Volume status in dialysis patients at extreme body habitus: a prospective observational study.

Background/Aims: Natriuretic peptides have been reported to be a valuable biomarker for predicting cardiac events and mortality for haemodialysis patients. However, there has been a debate as to whether these biomarkers can be used to assess volume overload and help determine dry weight. Methods: We measured the N-terminal probrain natriuretic peptide (NTproBNP) in 366 stable haemodialysis outpatients with a corresponding pre- and post-dialysis multifrequency bioimpedance assessment of extracellular water (ECW)/total body water (TBW). Results: Median age was 61 years (46–73); 58.5% were male, 28.5% diabetic, and 37.7% Caucasoid; 71.1% had a history of hypertension, 8.4% of myocardial infarction, and 9.3% of coronary artery bypass surgery; dialysis vintage was 54 months (22–85.5), and urea reduction ratio was 73.4 ± 7.6%. Median post-dialysis NTproBNP was 179 pmol/l (68–535), pre-dialysis ECW/TBW was 0.393 ± 0.014, and post-dialysis ECW/TBW was 0.385 ± 0.015. On multivariate analysis log NTproBNP was associated with post-dialysis ECW/TBW (β 9.09, 95% CI 3.22–14.95, p = 0.003), mean arterial pressure (β 0.0087, 95% CI –0.0045 to –0.013, p = 0.000), and ultrafiltration rate (ml/kg· h; β 0.038, 95% CI 0.01–0.06, p = 0.001). Conclusion: In this study postdialysis NTproBNP values were correlated with direct assessments of volume status in haemodialysis patients, i.e. by ECW/TBW, or indirect measures of volume overload, i.e. ultrafiltration rate and post-dialysis mean arterial blood pressure. This suggests that serial NTproBNP values may aid clinical assessments of volume status in dialysis patients.

Fluid management protocols in hemodialysis patients using bioimpedance validation: time to look elsewhere?

In patients with end stage renal failure, control of the fluid status of the body is lost and fluid accumulates continuously. By dialysis therapy, excess fluid can be removed, but there are no reliable methods to establish the amount of excess fluid to be removed. Severe and even lethal complications may be the consequence of longer term deviations from a normal fluid status in dialysis patients, but also in other patient groups. Therefore, a large medical need exists for a precise and pragmatic method to determine fluid status. Bioimpedance measurement, today mainly used for nutrition status assessment, is regarded as an interesting candidate method for fluid status determination. This paper presents a four-compartment model of the human body, developed to derive information on fluid status from extra- and intracellular volumes measured by bioimpedance spectroscopy. The model allows us to determine weights of each of four compartments (overhydration, fat, muscle and remaining ‘basic’ components) by analyzing extra- and intracellular water volumes in different tissues of the body. Thereby fluid status (overhydration volume, normohydrated weight of the patient) as well as nutrition and fitness status (lean body, fat and muscle mass) can be determined quantitatively from a single measurement. A preliminary evaluation of the performance of a system consisting of a bioimpedance spectrum analyzer and the four-compartment model is also provided.

Bioimpedance spectroscopy (BIS) is a noninvasive method used to evaluate body fluid volume status in dialysis patients, but reports on its effectiveness in pediatrics are scarce. We investigated the correlation between BIS and clinical characteristics and identified the changes in patients whose dialysis prescription was modified based on BIS. The medical records of children on maintenance dialysis who had undergone BIS between 2017 and 2019 were reviewed. Of the 49 patients, 14 were overhydrated, based on the >15% proportion of overhydration relative to extracellular water (OH/ECW) measured by BIS. Intake of ≥two antihypertensive medications was noted in the majority (85.7%) of children with fluid overload and only in 48.6% of those without fluid overload (p = 0.017). Elevated blood pressure despite medication use was significantly more common in patients with fluid overload than in those without fluid overload (78.6% vs. 45.7%, p = 0.037). Of the 14 overhydrated children, 13 (92.9%) had significant changes in body weight, OH/ECW, the number of antihypertensive drugs, left ventricular end-diastolic diameter, and cardiothoracic ratio after the change in dialysis prescription. BIS is a useful and noninvasive method to assess fluid status in dialysis children. Long-term follow-up and correlation with a more objective clinical indicator of fluid overload is necessary to verify the clinical effectiveness of BIS.

