Francis Dumler

Impedance Vector Distribution by Sex, Race, Body Mass Index, and Age in the United States: Standard Reference Intervals as Bivariate Z Scores

Bioelectrical impedance measurements were collected in the Third National Health and Nutrition Examination Survey (NHANES III), but their results have not been published. In the NHANES III population, resistance (R) and reactance (Xc) values at 50-kHz frequency were obtained with a Valhalla Scientific meter (model 1990B; San Diego, CA, USA). The RXc graph method was used to identify bivariate pattern distributions of mean vectors (95% confidence ellipses by sex, race, age, and body mass index [BMI]), and individual impedance vectors (50%, 75%, and 95% tolerance ellipses). Data from 10 222 adults (5261 men and 4961 women) formed 90 four-way classification groups, with two sexes, three races or ethnicities (non-Hispanic white, non-Hispanic black, Mexican American), five age classes (20-29, 30-39, 40-49, 50-59, and 60-69 y), and three BMI classes (19-24.9, 25-29.9, and 30-34.9 kg/m(2)). Sex, race or ethnicity, BMI and age, in decreasing order, influenced the vector distribution pattern. Mean vectors in women were significantly longer than those in men. Within each sex, the mean vector of non-Hispanic white subjects was shorter and with a smaller phase angle than that of corresponding BMIs from the two other race/ethnic populations. Tolerance ellipses were calculated from sex- and race-specific reference populations 20 to 69 y old and 19 < or = BMI < 30 kg/m(2) (8022 subjects, 4226 men and 3796 women). After transformation of impedance vector components into bivariate Z scores (standardized deviates, as differences from the mean divided by the standard deviation of the reference population), we constructed one standard, reference, RXc-score graph (50%, 75%, and 95% tolerance ellipses) that can be used with any analyzer in any population. The pattern of impedance vector distribution and reference bivariate intervals for the individual impedance vector are presented for comparative studies (free software at E-mail: apiccoli@unipd.it).

Dietary Sodium Intake and Arterial Blood Pressure

We sought to summarize major recent studies in the field of dietary sodium intake and arterial blood pressure, and discuss the following trials. INTERSALT: Sodium intake correlates with the rise in blood pressure with age, but not with the prevalence of hypertension. The population study identified a minimal impact of sodium intake on blood pressure (0.9 mm Hg/10 mmol difference in salt intake). DASH: This diet induced significant reductions in blood pressure compared with the control diet. Further decreases were observed with DASH and a 50 mmol/day sodium intake. VANGUARD: Blood pressure was inversely related to urinary potassium, calcium and magnesium but not to sodium excretion. TONE: Cardiovascular events were highest in the usual care group (83%) and lowest in the sodium reduction-plus-weight loss group (56%). META-ANALYSIS: A systematic review of 11 long-term controlled randomized trials reported a small decrease (1.1 mm Hg) in median systolic but not diastolic blood pressure with a reduced dietary sodium intake. In conclusion, (1) sodium restriction in hypertensive patients reduces blood pressure, and (2) the long-term impact of reduced salt intake on blood pressure, mortality, and morbidity remains to be defined.

Nutritional status assessment and body composition analysis in pre-end stage renal disease patients.

Malnutrition is a known risk factor for survival in renal failure patients. Of concern, a significant degree of malnutrition may develop in the predialysis period due to dietary restrictions and uremia. To further define this issue, we evaluated 25 predialysis patients using serum chemistries, body mass index (BMI), fat free mass (FFM), body cell mass (BCM), and protein appearance rate (PAR) as surrogates of nutritional status and compared their results to those obtained in established hemodialysis patients and recipients of living donor renal allografts during a nine-month observation period. Pre- dialysis patients had significantly (p<0.0001) higher body weight (28%), body mass index (26%), body cell mass (17%) and fat free mass (15%) than hemodialysis and transplant patients. Intracellular water content was similar in all groups. As many patients do not start dialysis until clearance values fall below 10 ml/min, it is possible that greater tissue mass losses occur in the weeks preceding initiation of dialytic therapy. Why renal transplant recipients fail to increase tissue mass may relate to the catabolic effects of immunosuppression. We conclude that the early stages of pre-end stage renal disease are associated with relatively good preservation of body cell mass.

