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E F Vonesh

Publications and source records attributed to E F Vonesh.

At least 19 recordsLinked to original sources
PubMed2006

Mortality studies comparing peritoneal dialysis and hemodialysis: what do they tell us?

Several recent large-scale epidemiological studies comparing mortality among end-stage renal disease (ESRD) patients receiving hemodialysis (HD) versus peritoneal dialysis (PD) show conflicting results. In this paper, we undertake a critical review of these studies. Our goal is to determine if there are any consistent trends in outcomes between HD and PD within select subgroups of patients once methodological differences have been accounted for. A total of six large-scale registry studies and three prospective cohort studies conducted in the United States (US), Canada, Denmark, and the Netherlands were reviewed. Summary findings from these studies are presented for comparative purposes. Additional summary analyses based on previously reported data on 398 940 incident US Medicare patients are included for the purpose of comparing results from this population of patients to those of the other select studies when similar methods of analysis are applied. Results are summarized in terms of the relative risk of death for PD versus HD (RR[PD:HD]). Differences in results between the nine studies can be attributed to the degree of case-mix adjustment carried out and to the use of different subgroups when comparing mortality between HD and PD. When these differences are accounted for, we found a remarkable degree of synergism in results between the registry studies and, to a lesser degree, the prospective cohort studies. PD was generally found to be associated with equal or better survival among non-diabetic patients and younger diabetic patients in all four countries. However, among older diabetic patients, results varied by country. The Canadian and Danish registries showed no difference in survival between PD and HD among older diabetics while in the US, HD was associated with better survival for diabetics aged 45 and older. All studies show a time-dependent trend in the RR of death with PD generally associated with equivalent or better survival during the first year or two of dialysis. However, results on longer-term survival varied according to study and to different subgroups within studies. Subgroup analyses in the prospective cohort studies were limited by small numbers of patients resulting in highly varied and somewhat controversial results when compared to the larger registry-based studies. Based on our review of recent publications and additional analyses of US Medicare data, we conclude that overall patient survival is similar for PD and HD but that important differences do exist within select subgroups of patients, particularly those subgroups defined by age and the presence or absence of diabetes.

Humans↗
PubMed2001

Validation of PD Adequest 2.0 for pediatric dialysis patients.

Kinetic modeling has proven to be a valuable tool for peritoneal dialysis (PD) prescription in adult PD patients. The clinical application of this procedure has rarely been studied in children. We therefore evaluated the PD Adequest 2.0 for Windows program (Baxter Healthcare Co., Deerfield, IL) as a prescription aid for the management of pediatric PD patients by comparing the measured and predicted PD clearances, total drain volumes, and net ultrafiltration in 34 children (15 males) (mean age 10.9 +/- 6.0 years) receiving long-term PD. In each case, a 4-h peritoneal equilibration test was conducted with a standardized test exchange volume of 1,100 ml/m2 BSA. A total of 43 24-h dialysate (plus urine in 12) collections were analyzed. The levels of agreement between measured and predicted values for weekly peritoneal and total urea Kt/V, weekly peritoneal and total creatinine clearance, daily drain volume, net ultrafiltration and daily peritoneal urea and creatinine mass removal were assessed with correlation coefficients (re) and Bland-Altman limits of agreement. The study revealed that there is a basic level of agreement between measured and modeled values for solute removal and total drain volume, with correlation coefficients ranging from 0.75 to 0.98. In contrast, the rc for net ultrafiltration was only 0.34. The majority (75%) of patients had modeled urea and creatinine clearances that were within 20% of their measured values. These data suggest that the PD Adequest 2.0 for Windows program can predict urea and creatinine clearances with reasonable accuracy in pediatric PD patients, making it a valuable resource in prescription management.

Child↗
PubMed2000

Patient survival among incident peritoneal dialysis and hemodialysis patients in an urban setting.