BackgroundEuvolemia is an important adequacy parameter in peritoneal dialysis (PD) patients. However, accurate tools to evaluate volume status in clinical practice and data on volume status in PD patients as compared to healthy population, and the associated factors, have not been available so far.MethodsWe used a bio-impedance spectroscopy device, the Body Composition Monitor (BCM) to assess volume status in a cross-sectional cohort of prevalent PD patients in different European countries. The results were compared to an age and gender matched healthy population.ResultsOnly 40% out of 639 patients from 28 centres in 6 countries were normovolemic. Severe fluid overload was present in 25.2%. There was a wide scatter in the relation between blood pressure and volume status. In a multivariate analysis in the subgroup of patients from countries with unrestricted availability of all PD modalities and fluid types, older age, male gender, lower serum albumin, lower BMI, diabetes, higher systolic blood pressure, and use of at least one exchange per day with the highest hypertonic glucose were associated with higher relative tissue hydration. Neither urinary output nor ultrafiltration, PD fluid type or PD modality were retained in the model (total R2 of the model = 0.57).ConclusionsThe EuroBCM study demonstrates some interesting issues regarding volume status in PD. As in HD patients, hypervolemia is a frequent condition in PD patients and blood pressure can be a misleading clinical tool to evaluate volume status. To monitor fluid balance, not only fluid output but also dietary input should be considered. Close monitoring of volume status, a correct dialysis prescription adapted to the needs of the patient and dietary measures seem to be warranted to avoid hypervolemia.

In general, central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) are used for control and management of circulating blood volume. It has been demonstrated that there is a good correlation between left atrial pressure and PCWP during spontaneous breathing and intermittent positive pressure ventilation [1, 2, 7]. However, the introduction of continuous pressure ventilation (CPPV) has complicated the use of, e.g., PCWP as the indicator of left ventricle (LV) preload greatly; more than 10 years ago it was shown that PCWP poorly reflects circulating volume status during CPPV in subjects with normal lungs [13, 16]. In an investigation by Shippy et al. [12] of over 1500 occasions of clinical indication or suspicion of either hypovolemia or hypervolemia during periods of critical illness in patients admitted to the surgical ICU or during early resuscitation from hypotensive shock with administration of a fluid load, blood volume and values of the commonly monitored variables, including CVP, PCWP, and cardiac output (CO.), improved appropriately. However, the correlation coefficients, in general, were not good. The authors concluded that the commonly monitored variables in and of themselves do not reflect adequately the blood volume status in critically ill patients.

The aims of this study were to evaluate the agreement of computed tomography (CT)-perfusion parameter values of the normal renal cortex and various renal tumors, which were obtained by different mathematical models, and to evaluate their diagnostic accuracy. Perfusion imaging was performed prospectively in 35 patients to analyze 144 regions of interest of the normal renal cortex and 144 regions of interest of renal tumors, including 21 clear-cell renal cell carcinomas (RCC), 6 papillary RCCs, 5 oncocytomas, 1 chromophobe RCC, 1 angiomyolipoma with minimal fat, and 1 tubulocystic RCC. Identical source data were postprocessed and analyzed on 2 commercial software applications with the following implemented mathematical models: maximum slope, Patlak plot, standard singular-value decomposition (SVD), block-circulant SVD, oscillation-limited block-circulant SVD, and Bayesian estimation technique. Results for blood flow (BF), blood volume (BV), and mean transit time (MTT) were recorded. Agreement and correlation between pairs of models and perfusion parameters were assessed. Diagnostic accuracy was evaluated by receiver operating characteristic (ROC) analysis. Significant differences and poor agreement of BF, BV, and MTT values were noted for most of model comparisons in both the normal renal cortex and different renal tumors. The correlations between most model pairs and perfusion parameters ranged between good and perfect (Spearman ρ = 0.79-1.00), except for BV values obtained by Patlak method (ρ = 0.61-0.72). All mathematical models computed BF and BV values, which differed significantly between clear cell RCCs, papillary RCCs, and oncocytomas, which introduces them as useful diagnostic tests to differentiate between different histologic subgroups (areas under ROC curve, 0.83-0.99). The diagnostic accuracy to discriminate between clear-cell RCCs and the renal cortex was the lowest based on the Patlak plot model (area under ROC curve, 0.76); BF and BV values obtained by other algorithms did not differ significantly in their diagnostic accuracy. Quantitative perfusion parameters obtained from different mathematical models cannot be used interchangeably. Based on BF and BV estimates, all models are a useful tool in the differential diagnosis of kidney tumors, with the Patlak plot model yielding a significantly lower diagnostic accuracy.