Impact of dialysis modality and acidosis on nutritional status.

Experimental evidence suggests that acidosis may have a deleterious effect on protein metabolism. We evaluated 124 chronic dialysis patients (59 +/- 17 years) and defined acidosis as an anion gap >18 meq/L. A direct correlation (p < 0.0001 was found between anion gap and serum albumin (R = 0.402), BUN (R = 0.488), and serum creatinine (R = 0.473) concentrations. Acidotic patients (43%), when compared with nonacidotic patients, had greater serum albumin concentrations (3.95 +/- 0.50 vs. 3.60 +/- 0.48 g/dl, p = 0.0001, respectively), higher normalized protein catabolic rates (1.12 +/- 0.27 vs. 0.96 +/- 0.26 g/kg/d, respectively; p = 0.0004), and higher BUN (70 +/- 19 vs. 55 +/- 17 mg/dl, p = 0.0001) and serum creatinine (11.1 +/- 3.4 vs. 8.3 +/- 3.2, p = 0.0001 mg/dl) concentrations. However, no differences in midarm muscle circumference, fat free mass, or body cell mass were noted between groups when assessed by dialysis modality or acidosis status. In conclusion, mild chronic metabolic acidosis, likely caused by increased dietary protein intake, does not independently and adversely impact nutritional status in chronic dialysis patients.

Anemia Management With Darbepoetin-alfa in Outpatient Hemodialysis Patients Switched From Epoetin-alfa: A Community Hospital Experience

Epoetin-alfa (EA) and darbepoetin-alfa (DA) are agents for treating anemia in dialysis patients. In September 2005, our free-standing outpatient hemodialysis center (community-hospital based) implemented an interchange from EA to DA. Since then, all hemodialysis patients receive DA as the preferred agent. We performed this observational study to compare effectiveness of DA with EA in anemia management in a cohort of hemodialysis outpatients. We studied 98 hemodialysis outpatients who received twice to thrice weekly EA from January to August 2005. These patients were switched to DA in September 2005, and baseline DA dose was calculated from the conversion table in the package insert. After a 4 month titration phase, the same cohort of patients, now on once weekly DA, was followed from January to September 2006. Dose of EA or DA was adjusted to maintain hemoglobin at 11 to 13 g/dL. Hematologic and dialysis parameters were collected on a monthly basis, and inpatient data were excluded. Mean ± standard deviation age was 65.8 ± 14.2 years, with 42 (42.9%) women. Mean ± standard deviation hemoglobin level was 12.5 ± 1.6 g/dL during EA and 12.5 ± 1.6 g/dL during DA therapy (P = 0.23). Proportion of patients achieving hemoglobin (11-13 g/dL) was 44.5% ± 28.9% with EA and 49.8% ± 25.8% with DA (P = 0.09). Average intrapatient absolute hemoglobin variability was 1.0 ± 0.5 g/dL on EA and 1.1 ± 0.5 g/dL on DA (P = 0.29). Median (and interquartile range) EA dose used was 11,400 (7,050-22,800) IU/week, and median DA dose was 59.8 (40-91.6) mcg/week with an EA:DA dose conversion ratio of 191:1. Patients on EA or DA had similar dialysis adequacy, albumin, and iron parameters. DA is as effective as EA in treating anemia in hemodialysis outpatients. Dose requirement of DA is greater than 200:1 of the amount of EA and may not translate into cost savings.

