Techniques for assessing fluids status in patients with kidney disease

A Survey for Charting Intake, Output, and Body Weight in the Electronic Medical Record

BACKGROUND

The accuracy of documentation of body weight and fluid balance in hospitalized patients is frequently questioned.

METHODS

We conducted a survey to understand provider perceptions of the accuracy of intake, output, and weight charting in the electronic medical record. We sent a six-item questionnaire to nurses and physicians who provide inpatient service in a community-based teaching hospital of the Northeastern United States. We compared the response difference between nurses and physicians by Fisher exact test.

RESULTS

One hundred eight nurses and 39 physicians participated in the survey. Both nurses and physicians responded that the accuracy of documentation is crucial. However, only 25.7% of participating physicians and 38.3% of participating nurses considered that documentation in the electronic medical record is reliable. Both physicians and nurses assumed that the nurses are too busy to collect and document the data, and the variability of non-patient weight and variations in body weight measurement under different conditions account for inaccuracies in the documented body weight.

CONCLUSIONS

Assessing the accuracy of documenting intake, output, and body weight in the electronic medical record is warranted. Providers believe that educating patients about fluid balance and volume assessment help to improve the accuracy in charting intake, output, and body weight in the electronic medical record.

Effect of absolute blood volume measurement-guided fluid management on the incidence of intradialytic hypotension-associated events: a randomised controlled trial

Background

Ultrafiltration to target weight during haemodialysis is complicated by intradialytic hypotension-associated adverse events (IHAAEs) in 10-30% of dialysis treatments. IHAAEs are caused by critical reductions in absolute blood volume (ABV), due to the interaction of ultrafiltration, refill and compensatory mechanisms. Non-randomised studies have suggested that ABV-guided treatment, using an indicator dilution technique employing the blood volume monitor on the dialysis machine, could reduce the incidence of IHAAEs.

Methods

We performed an open-label randomised controlled trial. Patients were randomly assigned to adjustment of target weight guided by ABV measurements or standard care. The primary outcome was the change in the incidence of IHAAEs from baseline, defined as the percentage of treatment episodes in a 4-week period where the patient had a systolic blood pressure <90 mmHg or symptoms of impending hypotension. ABV measurements were compared with anthropomorphometric estimation and the gold standard using isotope dilution.

Results

A total of 56 patients were randomised, of whom 29 were allocated to ABV-guided treatment and 27 to standard care. Overall baseline incidence of IHAAEs was 26.0%. ABV-guided treatment significantly reduced the incidence of IHAAEs compared with standard care, with a mean change from baseline of -9.6% [95% confidence interval (CI) -17.3 to -1.8) versus 2.4% (95% CI -2.3-7.2). The adjusted difference between the groups was 10.5% (95% CI 1.3-19.8; P = .026). ABV measurement had moderate agreement with other methods to estimate blood volume. The sensitivity for the previously suggested threshold of a post-dialysis normalised blood volume of 65 ml/kg was observed to be 74% in this study.

Conclusions

ABV-guided volume management significantly reduced IHAAEs compared with standard care. The clinical relevance of the previously suggested threshold of 65 ml/kg cannot be firmly concluded on the basis of our results. If confirmed in a larger trial, this intervention could potentially change dialysis practice and impact patient care in a clinically meaningful way.

Whole-body water mass and kidney function: a Mendelian randomization study

Background

The morbidity and mortality of chronic kidney disease (CKD) are increasing worldwide, making it a serious public health problem. Although a potential correlation between body water content and CKD progression has been suggested, the presence of a causal association remains uncertain. This study aimed to determine the causal effect of body water content on kidney function.

Methods

Genome-wide association study summary data sourced from UK Biobank were used to evaluate single-nucleotide polymorphisms (SNPs) associated with whole-body water mass (BWM). The summary statistics pertaining to kidney function were extracted from the CKDGen consortium. The primary kidney function outcome measures included estimated glomerular filtration rate (eGFR), albuminuria, CKD stages 3-5, and rapid progression to CKD (CKDi25). Two-sample Mendelian randomization (MR) analysis estimated a potential causal relationship between the BWM and kidney function. The inverse variance weighted MR method was used as the primary analysis, accompanied by several sensitive MR analyses.

