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BackgroundThe kidney is central for maintaining water balance. As a corollary, patients with impaired kidney function are prone to pathological fluid volumes. Total body water (TBW) is distributed between the extracellular (ECW) and intracellular fluid compartments (ICW). In clinical practice, the judgment of hydration status does not allow to distinguish between ECW and ICW. Here, we evaluate the hydration status in children with chronic kidney disease by analyzing TBW, ECW, and ICW.MethodsHydration was quantified using whole-body bioimpedance spectroscopy (BCM) in 128 outpatients (1–25 years, 52 girls). Forty-two were transplanted (TPL), 43 suffered from chronic kidney disease without kidney replacement therapy (CKD), 21 were on peritoneal dialysis (PD), and 22 on hemodialysis (HD). HD patients were investigated before, after, and sequentially during dialysis.ResultsThe ECW and ICW values obtained by BCM were of the same magnitude as those from the literature using isotope dilution. When compared with a healthy control group, TBW was increased in 9 TPL, 9 CKD, 1 PD, and 11 HD patients before but in none after dialysis. The decline of overhydration during dialysis (p < 0.001, n = 22) correlated with the change in body weight (R2 = 0.62). The kinetics of fluid compartment changes assessed twice in six HD patients revealed a reproducible linear decay of the ECW/ICW ratio due to an increase of ICW and a decrease of ECW.ConclusionBCM quantifies TBW and acute changes of ECW and ICW in children with chronic kidney failure. The clinical utility of measuring TBW, ECW, and ICW should be defined in the future.

In an elderly patient with chronic heart failure (CHF) and dementia, the extracellular fluid volume (ECW)/intracellular fluid volume (ICW) and ECW/total body water (TBW) ratios measured by bioelectrical impedance analysis (BIA) may serve as early and sensitive indicators of CHF status and effective markers for assessing medication adherence.

In the general population we recently reported a consistent association between plasma sodium and volume markers, suggesting that individuals with higher plasma sodium have higher extracellular fluid volume (ECFV). To test this hypothesis, we analyzed the association between plasma sodium and directly measured ECFV (iothalamate distribution volume) in healthy men. Second, we studied whether plasma sodium is associated with blood pressure. We analyzed data from 70 men (age 24 ± 7 years) at the end of two 7‐day periods on a low‐sodium diet (LS, 50 mmol Na/24 h) and a high‐sodium diet (HS, 200 mmol Na/24 h), respectively. The association of plasma sodium with blood pressure was assessed in the combined data of the different sodium intakes by linear mixed effects models. A positive univariable association between plasma sodium and ECFV was found during HS (β = 0.24, p = 0.042) and LS (β = 0.23, p = 0.058), respectively. Individual values of plasma sodium on LS and HS diet were strongly correlated (β = 0.68, p < 0.001), as were values for ECFV (β = 0.54, p < 0.001). In the combined data set plasma sodium level was significantly associated with ECFV (B [SE] = 0.10 [0.04], p = 0.02), and systolic blood pressure (SBP, B [SE] = 0.73 [0.26], p = 0.006), independent of ECFV. In conclusion, plasma sodium concentration is positively associated with ECFV on both LS and HS intake. Our data confirm and extend prior data on individual regulation of plasma sodium and suggest that this is associated with individuality of the regulation of ECFV. Finally, plasma sodium level is associated with SBP, independent of ECFV and diet. Plasma sodium concentration is positively associated with ECFV on both LS and HS intake. Our data confirm and extend prior data on individual regulation of plasma sodium and suggest that this is associated with individuality of the regulation of ECFV. Finally, plasma sodium level is associated with SBP, independent of ECFV and diet.

Key Clinical Message Extracellular fluid volume, rather than body weight, should guide chronic heart failure management in home‐care patients. Enhancing muscle mass through pharmacotherapy, nutrition, and exercise is essential to prevent heart failure exacerbation.

