, by daily peritoneal therapies. However, for a select group of patients with exhausted vascular access or inability to receive PD at home, in-center IPD may remain an option or may serve as an incremental strategy before initiation of full-dose PD. We investigated the residual kidney clearance requirements necessary to allow thrice-weekly IPD regimens to meet current adequacy targets.♦ Methods: The 3-pore model of peritoneal transport was used to examine 2 thrice-weekly IPD dialysis modalities: 5 – 6 dwells with 10 – 12 L total volume (low-dose IPD), and 50% tidal with 20 – 24 L total volume (high-dose IPD). We assumed an 8-hour dialysis duration and 1.5% dextrose solution, with a 2-L fill volume, except in tidal mode. The PD Adequest application (version 2.0: Baxter Healthcare Corporation, Deerfield, IL, USA) and typical patient kinetic parameters derived from a large dataset [data on file from Treatment Adequacy Review for Gaining Enhanced Therapy (Baxter Healthcare Corporation)] were used to model urea clearances. The minimum glomerular filtration rate (GFR) required to achieve a total weekly urea Kt/V of 1.7 was calculated.♦ Results: In the absence of any dialysis, the minimum residual GFR necessary to achieve a weekly urea Kt/V of 1.7 was 9.7 mL/min/1.73 m². Depending on membrane transport type, the low-dose IPD modality met urea clearance targets for patients with a GFR between 6.0 mL/min/1.73 m² and 7.6 mL/min/1.73 m². Similarly, the high-dose IPD modality met the urea clearance target for patients with a GFR between 4.7 mL/min/1.73 m² and 6.5 mL/min/1.73 m².♦ Conclusions: In patients with residual GFR of at least 7.6 mL/min/1.73 m², thrice-weekly low-dose IPD (10 L) achieved a Kt/V urea of 1.7 across all transport types. Increasing the IPD volume resulted in a decreased residual GFR requirement of 4.7 mL/min/1.73 m² (24 L, 50% tidal). In patients with residual kidney function and dietary compliance, IPD may be a viable strategy in certain clinical situations.     

Intermediate outcomes by race and ethnicity in peritoneal dialysis patients: results from the 1997 ESRD Core Indicators Project. National ESRD Core Indicators Workgroup.

BACKGROUND: Hispanics are the fastest growing minority group in the United States, and approximately 10% of all end-stage renal disease (ESRD) patients are Hispanic. Few data are available, however, regarding dialysis adequacy and anemia management in Hispanic patients receiving peritoneal dialysis in the U.S. METHODS: Data from the Health Care Financing Administration (HCFA) ESRD Core Indicators Project were used to assess racial and ethnic differences in selected intermediate outcomes for peritoneal dialysis patients. RESULTS: Of the 1219 patients for whom data were available from the 1997 sample, 9% were Hispanic, 24% were non-Hispanic blacks, and 59% were non-Hispanic whites. Hispanics were more likely to have diabetes mellitus as a cause of ESRD compared to blacks or whites, and both Hispanics and blacks were younger than white patients (both p < 0.001). Although whites had higher weekly Kt/V and creatinine clearance values compared to blacks or Hispanics (p < 0.05), blacks had been dialyzing longer (p < 0.01) and were more likely to be anuric compared to the other two groups (p < 0.001). Blacks had significantly lower mean hematocrit values (p < 0.001) and a greater proportion of patients who had a hematocrit level less than 28% (p < 0.05) compared to Hispanics or whites, despite receiving significantly larger weekly mean epoetin alfa doses (p < 0.05) and having significantly higher mean serum ferritin concentrations (p < 0.01). Multivariate logistic regression analysis revealed significant differences by race/ethnicity for experiencing a weekly Kt/V urea < 2.0 and hypertension, but not for other intermediate outcomes examined (weekly creatinine clearance < 60 L/week/1.73 m2, Hct < 30%, and serum albumin < 3.5/3.2 g/dL). CONCLUSION: Hispanics had adequacy values similar to blacks and anemia parameters similar to whites. Additional studies are needed to determine the etiologies of the differences in intermediate outcomes by racial and ethnic groupings in peritoneal dialysis patients.     

Independent effects of renal and peritoneal clearances on the mortality of peritoneal dialysis patients.