Results

The increase of BWM exhibited a correlation with a reduction in eGFR (β = -0.02; P = 6.95 × 10-16). Excluding 13 SNPs responsible for pleiotropy (P = 0.05), the increase of BWM was also associated with the decrease of the ratio of urinary albumin to creatinine (β = -0.16; P = 5.91 × 10-36). For each standard deviation increase in BWM, the risk of CKD stages 3-5 increases by 32% (OR, 1.32; 95% CI, 1.19-1.47; P = 1.43 × 10-7), and the risk of CKDi25 increases by 22% (OR, 1.22; 95% CI, 1.07-1.38; P = 0.002).

Conclusion

The increase of BWM is associated with impaired kidney function. Proactively managing body water content is of great significance in preventing the progression of CKD.

The severity of early fluid overload assessed by bioelectrical vector impedance as an independent risk factor for longer patient care after cardiac surgery

BACKGROUND AND AIMS

Fluid overload is a common postoperative complication in patients undergoing cardiac surgery. Although this condition is notably associated with relevant adverse outcomes, assessment of hydration status in clinical practice is challenging. Bioelectrical impedance vector analysis (BIVA) has emerged as a potentially effective method to monitor hydration changes, but the available evidence in critically ill patients undergoing cardiac surgery is limited and sometimes conflicting. The aim of this study was to explore by mean of BIVA the evolution over time of hydration status and its impact on relevant outcomes.

METHODS

Prospective observational study enrolling 130 patients undergoing cardiac surgery. Height normalized impedance was calculated both before surgery (baseline) and in the first five postoperative days. Relevant clinical and laboratory data were collected daily close to BIVA measurements. Length of mechanical ventilation (MV), intensive care unit (ICU) and hospital stay exceeding the 75th percentile of the study population were considered as study endpoints.

RESULTS

Compared to baseline, a significant reduction in impedance was found at first postoperative day, demonstrating a relevant fluid overload. An adjusted impedance at first postoperative day shorter than the best respective threshold was associated to longer MV (7.4 times), ICU stay (4.7 times) and hospital stay (5.6 times). A significant change in impedance and phase angle was documented throughout the observation days (p < 0.001), without returning to the baseline value. The co-existence of low impedance and high plasma osmolarity increased significantly the risk of incurring the study outcomes.

CONCLUSIONS

In patients with cardiac surgery-induced fluid overload, recovery to baseline conditions occurs slowly. A relevant early fluid overload should be considered predictive for longer time of MV, ICU and total hospital stay.

A Proposed Predictive Equation for Energy Expenditure Estimation Among Noncritically Ill Patients With Acute Kidney Injury

OBJECTIVE

The incidence of acute kidney injury (AKI) is identified more frequently in noncritical compared with intensive care settings. The prognosis of malnourished AKI patients is far worse than those with normal nutritional status. However, a method for estimating the optimal amount of energy required to guide nutritional support among noncritically ill AKI patients is yet to be determined.

METHODS

We evaluated the performance of weight-based formulas (20-30 kcal/kg/day) with the reference values of energy expenditure (EE) measured by indirect calorimetry (IC) among noncritically ill AKI patients during hospitalization. The statistics for assessing agreement, including total deviation index and accuracy within 10% represent the percentage of estimations falling within the IC value range of ±10%, were tested. Parameters for predicting the EE equation were also developed using a regression analysis model.

RESULTS

A total of 40 noncritically ill AKI patients were recruited. The mean age of participants was 62.5 ± 16.5 years with 50% being male. The average IC-derived EE was 1,124.6 ± 278.9 kcal/day with respiratory quotients 0.8-1.3, indicating good validity of the IC test. Receiving dialysis, protein catabolic rate, and age was not significantly associated with measured EE. Nearly all weight-based formulas overestimated measured EE. The magnitude of total deviation index values was broad with the proportion of patients achieving an accuracy of 10% being as low as 20%. The proposed equation to predict EE derived from this study was EE (kcal/day) = 618.27 + (8.98 x weight in kg) + 137.0 if diabetes - 199.7 if female (r2 = 0.68, P < .001). In the validation study with an independent group of noncritically ill AKI patients, predicted EE using the newly derived equation was also significantly correlated with measured EE by IC (r = 0.69, P = .004).

