Assessment of Extracellular Fluid Volume and Fluid Status in Hemodialysis Patients: Current Status and Technical Advances

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.

Concordance between bio-impedance analysis and clinical score in fluid-status assessment of maintenance haemodialysis patients: A single centre experience

BACKGROUND

The burden of chronic kidney disease (CKD) is rising rapidly globally. Fluid overload (FO), an independent predictor of mortality in CKD, should be accurately assessed to guide estimation of the volume of fluid to be removed during haemodialysis (HD). Clinical score (CS) and bio-impedance analysis (BIA) have been utilized in assessment of FO and BIA has demonstrated reproducibility and accuracy in determination of fluid status in patients on HD. There is need to determine the performance of locally-developed CSs in fluid status assessment when evaluated against BIA.

AIM

To assess the hydration status of patients on maintenance HD using BIA and a CS, as well as to evaluate the performance of that CS against BIA in fluid status assessment.

METHODS

This was a single-centre, hospital-based cross-sectional study which recruited adult patients with CKD who were on maintenance HD at Kenyatta National Hospital. The patients were aged 18 years and above and had been on maintenance HD for at least 3 mo. Those with pacemakers, metallic implants, or bilateral limbs amputations were excluded. Data on the patients’ clinical history, physical examination, and chest radiograph findings were collected. BIA was performed on each of the study participants using the Quantum^® II bio-impedance analyser manufactured by RJL Systems together with the BC 4^® software. In evaluating the performance of the CS, BIA was considered as the gold standard test. A 2-by-2 table of the participants’ fluid status at each of the CS values obtained compared to their paired BIA results was constructed (either ++, +-, -- or -+ for FO using the CS and BIA, respectively). The results from this 2-by-2 table were used to compute the sensitivity and specificity of the CS at the various reference points and subsequently plot a receiver operating characteristic (ROC) curve that was used to determine the best cut-off point. Those above and below the best CS cut-off point as determined by the ROC were classified as being positive and negative for FO, respectively. The proportions of participants diagnosed with FO by the CS and BIA, respectively, were computed and summarized in a 2-by-2 contingency table for comparison. McNemar’s chi-squared test was used to assess any statistically significant difference in proportions of patients diagnosed as having FO by CS and BIA. Logistic regression analysis was conducted to assess whether the variables for the duration of dialysis, the number of missed dialysis sessions, advisement by health care professional on fluid or salt intake, actual fluid intake, the number of anti-hypertensives used, or body mass index were associated with a patient’s odds of having FO as diagnosed by BIA.

RESULTS

From 100 patients on maintenance HD screened for eligibility, 80 were recruited into this study. Seventy-one (88.75%) patients were fluid overloaded when evaluated using BIA with mean extracellular volume of 3.02 ± 1.79 L as opposed to the forty-seven (58.25%) patients who had FO when evaluated using the CS. The difference was significant, with a P value of < 0.0001 (95% confidence interval: 0.1758-0.4242). Using CS, values above 4 were indicative of FO while values less than or equal to 4 denoted the best cut-off for no FO. The sensitivity and specificity for the CS were 63% and 78% respectively. None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.

CONCLUSION

FO is very prevalent in patients on chronic HD at the Kenyatta National Hospital. CS detects FO less frequently when compared with BIA. The sensitivity and specificity for the CS were 63% and 78% respectively. None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.

Estimation of fluid status using three multifrequency bioimpedance methods in hemodialysis patients

INTRODUCTION

Segmental eight-point bioimpedance has been increasingly used in practice. However, whether changes in bioimpedance analysis components before and after hemodialysis (HD) using this technique in a standing position is comparable to traditional whole-body wrist-to-ankle method is still unclear. We aimed to investigate the differences between two eight-point devices (InBody 770 and Seca mBCA 514) and one wrist-to-ankle (Hydra 4200) in HD patients and healthy subjects in a standing position.

METHODS

Thirteen HD patients were studied pre- and post-HD, and 12 healthy subjects once. Four measurements were performed in the following order: InBody; Seca; Hydra; and InBody again. Electrical equivalent models by each bioimpedance method and the fluid volume estimates by each device were also compared.

FINDINGS

Overall, total body water (TBW) was not different between the three devices, but InBody showed lower extracellular water (ECW) and higher intracellular water (ICW) compared to the other two devices. When intradialytic weight loss was used as a surrogate for changes in ECW (∆ECW) and changes in TBW (∆TBW), ∆ECW was underestimated by Hydra (-0.79 ± 0.89 L, p < 0.01), InBody (-1.44 ± 0.65 L, p < 0.0001), and Seca (-0.32 ± 1.34, n.s.). ∆TBW was underestimated by Hydra (-1.14 ± 2.81 L, n.s.) and InBody (-0.52 ± 0.85 L, p < 0.05) but overestimated by Seca (+0.93 ± 3.55 L, n.s.).

DISCUSSION

Although segmental eight-point bioimpedance techniques provided comparable TBW measurements not affected by standing over a period of 10-15 min, the ECW/TBW ratio appeared to be significantly lower in InBody compared with Seca and Hydra. Results from our study showed lack of agreement between different bioimpedance devices; direct comparison of ECW, ICW, and ECW/TBW between different devices should be avoided and clinicians should use the same device to track the fluid status in their HD population in a longitudinal direction.

Inter- and intradialytic fluid volume changes and vascular stiffness parameters in patients on hemodialysis

BACKGROUND

Whether fluid overload is associated with vascular stiffness parameters in hemodialysis (HD) patients has not been fully elucidated. We hypothesized that interdialytic fluid accumulation increases vascular stiffness parameters, which improves with intradialytic ultrafiltration.

METHODS

Fluid overload and vascular stiffness parameters were assessed in 39 HD patients (20 with and 19 without fluid overload) and compared to 26 healthy controls. Fluid status was assessed 15 minutes before the mid-week HD session by bio-impedance spectroscopy. Following this, ambulatory pulse wave velocity (PWV) and augmentation index (AIx) were measured for 24 hours before another mid-week HD session and then for 5 hours starting 30 minutes before and ending 30 minutes after the session.