We retrospectively evaluated 432 patients (336 black; 78%; and 96 white; 22%) incident to our peritoneal dialysis (PD; 195 patients; 45%) and hemodialysis (HD; 237 patients; 55%) programs from January 1987 to December 1997 who survived their first 90 days of dialysis therapy. Black patients comprised 70% of the PD and 84% of the HD patients (P: < 0.01). PD patients were more often men and younger than HD patients and less often had diabetes (40% versus 56% of HD patients; P: < 0.01) and cardiac disease (44% versus 58% of HD patients; P: < 0.01) than HD patients. Adjusting for baseline clinical and comorbid features, patient survival was determined by Cox regression analysis. Survival was better on PD therapy overall (relative risk [RR] for PD versus HD, 0.80; 1-, 2-, and 5-year survival rates, 90%, 77%, and 43% on PD versus 88%, 72%, and 35% on HD, respectively; P: = 0.21) and among black patients (RR for PD versus HD, 0.69; 1-, 2-, and 5-year survival rates, 92%, 80%, and 52% on PD versus 88%, 74%, and 40% on HD, respectively; P: = 0.09), but these were not statistically significant. The RR for PD versus HD was 1.08 for white patients (1-, 2-, and 5-year survival rates, 82%, 61%, and 23% for PD versus 82%, 62%, and 24% for HD; P: = 0.79). Significant predictors of mortality were race (RR for whites versus blacks, 1.51), age (RR, 1.03), cardiac disease (RR, 1.57), baseline albumin level (RR, 0.60), baseline serum creatinine level (RR, 0.91), baseline blood urea nitrogen level (RR, 1.01), and baseline weight (RR, 0.98). In conclusion, patient survival on dialysis therapy is significantly better for black patients and for patients entering dialysis with signs of adequate nutrition (increased weight and creatinine and albumin levels) and without evidence of cardiac disease. In an urban dialysis program, we find that adjusted patient survival on PD equals or is better than that on HD therapy, particularly among black patients, making PD a viable alternative to HD in our patient population.

Humans↗
PubMed1999

Racial differences in survival in an urban peritoneal dialysis program.

We retrospectively evaluated 233 incident patients (61% black, 27% white, and 12% Hispanic/Asian) to our peritoneal dialysis (PD) program from January 1987 to September 1997 to identify any possible racial differences in patient survival. Information collected included clinical features, comorbid conditions, nutritional status, and dialysis dose at initiation of dialysis. The average age was 52 +/- 16 (SD) years, and 49% were men. Diabetes mellitus was present in 41% of patients. Overall follow-up was 31 +/- 24 (median 26) months during which time 21% of patients underwent transplant, 29% of patients transferred to hemodialysis (HD), and 42% of patients died. The Cox proportional hazards analysis, based on intent-to-treat, identified age (RR: 1.03), race (RR: 2.35, white versus black), cardiac disease (RR: 1.97), and serum albumin (RR: 0. 44) to independently predict mortality. Further analysis was performed based on diabetic status, and the analysis identified age (RR: 1.06), race (RR: 2.45, white versus black), and peripheral vascular disease (RR: 2.88) as predictors of mortality in diabetic patients. In nondiabetic patients, age (RR: 1.03), race (RR: 2.24, white versus black), cardiac disease (RR: 2.48), cerebrovascular disease (RR: 3.17), and serum albumin (RR: 0.39) were significant predictors of mortality. The significance of race persisted even after adjusting patients transferring to hemodialysis. The adjusted patient survival at 1, 2, and 5 years was 94%, 87% and 53% for black patients, and 86%, 72%, and 23% for white patients. The adjusted patient survival in diabetics at 1, 2, and 5 years was 92%, 79%, and 37% for black patients, and 82%, 56%, and 9% for white patients. The adjusted patient survival in nondiabetics at 1, 2, and 5 years was 94%, 91%, and 63% for black patients, and 88%, 82%, and 35% for white patients. In conclusion, long-term patient survival is better for black patients than white patients in our peritoneal dialysis program. Peritoneal dialysis should be considered a viable dialytic option for black patients entering an end-stage renal disease program.

Adult↗
PubMed1999

Mortality in end-stage renal disease: a reassessment of differences between patients treated with hemodialysis and peritoneal dialysis.

