Identification of fluid overload in elderly patients with chronic kidney disease using bioimpedance techniques.

Diagnosis of fluid overload (FO) in early stage is essential to manage fluid balance of patients with chronic kidney disease (CKD) and to prevent cardiovascular disease (CVD). However, the identification of fluid status in patients with CKD is largely dependent on the physician's clinical acumen. The ratio of fluid overload to extracellular volume (FO/ECV) has been used as a reference to assess fluid status. The primary aim of this study was to compare FO/ECV with other bioimpedance methods and clinical assessments in patients with CKD. Whole body ECV, intracellular volume (ICV), total body water (TBW), and calf normalized resistivity (CNR) were measured (Hydra 4200). Thresholds of FO utilizing CNR and ECV/TBW were derived by receiver operator characteristic (ROC) analysis based on data from pooled patients with CKD and healthy subjects (HSs). Clinical assessments of FO in patients with CKD were performed by nephrologists. Patients with CKD (stage 3 and stage 4) (n = 50) and HSs (n = 189) were studied. The thresholds of FO were ≤14.3 (10-2 Ωm3/kg) for females and ≤13.1 (10-2 Ωm3/kg) for males using CNR and ≥0.445 in females and ≥0.434 in males using ECV/TBW. FO was diagnosed in 78%, 62%, and 52% of patients with CKD by CNR, FO/ECV, and ECV/TBW, respectively, whereas only 24% of patients with CKD were diagnosed to be FO by clinical assessment. The proportion of FO in patients with nondialysis CKD was largely underestimated by clinical assessment compared with FO/ECV, CNR, and ECV/TBW. CNR and FO/ECV methods were more sensitive than ECV/TBW in identifying fluid overload in these patients with CKD.NEW & NOTEWORTHY We found that fluid overload (FO) in patients with nondialysis CKD was largely underestimated by clinical assessment compared with bioimpedance methods, which was majorly due to lack of appropriate techniques to assess FO. In addition, although degree of FO by bioimpedance markers positively correlated with the age in healthy subjects (HSs), no difference was observed in the three hydration markers between groups of 50 ≤ age <70 yr and age ≥70 yr in the patients with CKD.

Ferric pyrophosphate citrate: interactions with transferrin.

There are several options available for intravenous application of iron supplements, but they all have a similar structure:-an iron core surrounded by a carbohydrate coating. These nanoparticles require processing by the reticuloendothelial system to release iron, which is subsequently picked up by the iron-binding protein transferrin and distributed throughout the body, with most of the iron supplied to the bone marrow. This process risks exposing cells and tissues to free iron, which is potentially toxic due to its high redox activity. A new parenteral iron formation, ferric pyrophosphate citrate (FPC), has a novel structure that differs from conventional intravenous iron formulations, consisting of an iron atom complexed to one pyrophosphate and two citrate anions. In this study, we show that FPC can directly transfer iron to apo-transferrin. Kinetic analyses reveal that FPC donates iron to apo-transferrin with fast binding kinetics. In addition, the crystal structure of transferrin bound to FPC shows that FPC can donate iron to both iron-binding sites found within the transferrin structure. Examination of the iron-binding sites demonstrates that the iron atoms in both sites are fully encapsulated, forming bonds with amino acid side chains in the protein as well as pyrophosphate and carbonate anions. Taken together, these data demonstrate that, unlike intravenous iron formulations, FPC can directly and rapidly donate iron to transferrin in a manner that does not expose cells and tissues to the damaging effects of free, redox-active iron.

A Simplified Sample Preparation Method for the Assessment of Plasma Ascorbic Acid in Clinical Settings.