RESULTS

HD patients had significant fluid overload compared to healthy controls (2.0±2.4 vs. -0.2±0.6 L; P<0.001) and baseline PWV was higher (10.3±1.7 vs. 8.8±1.4 m/s; P<0.001). There was no significant difference between PWV and AIx in fluid overloaded and non-fluid overloaded HD patients prior to, or during the HD session. AIx of non-fluid overloaded HD patients improved after the HD session (P = 0.04). Average 24-hour AIx was higher in fluid overloaded HD patients (P<0.001).

CONCLUSIONS

Inter- and intradialytic changes in fluid volume were only weakly related to vascular stiffness parameters in HD patients. Although there was a modest reduction in AIx in non-fluid overloaded HD patients after the dialysis session, fluid removal did not improve vascular stiffness parameters during the HD session. We speculate that the effect of fluid overload correction on vascular stiffness parameters requires long-term adjustments in the vasculature.

Body Fat Plays an Important Role in of Bioimpedance Spectroscopy-Based Dry Weight Measurement Error for Patients with Hemodialysis

Accurate dry weight (DW) estimation is important for hemodialysis patients. Although bioimpedance spectroscopy (BIS) is commonly used to measure DW, the BIS-based DW frequently differs from the clinical DW. We analyzed the characteristics of patients whose BIS-based DWs were over- and underestimated. In this retrospective cohort study, we evaluated 1555 patients undergoing maintenance hemodialysis in Chungnam National University Hospital. The gap (DWCP-BIS) was calculated by comparing the BIS and clinical DWs. We analyzed the clinical characteristics of patients with positive (n = 835) and negative (n = 720) gaps. Compared with other patients, the DWCP-BIS-positive group had higher extracellular water (ECW) level and extracellular/intracellular water index (E/I) and had lower weight, body mass index (BMI), lean tissue index (LTI), fat tissue index (FTI), fat mass (FAT), and adipose tissue mass (ATM). The DWCP-BIS-negative group exhibited elevated BMI, FTI, FAT, and ATM; however, it had lower height, ECW, and E/I. Linear regression analysis revealed that FAT significantly predicted DWCP accuracy. The clinical DW of patients with a low fat mass tended to be underestimated, while the clinical DW of patients with comparatively large fat reserves tended to be overestimated. These characteristics will aid in the reduction of BIS-based DW errors.

Chest Ultrasound as a New Tool for Assessment of Volume Status in Hemodialysis Patients

Accurate assessment of volume status (VS) in hemodialysis (HD) patients is challenging. The use of chest ultrasound (CUS) for detection of extravascular lung water has recently gained wide acceptance. The aim of this study was to evaluate the use of CUS in VS assessment in HD patients in comparison to clinical and inferior vena cava (IVC) indices and to assess their relation with volume displacement after ultrafiltration. This prospective cohort study was carried out on 38 patients on regular HD. VS was assessed using a 13-point clinical score, and IVC indices and CUS score were measured pre- and post-ultrafiltration. Correlation between these parameters and with ultrafiltration volume was tested. There was a statistically significant reduction in post-ultrafiltration CUS score and the 13-point clinical score (P < 0.01). Moreover, reduction in all the IVC indices (inspiratory and expiratory diameters and collapsing index) was detected, but did not reach statistical significance (P = 0.185, P = 0.296, and P = 0.194, respectively). CUS score had statistically significant correlations with ultrafiltration volume and New York Heart Association classes (P < 0.001 and <0.001, respectively). Neither clinical signs nor IVC indices can be used independently for the assessment of VS in HD patients. CUS is a useful guide in VS assessment, and we recommend its routine use in the management of HD patients. Concomitant use of bio- impedance analysis (BIA) may be needed in addition to CUS for more accurate assessment of VS in HD patients.

Electrolyte-based calculation of fluid shifts after infusing 0.9% saline in severe hyperglycemia

Background

Early treatment of severe hyperglycemia involves large shifts of body fluids that entail a risk of hemodynamic instability. We studied the feasibility of applying a new electrolyte equation that estimates the degree of volume depletion and the distribution of infused 0.9% saline in this setting.

Methods

The new equation was applied to plasma and urinary concentrations of sodium and chloride measured before and 30 min after a 30-min infusion of 1 L of 0.9% saline on two consecutive days in 14 patients with severe hyperglycemia (mean age 50 years). The extracellular fluid (ECF) volume was also estimated based on the volume dilution kinetics of chloride.

Results

On day 1, the baseline ECF volume amounted to 11.5 L. The saline infusion expanded the ECF space by 160 mL and the intracellular fluid space by 375 mL. On day 2, the ECF volume was 15.5 L, and twice as much of the infused fluid remained in the ECF space. The chloride dilution kinetics yielded baseline ECF volumes of 11.6 and 15.2 L on day 1 and day 2, respectively. No net uptake of glucose to the cells occurred during the two 1-h measurement periods despite insulin administration in the intervening time period.

Conclusions

The electrolyte equation was feasible to apply in a group of hyperglycemic patients. The ECF space was 3 L smaller than expected on admission but normal on the second day. Almost half of the infused fluid was distributed intracellularly.

Clinical efficacy of biomarkers for evaluation of volume status in dialysis patients

Volume status is a key parameter for cardiovascular-related mortality in dialysis patients. Although N-terminal pro-B-type natriuretic peptide (NT-proBNP), myeloperoxidase, copeptin, and pro-adrenomedullin have been reported as volume markers, the relationship between body fluid status and volume markers in dialysis patients is uncertain. Therefore, we investigated the utility of volume status biomarkers based on body composition monitor (BCM) analyses.We enrolled pre-dialysis, hemodialysis (HD), and peritoneal dialysis (PD) patients and age- and gender-matched healthy Korean individuals (N = 80). BCM and transthoracic echocardiography were performed and NT-proBNP, myeloperoxidase, copeptin, and pro-adrenomedullin concentrations were measured. Relative hydration status (ΔHS, %) was defined in terms of the hydration status-to-extracellular water ratio with a cutoff of 15%, and hyperhydrated status was defined as ΔHS > 15%.Although there were no significant differences in total body water, extracellular water, or intracellular water among groups, mean amount of volume overload and hyperhydrated status were significantly higher in HD and PD patients compared with control and pre-dialysis patients. Mean amount of volume overload and hyperhydrated status were also significantly associated with higher NT-proBNP and pro-adrenomedullin levels in HD and PD patients, although not with myeloperoxidase or copeptin levels. Furthermore, they were significantly associated with cardiac markers (left ventricular mass index, ejection fraction, and left atrial diameter) in HD and PD patients compared with those in the control and pre-dialysis groups.On the basis of increased plasma NT-proBNP and pro-adrenomedullin concentrations, we might be able to make predictions regarding the volume overload status of dialysis patients, and thereby reduce cardiovascular-related mortality through appropriate early volume control.