CONCLUSION

Estimation of EE by weight-based formulas usually overestimated measured EE among noncritically ill AKI patients. In the absence of IC, the proposed predictive equation, specifically for noncritically ill AKI patients might be useful, in addition to weight-based formulas, for guiding caloric dosing in clinical practice.

Lung Ultrasound and Bioelectrical Impedance Analysis for Fluid Status Assessing Patients Undergoing Maintenance Hemodialysis

Background

Volume overload is a fatal complication for people undergoing hemodialysis. Therefore, regulating a patient's "dry weight" based on their fluid status is imperative. Clinical experiences are too subjective to accurately judge a patient's fluid status, but techniques have emerged for improved fluid control in the two decades. Specifically, lung ultrasonography (LUS) uses a unique aspect of ultrasound images, the B-lines, to evaluate extravascular lung water, which has increasingly attracted attention. However, the role of B-line quantification in predicting short-mid-term death and/or cardiovascular complications is unclear.

Methods

Patients undergoing MHD at the hemodialysis center of Zhejiang Provincial People's Hospital from October 1, 2020, to February 28, 2021, were examined using LUS and a bioelectrical impedance analysis before and after dialysis, and related clinical data were collected. All patients were followed up for one year after the examination, and deaths and first cardiovascular events (e.g., stroke, myocardial infarction, and heart failure) during this period were recorded.

Results

98 patients were enrolled and divided into three groups in relation to their mild (<16 B-lines), moderate (16-30 B-lines), or severe (>30 B-lines) hypervolemia, defined by the number of B-lines. The long-term survival rate was significantly lower in the severe group than in the mild and moderate groups. LUS and bioelectrical impedance-related parameters (e.g., extracellular water-to-water ratio) were closely related to cardiac ultrasound parameters (left ventricular ejection fraction) (P < 0.001). The optimal B-line cutoff value on LUS for predicting fluid overload (defined clinically) in patients on hemodialysis was 11.5 lines (AUC = 0.840, 95% confidence interval 0.735-0.945, P < 0.001), and the diagnostic sensitivity and specificity were both 76.5%. During the one-year follow-up period, ten deaths and six cardiovascular events occurred. The survival rate was significantly lower in the severe group than in the mild group (log-rank test χ2 = 10.050, P=0.002) but did not differ between the severe and moderate groups (χ2 = 2.629, P=0.105).

Conclusion

LUS is a cheap, noninvasive, simple, and repeatable volume-monitoring method that can assist with individualized fluid volume management in patients undergoing MHD. LUS results may also help to predict the short-mid-term survival rate of patients to a certain extent.

Applications of cardiac biomarkers in chronic kidney disease

PURPOSE OF REVIEW

Cardiovascular disease is the leading cause of death in individuals with chronic kidney disease (CKD). The mechanisms connecting CKD and cardiovascular disease are complex, and serum biomarkers can help improve our understanding. Nt-proBNP and troponin have documented success as biomarkers to diagnose and provide mechanistic insights in non-CKD populations. The purpose of this review is to summarize evidence suggesting efficacy and potential for clinical application of Nt-proBNP and troponin in individuals with CKD.

RECENT FINDINGS

Our understanding of how Nt-proBNP and Troponin should be interpreted in those with CKD is evolving. Although both biomarkers are in part cleared by the kidney, elevated levels predominantly reflect cardiovascular disease. Both Nt-proBNP and troponin are associated with risk for future cardiovascular events in CKD. Determining CKD-specific cutoffs and using biomarkers to guide therapy remains under active investigation.

SUMMARY

Of the many serum biomarkers under investigation, Nt-proBNP and troponin best meet the criteria for effective biomarkers in CKD. Assays are widely available and proven to be accurate in CKD populations. Nt-proBNP and troponin deserve special focus in ongoing research of cardiovascular risk reduction in CKD, especially to identify patients at the highest risk, suggest targetable mechanisms and assess treatment efficacy.

Bioimpedance Vector Analysis for Heart Failure: Should We Put It on the Agenda?

Heart failure is a clinical syndrome, resulting in increased intracardiac pressure and/or decreased cardiac output under rest or stress. In acute decompensated heart failure, volume assessment is essential for clinical diagnosis and management. More and more evidence shows the advantages of bioimpedance vector analysis in this issue. Here, we critically present a brief review of bioimpedance vector analysis in the prediction and management of heart failure to give a reference to clinical physicians and guideline makers.