Hepatic Blood Volume Imaging with the Use of Flat-Detector CT Perfusion in the Angiography Suite: Comparison with Results of Conventional Multislice CT Perfusion

Exercise intolerance in heart failure with preserved ejection fraction: time to scrutinize diuretic therapy?

Hemodialysis (HD) patients are vulnerable to multiple metabolic and nutrition derangements, leading to changes in body composition. Handgrip strength (HGS) has been used as a nutrition marker. We aimed to evaluate the relationship between HGS and lean tissue mass (LTM) with several parameters in HD patients and develop HGS predictive equations. Cross-sectional study with 155 patients in HD treatment for ≥3 months. Body composition was assessed through bioimpedance spectroscopy. HGS was measured with a hydraulic hand dynamometer. Biochemical parameters were evaluated. Data were analyzed by sex. Ninety-four were men, and mean age was 64.4 ± 14.7 years. We found positive correlation of HGS with LTM, lean tissue index, and body cell mass and negative correlation between HGS, age, and overhydration in both sexes. Serum albumin level presented a positive correlation and magnesium a negative correlation with HGS only in men. The LTM presented a positive correlation with protein intake, serum albumin level, and body cell mass and a negative correlation with age in both groups. A significant positive correlation with magnesium and a negative correlation with overhydration were observed in men. The predictability of the models was R2 = 0.618 for men and R2 = 0.500 for women. HGS is highly correlated with LTM, and both differ between sexes and are, therefore, differently correlated with the parameters studied. Body composition, overhydration, and some biochemical parameters explain changes in HGS. Predictive models including body composition and biochemical parameters may explain at least 50% of the variance of HGS.

The phenotype associated to reduced physical activity (PA) in dialysis patients is poorly documented. We here evaluate weekly PA in two independent cohorts. Cross-sectional study with PA assessed by the number of steps/day measured by pedometer in two cohorts of prevalent dialysis patients: (1) peritoneal dialysis (PD) patients (n = 64; 62 ± 14 years; 70 % men) from Stockholm, Sweden using the pedometer for 7 consecutive days; (2) hemodialysis (HD) patients (n = 78; 63 ± 12 years; 65% men) from a single center in Madrid, Spain using the pedometer for 6 consecutive days: 2 HD days, 2 non-HD midweek days and 2 non-HD weekend days. In both cohorts, comorbidities, body composition, nutritional status, and related biomarkers were assessed. Cohorts were not merged; instead data were analyzed separately serving as reciprocal replication analyses. Most patients (63% of PD and 71% of HD) were considered sedentary (<5,000 steps/day). PD patients had on average 4,839 ± 3,313 steps/day. HD patients had 3,767 ± 3,370 steps/day on HD-free days, but fewer steps/day on HD days (2,274 ± 2,048 steps/day; p < 0.0001). In both cohorts, and across increasing PA tertiles, patients were younger and had less comorbidities. Higher PA was also accompanied by better nutritional status (depicted by albumin, pre-albumin, creatinine and normalized protein catabolic rate in HD, and by albumin and subjective global assessment [SGA] in PD), higher lean body mass, and lower fat body mass (bioimpedance and/or dual-energy X-ray absorptiometry [DEXA]). Higher levels of PA were accompanied by lower levels of C-reactive protein in PD. Age and lean body mass were the strongest multivariate predictors of PA in both cohorts. There is a high prevalence of sedentary behavior in dialysis patients. Better physical activity was consistently associated with younger age, lower presence of comorbidities and better nutritional status. Pedometers represent a simple and inexpensive tool to objectively evaluate physical activity in this patient population.