Recent registry studies comparing mortality between peritoneal dialysis (PD) and hemodialysis (HD) patients show conflicting results. The purpose of this study is to determine whether previously published results showing higher mortality for patients treated with PD versus HD in the United States continue to hold true over the period 1987-1993. National mortality rates for PD and HD were extracted from the U.S. Renal Data System (USRDS) annual reports for the cohort periods: 1987-1989, 1988-1990, 1989-1991, 1990-1992, and 1991-1993. Using Poisson regression, death rates per 100 patient years were compared between PD and HD for each cohort period controlling for age, gender, race, and cause of end-stage renal disease (diabetes versus nondiabetes). When incident patients and patients with a prior transplant were included in the analysis, starting with the 1989-1991 cohort, we found little or no difference in the relative risk (RR PD:HD) of death between PD and HD (1987-1989: RR = 1.17, P < 0.001; 1988-1990: RR = 1.12, P < 0.001; 1989-1991: RR = 1.06, P = NS; 1990-1992: RR = 1.06, P = NS; 1991-1993: RR = 1.08, P = 0.043). After a test for goodness-of-fit, separate analyses for diabetic patients and nondiabetic patients were done to examine unexplained variation in death rates. For nondiabetic patients, there was less than a 1% difference in the adjusted 1-yr survival between PD and HD from 1989-1993 (1989-1991: RR = 1.05, P = NS; 1990-1992: RR = 1.04, P = NS; 1991-1993: RR = 1.07, P < 0.01). Among diabetic patients, the PD:HD death rate ratio varied significantly according to gender and age. For the average male diabetic patient, there was little or no difference in risk between PD and HD from 1989-1993 (1989-1991: RR = 1.02, P = NS; 1990-1992: RR = 1.05, P = NS; 1991-1993: RR = 1.08, P < 0.01). For diabetic patients under the age of 50, those treated with PD had a significantly lower risk of death than those treated with HD (1989-1993: 0.84 < or = RR < or = 0.89, P < 0.005). Over the same period, female diabetic patients treated with PD had a higher risk, on average, than HD (1.18 < or = RR < or = 1.19, P < 0.001) as did diabetic patients over the age 50 (1.28 < or = RR < or = 1.30, P < 0.001). Unlike previously published results that were restricted to prevalent-only patients, this national study of both prevalent and incident patients found little or no difference in overall mortality between PD and HD. The recent trends in mortality likely reflect the inclusion of incident patients, but they may also reflect changes in case-mix differences and/or improved PD practice. Additional incident-based studies that allow for additional case-mix adjustments are needed to better compare outcomes between HD and PD.

Adult↗
PubMed1999

Quantifying the effect of changes in the hemodialysis prescription on effective solute removal with a mathematical model.