IntroductionPatients with type 1 diabetes are susceptible to hypertension, possibly resulting from increased salt sensitivity and accompanied changes in body fluid composition. We examined the effect of a high-salt diet (HSD) in type 1 diabetes on hemodynamics, including blood pressure (BP) and body fluid composition.Research design and methodsWe studied eight male patients with type 1 diabetes and 12 matched healthy controls with normal BP, body mass index, and renal function. All subjects adhered to a low-salt diet and HSD for eight days in randomized order. On day 8 of each diet, extracellular fluid volume (ECFV) and plasma volume were calculated with the use of iohexol and 125I-albumin distribution. Hemodynamic measurements included BP, cardiac output (CO), and systemic vascular resistance.ResultsAfter HSD, patients with type 1 diabetes showed a BP increase (mean arterial pressure: 85 (5) mm Hg vs 80 (3) mm Hg; p<0.05), while BP in controls did not rise (78 (5) mm Hg vs 78 (5) mm Hg). Plasma volume increased after HSD in patients with type 1 diabetes (p<0.05) and not in controls (p=0.23). There was no significant difference in ECFV between diets, while HSD significantly increased CO, heart rate (HR) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in type 1 diabetes but not in controls. There were no significant differences in systemic vascular resistance, although there was a trend towards an HSD-induced decrease in controls (p=0.09).ConclusionsIn the present study, patients with type 1 diabetes show a salt-sensitive BP rise to HSD, which is accompanied by significant increases in plasma volume, CO, HR, and NT-proBNP. Underlying mechanisms for these responses need further research in order to unravel the increased susceptibility to hypertension and cardiovascular disease in diabetes.Trial registration numbersNTR4095 and NTR4788.

Introduction: Increased natriuretic peptides are associated with increased cardiovascular and all-cause mortality for haemodialysis (HD) patients. However, debate continues whether these biomarkers are increased by extracellular water (ECW) excess and can be used to aid clinical assessment of volume status and help determine target weight. Methods: We measured N terminal probrain natriuretic peptide (NT-proBNP) predialysis in 375 stable haemodialysis outpatients with corresponding pre and postdialysis multifrequency bioelectrical impedance assessments (MFBIA) of (ECW)/total body water (TBW). Results: Median age 64 (51-75), 63.9% male, 42.9% diabetic, 43.2% Caucasoid, 14.4% with a history of myocardial infarction, 8.4% coronary artery bypass surgery, dialysis vintage 28.2 (12.3-55.5) months. Median predialysis NT-proBNP 283 (123-989) pmol/l, and predialysis ECW/TBW ratio 0.397 ± 0.029. On multivariate analysis, predialysis log NT-proBNP was associated with predialysis systolic blood pressure (β 0.007, p = 0.000), weight (β −0.008, p = 0.001), valvular heart disease (β 0.342, p = 0.015, ECW/TBW (β 1.3, p = 0.019) and log CRP (β 0.145, p = 0.037). Dividing patients into NTproBNP quartiles, %ECW/TBW and relative ECW overhydration were significantly greater for the highest quartile vs. lowest (40.5 ± 4.1 vs. 39.0 ± 1.1, and 1.51 ± 1.24 vs. 0.61 ± 0.69 l, respectively, p < 0.001). Conclusion: In this study, predialysis NTproBNP values were associated with direct assessments of the extracellular volume excess measured by MFBIA and systolic arterial blood pressure. This suggests that predialysis NTproBNP values can potentially be used to aid clinical assessment of volume status in dialysis patients to determine target weight.

Regression of left ventricular hypertrophy after conversion to nocturnal hemodialysis. Left ventricular hypertrophy (LVH) is an independent risk factor for mortality in the dialysis population. LVH has been attributed to several factors, including hypertension, excess extracellular fluid (ECF) volume, anemia and uremia. Nocturnal hemodialysis is a novel renal replacement therapy that appears to improve blood pressure control. This observational cohort study assessed the impact on LVH of conversion from conventional hemodialysis (CHD) to nocturnal hemodialysis (NHD). In 28 patients (mean age 44 ± 7 years) receiving NHD for at least two years (mean duration 3.4 ± 1.2 years), blood pressure (BP), hemoglobin (Hb), ECF volume (single-frequency bioelectrical impedance) and left ventricular mass index (LVMI) were determined before and after conversion. For comparison, 13 control patients (mean age 52 ± 15 years) who remained on self-care home CHD for one year or more (mean duration 2.8 ± 1.8 years) were studied also. Serial measurements of BP, Hb and LVMI were also obtained in this control group. There were no significant differences between the two cohorts with respect to age, use of antihypertensive medications, Hb, BP or LVMI at baseline. After transfer from CHD to NHD, there were significant reductions in systolic, diastolic and pulse pressure (from 145 ± 20 to 122 ± 13mm Hg, P < 0.001; from 84 ± 15 to 74 ± 12mm Hg, P = 0.02; from 61 ± 12 to 49 ± 12mm Hg, P = 0.002, respectively) and LVMI (from 147 ± 42 to 114 ± 40 g/m2, P = 0.004). There was also a significant reduction in the number of prescribed antihypertensive medications (from 1.8 to 0.3, P < 0.001) and an increase in Hb in the NHD cohort. Post-dialysis ECF volume did not change. LVMI correlated with systolic blood pressure (r = 0.6, P = 0.001) during nocturnal hemodialysis. There was no relationship between changes in LVMI and changes in BP or Hb. In contrast, there were no changes in BP, Hb or LVMI in the CHD cohort over the same time period. Reductions in BP with NHD are accompanied by regression of LVH.