BACKGROUND: Vitamin C deficiency is difficult to diagnose on the basis of clinical presentation alone and requires plasma levels for confirmation. Reference laboratories typically specify shipment of plasma on dry ice. This requirement may complicate clinic work flow and delay vitamin C measurement. Additionally, patients with vitamin C deficiency may experience unnecessary testing and increased health-care costs, as other diagnoses are often considered first. We examined an alternative, more practical shipping method. METHODS: Plasma was collected from 17 healthy volunteers by use of heparin tubes with gel separators, and all tubes were centrifuged immediately to separate the plasma layer from the cells. Baseline vitamin C was measured in plasma obtained immediately after specimen collection. Remaining sample tubes were held in Styrofoam containers with cold packs for 30 h or 48 h, followed by vitamin C measurement. Additional samples were exposed to conditions that simulated harsher shipping conditions. RESULTS: Mean plasma vitamin C was 69.6 µmol/L (SD = 21.5 µmol/L). Vitamin C losses were 5.4% at 30 h (SD = 5.55%, P < 0.05) and 7.6% at 48 h (SD = 5.56%, P < 0.05), which is slightly more than freeze-and-thaw treatment (average loss of 1.4%, SD = 6.9%, NS). The vitamin C method had an intraday variation of 1.88%. Vigorous shaking of 2 samples for 24 h resulted in a -1.9% change in 1 sample, and a +4.1% change in another sample. Exposure of the shipping container to elevated temperature (35 °C for 30 h) did not change the internal temperature of the container. CONCLUSIONS: The shipping procedure uses routine sample handling, standard vacutainers, and can be replicated by health-care centers seeking to evaluate patient vitamin C status.

Tryptophan and Kynurenine Levels and Its Association With Sleep, Nonphysical Fatigue, and Depression in Chronic Hemodialysis Patients.

OBJECTIVE: Sleep and mood disorders are common in hemodialysis (HD) patients and the pathophysiology is still unclear. Tryptophan (TRP) and its metabolites may play a prominent role in neural pathways related to sleep, fatigue, and depression. Here, we sought to compare the levels of TRP and its metabolites between HD patients and healthy subjects and examine their association with sleep, fatigue, and depression in HD patients. The design was cross-sectional analysis. SUBJECTS: Ninety-nine adult patients on stable thrice weekly HD schedule between September 2011 and March 2014 and 10 healthy controls. INTERVENTION: Venous blood samples were drawn in healthy subjects and immediately before dialysis in chronic HD patients. TRP and kynurenine (KYN) metabolites were measured by high-performance liquid chromatography. The Medical Outcomes Study Sleep Scale, the PROMIS Short form Fatigue, and the Patient Health Questionnaire were administered concurrently. MAIN OUTCOME MEASURE: Sleep, fatigue, and depression as assessed by subjective questionnaire. RESULTS: TRP levels were significantly lower (52.4 ± 15.2 vs. 67.9 ± 3.1 µmol/L; P < .0001) and KYN (3.2 ± 1.2 vs. 1.4 ± 0.1 µmol/L; P < .0001) were significantly higher in the 99 HD patients relative to 10 healthy controls. In HD patients, higher KYN levels were correlated with worse depression and fatigue scores (r2 = 0.23 and 0.21; P ≤ .05, respectively). We found no association between TRP and KYN/TRP ratio with sleep disturbances, fatigue, and depression in HD patients. CONCLUSIONS: Our study indicates disturbed TRP metabolism in HD patients, but low TRP levels were not related with sleep disturbances, depression, and fatigue. In contrast, KYN levels, a metabolite of TRP, were much higher in HD patients compared with controls, and higher KYN associated with depression and fatigue. Further studies exploring the biological and functional consequences of increased TRP catabolism in HD patients are warranted.

Plasma vitamin C levels in ESRD patients and occurrence of hypochromic erythrocytes.