All-cause mortality in relation to changes in relative blood volume during hemodialysis

Background

Relative blood volume (RBV) monitoring is widely used in hemodialysis (HD) patients, yet the association between intradialytic RBV and mortality is unknown.

Methods

Intradialytic RBV was recorded once/min during a 6-month baseline period; all-cause mortality was noted during follow-up. RBV at 1, 2 and 3 h into HD served as a predictor of all-cause mortality during follow-up. We employed Kaplan–Meier analysis, univariate and adjusted Cox proportional hazards models for survival analysis.

Results

We studied 842 patients. During follow-up (median 30.8 months), 249 patients (29.6%) died. The following hourly RBV ranges were associated with improved survival: first hour, 93–96% [hazard ratio (HR) 0.58 (95% confidence interval (CI) 0.42–0.79)]; second hour, 89–94% [HR 0.54 (95% CI 0.39–0.75)]; third hour, 86–92% [HR 0.46 (95% CI 0.33–0.65)]. In about one-third of patients the RBV was within these ranges and in two-thirds it was above. Subgroup analysis by median age (≤/> 61 years), sex, race (white/nonwhite), predialysis systolic blood pressure (SBP; ≤/> 130 mmHg) and median interdialytic weight gain (≤/> 2.3 kg) showed comparable favorable RBV ranges. Patients with a 3-h RBV between 86 and 92% were younger, had higher ultrafiltration volumes and rates, similar intradialytic average and nadir SBPs and hypotension rates, lower postdialysis SBP and a lower prevalence of congestive heart failure when compared with patients with an RBV >92%. In the multivariate Cox analysis, RBV ranges remained independent and significant outcome predictors.

Conclusion

Specific hourly intradialytic RBV ranges are associated with lower all-cause mortality in chronic HD patients.

Extracellular resistance is sensitive to tissue sodium status; implications for bioimpedance-derived fluid volume parameters in chronic kidney disease

Multifrequency bioimpedance spectroscopy (BIS) is an established method for assessing fluid status in chronic kidney disease (CKD). However, the technique is lacking in predictive value and accuracy. BIS algorithms assume constant tissue resistivity, which may vary with changing tissue ionic sodium concentration (Na+). This may introduce significant inaccuracies to BIS outputs. To investigate this, we used 23Na magnetic resonance imaging (MRI) to measure Na+ in muscle and subcutaneous tissues of 10 healthy controls (HC) and 20 patients with CKD 5 (not on dialysis). The extracellular (Re) and intracellular (Ri) resistance, tissue capacitance, extracellular (ECW) and total body water (TBW) were measured using BIS. Tissue water content was assessed using proton density-weighted MRI with fat suppression. BIS-derived volume indices were comparable in the two groups (OH: HC - 0.4 ± 0.9 L vs. CKD 0.5 ± 1.9 L, p = 0.13). However, CKD patients had higher Na+ (HC 21.2 ± 3.0, CKD 25.3 ± 7.4 mmol/L; p = 0.04) and significantly lower Re (HC 693 ± 93.6, CKD 609 ± 74.3 Ohms; p = 0.01); Ri and capacitance did not vary. Na+ showed a significant inverse linear relationship to Re (rs = - 0.598, p < 0.01) but not Ri. This relationship of Re (y) and Na+ (x) is described through equation y = - 7.39x + 814. A 20% increase in tissue ionic Na+ is likely to overestimate ECW by 1.2-2.4L. Tissue Na+ concentration has a significant inverse linear relationship to Re. BIS algorithms to account for this effect could improve prediction accuracy of bioimpedance derived fluid status in CKD.

Fluid assessment in dialysis patients by point-of-care magnetic relaxometry

Magnetic resonance imaging (MRI) is a powerful diagnostic tool, but its use is restricted to the scanner suite. Here, we demonstrate that a bedside nuclear magnetic resonance (NMR) sensor can assess fluid status changes in individuals at a fraction of the time and cost compared to MRI. Our study recruited patients with end-stage renal disease (ESRD) who were regularly receiving hemodialysis treatments with intradialytic fluid removal as a model of volume overload and healthy controls as a model of euvolemia. Quantitative T 2 measurements of the lower leg of patients with ESRD immediately before and after dialysis were compared to those of euvolemic healthy controls using both a 0.28-T bedside single-voxel NMR sensor and a 1.5-T clinical MRI scanner. In the MRI data, we found that the first sign of fluid overload was an expanded muscle extracellular fluid (ECF) space, a finding undetectable at this stage using physical exam. A decrease in muscle ECF upon fluid removal was similarly detectable with both the bedside sensor and MRI. Bioimpedance measurements performed comparably to the bedside NMR sensor but were generally worse than MRI. These findings suggest that bedside NMR may be a useful method to identify fluid overload early in patients with ESRD and potentially other hypervolemic patient populations.