One potential benefit of chronic hemodialysis (HD) regimens of longer duration or greater frequency than typical three-times-weekly schedules is enhanced solute removal over a relatively wide molecular weight spectrum of uremic toxins. This study assesses the effect of variations in HD frequency (F: per week), duration (T: min per treatment), and blood/dialysate flow rates (QB/QD: ml/min) on steady-state concentration profiles of five surrogates: urea (U), creatinine (Cr), vancomycin (V), inulin (I), and beta2-microglobulin (beta2M). The regimens assessed for an anephric 70-kg patient were: A (standard): F = 3, T = 240, QB = 350, QD = 600; B (daily/short-time): F = 7, T = 100, QB = 350, QD = 600; C/D/E (low-flow/long-time): F = 3/5/7, T = 480, QB = 300, QD = 100. HD was simulated with a variable-volume double-pool model, which was solved by numerical integration (Runge-Kutta method). Endogenous generation rates (G) for U, Cr, and beta2M were 6.25, 1.0, and 0.17 mg/min, respectively; constant infusion rates for V and I of 0.2 and 0.3 mg/min, respectively, were used to simulate middle molecule (MM) G values. Intercompartment clearances of 600, 275, 125, 90, and 40 ml/min were used for U, Cr, V, I, and beta2M, respectively, For each solute/regimen combination, the equivalent renal clearance (EKR: ml/min) was calculated as a dimensionless value normalized to the regimen A EKR, which was 13.4, 10.8, 6.6, 3.7, and 4.8 ml/min for U, Cr, V, I, and beta2M, respectively. For regimens B, C, D, and E, respectively, these normalized EKR values were U: 1.04, 0.96, 1.58, and 2.22; Cr: 1.03, 1.08, 1.80, and 2.55; V: 1.06, 1.32, 2.21, and 3.12; I: 1.05, 1.54, 2.57, and 3.62; beta2M: 1.00, 1.27, 1.73, and 2.19. The extent of post-HD rebound (%) was highest for regimens A and B, ranging from 16% (urea) to 50% (inulin), and lowest for regimen E, ranging from 6% (urea) to 28% (beta2M). The following conclusions can be made: (1) Relative to a standard three-times-weekly HD regimen of approximately the same total (weekly) treatment duration, a daily/short-time regimen results in modest (3 to 6%) increases in effective small solute and MM removal. (2) Relative to a standard three-times-weekly HD regimen, a three-times-weekly low-flow/long-time regimen results in comparable effective small solute removal and progressive increases in MM and beta2M removal. A daily low-flow/long-time regimen substantially increases the effective removal of all solutes.

Body Fluid Compartments↗
PubMed1997

Lower probability of patient survival with continuous peritoneal dialysis in the United States compared with Canada. Canada-USA (CANUSA) Peritoneal Dialysis Study Group.

In a prospective cohort study of 680 incident continuous peritoneal dialysis (PD) patients in North America, dialysis in the United States compared with Canada was associated with a relative risk (RR) of death of 1.93 (95% confidence interval [CI], 1.14 to 3.28). The 2-yr survival probability was 79.7% in Canada and 63.2% in the United States. This difference was not explained by race, age, gender, functional status, insulin-dependent diabetes mellitus, history of cardiovascular disease (CVD), nutritional status, or adequacy of dialysis. Other potential explanatory variables were further evaluated. These included severity of CVD, residual renal function, race, differential transfer to hemodialysis or transplantation, patient compliance, modality selection bias, and incidence of endstage renal disease requiring dialysis. Cardiovascular morbidity and peritonitis probabilities were compared. The CVD severity index was not different between countries; the RR risk associated with dialysis in the United States remained high at 1.87 (95% CI, 1.09 to 3.19). Residual renal function at initiation of dialysis was not different between countries. The 2-yr survival for Caucasians was 77% in Canada and 55% in the United States. There was no difference in the probability of transfer to hemodialysis or transplantation. The RR of a nonfatal cardiovascular event in the United States compared with Canada was 1.80 (95% CI, 1.21 to 2.67). There was no difference in time to first peritonitis. The observed to predicted creatinine ratio, as an estimate of compliance, was 1.13 in Canada and 1.00 in the United States. The prevalence of PD in the study centers was 48% in Canada and 22% in the United States. The incidence of new dialysis patients in 1992 was 100/million population in Canada compared with 211/ million in the United States. The survival difference is not explained by age, gender, insulin-dependent diabetes mellitus, nutritional status, or adequacy of dialysis. Neither is it explained by race, severity of CVD, transfer to hemodialysis, transplantation, or an estimate of compliance. The lower proportion of patients receiving PD in the United States may represent a selection bias of uncertain direction. The higher acceptance rate for dialysis in the United States may explain, in part, the greater cardiovascular morbidity and the decreased survival observed.

Adult↗
PubMed1996

Goodness-of-fit in generalized nonlinear mixed-effects models.