OBJECTIVE: Previous studies show that peritoneal Kt/V is an independent predictor of survival in anuric patients receiving continuous ambulatory peritoneal dialysis (CAPD). We studied whether peritoneal Kt/V has the same effect in CAPD patients with residual renal function. DESIGN: Observational cohort study. SETTING: Single dialysis center in a university teaching hospital. PATIENTS: New and prevalent CAPD patients. METHODS: We examined the 5-year follow-up results of our prospective study previously reported (Kidney Int 2000; 58:400-7). A total of 270 CAPD patients were followed for up to 6 years. Dialysis adequacy indices, residual renal function, and nutritional data were monitored. OUTCOME MEASURES: Primary outcomes included mortality and technique failure. Peritoneal Kt/V rather than total Kt/V was used for multivariate survival analysis. RESULTS: Average duration of follow-up was 35.1 +/- 22.0 months. Average peritoneal Kt/V throughout the study was 1.59 +/- 0.37; median residual glomerular filtration rate (GFR) 0.82 mL/minute. Five-year actuarial patient survival was 41.5%, and technique survival was 23.1%. Multivariate analysis showed that sex, age, duration of dialysis, presence of diabetes, serum albumin, dialysate-to-plasma creatinine ratio at 24 hours, peritoneal Kt/V, residual GFR, and normalized protein nitrogen appearance were independent factors of both actuarial patient survival and technique survival. For every 0.1 unit higher peritoneal Kt/V, relative mortality risk was 0.94 (95% Cl 0.89 - 0.99, p = 0.03). When prevalent and new CAPD cases were analyzed separately, peritoneal Kt/V predicted survival only for prevalent CAPD patients. CONCLUSION: We conclude that, in prevalent CAPD patients with relatively low levels of peritoneal clearance and residual renal function, a higher peritoneal Kt/V is associated with better survival. Peritoneal clearance below 1.6-1.7 likely has a major detrimental effect on the clinical outcome of CAPD patients with little residual renal function.     

Impact of fill volume on peritoneal clearances and cytokine appearance in peritoneal dialysis.

BACKGROUND: Current adequacy guidelines for peritoneal dialysis encourage the use of large fill volumes for the attainment of small solute clearance targets. These guidelines have influenced clinical practice in a significant way, and adoption of higher fill volumes has become common in North America. Several studies, however, have challenged the relevance of increasing small solute clearance; this practice may result in untoward consequences in patients. OBJECTIVE: The present study was designed to explore the relationship between dialysate volume and the clearance of different sized molecules, fluid dynamics, and appearance of peritoneal cytokines. METHODS: Thirteen adult prevalent patients on continuous ambulatory peritoneal dialysis were studied. Three different dialysate volumes (2.0, 2.5, and 3.0 L) were infused on consecutive days in a random order. Several measurements of peritoneal fluid dynamics (intraperitoneal pressure, net ultrafiltration, fluid absorption), solute clearances (urea, creatinine, beta2-microglobulin, albumin, IgG, and transferrin), and appearance of interleukin-6 and tumor necrosis factor alpha (TNFalpha) were assessed. RESULTS: Increase in dialysate fill volume (from 2 to 2.5 to 3 L) was examined in relationship to body surface area (BSA). The dialysate volume/BSA (DV/BSA) ratio increased from 1262 to 1566 to 1871 mL/m2 on 2.0, 2.5, and 3.0 L dialysate volumes, respectively. In parallel, diastolic blood pressure increased from 82.7 +/- 8.8 to 87.0 +/- 9.5 to 92 +/- 8.3 mmHg (p < 0.05). Net ultrafiltration rate also increased, from 0.46 +/- 0.48 to 0.72 +/- 0.42 to 0.97 +/- 0.49 mL/minute (p < 0.01), despite a concomitant increase in fluid absorption, from 1.05 +/- 0.34 to 1.21 +/- 0.40 to 1.56 +/- 0.22 mL/min (p < 0.01). Urea peritoneal clearance increased from 8.27 +/- 0.68 to 9.92 +/- 1.6 to 12.98 +/- 4.03 mL/min (p < 0.01); creatinine peritoneal clearance increased from 6.69 +/- 1.01 to 7.64 +/- 1.12 to 8.69 +/- 1.76 mL/min (p < 0.01). Clearance of the other measured molecules did not change. Appearance of interleukin-6 increased 17% and 43% (p < 0.01), and TNFalpha appearance increased 14% and 50% (p < 0.01) when dialysate volumes of 2.5 and 3.0 L were used, compared with 2.0 L. CONCLUSIONS: These results show that, with higher values of DV/BSA ratio, small solute peritoneal clearance is increased, but clearances of large molecules remain unchanged. With the use of higher volumes, fluid absorption rate and the appearance of proinflammatory cytokines in the dialysate are increased.     

Correlation of intraperitoneal antibiotic pharmacokinetics and peritoneal membrane transport characteristics.