Using Technology to Inform and Deliver Precise Personalized Care to Patients With End-Stage Kidney Disease

Consistent with the increase of precision medicine, the care of patients with end-stage kidney disease (ESKD) requiring maintenance dialysis therapy should evolve to become more personalized. Precise and personalized care is nuanced and informed by a number of factors including an individual's needs and preferences, disease progression, and response to and tolerance of treatments. Technology can support the delivery of more precise and personalized care through multiple mechanisms, including more accurate and real-time assessments of key care elements, enhanced treatment monitoring, and remote monitoring of home dialysis therapies. Data from health care and non-health care sources and advanced analytical methods such as machine learning can be used to create novel insights, and large volumes of data can be integrated to support clinical decisions. Health care models continue to evolve and the opportunities and need for novel care approaches supported by technology and health informatics continue to expand as the delivery and organization of health care changes. Ultimately, precise personalized care for ESKD, including dialysis therapy, will become more feasible as the biological, social, and environmental determinants of health are more broadly understood and as advances in science, engineering, and information management create the means to provide truly precise care for ESKD.

Monitoring Volume Status Using Bioelectrical Impedance Analysis in Chronic Hemodialysis Patients

Fluid overload can be an independent risk factor of cardiovascular events and all-cause death in end-stage renal disease (ESRD) patients on chronic hemodialysis. We performed a retrospective study to investigate whether intermittent control of fluid status decreases the rate of these complications using bioelectrical impedance analysis (BIA). In ESRD patients on chronic hemodialysis, we identified the ratio of extracellular water to total body water (ECW/TBW) every 6 months using InBody S10 (Biospace, Seoul, Korea), which was measured within 30 minutes after dialysis initiation on the first dialysis day of the week. The uncontrolled group included 57 (40.1%) patients with all ECW/TBW measurements ≥0.40; in contrast, the controlled group included 85 (59.9%) with any measured ECW/TBW <0.40. Included patients were followed for 29 (12-42) months. The risk of cardiovascular events was higher in the uncontrolled group (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.2-5.1; p < 0.05) than it was in the controlled group; however, this difference disappeared after adjusting for age, sex, and Charlson comorbidity index (not significant). On the other hand, the patients in the uncontrolled group had a higher risk of all-cause death than did those in the controlled group, independent of age, sex, and Charlson comorbidity index (HR, 4.7; 95% CI, 1.4-16.1; p < 0.05). In conclusion, monitoring volume status using BIA may help to predict all-cause death in chronic hemodialysis patients. Further controlled studies are needed to confirm that strict volume control could reduce the rates of cardiovascular events and mortality in this population.

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.

Techniques for assessing fluids status in patients with kidney disease

PURPOSE OF REVIEW

The aim of this article is to present current information on techniques for fluid status assessment in patients with kidney disease. The methods can be broadly categorized into biomarkers, ultrasound, blood volume monitoring, and bioimpedance.

RECENT FINDINGS

Biomarkers including atrial natriuretic peptide and B-type natriuretic peptide have been shown to provide information about relative changes in fluid status. Ultrasound is applied to measure inferior vena cava indices, pulmonary indicators, and vascular indicators of fluid overload. Relative blood volume monitoring is used to measure change in intravascular fluid during hemodialysis. While in principle appealing, measurement of absolute blood volume has seen limited use to date. Bioimpedance techniques such as vector analysis, whole body, and regional bioimpedance spectroscopy, have shown their ability to estimate fluid status.

SUMMARY

The interpretation of biomarkers is complicated by the presence of cardiac disease. All ultrasound methods have some correlation with fluid status; however, operator dependency limits their routine use. Bioimpedance methods and relative blood volume monitoring are increasingly used to assess fluid status in patients with acute or chronic kidney disease. Measurement of absolute blood volume holds promise for the future.

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.

Utility of Volume Assessment Using Bioelectrical Impedance Analysis in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Prospective Observational Study

Background

Fluid overload prior to continuous renal replacement therapy (CRRT) is an important prognostic factor. Thus, precise evaluation of fluid status is necessary to treat such patients. In this study, we investigated whether fluid assessment using bioelectrical impedance analysis (BIA) can predict outcomes in critically ill patients requiring CRRT.

Methods

A prospective observational study was performed in patients who were admitted to the intensive care unit and who required CRRT. BIA was conducted before CRRT; then, the ratio of extracellular water to total body water (ECW/TBW) was derived to estimate volume status.

Results

A total of 31 patients treated with CRRT were included. There were 18 men (58.1%), and the median age was 67 years (interquartile range, 51 to 78 years). Fourteen patients (45.2%) died within 28 days after CRRT initiation. Patients were divided into 16 with ECW/TBW ≥0.41 and 15 with ECW/TBW <0.41. Survival rate within 28 days was different between the two groups (P = 0.044). Cox regression analysis revealed a relationship between ECW/TBW ≥0.41 and 28-day mortality, but it was not statistically significant (hazard ratio, 3.0; 95% confidence interval, 0.9 to 9.8; P = 0.061). Lastly, the area under the curve of ECW/TBW for 28-day mortality was analyzed. The area under the curve of ECW/TBW was 0.73 (95% confidence interval, 0.54 to 0.92), and this was significant (P = 0.037).

Conclusions

Fluid status can be assessed using BIA in critically ill patients requiring CRRT, and BIA can predict mortality. Further large trials are needed to confirm the usefulness of BIA in critically ill patients.

The role of bioelectrical impedance analysis, NT-ProBNP and inferior vena cava sonography in the assessment of body fluid volume in children with nephrotic syndrome

BACKGROUND

Assessment of volume status and differentiating "underfill" and "overfill" edema is essential in the management of patients with nephrotic syndrome (NS).

OBJECTIVES

Our aim was to evaluate the volume status of NS patients by using different methods and to investigate the utility of bioelectrical impedance analysis (BIA) in children with NS.

METHODS

The hydration status of 19 patients with NS (before treatment of NS and at remission) and 25 healthy controls was assessed by multifrequency BIA, serum N-terminal-pro-brain natriuretic peptide (NT-proBNP) levels, inferior vena cava (IVC) diameter, left atrium diameter (LAD) and vasoactive hormones.