In recent years, generalized linear and nonlinear mixed-effects models have proved to be powerful tools for the analysis of unbalanced longitudinal data. To date, much of the work has focused on various methods for estimating and comparing the parameters of mixed-effects models. Very little work has been done in the area of model selection and goodness-of-fit, particularly with respect to the assumed variance-covariance structure. In this paper, we present a goodness-of-fit statistic which can be used in a manner similar to the R2 criterion in linear regression for assessing the adequacy of an assumed mean and variance-covariance structure. In addition, we introduce an approximate pseudo-likelihood ratio test for testing the adequacy of the hypothesized convariance structure. These methods are illustrated and compared to the usual normal theory likelihood methods (Akaike's information criterion and the likelihood ratio test) using three examples. Simulation results indicate the pseudo-likelihood ratio test compares favorably with the standard normal theory likelihood ratio test, but both procedures are sensitive to departures from normality.

Adolescent↗
PubMed1995

Peritonitis in an urban peritoneal dialysis program: an analysis of infecting pathogens.

We have previously found that race, level of education, and peritoneal dialysis system are factors that significantly and independently influence peritonitis rates in our patient population. We now extend these observations by assessing the pathogens responsible for peritonitis in these subgroups. Between January 1, 1981, and May 15, 1993, 248 peritoneal dialysis patients underwent dialysis at our facility. The rate of peritonitis by pathogen was determined in these patients using the fixed effects Poisson model. Total peritonitis rates in black patients (1.89 episodes/patient-year) were significantly greater compared with white patients (1.11 episodes/patient-year; P < 0.0001). Increased infection rates in black patients were significant for Staphylococcus epidermidis, Staphylococcus aureus, and gram-negative pathogens. The level of education had a negative correlation with peritonitis rates (< or = 8 years, 2.00 episodes/patient-year; 9 to 12 years, 1.64 episodes/patient-year; and > or = 13 years, 1.24 episodes/patient-year) with patients having > or = 13 years of education at the start of dialysis demonstrating a significantly lower total peritonitis rate compared with patients with 9 to 12 years (P = 0.001) or < or = 8 years (P < 0.001) of education. This was accounted for by a significant decrease in infection rates for S epidermidis, polymicrobial, and gram-negative organisms. Finally, patients on automated peritoneal dialysis had significantly lower total peritonitis rates (0.59 episodes/patient-year) compared with patients on either a connect (2.11 episodes/patient-year) or disconnect (1.46 episodes/patient-year) system.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Blood pressures in hemodialysis and peritoneal dialysis using ambulatory blood pressure monitoring.

To define the influence that dialytic modality has on the blood pressure (BP) level and pattern, 33 hemodialysis (HD) and 27 peritoneal dialysis (PD) patients had their BP monitored hourly over an approximate 48-hour period using an ambulatory blood pressure monitoring (ABPM) device. A trigonometric cosine model was used to describe the diurnal BP pattern. Regression coefficients obtained from fitting this model to the observed hourly blood pressures were then compared between HD and PD patients to determine if the dialytic modality had any influence on BP level or pattern. The results indicate that HD and PD patients both exhibit similar diurnal patterns, but that HD patients have significantly higher average systolic BPs (142.1 +/- 16.3 v 130.4 +/- 17.1 mmHg, P < 0.01) and "systolic loads" (percent systolic values > 140 mmHg [54% +/- 29% v 30% +/- 31%, P < 0.01]) compared with PD patients. There were no significant differences in their diastolic BPs, diastolic loads, mean arterial pressures, or heart rates. No other factors (demographic or biochemical data, or medication usage) were found to significantly affect BP. In addition, a single BP reading for PD patients and predialysis and postdialysis BP readings for HD patients were measured by the dialysis nurse or technician on the day that the ABPM device was attached and removed, and were compared with the mean BP readings as determined by ABPM. These single values did not achieve good concordance with the 24-hour average BPs. ABPM and the cosine model have demonstrated that the diurnal pattern of BP is maintained in both PD and HD, and that HD is associated with higher systolic BPs and greater systolic loads than PD.

Adult↗
PubMed1994

Relationship between body size, fill volume, and mass transfer area coefficient in peritoneal dialysis.