The Conundrum of Volume Status Assessment: Revisiting Current and Future Tools Available for Physicians at the Bedside

Assessment of patients’ volume status at the bedside is a very important clinical skill that physicians need in many clinical scenarios. Hypovolemia with hypotension and tissue under-perfusion are usually more alarming to physicians, but hypervolemia is also associated with poor outcomes, making euvolemia a crucial goal in clinical practice. Nevertheless, the assessment of volume status can be challenging, especially in the absence of a gold standard test that is reliable and easily accessible to assist with clinical decision-making. Physicians need to have a broad knowledge of the individual non-invasive clinical tools available for them at the bedside to evaluate volume status. In this review, we will discuss the strengths and limitations of the traditional tools, which include careful history taking, physical examination, and basic laboratory tests, and also include the relatively new tool of point-of-care ultrasound.

Volume overload in hemodialysis: diagnosis, cardiovascular consequences, and management

Volume overload in haemodialysis (HD) patients associates with hypertension and cardiac dysfunction and is a major risk factor for all-cause and cardiovascular mortality in this population. The diagnosis of volume excess and estimation of dry weight is based largely on clinical criteria and has a notoriously poor diagnostic accuracy. The search for accurate and objective methods to evaluate dry weight and to diagnose subclinical volume overload has been intensively pursued over the last 3 decades. Most methods have not been tested in appropriate clinical trials and their usefulness in clinical practice remains uncertain, except for bioimpedance spectroscopy and lung ultrasound (US). Bioimpedance spectroscopy is possibly the most widely used method to subjectively quantify fluid distributions over body compartments and produces reliable and reproducible results. Lung US provides reliable estimates of extravascular water in the lung, a critical parameter of the central circulation that in large part reflects the left ventricular end-diastolic pressure. To maximize cardiovascular tolerance, fluid removal in volume-expanded HD patients should be gradual and distributed over a sufficiently long time window. This review summarizes current knowledge about the diagnosis, prognosis and treatment of volume overload in HD patients.

Three compartment bioimpedance spectroscopy in the nutritional assessment and the outcome of patients with advanced or end stage kidney disease: What have we learned so far?

Bioimpedance spectroscopy (BIS) is an easily applicable tool to assess body composition. The three compartment model BIS (3C BIS) conventionally expresses body composition as lean tissue index (LTI) (lean tissue mass [LTM]/height in meters squared) and fat tissue index (FTI) (adipose tissue mass/height in meters squared), and a virtual compartment reflecting fluid overload (FO). It has been studied extensively in relation to diagnosis and treatment guidance of fluid status disorders in patients with advanced‐stage or end‐stage renal disease. It is the aim of this article to provide a narrative review on the relevance of 3C BIS in the nutritional assessment in this population. At a population level, LTI decreases after the start of hemodialysis, whereas FTI increases. LTI below the 10th percentile is a consistent predictor of outcome whereas a low FTI is predominantly associated with outcome when combined with a low LTI. Recent research also showed the connection between low LTI, inflammation, and FO, which are cumulatively associated with an increased mortality risk. However, studies toward nutritional interventions based on BIS data are still lacking in this population. In conclusion, 3C BIS, by disentangling the components of body mass index, has contributed to our understanding of the relevance of abnormalities in different body compartments in chronic kidney disease patients, and appears to be a valuable prognostic tool, at least at a population level. Studies assessing the effect of BIS guided nutritional intervention could further support its use in the daily clinical care for renal patients.

Brain natriuretic peptide reflects individual variation in hydration status in hemodialysis patients

Introduction: Fluid management in hemodialysis patients is a controversial topic. Brain natriuretic peptide (BNP) is secreted from the heart in response to volume overload, and may be a marker of overhydration in hemodialysis patients. Our aim was to investigate the correlation between BNP and overhydration in a cohort of hemodialysis patients, and to find out whether BNP and overhydration correlate in repeated measurements within individuals with elevated BNP.