RESULTS

Renin, aldosterone levels, IVC diameter and LAD were not statistically different between the groups. NT-proBNP values were statistically higher in the attack period compared to remission and the control group (p=0.005 for each). Total body water (TBW), overhydration (OH) and extracellular water (ECW) estimated by the BIA measurement in the attack group was significantly higher than that of the remission group and controls. There were no significant correlations among volume indicators in group I and group II. However, significant correlations were observed between NT-proBNP and TBW/BSA (p=0.008), ECW/BSA (p=0.003) and ECW/ICW (p=0.023) in the healthy group. TBW was found to be higher in patients with NS in association with increased ECW but without any change in ICW. NT-proBNP values were higher in patients during acute attack than during remission.

CONCLUSIONS

Our findings support the lack of hypovolaemia in NS during acute attack. In addition, BIA is an easy-to-perform method for use in routine clinical practice to determine hydration status in patients with NS.

The Dialysis Sodium Gradient: A Modifiable Risk Factor for Fluid Overload

Background

Fluid overload in patients on conventional hemodialysis is a frequent complication, associated with increased cardiovascular morbidity and mortality. The dialysate sodium prescription is a potential modifiable risk factor. Our primary objective was to describe associations between dialysate-to-serum sodium gradient and parameters of fluid status. A secondary objective was to evaluate the 6-month risk of hospitalization and mortality in relation to sodium gradient.

Methods

We performed a cross-sectional study of 110 prevalent conventional hemodialysis patients at a single center. The associations of sodium gradient with interdialytic weight gain index (IDWG%), ultrafiltration (UF) rate, and blood pressure (BP) were analyzed.

Results

The mean serum sodium gradient was 4.6 ± 3.6 mEq/L. There was a direct correlation between sodium gradient and IDWG% (r = 0.48, p < 0.01) as well as UF rate (r = 0.44, p < 0.01). In a logistic regression model, a 1 mEq/L higher sodium gradient was associated with increased risk of IDWG% >3% (OR 1.33, p < 0.01) and increased risk of UF rate >10 mL/kg/h (OR 1.16, p = 0.03), but there were no associations with intradialytic hypotension, intradialytic hypertension or BP. No significant differences were found with 6-month hospitalization or mortality risk in relation to sodium gradient.

Conclusion

A higher sodium gradient was associated with significant increases in IDWG and UF rates, known to be associated with poor outcomes, but was not associated with intradialytic hypotension. Individualizing the dialysate sodium prescription to minimize sodium gap may lead to less fluid overload in conventional hemodialysis patients.

Clinical Significance of the Edema Index in Incident Peritoneal Dialysis Patients

Background

Proper monitoring for volume overload is important to improve prognosis in peritoneal dialysis (PD) patients. The association between volume status and residual renal function (RRF) remains an unresolved issue. The aim of the present study was to evaluate the association between the edema index and survival or RRF in incident PD patients.

Patients and Methods

We identified all adults who underwent PD. The edema index was defined as the ratio of extracellular fluid to total body fluid. Participants with available data regarding survivorship or non-survivorship during the first year after PD initiation were included in the area under the receiver operating characteristic curve analysis. The cutoff value of the edema index for 1-year mortality was >0.371 in men and >0.372 in women. Participants were divided into two groups according to the cutoff value of their baseline edema indices: High (>cutoff value) and Low (≤cutoff value). Survivors during the first year after PD initiation were divided into two groups according to the initial and 1-year edema index: Non-improvement (maintenance of criteria in the initial Low group during the year) and Other (all participants except those in the Non-improvement group).

Results

In total, 631 patients were enrolled in the present study. The cutoff value of the edema index for 1-year mortality was >0.371 in men and >0.372 in women. The respective mean initial RRF values (mL·min^-1·1.73 m^-2) in the Low and High groups, respectively, were 4.88 ± 4.09 and 4.21 ± 3.28 in men (P = 0.108), and 3.19 ± 2.57 and 2.98 ± 2.70 in women (P = 0.531). There were no significant differences between groups in either sex. The respective mean RRF values at 1 year after PD initiation in the Low and High groups, respectively, were 3.56 ± 4.35 and 2.73 ± 2.53 in men, and 2.80 ± 2.36 and 1.85 ± 1.51 in women. RRF at 1 year after PD initiation was higher in the Low group than in the High group (men: P = 0.027; women: P = 0.001). In men, the cumulative 5-year survival rates were 78.7% and 46.2% in the Low and High groups, respectively, whereas in women, rates were 77.2% and 58.8% in the Low and High groups, respectively. For survivors during the first year after PD initiation, the Non-improvement group was associated with a poor survival rate compared with the Other group for both sexes.

Conclusion

A high edema index was associated with mortality in incident PD patients at baseline and follow-up. The edema index may be used as a new marker for predicting mortality in PD patients.

Fluid volume expansion and depletion in hemodialysis patients lack association with clinical parameters

BACKGROUND

Achievement of normal volume status is crucial in hemodialysis (HD), since both volume expansion and volume contraction have been associated with adverse outcome and events.

OBJECTIVES

The objectives of this study are to assess the prevalence of fluid volume expansion and depletion and to identify the best clinical parameter or set of parameters that can predict fluid volume expansion in HD patients.

DESIGN

This study is cross-sectional.

SETTING

This study was conducted in three hemodialysis units.

PATIENTS

In this study, there are 194 HD patients.

METHODS

Volume status was assessed by multifrequency bio-impedance spectroscopy (The Body Composition Monitor, Fresenius) prior to the mid-week HD session.

RESULTS

Of all patients, 48 % (n = 94) were volume-expanded and 9 % of patients were volume-depleted (n = 17). Interdialytic weight gain was not different between hypovolemic, normovolemic, and hypervolemic patients. Fifty percent of the volume-expanded patients were hypertensive. Paradoxical hypertension was very common (31 % of all patients); its incidence was not different between patient groups. Intradialytic hypotension was relatively common and was more frequent among hypovolemic patients. Multivariate regression analysis identified only four predictors for volume expansion (edema, lower BMI, higher SBP, and smoking). None of these parameters displayed both a good sensitivity and specificity.

LIMITATIONS

The volume assessment was performed once.

CONCLUSIONS

The study indicates that volume expansion is highly prevalent in HD population and could not be identified using clinical parameters alone. No clinical parameters were identified that could reliably predict volume status. This study shows that bio-impedance can assist to determine volume status. Volume status, in turn, is not related to intradialytic weight gain and is unable to explain the high incidence of paradoxical hypertension.