INTRODUCTION: The achievement of erythropoiesis in hemodialysis (HD) patients is typically managed with erythropoiesis-stimulating-agents (ESA's) and intravenous iron (IV-iron). Using this treatment strategy, HD patients frequently show an elevated fraction of red blood cells (RBC) with hemoglobin (Hb) content per cell that is below the normal range, called hypochromic RBC. The low Hb content per RBC is the result of the clinical challenge of providing sufficient iron content to the bone marrow during erythropoiesis. Vitamin C supplements have been used to increase Hb levels in HD patients with refractory anemia, which supports the hypothesis that vitamin C mobilizes iron needed for Hb synthesis. METHODS: We conducted a cross-sectional survey in 149 prevalent HD patients of the percent hypochromic RBC, defined as RBC with Hb < 300 ng/uL of packed RBC, in relation to plasma vitamin C levels. We also measured high-sensitivity CRP, (hs-CRP), iron, and ferritin levels. and calculated ESA dose. FINDINGS: High plasma levels of vitamin C were negatively associated with hypochromic RBC (P < 0.003), and high ESA doses were positively associated (P < 0.001). There was no significant association of hs-CRP with percent hypochromic RBC. DISCUSSION: This finding supports the hypothesis that vitamin C mobilizes iron stores, improves iron delivery to the bone marrow, and increase the fraction of RBC with normal Hb content. Further research is warranted on development of protocols for safe and effective use of supplemental vitamin C for management of renal anemia.

Plasma oxalate levels in prevalent hemodialysis patients and potential implications for ascorbic acid supplementation.

OBJECTIVES: Ascorbic acid (AA) supplementation may increase hemoglobin levels and decrease erythropoiesis-stimulating agent dose requirement in patients with end stage renal disease (ESRD). While plasma AA levels >100µM may be supratherapeutic, levels of at least 30µM may be needed to improve wound healing and levels may need to reach 70µM to optimize erythropoiesis. Of concern, oxalate (Ox), an AA metabolite, can accumulate in ESRD. Historically, if plasma Ox levels remain ≥30µM, oxalosis was of concern. Contemporary hemodialysis (HD) efficiencies may decrease the risk of oxalosis by maintaining pre-HD Ox levels <30µM. This study focuses on the plasma Ox levels in HD patients. DESIGN AND METHODS: A prospective, observational study of 197 HD patients with pre-HD AA levels and pre-HD and post-HD Ox levels. RESULTS: Mean plasma Ox levels decreased 71% during the intradialytic period (22.3±11.1µM to 6.4±3.2µM, P<0.001). In regression analysis, pre-HD plasma AA levels ≤100µM were not associated with a pre-HD plasma Ox level≥30µM, even if ferritin levels were increased. Pre-HD plasma Ox levels ≥20 or ≥30µM were not associated with lower cumulative 4-year survival. CONCLUSIONS: Pre-HD plasma AA levels up to 100µM in HD patients do not appear to be associated with an increased risk of developing secondary oxalosis, as the corresponding pre-HD plasma Ox level appears to be maintained at tolerable levels.

Plasma ascorbic acid concentrations in prevalent patients with end-stage renal disease on hemodialysis.

OBJECTIVE: To determine the prevalence of vitamin C (ascorbic acid [AA]) deficiency in patients with end-stage renal disease, the effect of supplemental AA on plasma AA concentrations, and the extrinsic and intrinsic factors that affect plasma AA concentrations in this patient population. DESIGN: In study 1, we compared the effect of hemodialysis (HD) on plasma AA concentrations between patients with low and high pre-HD AA concentrations. In study 2, we analyzed kinetic and nonkinetic factors for their association with increased plasma AA concentrations in patients on maintenance HD. Study 1 was performed in a single outpatient HD clinic in Cherry Hill, New Jersey. Study 2 was performed in 4 outpatient HD clinics in Southern New Jersey. SUBJECTS AND INTERVENTION: In study 1, we collected plasma samples from 8 adult patients on maintenance HD at various time points around their HD treatment and assayed them for AA concentration. In study 2, we enrolled 203 adult patients and measured pre-HD plasma AA concentrations. We ascertained supplemental AA use and assessed dietary AA intake. MAIN OUTCOME MEASURE: In study 1, plasma AA concentrations were compared during the intradialytic and interdialytic period. In study 2, pre-HD plasma AA concentrations were correlated with supplement use and demographic factors. RESULTS: Study 1 showed that over the course of a single HD treatment, the plasma AA concentration decreased by a mean (±standard deviation) of 60% (±6.6). In study 2, the median pre-HD plasma AA concentration was 15.7 µM (interquartile range, 8.7-66.8) in patients who did not take a supplement and 50.6 µM (interquartile range, 25.1-88.8) in patients who did take a supplement (P < .001). Supplement use, increasing age, and diabetes mellitus were associated with a pre-HD plasma AA concentration ≥30 µM. CONCLUSION: HD depletes plasma AA concentrations, and AA supplementation allows patients to achieve higher plasma AA concentrations.