Methods: The study was prospective, observational, and had a cross‐sectional part and a longitudinal follow‐up. The distribution of BNP was investigated in a cohort of 64 hemodialysis patients. Blood samples and bioimpedance spectroscopy measurements were performed before midweek dialysis. Subsequently, 11 study participants with elevated BNP concentrations (>500 pg/mL) were assessed in another nine dialysis sessions each. These individuals also had their cardiac function and heart rate variability (HRV) examined.

Findings: BNP was above 500 pg/mL in 38% of the participants, and correlated positively with overhydration (r_s = 0.381), inflammation and malnutrition, but not with systolic blood pressure. In comparison to participants with BNP below 500 pg/mL, participants with elevated BNP were older, had lower muscle strength, lower bodyweight and lower levels of hemoglobin and albumin. Echocardiography revealed cardiac anomalies in all 11 participants in the longitudinal follow‐up, and HRV, as measured by SDNN, was pathologically low. In repeated measurements, the between‐individuals variation of BNP in relation to overhydration was greater (SD = 0.581) than the within‐person variation (SD = 0.285).

Discussion: BNP correlates positively to overhydration, malnutrition, and inflammation. In a subgroup of patients with elevated BNP, who are mainly elderly and frail, BNP reflects individual variation in hydration status, and hence seems to be a modifiable marker of overhydration. These data suggest that BNP is best applied for measuring changes in hydration status within an individual over time.

Fluid status assessment in hemodialysis patients and the association with outcome: review of recent literature

PURPOSE OF REVIEW

In this review, we will discuss the most recent literature regarding fluids status assessment in hemodialysis patients, and the associations with outcome.

RECENT FINDINGS

Research toward technique-assisted assessment of fluid status in hemodialysis patients has been going on for many years. However, there is no absolute agreement between techniques, such as bioimpedance, lung ultrasound, biochemical markers or vena caval diameter, likely because they reflect different fluid compartments with potentially altered distribution in hemodialysis patients. Recent studies, mostly based on bioimpedance, have shown not only an association of severe, but also of moderate predialysis fluid overload with overall survival. Also predialysis fluid depletion has been found to associate with and increased mortality risk. Interventional studies with fluid-guided management are scarce and outline the difficulties of achieving dry weight is the dialysis population.

SUMMARY

Optimal estimation of predialysis fluid status remains challenging and may require a combination of clinical and technical derived parameters. There appears to be a narrow window of optimal predialysis fluid status. Further clinical studies are necessary to identify strategies to improve survival in hemodialysis patients with abnormalities in fluid status.

Knee-to-knee Bioimpedance Measurements to Monitor Changes in Extracellular Fluid in Haemodynamic-unstable Patients During Dialysis

The feasibility of bioimpedance spectroscopy (BIS) techniques for monitoring intradialytic changes in body fluids is advancing. The aim of this study was to compare the knee-to-knee (kkBIS) with the traditional whole-body (whBIS) with respect to continuous assessment of fluid volume status in hemodialysis patients. Twenty patients divided into two groups, hemodynamically stable and unstable, were recruited. Bioimpedance data from two different electrodes configurations (hand-to-foot and knee-to-knee) were collected and retrospectively analysed. A good correlation between the two methods with respect to changes in extracellular resistance (R_e) and R_e normalized for ultrafiltration volume (ΔR_e/UFV) with p < 0.001 was observed. The relationship between relative change (%) in ΔR_e and that in patient weight was most notable with kkBIS (4.82 ± 3.31 %/kg) in comparison to whBIS (3.69 ± 2.90 %/kg) in unstable patients. Furthermore, results based on kkBIS showed a reduced ability of the thigh compartments to keep up with the volume changes in the trunk for unstable patients. kkBIS provided a comparable sensitivity to whBIS even in patients at risk of intradialytic hypotension while avoiding the need for the complex implementation imposed by whBIS or other configurations.

Hypertension in Pediatric Dialysis Patients: Etiology, Evaluation, and Management

PURPOSE OF REVIEW

Review epidemiology, pathophysiology, and management of hypertension in the pediatric dialysis population.