Association of bioimpedance spectroscopy-based volume estimation with postdialysis hypotension in patients receiving hemodialysis

Clinical examination to determine the dry weight of patients on hemodialysis (HD) has been problematic, with studies showing discordance between physician assessment and objective measures of volume status.We studied the association between predialysis bioimpedance spectroscopy (BIS)-based estimates of fluid overload and postdialysis hypotension in 635 patients in the United States Renal Data System ACTIVE/ADIPOSE (A Cohort study To Investigate the Value of Exercise/Analyses Designed to Investigate the Paradox of Obesity and Survival in ESRD) study receiving HD in 2009-2011. We recorded predialysis and postdialysis weight and blood pressures over 3 consecutive HD sessions and performed BIS before a single session. Using a previously reported method of estimating normohydration weight, we estimated postdialysis fluid overload (FOpost ) in liters. We used logistic regression with extracellular water/total body water (ECW/TBW) or estimated FOpost as the primary predictor and 1 or more postdialysis systolic blood pressures less than 110 mmHg as the dependent variable. Models were adjusted for age, sex, race, ultrafiltration rate per kilogram of body weight, end-stage renal disease vintage, diabetes mellitus, heart failure, and albumin. Higher ECW/TBW was associated with lower odds of postdialysis hypotension (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.15-0.84 per 0.1, P = 0.02). Every liter of FOpost was associated with lower adjusted odds of postdialysis hypotension (OR 0.86, 95% CI 0.79-0.95, P = 0.003). Prospective studies are needed to determine whether this application of BIS could improve current clinical efforts to minimize episodes of postdialysis hypotension without leading to volume overload.

Estimation of Body Composition and Normal Fluid Status Using a Calf Bioimpedance Technique

The aims of this study in hemodialysis (HD) patients were: 1. To evaluate the relationship of calf bioimpedance with total body composition and fluid status as measured by gold standard methods. 2. To investigate the ability of calf normalized resistivity (CNR) to predict the normal fluid status (dry weight: DW) in a prospective study. In the body composition study (n = 41), fluid status (ECVBr/FFMMRI), muscle mass (MMMRI), and total adipose tissue (TATMRI) were measured by dilution (D2O and Br) and MRI methods three hours prior to HD treatment. Calf extracellular and intracellular resistance, resistivity, and CNR were measured with a multi-frequency bioimpedance device (Hydra 4200). In the fluid status study (n = 32 with 429 measurements), a nonlinear model based on the differences in CNR between patients and healthy subjects was established to predict DWcBIS previously determined by a separate continuous calf bioimpedance spectroscopy (cBIS) method. CNR significantly correlated with a gold standard hydration marker (ECVBr/FFMMRI). Calf body composition models were highly correlated with MMMRI (R2 = 0.85) and TATMRI (R2 = 0.85). DWcBIS prediction was validated with a CNR model in the degree of differences of 0.94 ± 0.18, 0.39 ± 0.7 and -0.02 ± 0.8 kg from DWcBIS when post HD fluid overload was 1.8 ± 1.2, 1.15 ± 0.8 and 0.54 ± 0.5 kg, respectively. These differences are not considered to be clinically significant. Conclusion: This practical method of calf bioimpedance is useful to predict body composition and normal fluid status in dialysis patients.

Bioimpedance can solve problems of fluid overload

Bioimpedance (BI) techniques for measuring normal hydration status (NHS) can be generally classified as (1) by frequency as single frequency at 50 kHz, BI analysis, and multifrequency BI spectroscopy and (2) by method as whole body (wrist to ankle) measurement and calf BI spectroscopy. The aim of this article was to review current BI methods for clinical practice in patients with end-stage of kidney disease. BI vector analysis using whole-body single-frequency BI at 50 kHz may be useful for population studies to indicate a range of degree of fluid loading and of nutritional status. Whole body multifrequency BI spectroscopy is used to estimate extracellular (ECV), intracellular fluid volume, and total body water in dialysis patients. The whole-body BI model is used in the body composition monitor (BCM). The whole-body BI model is established with ECV, intracellular fluid volume, and body weight based on parameters from regression analysis in healthy subjects to calculate fluid overload in dialysis patients. Calf BI methods have been developed to measure NHS by 2 ways: (1) continuous measurement of the intradialytic resistance curve until flattening occurs; (2) calf normalized resistivity in the range of healthy subjects (18.5 × 10(-2) Ω m(3)/kg in male and 19.1 × 10(-2) Ω m(3)/kg in female). In general, for population studies, BI vector analysis or ECV/total body water may be useful; BCM is a commercially available device that can certainly guide volume reduction safely over time. For more exact measure of fluid overload, calf BI methods appear to be most accurate, but these are at present research tools. BI techniques are not only useful in assessing NHS but also in the study of nutrition and body composition.

Techniques for the assessment of volume status in patients with end stage renal disease

While advances in assessing extracellular volume status have occurred, no methodology is sufficiently robust and accurate in all patients to recommend routine use in clinical practice. All of the methods described also perform best when measured serially in patients and when correlated with other ancillary methods of volume assessment such as body weight, physical examination and determination of vital signs and symptomatology. Perhaps, the best method for assessing and modifying dry weight is to utilize multiple complementary methods such as advocated by Ronco et in the “5B” approach (39). In this approach, the clinician utilizes data from: fluid balance (body weight changes), blood pressure, biomarkers (such as the natriuretic peptides), bioimpedance, and blood volume changes. Body (thoracic and IVC) ultrasound can also be included (Fig. 1). These combined data sources will likely lead to greater detection of subtle volume overload, a finding likely to contribute to excess mortality and morbidity. Clinical trials of such strategies are needed to better inform clinicians.

A multicentric, international matched pair analysis of body composition in peritoneal dialysis versus haemodialysis patients

BACKGROUND

Volume status, lean and fat tissue are gaining interest as prognostic predictors in patients on dialysis. Comparative data in peritoneal dialysis (PD) versus haemodialysis (HD) patients are lacking.