Transfer of low-molecular weight single-stranded DNA through the membrane of a high-flux dialyzer.

PURPOSE: Microbial contamination is often present in dialysate used for hemodialysis. Small single-stranded bacterial DNA sequences are capable of activating human inflammatory pathways, through mechanisms that include the Toll-like-receptor 9, and dialysis patients frequently show severe inflammation. Since these molecules have been found in dialysate and in patients' bloodstreams, we studied the potential of low-molecular weight DNA sequences, of the same structure as found in bacteria, to cross from the dialyzer circuit to the blood circuit of a dialysis filter. METHODS: The mass transfer of DNA fragments across a high-flux dialyzer was evaluated with an in vitro dialysis model, in both conventional dialysis and pure convection mode. Measurement of DNA was performed by HPLC. RESULTS: In dialysis mode, these mass transfer coefficients were calculated for different single-stranded DNA chain lengths: 5-bases = 28.5%, 9-bases = 20.5%, 20-bases = 9.4%, 35-bases = 2.4%, 50-bases and 100-bases, no transfer detected. In convection mode, these sieving coefficients were calculated: 5-bases = 1.0, 9-bases = 1.0, 20-bases = 0.68, 35-bases = 0.40, 50-bases = 0.17, 100-bases, no convective transfer detected. The physical size of DNA molecules could be the major factor that influences their movement through dialyzer pores. CONCLUSIONS: This study establishes that significant transfer across the dialyzer may occur with single-stranded DNA in the size range of 20-bases or less. These findings need to be confirmed with an in vitro whole blood model and with clinical investigations. Previous studies have described the clinical benefits of achieving high-purity dialysate. Precautions are warranted to minimize the presence of these DNA compounds in fluids utilized for hemodialysis treatment.

Hospitalization and mortality in hemodialysis patients: association with hemoglobin variability.

BACKGROUND/AIMS: Hemodialysis patients show complications associated with low or high hemoglobin (Hb), which occur frequently in clinical practice. We sought to determine the clinical importance of these changes in Hb levels. METHODS: From our clinic cohorts, we identified 1,634 who met inclusion criteria for analysis of hospitalization frequency and 1,953 analysis of mortality; many patients were in both groups. Hb excursions outside the target range (11-12.5 g/dl) were studied in relation to patient outcomes. RESULTS: Hb measures below range were associated with more frequent hospitalization (p < 0.001), increased length of stay (p < 0.001), and increased mortality (p < 0.01), whereas Hb above range was associated with a reduced frequency of hospitalization (p < 0.01) and shorter length of stay (p < 0.01), and tended to be associated with reduced mortality. CONCLUSIONS: Excursions below range were associated with negative outcomes, but excursions above range were either beneficial or neutral. Our findings indicate that clinicians should focus on low Hb as a negative indicator of patient status, whereas transient Hb above range is a marker for patient health and well-being.

Estimation of normal hydration in dialysis patients using whole body and calf bioimpedance analysis.