Detection limit of methods to assess fluid status changes in dialysis patients

Under physiological conditions, blood volume and extracellular volume are in a ratio of 1-3, even in hemodialysis patients. The question therefore arises: can blood volume be inferred from the bioimpedance analysis data? The aim of the study was to compare the blood volumes calculated from extracellular volume determined by bioimpedance analysis data to the actually measured blood volumes. Immediately before treatment, extracellular volume and volume overload were evaluated by bioimpedance spectroscopy. The actual blood volume was determined by indicator dilution, using an on-line infusate bolus and subsequent calculation with the data from the relative blood volume monitor. Alternatively, blood volume was calculated from extracellular volume divided by 3 and compared to the measured blood volume. Overall, there were no significant differences between measured (5.56 ± 1.47 L) and calculated (5.79 ± 1.30 L) blood volumes. However, intra-individually, there were very large discrepancies with a range of -1.409 to 1.450 L. Median absolute deviation was 382 mL corresponding to 6.2 mL/kg. The differences between measured and calculated blood volumes correlated significantly (r = -0.98; p < 0.001) with the blood to extracellular volume ratio. In almost half of patients, blood volume can be inferred from bioimpedance data with sufficient certainty. But the greater the deviation from the physiological blood to extracellular volume ratio of 1-3, the more the calculated blood volumes differ from the measured values. For this reason, bioimpedance data should not be used uncritically to set the ultrafiltration.

The incidence of hepatitis B virus (HBV) infection in dialysis populations has declined over recent decades, largely because of improvements in infection control and widespread implementation of HBV vaccination. Regardless, outbreaks of infection continue to occur in dialysis units, and prevalence rates remain unacceptably high. For a variety of reasons, dialysis patients are at increased risk of acquiring HBV. They also demonstrate different disease manifestations compared with healthy individuals and are more likely to progress to chronic carriage. This paper will review the epidemiology, modes of transmission and diagnosis of HBV in this population. Prevention and treatment will be discussed, with a specific focus on strategies to improve vaccination response, new therapeutic options and selection of patients for therapy.

Because estrogens have been reported to produce sodium retention, this study investigated the possibility that hypertension in rats resulting from the ingestion of an estrogen used as an oral contraceptive could be due to increases in body fluid volumes. Female rats were given feed containing mestranol for 1, 3, and 6 mo; control rats were given the feed without mestranol. The mestranol-treated rats had higher arterial pressures than the controls only after 6 mo of treatment. Plasma volume, extracellular fluid volume, and total body water were measured in each rat by the distribution volumes of radioiodinated serum albumin, 35SO4, and tritiated water, respectively. Values for blood volume, interstitial fluid volume, and intracellular fluid volume were derived from these measurements. These body fluid volumes, expressed per 100 g of body weight, were not different between the mestranol-treated rats and their controls at any of the three treatment times. Due to differences in body weight and lean body mass between the mestranol-treated and the control rats, these volumes also were expressed per 100 g of lean body mass. Again, no differences were observed between the mestranol-treated rats and the control rats for any of these body fluid compartments at any of the treatment times. These studies, therefore, were unable to provide evidence that increases in body fluid volumes contributed to the elevated arterial pressure in this rat model of oral contraceptive hypertension.