RECENT FINDINGS

Interdialytic blood pressure measurement, especially with ambulatory blood pressure monitoring, is the gold standard to assess for hypertension. Tools to assess dry weight aid in achievement of euvolemia, the primary therapy for management of hypertension. Persistent hypertension should be treated with antihypertensive medications and potentially with native nephrectomies. Cardiovascular disease continues to be the primary cause of morbidity and mortality in the dialysis population with hypertension as an important modifiable factor. Achievement on dry weight and limiting both aggressiveness of interdialytic weight gain and ultrafiltration rate underlie the best approach. Tools to assess volume status beyond clinical assessment have shown promise in achieving euvolemia. When hypertension persists despite achievement of euvolemia, antihypertensive medications may be required and in some cases native nephrectomies. Future studies in children are needed to determine the best antihypertensive class and ideal rate of ultrafiltration on hemodialysis towards achievement of normotension and reduction of cardiovascular risk.

Fluid Overload and Inflammation Axis

Extracellular fluid overload (FO), which is assessed using bioimpedance technologies, is an important predictor of outcome in dialysis patients and in patients with early stages of chronic kidney disease. While traditional cardiovascular abnormalities are assumed to mediate this risk, recently also, the importance of noncardiovascular factors, such as systemic inflammation and malnutrition has been shown. While both FO and inflammation are independent risk factors for mortality, recent studies have shown that their combined presence can lead to a cumulative risk profile. From a pathophysiologic viewpoint, FO and inflammation can also be mutually reinforcing. Inflammation could contribute to FO by hypoalbuminemia, capillary leakage, and a (unnoticed) decline in lean and/or fat tissue mass resulting in incorrect estimation of dry weight. Reciprocally, FO could lead to inflammation by the translocation of endotoxins through a congested bowel wall or by a proinflammatory effect of tissue sodium. The relative importance of these putative factors is, however, not clear yet and epidemiological studies have shown no clear temporal direction regarding the relationship between FO and inflammation. FO and inflammation appear to be part of (dynamic) clusters of risk factors, including malnutrition and hyponatremia. Technology-guided fluid management of the often vulnerable dialysis patient with FO and inflammation cannot yet be based on evidence from randomized controlled trials, in which these specific patients were in general not included. In the absence of those trials, treatment should be based on identifying actionable causes of inflammation and on the judicious removal of excess volume based on frequent clinical reassessment.

The Influence of Colloid Osmotic Pressure on Hydrostatic Pressures in High- and Low-Flux Hemodialyzers

The aim of this study was to examine the relationship between hydrostatic trans-membrane pressure (TMP_h ) and colloid osmotic pressure (COP) in low-flux (LF) and high-flux (HF) dialyzers. Hydrostatic pressures were measured in dialyzers distinguished by their ultrafiltration coefficient K_uf (16 and 85 mL/h/mm Hg) under constant dialysate flow and variable blood flow (Q_b ) ranging from 0 to 400 mL/min using (i) alginate (70 kDa) dissolved in dialysate, (ii) diluted, undiluted, and concentrated plasma, or (iii) whole blood at different hematocrit, all in absence of ultrafiltration (UF). For a given fluid, TMP_h linearly increased with increasing Q_b . The intercept of the linear TMP_h to Q_b relationship correlated with measured COP with an average bias of 1.00 ± 2.26 mm Hg and a concordance correlation coefficient of 0.98. The slope of the linear TMP_h to Q_b relationship increased with increasing sample viscosity and was much larger in HF dialyzers under otherwise identical operating conditions, most likely because of increased internal filtration. The TMP_h to Q_b relationship measured in dialyzers in absence of UF can be described by the intercept related to measured COP and the slope related to internal filtration. This relationship could be of interest to estimate internal filtration and COP under in vivo conditions.

Effect of age and blood pressure on determination of normal fluid status in a general population using whole body and calf bioimpedance techniques