Prescription of an appropriate dialysis target weight (dry weight) requires accurate evaluation of the degree of hydration. The aim of this study was to investigate whether a state of normal hydration (DW(cBIS)) as defined by calf bioimpedance spectroscopy (cBIS) and conventional whole body bioimpedance spectroscopy (wBIS) could be characterized in hemodialysis (HD) patients and normal subjects (NS). wBIS and cBIS were performed in 62 NS (33 m/29 f) and 30 HD patients (16 m/14 f) pre- and post-dialysis treatments to measure extracellular resistance and fluid volume (ECV) by the whole body and calf bioimpedance methods. Normalized calf resistivity (ρ(N)(,5)) was defined as resistivity at 5 kHz divided by the body mass index. The ratio of wECV to total body water (wECV/TBW) was calculated. Measurements were made at baseline (BL) and at DW(cBIS) following the progressive reduction of post-HD weight over successive dialysis treatments until the curve of calf extracellular resistance is flattened (stabilization) and the ρ(N)(,5) was in the range of NS. Blood pressures were measured pre- and post-HD treatment. ρ(N)(,5) in males and females differed significantly in NS. In patients, ρ(N)(,5) notably increased with progressive decrease in body weight, and systolic blood pressure significantly decreased pre- and post-HD between BL and DW(cBIS) respectively. Although wECV/TBW decreased between BL and DW(cBIS), the percentage of change in wECV/TBW was significantly less than that in ρ(N)(,5) (-5.21 ± 3.2% versus 28 ± 27%, p < 0.001). This establishes the use of ρ(N)(,5) as a new comparator allowing a clinician to incrementally monitor removal of extracellular fluid from patients over the course of dialysis treatments. The conventional whole body technique using wECV/TBW was less sensitive than the use of ρ(N)(,5) to measure differences in body hydration between BL and DW(cBIS).

New insight on vitamin C in patients with chronic kidney disease.

Patients on dialysis often develop anemia, which is accompanied by the development of substantial iron stores after administration of intravenous iron. This can be remedied in some instances with administration of supplemental vitamin C, either intravenously or orally. This is because of the mobilization of stored iron, which results in correction of anemia and in improvement of iron-indices of red cells and reticulocytes. The short red cell survival often seen in patients on dialysis creates a situation in which very large amounts of iron are needed to be supplied for new erythropoiesis, and vitamin C therefore contributes to necessary iron delivery. The safety of this therapy needs careful study so as to determine vitamin C dosage that is effective and also avoids complications of oxalosis.

Guidelines for vitamin supplements in chronic kidney disease patients: what is the evidence?

Wide discrepancies exist in the use of vitamins in kidney disease, and evidence-based recommendations are sparse. Water-soluble vitamin levels may be inadequate in patients not receiving supplements and this may be associated with increased mortality, which deserves further attention to increase strength of evidence. Supplements should be administered cautiously as renal mechanisms to prevent hypervitaminosis are no longer functional. The most reliable assays for vitamin status examine tissue mechanisms that rely on vitamins as cofactors. Vitamin A levels are generally quite high, vitamin D is low and requires supplementation, and the benefits of vitamin E may be linked to its usage in a modified dialysis membrane. Because of restricted diets that provide limited vitamin intake from food, many renal patients can benefit from a tablet that adds an amount equal to one recommended daily allowance of water-soluble vitamins, but larger amounts are not appropriate or beneficial. Vitamin status is influenced by interaction of many variables, and individual attention to each patient is warranted to achieve optimal vitamin status.

Hemoglobin and plasma vitamin C levels in patients on peritoneal dialysis.

OBJECTIVE: To determine the contribution of vitamin C (Vit C) status in relation to hemoglobin (Hb) levels in patients on long-term peritoneal dialysis (PD). METHODS: 56 stable PD patients were evaluated in a cross-sectional survey. Plasma samples were collected for Vit C (analyzed by HPLC with electrochemical detection) and high-sensitivity C-reactive protein (hs-CRP) determinations. Clinical records were reviewed for Hb, transferrin saturation (TSAT), ferritin, erythropoietin (EPO) dose, and other clinical parameters. Dietary Vit C intake was evaluated by patient survey and from patient records. Total Vit C removed during PD treatment was measured in 24-hour dialysate collections. RESULTS: Patients showed a highly skewed distribution of plasma Vit C levels, with 40% of patients below normal plasma Vit C levels (<30 µmol/L) and 9% at higher than normal levels (>80 µmol/L). Higher plasma Vit C levels were associated with higher Hb levels (Pearson r = 0.33, p < 0.004). No direct connection between Vit C levels and reported dietary intake could be established. In stepwise multiple regression, plasma Vit C remained significantly associated with Hb (p = 0.017) but there was no significant association with other variables (dialysis vintage, age, ferritin, TSAT, hs-CRP, residual renal function, and EPO dose). In 9 patients that were evaluated for Vit C in dialysate, plasma Vit C was positively associated (Spearman r = 0.85, p = 0.01) with the amount of Vit C removed during dialysis treatment. CONCLUSIONS: These data indicate that plasma Vit C is positively associated with higher Hb level. Vit C status could play a major role in helping PD patients to utilize iron for erythropoiesis and achieve a better Hb response during anemia management.

