Body composition assessed by neutron activation analysis in dialysis patients.

Malnutrition is prevalent in end-stage renal disease (ESRD) patients treated with hemodialysis (HD) and peritoneal dialysis (PD). In addition, there is increased incidence of morbidity in this group. Evaluation of nutritional status is important. Application of body composition in the ESRD population to evaluate body compartments and to assess nutritional health has become more common in clinical practice. Neutron activation analysis (NAA) may provide data on metabolically active tissue by quantification of total body potassium (TBK) for body cell mass and assessment of protein by total body nitrogen (TBN). This method may be able to detect changes in body composition before clinical signs of malnutrition are apparent. Ten HD (5 male and 5 female) and 10 PD patients (7 male and 3 female) were evaluated by NAA, TBK, and isotope dilution. Female PD patients had an increased total body water (TBW) and increased intracellular water compared to HD females. Albumin was lower in PD women. There was no significant difference between PD men and laboratory controls in TBW, extracellular water, and TBN. The clinical application of body composition methods for evaluation of dialysis patients by serial assessment and for development of a bedside tool needs further study.

Dual-energy X-ray absorptiometry: a review.

Dual-energy X-ray absorptiometry (DXA) has been recently used for body composition analysis in dialysis patients. It is based on the principle that X-rays passed through various body tissues have different attenuation and, therefore, can be differentiated. By using X-rays at two different energy levels, better tissue differentiation is possible compared with single energy systems. This article will review the evolution of DXA scanners and the role DXA has in assessing body composition in dialysis patients. Overall, this technique has excellent precision and holds promise for use in the serial evaluation of body composition and nutritional evaluation of dialysis patients.

Percentage body fat determination in hemodialysis and peritoneal dialysis patients: a comparison.

OBJECTIVE: To evaluate percentage body fat in hemodialysis (HD) and peritoneal dialysis (PD) patients. DESIGN: A prospective study of 20 HD patients and 20 PD patients. SETTING: Sol Goldman Renal Therapy Center, Lenox Hill Hospital, New York, NY; Baumritter Kidney Center Albert Einstein College of Medicine, Bronx, NY; Body Composition Unit, St Luke's Roosevelt Hospital, Columbia University, New York, NY. PATIENTS: Twenty HD (10 men, 10 women) patients, mean age 41.8 +/- 2.4 years and 20 PD (12 men, 8 women) patients, mean age 48.6 years +/- 3.0 years. INTERVENTION: This is a noninterventional study. PATIENTS signed consent to undergo dual-energy x-ray absorptiometry, total body potassium counting bioelectrical impedance analysis, total body water determination, and anthropmetric evaluation. MAIN OUTCOME MEASURES: Present and compare percentage body fat between HD and PD patients as determined by the methods used. RESULTS: Percentage fat is not different between HD and PD patients. Differences in absolute values of percent fat between techniques exist. CONCLUSION: HD patients and PD patients may be evaluated by the methods of body composition used. Percentage body fat will vary among techniques; therefore the same method should be used to follow a patient over time.

Neuroendocrine pharmacology of three serotonin releasers: 1-(1,3-benzodioxol-5-yl)-2-(methylamino)butane (MBDB), 5-methoxy-6-methyl-2-aminoindan (MMAi) and p-methylthioamphetamine (MTA).