Normal fluid status (dry weight) can be identified by hydration markers established in the healthy population. The general population average could be influenced by age with its accompanying physiological changes and/or illness. The aims of this study were (1) to evaluate the effect of age and systolic blood pressure (SBP) on these markers; (2) to compare mean values of hydration markers as assessed by different bioimpedance techniques. Subjects from the general population (n  =  212, males 105, 57.1% White, 31.6% Black, and 11.3% others) were studied. Body weight, height and SBP were measured. Whole body and calf bioimpedance (Hydra 4200) methods were utilized with subjects in the supine position. Calf normalized resistivity (CNR), fluid overload (FO), extracellular (ECV) and intracellular (ICV) volume measurements ECV/total body water (TBW) were calculated. Subjects were stratified by age; young (Group1): 18-35 years; middle (Group2): 36-60 years, senior (Group3): 61-80 years. Body mass index (BMI), CNR, and ECV/TBW differed significantly between age groups, and genders. ECV and FO increased with age in males. Decreased CNR (indicating relative increased fluid load) (p  <  0.001) and increased SBP (p  <  0.001) were associated with age in all three groups. CNR in Group1 was the same as in 36.0% of subjects in Group2 and 12.5% of subjects in Group3. In those subjects in Group2 and Group3, with CNR levels comparable to Group1 subjects, SBP was lower than in their peers in each respective age group. In conclusion average CNR in Group1 represents the range of healthy subjects. Since CNR is correlated with age, subjects in Group2 and Group3 are more likely to have fluid overload. Although about a third of subjects in Group2 and Group3 were in the range of Group1, the age and associated factors should be considered when CNR is used to identify fluid status in senior patients.

Effect of Change in Fluid Status Evaluated by Bioimpedance Techniques on Body Composition in Hemodialysis Patients

OBJECTIVE

This prospective study uses calf bioimpedance spectroscopy (cBIS) to guide the attainment of dry weight (DW_cBIS) in chronic hemodialysis (HD) patients. The primary aim of this study was to evaluate whether body composition is altered when fluid status is reduced to DW_cBIS.

METHODS

Target post-HD weight was gradually reduced from baseline (BL) until DW_cBIS was achieved. DW_cBIS was defined as the presence of both flattening of the curve of extracellular resistance and the attainment calf normalized resistivity in the normal range during the dialysis treatment. Extracellular volume (ECV), intracellular volume, and total body water (TBW) were measured using whole body BIS (Hydra 4200). Fluid overload, lean body mass, and fat mass were calculated according to a body composition model.

RESULTS

Seventy-three patients enrolled and 60 completed the study (55 ± 13 years, 49% male). Twenty-eight patients (25% diabetes) achieved DW_cBIS, whereas 32 patients (47% diabetes) did not. Number of treatment measurements were 16 ± 10 and 12 ± 13 studies per patient in the DW_cBIS and non-DW_cBIS groups, respectively. Although significant decreases in body weight and ECV were observed, lean body mass and FM did not differ significantly in both groups from BL to the end of study. ECV, ECV/TBW, and fluid overload were higher in the non-DW_cBIS than in the DW_cBIS group both at BL and at the end of study. Ratios of intradialytic changes in calf normalized resistivity, ECV, and ECV/TBW to ultrafiltration volume were significantly lower in diabetic than in non-diabetic patients.

CONCLUSIONS

This study shows that decreasing fluid status by gradual reduction of post-HD weight in both DW_cBIS and Non-DW_cBIS groups did not affect body composition significantly over a period of about 4 weeks.

Hypertension in dialysis patients: a consensus document by the European Renal and Cardiovascular Medicine (EURECA-m) working group of the European Renal Association - European Dialysis and Transplant Association (ERA-EDTA) and the Hypertension and the Kidney working group of the European Society of Hypertension (ESH)

In patients with end-stage renal disease treated with hemodialysis or peritoneal dialysis, hypertension is very common and often poorly controlled. Blood pressure (BP) recordings obtained before or after hemodialysis display a J-shaped or U-shaped association with cardiovascular events and survival, but this most likely reflects the low accuracy of these measurements and the peculiar hemodynamic setting related with dialysis treatment. Elevated BP by home or ambulatory BP monitoring is clearly associated with shorter survival. Sodium and volume excess is the prominent mechanism of hypertension in dialysis patients, but other pathways, such as arterial stiffness, activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, endothelial dysfunction, sleep apnea and the use of erythropoietin-stimulating agents may also be involved. Nonpharmacologic interventions targeting sodium and volume excess are fundamental for hypertension control in this population. If BP remains elevated after appropriate treatment of sodium-volume excess, the use of antihypertensive agents is necessary. Drug treatment in the dialysis population should take into consideration the patient's comorbidities and specific characteristics of each agent, such as dialysability. This document is an overview of the diagnosis, epidemiology, pathogenesis and treatment of hypertension in patients on dialysis, aiming to offer the renal physician practical recommendations based on current knowledge and expert opinion and to highlight areas for future research.