OBJECTIVE: To identify correlations between the pharmacokinetic variables that describe drug disposition in peritoneal dialysis (PD) patients and the measures used to assess dialysis adequacy. DESIGN AND METHODS: This retrospective study re-evaluated data collected during previous pharmacokinetic studies for intraperitoneally administered cefazolin, ceftazidime, and gentamicin in continuous ambulatory peritoneal dialysis (CAPD) patients, and intravenous cefazolin and tobramycin in automated PD patients. Pharmacokinetic variables were compared to creatinine clearance (CCr), Kt/V, and peritoneal equilibration test data using the Pearson product correlation coefficient (r). RESULTS: Prominent correlations were found between renal CCr and renal Kt/V, with renal clearances of CAPD cefazolin and ceftazidime, and automated PD tobramycin and cefazolin (r values ranged from 0.698 to 0.986; p < 0.05). CONCLUSION: These findings support current peritonitis treatment recommendations that patients with residual renal function may require higher doses or more frequent drug administration.     

Effects of two simplified methods of dialysate sampling on estimations of adequacy indices in automated peritoneal dialysis.

OBJECTIVE: To assess the effects of two simplified methods of dialysate sampling on the estimation of adequacy markers in automated peritoneal dialysis (APD). DESIGN: Cross-sectional noninterventional study. SETTING: Tertiary-care hospital. PATIENTS: Forty-nine patients undergoing standard APD therapy (36 nontidal, 13 tidal with low reserve volume). INTERVENTION: We estimated creatinine clearance (CCr), Kt/V urea, sodium removal, and peritoneal protein loss using two simplified methods. We calculated separate diurnal and nocturnal adequacies. Nocturnal concentrations of urea, creatinine, sodium, and proteins were extrapolated from dialysate samples taken after the first (method A) or the last (method B) cycle of the night. For the reference method, we estimated adequacy from a complete 24-hour dialysate collection. RESULTS: Spearman correlations versus the reference method were, for CCr, 0.82 for method A and 0.87 for method B; and for Kt/V, 0.78 (A) and 0.72 (B). Method A overestimated CCr by 19.6% (4.5 L/week)(median values) and Kt/V by 8.8% (0.12). Method B overestimated CCr by 5.0% (1.7 L/week) and Kt/V by 4.4% (0.06). Both methods estimated sodium removal accurately, but estimated protein loss poorly. Tidal APD was associated with a clear overestimation of adequacy indices with both methods. In fact, when only nontidal patients were considered, method B slightly underestimated CCr and Kt/V. CONCLUSIONS: In APD, estimation of nocturnal adequacy from dialysate samples taken after the first cycle is inaccurate. Estimation from samples taken after the last cycle yields suboptimal but acceptable results; the deviation is small and the dose of dialysis delivered to the patients is not overestimated.     

Normalization of clearances in peritoneal dialysis using a formula for body water derived from an end-stage renal disease population.

OBJECTIVE: To compare body water (V) estimates from the Chertow formula (Vc), which was derived in an end-stage renal disease population, to V estimates from the Watson formulas (Vw) in continuous ambulatory peritoneal dialysis (CAPD) patients. To identify CAPD patients in whom Vc is preferred to Vw for clearance studies. DESIGN: Retrospective analysis of clearance studies. SETTING: Dialysis units of four academic medical centers. PARTICIPANTS: 302 subjects on CAPD. INTERVENTION: 613 clearance studies by standard methods. MAIN OUTCOME MEASURES: Comparisons between Vc and Vw, and between urea clearance normalized by Vc [(KtVc)ur] and Vw [(Kt/Vw)ur]. RESULTS: Vc exceeded Vw by 3.5 +/- 1.6 L (p < 0.001), or 9.6% on average. This degree of overestimation of Vw is in the range of body water estimates found in CAPD subjects with severe volume overload (> 5% of body weight) in previous studies.Total (Kt/Nw)ur exceeded total (Kt/Vc)ur by 8.6%. By linear regression, Vc = -0.589 + (1.112 x Vw), r = 0.983. Vw exceeded Vc in only 12 studies. Young age, short height, low body weight, and low prevalence of diabetes characterized the studies with Vw > Vc. Total (Kt/Vw)ur was adequate (> or = 2.0 weekly) in 276 studies. Among these, 74 studies had inadequate total (Kt/Vc)ur (< 2.0 weekly). By logistic regression, the predictors of inadequate (Kt/Vc)ur, when (Kt/Vw)ur was adequate, included the presence of diabetes, great height, and long duration of CAPD. CONCLUSIONS: Vc provides estimates of body water exceeding those provided by Vw in a great majority of CAPD patients. Consequently, approximately 25% of the clearance studies that are adequate when Vw is used as the normalizing parameter may be inadequate when Vc is used. Vc may provide a more appropriate estimate of body water than Vw in CAPD patients with volume overload.