A peritoneal dialysate fill volume of 2 L has become the standard of clinical practice, but the relationships between body size, fill volume, and mass transfer area coefficient (KoA) have not been well established. These relationships were studied in 10 stable peritoneal dialysis patients who underwent six peritoneal equilibration studies (2 h each) at fill volumes of 0.5, 1, 1.5, 2, 2.5, and 3 L. The concentration-time profiles for urea, creatinine, and glucose were measured at each fill volume, and residual volumes were calculated from the preceding dwell period. A modified Henderson equation was used to calculate the KoA for the three solutes as a function of fill volume. By normalizing the KoA for each solute to the value at 2 L, the data for all three solutes collapsed onto the same trend line when plotting the normalized KoA versus dialysate volume. Between 0.5- and 2-L fill volumes, the average normalized KoA increases in an almost linear fashion, its value almost doubling over this range. Between 2- and 3-L fill volumes, there is less than a 10% change in the normalized KoA. However, fill volumes for peak urea KoA were found to increase with increasing body surface area (R = 0.76), being around 2.5 L for an average-sized patient and increasing to between 3 and 3.5 L for body surface areas > 2 m2. To maximize solute transport, these relationships between body size, volume, and KoA should be considered when choosing fill volumes for continuous ambulatory peritoneal dialysis and automated peritoneal dialysis and when deciding reserve and tidal volumes for tidal peritoneal dialysis.

Body Surface Area↗
PubMed1993

A retrospective assessment of risk factors for peritonitis among an urban CAPD population.

Peritonitis is a major reason why patients transfer from peritoneal dialysis (PD) to hemodialysis. We evaluated the peritonitis infection rates in 146 peritoneal dialysis patients who underwent dialysis at our facility between 1 January 1981 and 31 December 1989. Peritonitis was the primary cause for changing treatment, with 24 (16.4%) of the patients transferring because of this complication. This represented 54.5% of all patients discontinuing CAPD due to method failure. A gamma-Poisson regression analysis was performed in an attempt to identify potential risk factors associated with an increased incidence of peritonitis. The results indicated that race, education level, and PD system used were significantly associated with the rate at which peritonitis occurred in our patient population. There was an almost twofold increase in the rate of peritonitis among blacks as compared to whites (2.2 vs 1.2 episodes/patient year). The level of education completed at the start of dialysis had a negative correlation with peritonitis rates. Patients with < or = 8, 9-12, and > or = 13 years of education had peritonitis rates of 2.4, 1.8, and 1.2 episodes/patient year, respectively. Finally, the system used had a significant effect with our patients on CCPD having lower peritonitis rates as compared to patients on either a connect or disconnect system (0.6 vs 2.5 vs 1.8 episodes/patient year, respectively). Recognizing potential risk factors for peritonitis will help us better understand and address this significant problem in our PD programs. Reducing peritonitis rates should facilitate a decrease in patient transfer due to method failure.

Adolescent↗
PubMed1992

A random coefficient growth curve analysis of mental development in low-birth-weight infants.

In many medical studies, longitudinal data are collected on each of a sample of patients. The objectives of such studies often are: to estimate and test bivariate or multivariate relationships within each of several groups of patients from these repeated measures data; to compare these relationships among groups; and to test for the effects of baseline covariates on the relationships. This paper illustrates the use of statistical methods for growth curve analysis recently proposed by Vonesh and Carter for achieving these goals by relating a measure of preschool cognitive development to age in four race by sex groups of low-birth-weight infants. Significant declines in Bayley's Mental Development Index (MDI) with increasing age were found in all groups. Birth-weight did not significantly influence the rate of decline but did influence the overall level of performance. Even so, in the group most comparable to Bayley's normative population, predicted MDI was near the norm even for extremely low-birth-weight infants (that is, 1000 grams). Although there is some risk of mental deficit associated with prematurity, eventual developmental delays in low-birth-weight infants frequently are acquired with age. The rate of decline in MDI was significantly associated with race and mother's education. Assumptions required for the valid application of these methods are discussed and tested in the setting of this applied problem. The assumptions appeared valid in this application. We conclude with a brief discussion of available alternatives when the assumptions are violated and point to areas for future research.

Age Factors↗