Pre-operative Duplex Ultrasonography in Arteriovenous Fistula Creation: Intra- and Inter-observer Agreement

OBJECTIVE

Although clinical guidelines on arteriovenous fistula (AVF) creation advocate minimum luminal arterial and venous diameters, assessed by duplex ultrasonography (DUS), the clinical value of routine DUS examination is under debate. DUS might be an insufficiently repeatable and/or reproducible imaging modality because of its operator dependency. The present study aimed to assess intra- and inter-observer agreement of DUS examination in support of AVF surgery planning.

METHODS

Ten end stage renal disease patients were included, to assess intra- and inter-observer agreement of pre-operative DUS measurements. All measurements were performed by two trained and experienced vascular technicians, blinded to measurement readings. From the routine DUS protocol, representative measurements (venous diameters, and arterial diameters and volume flow in the upper arm and forearm) were selected. For intra-observer agreement the measurements were performed in triplicate, with the probe released from the skin between each. Intraclass correlation coefficients were calculated for intra- and inter-observer agreement, and Bland-Altman plots used to graphically display mean measurement differences and limits of agreement.

RESULTS

Ten patients (6 male, 59.4±19.7 years) consented to participate, and all predefined measurements were obtained. Intraclass correlation coefficients for intra-observer agreement of diameter measurements were at least 0.90 (95% CI 0.74-0.97; radial artery). Inter-observer agreement was at least 0.83 (0.46-0.96; lateral diameter upper arm cephalic vein). The Bland-Altman plots showed acceptable mean measurement differences and limits of agreement.

CONCLUSION

In experienced hands, excellent intra- and inter-observer agreement can be reached for the discrete pre-operative DUS measurements advocated in clinical guidelines. DUS is therefore a reliable imaging modality to support AVF surgery planning. The content of DUS protocols, however, needs further standardisation.

Hypertension in dialysis patients: a consensus document by the European Renal and Cardiovascular Medicine (EURECA-m) working group of the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) and the Hypertension and the Kidney working group of the European Society of Hypertension (ESH)

In patients with end-stage renal disease (ESRD) treated with haemodialysis or peritoneal dialysis, hypertension is common and often poorly controlled. Blood pressure (BP) recordings obtained before or after haemodialysis display a J- or U-shaped association with cardiovascular events and survival, but this most likely reflects the low accuracy of these measurements and the peculiar haemodynamic setting related to dialysis treatment. Elevated BP detected by home or ambulatory BP monitoring is clearly associated with shorter survival. Sodium and volume excess is the prominent mechanism of hypertension in dialysis patients, but other pathways, such as arterial stiffness, activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, endothelial dysfunction, sleep apnoea and the use of erythropoietin-stimulating agents may also be involved. Non-pharmacologic interventions targeting sodium and volume excess are fundamental for hypertension control in this population. If BP remains elevated after appropriate treatment of sodium and volume excess, the use of antihypertensive agents is necessary. Drug treatment in the dialysis population should take into consideration the patient's comorbidities and specific characteristics of each agent, such as dialysability. This document is an overview of the diagnosis, epidemiology, pathogenesis and treatment of hypertension in patients on dialysis, aiming to offer the renal physician practical recommendations based on current knowledge and expert opinion and to highlight areas for future research.

Vascular Refilling Is Not Reduced in Dialysis Sessions with Morbid Events

Background: It is commonly believed that insufficient vascular refilling leads to hypovolemia during hemodialysis and contributes to intradialytic morbid events (IME). But data of refilling volumes at the time of IME are lacking. Methods: We compared the vascular refilling in 10 patients with IME with 14 stable patients with normal blood volume at the dialysis end (66-80 mL/kg). Results: The refilling characteristics in patients with IME did not differ from those in stable patients. The refilling fraction (refilling/ultrafiltration [UF] ratio) was 73.8 ± 9.4% in patients with IME, and 70.2 ± 6.4% in patients with normal blood volume at the end of the treatment. Refilling volume strongly correlated with UF volume in both patient groups (r2 = 0.93 and r2 = 0.81, respectively). Conclusion: IME are associated with a specific blood volume below 65 mL/kg. Vascular refilling is a constant fraction of UF in stable as well as in symptomatic dialysis sessions.