Serotonin (5-hydroxytryptamine, 5-HT)-releasing drugs are important experimental tools to examine the role of serotonergic nerve terminals in the secretion of hormones. The drugs 1-(1,3-benzodioxol-5-yl)-2-(methylamino)butane (MBDB), 5-methoxy-6-methyl-2-aminoindan (MMAI) and p-methylthioamphetamine (MTA) have been suggested to be 5-HT releasers. The present study characterized MBDB, MMAI and MTA by using their effects on the secretion of the hormones adrenal corticotrophin (ACTH), corticosterone, prolactin, oxytocin and renin. The time course of the effect of MBDB, MMAI and MTA (5 mg/kg, i.p.) showed that the peak effect on plasma ACTH occurred 10 min after the injection, whereas the prolactin response did not reach a maximum until 30 min after injection. MBDB increased plasma renin concentration within 10 min, whereas the effect of MTA was significant only at 30 min after injection. All three 5-HT releasers decreased HR (within 5 min) and blood pressure (at 15 min after injection). MBDB, MMAI and MTA increased plasma ACTH, corticosterone, prolactin and renin levels in a dose-dependent manner, whereas no changes were observed in plasma vasopressin concentrations. MTA and MMAI, but not MBDB, significantly increased plasma oxytocin concentrations in a dose-dependent manner. Pretreatment of rats with fluoxetine blocked the ACTH response to MBDB and MMAI, but not to MTA. The prolactin response to all three 5-HT releasers was blocked by fluoxetine. The oxytocin response to MTA and MMAI was inhibited by fluoxetine. The renin responses to all three 5-HT releasers were not significantly inhibited by fluoxetine. The results suggest that MBDB, MMAI and MTA can increase the secretion of several hormones, at least in part, through stimulation of serotonergic neurotransmission. However, these three 5-HT releasers seem to have effects on other (and as yet uncharacterized) mechanisms that can stimulate the secretion of some hormones.

Comparison of five body-composition methods in peritoneal dialysis patients.

Body-composition assessment is an important method of evaluating nutritional status in peritoneal dialysis patients. Because body-composition measurement estimates have not been fully validated in this population, we assessed five body-composition methods in 30 well-dialyzed peritoneal dialysis patients. The techniques studied included bioelectrical impedance analysis, dual-energy X-ray absorptiometry, total-body potassium counting, and anthropometry by two techniques. The dialysis patients were matched for age, race, sex, height, weight, and body mass index with 29 healthy control subjects in our laboratory database. By 5 x 2 x 2 analysis of variance, significant differences were found between results by modality (P < 0.0001) as well as by sex, with women having an increased percentage of fat (P < 0.0001). However, there was no significant intermethod difference by condition (peritoneal dialysis or control). That is, although significantly different percentage fat values were found between the body-composition techniques, this variability was independent of whether the measurement was made on control or peritoneal dialysis patients. Despite the differences between modalities, all techniques were found to correlate significantly with each other (P < 0.01 or better for men and P < 0.001 or better for women). Our experience shows that these routine techniques for measuring body composition can be readily applied to stable peritoneal dialysis patients.

Bioelectrical impedance analysis and dual energy x-ray absorptiometry to monitor nutritional status.

There exists an imperative to monitor changes in body composition in all dialysis patients on a regular basis to avoid overt malnutrition. In this regard, the absolute measurement of the fat-free mass assessment may not be as crucial as the serial measurement of fat-free mass with the same modality. A significant difference in measured fat and fat-free mass should be expected if different techniques are employed. Therefore, when attempting to monitor patients over time or to assess the effects of changes in therapeutic regimens, a single methodology should be employed. Our data validate the use of BIA in the stable PD patient, indicating that BIA can predict the DXA results. Considering the ease with which BIA measurements can be obtained and the lack of dependency on operator interpretation, BIA is an ideal technique for use in the clinical setting. The applicability of this technique for use in monitoring longitudinal changes in body composition has, in fact, been well established (25, 30, 31). BIA appears to be an excellent method for routine fat-free mass measurement in dialysis patients. In as much as malnutrition continues to remain a significant problem in PD patients, measuring and monitoring body composition is strongly recommended.

Use of the BACTEC system for drug susceptibility testing of Mycobacterium tuberculosis, M. kansasii, and M. avium complex.

A total of 199 Mycobacterium tuberculosis, 182 M. kansasii, and 32 M. avium complex isolates were tested for susceptibility to either three or 10 color-coded drugs in a four-phase study using the conventional 7H10 plate method and the BACTEC system. Agreement between the two test systems for M. tuberculosis isolates against isoniazid, ethambutol, and rifampin was 96%; it was 93.6% against all 10 drugs. Disagreement was highest for ethionamide and cycloserine. M. kansasii data were encouraging, with 88.9% drug agreement against 10 drugs, but M. avium complex agreement was only 51.6% against 10. Average time required for reportable results was 4.8 days for M. tuberculosis, 4.3 days for M. kansasii, and 3.4 days for M. avium complex. Growth for 3 days in an enrichment medium yielded suspensions of the organisms in a logarithmic growth phase and reduced problems of clumps of cells in inocula.