METHODS

In a cohort of PD (EuroBCM) and HD (Euclid database) patients, matched for country, gender, age and dialysis vintage, body composition was assessed by bioimpedance spectroscopy (BCM, Fresenius Medical Care). Time-averaged volume overload (TAVO) was defined as the mean of pre- and post-dialysis volume overload (VO), and relative (%) (TA)VO as (TA)VO/ECV.

RESULTS

Four hundred and ninety-one matched pairs (55.2% males, median age 60.0 years) were included. The body mass index (BMI, PD = 26.5 ± 4.7 versus HD = 25.9 ± 4.6 kg/m(2), P = 0.18 in males and 27.4 ± 5.8 versus 27.5 ± 6.6 kg/m(2), P = 0.75 in females) and fat tissue index (males: 11.5 ± 5.3 versus 11.4 ± 5.4 kg/m(2), P = 0.90, females: 14.8 ± 6.7 versus 15.4 ± 7.2 kg/m(2), P = 0.30) were not different in PD versus HD patients, whereas the lean tissue index (LTI) was higher in PD versus HD patients (males: 14.5 ± 3.4 versus 13.7 ± 3.1 kg/m(2), P = 0.001, females: 12.6 ± 3.3 versus 11.5 ± 2.6 kg/m(2), P < 0.0001). VO/extracellular water (ECW) was not different between PD versus just before the HD treatment (males: 10.8 ± 12.1 versus 9.2 ± 10.2%, P = 0.09; females: 6.5 ± 10.8 versus 7.7 ± 9.4%, P = 0.19). The relative TAVO was higher in PD versus HD (10.8 ± 12.1% versus 3.2 ± 11.2%, and 6.5 ± 10.8% versus 1.2 ± 10.9%, both P < 0.0001).

CONCLUSIONS

The LTI was impaired, and this was more in males versus females, but was better preserved on PD versus HD, whereas fat tissue index (FTI) was increased, but not different between PD and HD. Volume overload was more present in PD versus HD when TAVO, but not when predialysis volume status, was used as a reference.

The consequences of sudden fluid shifts on body composition in critically ill patients

INTRODUCTION

Estimation of body composition as fat-free mass (FFM) is subjected to many variations caused by injury and stress conditions in the intensive care unit (ICU). Body cell mass (BCM), the metabolically active part of FFM, is reported to be more specifically correlated to changes in nutritional status. Bedside estimation of BCM could help to provide more valuable markers of nutritional status and may promote understanding of metabolic consequences of energy deficit in the ICU patients. We aimed to quantify BCM, water compartments and FFM by methods usable at the bedside for evaluating the impact of sudden and massive fluid shifts on body composition in ICU patients.

METHODS

We conducted a prospective experimental study over an 6 month-period in a 18-bed ICU. Body composition of 31 consecutive hemodynamically stable patients requiring acute renal replacement therapy for fluid overload (ultrafiltration ≥5% body weight) was investigated before and after the hemodialysis session. Intra-(ICW) and extracellular (ECW) water volumes were calculated from the raw values of the low- and high-frequency resistances measured by multi-frequency bioelectrical impedance. BCM was assessed by a calculated method recently developed for ICU patients. FFM was derived from BCM and ECW.

RESULTS

Intradialytic weight loss was 3.8 ± 0.8 kg. Percentage changes of ECW (-7.99 ± 4.60%) and of ICW (-7.63 ± 5.11%) were similar, resulting ECW/ICW ratio constant (1.26 ± 0.20). The fall of FFM (-2.24 ± 1.56 kg, -4.43 ± 2.65%) was less pronounced than the decrease of ECW (P < 0.001) or ICW (P < 0.001). Intradialytic variation of BCM was clinically negligible (-0.38 ± 0.93 kg, -1.56 ± 3.94%) and was significantly less than FFM (P < 0.001).

CONCLUSIONS

BCM estimation is less driven by sudden massive fluid shifts than FMM. Assessment of BCM should be preferred to FFM when severe hydration disturbances are present in ICU patients.

Attending rounds: A patient with intradialytic hypotension

Intradialytic hypotension is the most common adverse event that occurs during the hemodialysis procedure. Despite advances in machine technology, it remains a difficult management issue. The pathophysiology of intradialytic hypotension and measures to reduce its frequency are discussed. An accurate assessment of dry weight is crucial in all patients on dialysis and especially those patients prone to intradialytic hypotension. The presence of edema and hypertension has recently been shown to be a poor predictor of volume overload. Noninvasive methods to assess volume status, such as whole body and segmental bioimpedance, hold promise to more accurately assess fluid status. Reducing salt intake is key to limiting interdialytic weight gain. A common problem is that patients are often told to restrict fluid but not salt intake. Lowering the dialysate temperature, prohibiting food ingestion during hemodialysis, and midodrine administration are beneficial. Sodium modeling in the absence of ultrafiltration modeling should be abandoned. There is not enough data on the efficacy of l-carnitine to warrant its routine use.

Association between body composition and frailty among prevalent hemodialysis patients: a US Renal Data System special study

Studies of frailty among patients on hemodialysis have relied on definitions that substitute self-reported functioning for measures of physical performance and omit weight loss or substitute alternate criteria. We examined the association between body composition and a definition of frailty that includes measured physical performance and weight loss in a cross-sectional analysis of 638 adult patients receiving maintenance hemodialysis at 14 centers. Frailty was defined as having three of following characteristics: weight loss, weakness, exhaustion, low physical activity, and slow gait speed. We performed logistic regression with body mass index (BMI) and bioelectrical impedance spectroscopy (BIS)-derived estimates of intracellular water (ICW), fat mass, and extracellular water (ECW) as the main predictors, and age, sex, race, and comorbidity as covariates. Overall, 30% of participants were frail. Older age (odds ratio [OR], 1.31 per 10 years; 95% confidence interval [95% CI], 1.14 to 1.50), diabetes (OR, 1.65; 95% CI, 1.13 to 2.40), higher fat mass (OR, 1.18; 95% CI, 1.02 to 1.37), and higher ECW (OR, 1.33; 95% CI, 1.20 to 1.47) associated with higher odds of frailty. Higher ICW associated with lower odds of frailty (OR, 0.80 per kg; 95% CI, 0.73 to 0.87). The addition of BMI data did not change the area under the receiver operating characteristics curve (AUC; AUC=0.66 versus 0.66; P=0.71), but the addition of BIS data did change the AUC (AUC=0.72; P<0.001). Thus, individual components of body composition but not BMI associate strongly with frailty in this cohort of patients receiving hemodialysis.