Surveillance of Nutritional Status in Chronic Dialysis Patients

Abstract Objective: To evaluate the clinical use of upper arm anthropometry and bioelectrical impedance techniques for body composition analysis in the routine nutritional assessment of patients in a free-standing dialysis unit. Design: Cross-sectional. Setting: Tertiary care community medical center. Patients: One hundred thirty-four patients (77 on hemodialysis and 67 on peritoneal dialysis) treated at a free-standing dialysis center (age: 59 ± 17 years; 37% female; 21% black). Intervention: None. Main Outcome Measures: Midarm muscle circumference (MAMC), fat-free mass by bioelectrical impedance (FFM-BEI). A value less than 90% of predicted (calculated in age- and gender-matched controls) defined risk for malnutrition. Results: The prevalence of risk for malnutrition ranged between 30% (FFM-BEI) and 37% (MAMC), and was similar in hemodialysis and peritoneal dialysis patients. A serum albumin concentration less than 35 g/L was observed in only 19% of patients. On average, 33% of patients with muscle mass less than 90% of predicted had a normal serum albumin concentration. Among hypoalbuminermic patients, only 9% had a normal muscle mass content. Normalized protein catabolic rates were lower in hypoalbuminemic than normoalbuminemic patients (0.61 ± 0.28 versus 0.90 ± 0.35 g/kg/d, respectively; P = .0001). Conclusions: MAMC and FFM-BEI are practical tools for routine clinical surveillance of patients at risk for protein malnutrition.

Reuse of Dialyzers

Reprocessing of hemodialyzers (reuse) is an increasingly common practice in the United States and is regularly surveyed by the U.S. Centers for Disease Control (CDC). Data for 1990 indicate that approximately 70% of hemodialysis centers reprocess dialyzers on a regular basis (1). Historical reasons for reusing dialyzers have included availability and cost. A recent Canadian study has estimated savings of

Primary Nonfunction of Renal Allograft Secondary to Acute Oxalate Nephropathy

3,629 per patient per year (assuming an average of five reuses per dialyzer), if a national policy for reuse were implemented (2). Although there are important financial reasons for establishing a dialyzer reprocessing program in any given hemodialysis center, the major concern is its impact on patient care., There are three major areas to consider: ( i ) clinical advantages from use of reprocessed dialyzers, (ii) complications directly related to reprocessing, and (iii) long-term surveillance of the reprocessing program and its clinical impact on patient well-being.

Body composition analysis in chronic dialysis patients: a longitudinal study

Primary nonfunction (PNF) accounts for 0.6 to 8% of renal allograft failure, and the focus on causes of PNF has changed from rejection to other causes. Calcium oxalate (CaOx) deposition is common in early allograft biopsies, and it contributes in moderate intensity to higher incidence of acute tubular necrosis and poor graft survival. A-49-year old male with ESRD secondary to polycystic kidney disease underwent extended criteria donor kidney transplantation. Posttransplant, patient developed delayed graft function (DGF), and the biopsy showed moderately intense CaOx deposition that persisted on subsequent biopsies for 16 weeks, eventually resulting in PNF. The serum oxalate level was 3 times more than normal at 85 μmol/L (normal <27 μmol/L). Allograft nephrectomy showed massive aggregates of CaOx crystal deposition in renal collecting system. In conclusion, acute oxalate nephropathy should be considered in the differential diagnosis of DGF since optimal management could change the outcome of the allograft.

Use of bioelectrical impedance techniques for monitoring nutritional status in patients on maintenance dialysis

Abstract Objective Nutritional status is an important determinant of morbidity and mortality in dialysis patients. Body composition analysis bioelectrical impedance techniques are becoming commonplace in the clinical setting. Our objective is to report our clinical experience using bioelectrical impedance analysis for the prospective nutritional surveillance of dialysis patients. Methods A total of 204 patients, 157 on hemodialysis and 47 on peritoneal dialysis were followed for a median of 21 months. Values from the first trimester were averaged and compared to those obtained in the last trimester. Bioelectrical impedance values were obtained using a single frequency (50 kHz) bioimpedance analyzer. Results Baseline values for body weight, height, body mass index and body surface area were similar in both treatment modalities. Hemodialysis patients lost a discreet amount of body weight (1.5%, p=0.0334). Body weight did not change in peritoneal dialysis patients. Significant decreases in resistance (p=0.l0023) and phase angle (p=0.0481) were noted in hemodialysis but not peritoneal dialysis patients. A small but significant decrease in fat free (1.8%; p=0.0028) and body cell free (3.3%; p=0.0036) mass was noted in hemodialysis but not peritoneal dialysis patients. Conclusions 1. Bioelectrical impedance analysis may detect losses in fat free mass and body cell mass that are not apparent by body weight monitoring. 2. Bioelectrical impedance analysis is a practical clinical tool for evaluating body composition in dialysis patients.