Facile fingerstick insulin analysis: Application to monitoring postprandial insulin responses to snack foods.

BACKGROUND: Energy intake from snacks has been increasing in the American diet, but insulin and glucose responses to foods are generally reported for meal-sized portions (800-1200 kJ). Established methods for insulin determination routinely use indwelling catheters and radioimmunoassay (RIA). The aim of the present study was to develop a more facile method, collecting fingerstick blood samples and measuring insulin with precise ELISA, and then applying this method to determine responses to snack-sized food portions. METHODS: Six healthy, fasting adult volunteers consumed seven different snack foods on separate days, containing approximately 400 kJ/portion. Insulin was measured by ELISA and glucose was measured with the hexokinase procedure in samples collected by fingerstick at 0, 30, and 60 min after consumption of the snack food. RESULTS: A portion of doughnut (half a glazed doughnut) led to marked changes in insulin and glucose; skim milk, an apple, and oatmeal changed insulin significantly; wrinkled peas resulted in a lower glucose response than smooth peas; and walnuts led to non-significant changes in both insulin and glucose over a 60-min period. CONCLUSIONS: The fingerstick sampling and insulin measurement procedure is simple, economical, and more precise than established RIA. The method can be applied to children and adults to monitor insulin responses following food consumption, as well as during therapeutic assessments or intervention trials. Public health advisories regarding snacks that minimize increases in insulin are desirable for individuals trying to reduce or maintain their weight, because elevated insulin stimulates carbohydrate conversion to fat and suppresses the mobilization of stored triglycerides for energy generation.

Red cell survival: relevance and mechanism involved.

Red blood cells (RBCs) often have a short circulating half-life in hemodialysis patients, which increases the difficulty of achieving a stable hemoglobin level. Fluctuations in erythropoietin (EPO) levels contribute to this increased RBC turnover because a decline in the level of EPO triggers the preferential destruction of newly-formed RBC, a process termed neocytolysis. The RBCs that are released during the treatment of renal anemia are often hypochromic, with a low content of iron; these RBCs are vulnerable to rapid turnover because iron-deficiency affects RBCs in several ways, such as, increased exposure of the phagocytic signaling molecule phosphatidylserine, loss of deformability, and increased oxidative stress. Both EPO fluctuation and the release of iron-deficient RBCs are characteristic events occurring during the management of renal anemia, and the shorter RBC lifetime is a component of the large fluctuations in hemoglobin level seen in patients on hemodialysis.

A simplified method to distinguish farmed (Salmo salar) from wild salmon: fatty acid ratios versus astaxanthin chiral isomers.

Mislabeling of farmed and wild salmon sold in markets has been reported. Since the fatty acid content of fish may influence human health and thus consumer behavior, a simplified method to identify wild and farmed salmon is necessary. Several studies have demonstrated differences in lipid profiles between farmed and wild salmon but no data exists validating these differences with government-approved methods to accurately identify the origin of these fish. Current methods are both expensive and complicated, using highly specialized equipment not commonly available. Therefore, we developed a testing protocol using gas chromatography (GC), to determine the origin of salmon using fatty acid profiles. We also compared the GC method with the currently approved FDA (United States Food and Drug Administration) technique that uses analysis of carotenoid optical isomers and found 100% agreement. Statistical validation (n = 30) was obtained showing elevated 18:2n-6 (z = 4.56; P = 0.0001) and decreased 20:1n-9 (z = 1.79; P = 0.07) in farmed samples. The method is suitable for wide adaptation because fatty acid methyl ester analysis is a well-established procedure in labs that conduct analysis of lipid composition and food constituents. GC analysis for determining the origin of North American salmon compared favorably with the astaxanthin isomer technique used by the FDA and showed that the fatty acid 18:2n-6 was the key indicator associated with the origin of these salmon.