Hyponatremia is a common electrolyte derangement in the setting of the intensive care unit. Life-threatening neurological complications may arise not only in case of a severe (<120 mmol/L) and acute fall of plasma sodium levels, but may also stem from overly rapid correction of hyponatremia. Additionally, even mild hyponatremia carries a poor short-term and long-term prognosis across a wide range of conditions. Its multifaceted and intricate physiopathology may seem deterring at first glance, yet a careful multi-step diagnostic approach may easily unravel the underlying mechanisms and enable physicians to adopt the adequate measures at the patient’s bedside. Unless hyponatremia is associated with obvious extracellular fluid volume increase such as in heart failure or cirrhosis, hypertonic saline therapy is the cornerstone of the therapeutic of profound or severely symptomatic hyponatremia. When overcorrection of hyponatremia occurs, recent data indicate that re-lowering of plasma sodium levels through the infusion of hypotonic fluids and the cautious use of desmopressin acetate represent a reasonable strategy. New therapeutic options have recently emerged, foremost among these being vaptans, but their use in the setting of the intensive care unit remains to be clarified.

Background Rural-dwelling hemodialysis patients have less frequent contact with nephrologists than urban-dwelling patients, and are known to have higher mortality. We hypothesized that rural-dwelling hemodialysis patients would have more evidence of poorly controlled extracellular fluid volume (ECVF) than otherwise similar urban-dwellers. Methods We studied prevalent hemodialysis patients within a single renal program in Alberta, Canada and assessed ECFV using bioimpedance spectroscopy (BIS). Our primary outcome was impedance vector length (ohm/m) as assessed by BIS using the Xitron Hydra 4200 device, where shorter vector length indicated poorer ECFV control. Because poor ECFV control can lead to hypertension, we also assessed pre- and post-dialysis blood pressure. We measured outcomes at baseline. Results We studied 228 hemodialysis patients, of whom 115 (50.4 %) and 113 (49.6 %) were urban- and rural-dwelling, respectively. There were no differences in volume control in urban versus rural participants; odds ratio (OR) for vector length in the lowest sex-specific quartile of vector length was 0.93 (95 % CI 0.54, 1.59) after adjusting for age, sex, diabetic status, years since dialysis initiation and phase angle. The odds of very poor blood pressure control (pre-dialysis blood pressure ≥180/100) did not differ between urban and rural participants [fully adjusted OR 0.96 (0.36, 2.60)]. Conclusions Differences in ECFV control do not appear to explain higher mortality among remote- and rural- dwelling hemodialysis patients, compared to urban-dwellers.

Purpose The objective of the study was to undertake a clinical audit of departmental performance in the measurement of glomerular filtration rate (GFR) using the coefficient of variation (CV) of extracellular fluid volume (ECFV) as the benchmark. ECFV is held within narrow limits in healthy subjects, narrower than GFR, and should therefore have a low CV. Methods Fifteen departments participated in this retrospective study of healthy renal transplant donors. Data were analysed separately for men ( n ranged from 28 to 115 per centre; total = 819) and women ( n  = 28–146; 1,059). All centres used the slope-intercept method with blood sample numbers ranging from two to five. Subjects did not fast prior to GFR measurement. GFR was scaled to body surface area (BSA) and corrected for the single compartment assumption. GFR scaled to ECFV was calculated as the terminal slope rate constant and corrected for the single compartment assumption. ECFV/BSA was calculated as the ratio of GFR/BSA to GFR/ECFV. Results The departmental CVs of ECFV/BSA and GFR/BSA ranged from 8.3 to 25.8% and 12.8 to 21.9%, respectively, in men, and from 9.6 to 21.1% and 14.8 to 23.7%, respectively, in women. Both CVs correlated strongly between men and women from the same centre, suggesting department-specific systematic errors. GFR/BSA was higher in men in 14 of 15 centres, whereas GFR/ECFV was higher in women in 14 of 15 centres. Both correlated strongly between men and women, suggesting regional variation in GFR. Conclusion The CV of ECFV/BSA in normal subjects is a useful indicator of the technical robustness with which GFR is measured and, in this study, indicated a wide variation in departmental performance.