[Fluid overload and arterial hypertension in hemodialysis patients]

The water sodium overload is a factor of morbi-mortality and its treatment is one of the markers of adequacy of the hemodialysis treatment. Its first clinical assessment was improved by tools such as echocardiography and ultrasonography of the inferior vena cava, the per-dialytic curve of plasma volume, measuring BNP or proBNP and by impedancemetry. The combination of the evaluation of these parameters and of the clinical situation allows one to assess the extracellular overload, the state of the blood volume and the potential of plasma refilling. The latter is a key factor of the per-dialytic hemodynamic tolerance. It is itself a determining factor in weight can be achieved at the end of the session. Getting the "dry" weight can require modifications of the prescriptions of the hemodialysis sessions, a filling by albumin even a drugs support. Finally, the overload treatment is the central part of the treatment of arterial hypertension, which has to benefit however often from antihypertensive treatment the profit of which is demonstrated.

Lung ultrasound during hemodialysis: the role in the assessment of volume status

OBJECTIVE

Fluid balance is important in patients undergoing hemodialysis. "Dry" weight is usually estimated clinically, and also, bioimpedance is considered reliable. Ultrasonography of inferior vena cava (IVC) estimates central venous pressure, and lung ultrasound evaluates extravascular (counting B-lines artifact) lung water. Our study was aimed to clarify their usefulness in the assessment of volume status during hemodialysis.

METHODS

A total of 71 consecutive patients undergoing hemodialysis underwent lung and IVC ultrasound and bioimpedance spectroscopy immediately before and after dialysis.

RESULTS

There was a significant reduction in the number of B-lines (3.13 vs 1.41) and in IVC diameters (end-expiratory diameter 1.71 vs 1.37; end-inspiratory diameter 1.19 vs 0.95) during dialysis. The reduction in B-lines correlated with weight reduction during dialysis (p 0.007); none of the parameters concerning the IVC correlated with fluid removal. At the end of the dialysis session, the total number of B-lines correlated with bioimpedance residual weight (p 0.002).

DISCUSSION

The reduction in B-lines correlated with fluid loss due to hemodialysis, despite the small pre-dialysis number, confirming that lung ultrasound can identify even modest variations in extravascular lung water. IVC ultrasound, which reflects the intravascular filling grade, might not be sensitive enough to detect rapid volume decrease. Clinically estimated dry weight had a poor correlation with both bioimpedance and ultrasound techniques. Post-dialysis B-lines number correlates with residual weight assessed with bioimpedance, suggesting a role for ultrasound in managing hemodialysis patients.

Rationale and design of the Sodium Lowering In Dialysate (SoLID) trial: a randomised controlled trial of low versus standard dialysate sodium concentration during hemodialysis for regression of left ventricular mass

BACKGROUND

The current literature recognises that left ventricular hypertrophy makes a key contribution to the high rate of premature cardiovascular mortality in dialysis patients. Determining how we might intervene to ameliorate left ventricular hypertrophy in dialysis populations has become a research priority. Reducing sodium exposure through lower dialysate sodium may be a promising intervention in this regard. However there is clinical equipoise around this intervention because the benefit has not yet been demonstrated in a robust prospective clinical trial, and several observational studies have suggested sodium lowering interventions may be deleterious in some dialysis patients.

METHODS/DESIGN

The Sodium Lowering in Dialysate (SoLID) study is funded by the Health Research Council of New Zealand. It is a multi-centre, prospective, randomised, single-blind (outcomes assessor), controlled parallel assignment 3-year clinical trial. The SoLID study is designed to study what impact low dialysate sodium has upon cardiovascular risk in dialysis patients. The study intends to enrol 118 home hemodialysis patients from 6 sites in New Zealand over 24 months and follow up each participant over 12 months. Key exclusion criteria are: patients who dialyse more frequently than 3.5 times per week, pre-dialysis serum sodium of <135 mM, and maintenance hemodiafiltration. In addition, some medical conditions, treatments or participation in other dialysis trials, which contraindicate the SoLID study intervention or confound its effects, will be exclusion criteria. The intervention and control groups will be dialysed using dialysate sodium 135 mM and 140 mM respectively, for 12 months. The primary outcome measure is left ventricular mass index, as measured by cardiac magnetic resonance imaging, after 12 months of intervention. Eleven or more secondary outcomes will be studied in an attempt to better understand the physiologic and clinical mechanisms by which lower dialysate sodium alters the primary end point.

DISCUSSION

The SoLID study is designed to clarify the effect of low dialysate sodium upon the cardiovascular outcomes of dialysis patients. The study results will provide much needed information about the efficacy of a cost effective, economically sustainable solution to a condition which is curtailing the lives of so many dialysis patients.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry number: ACTRN12611000975998.

Significance of interdialytic weight gain versus chronic volume overload: consensus opinion

Predialysis volume overload is the sum of interdialytic weight gain (IDWG) and residual postdialysis volume overload. It results mostly from failure to achieve an adequate volume status at the end of the dialysis session. Recent developments in bioimpedance spectroscopy and possibly relative plasma volume monitoring permit noninvasive volume status assessment in hemodialysis patients. A large proportion of patients have previously been shown to be chronically volume overloaded predialysis (defined as >15% above 'normal' extracellular fluid volume, equivalent to >2.5 liters on average), and to exhibit a more than twofold increased mortality risk. By contrast, the magnitude of the mortality risk associated with IDWG is much smaller and only evident with very large weight gains. Here we review the available evidence on volume overload and IDWG, and question the use of IDWG as an indicator of 'nonadherence' by describing its association with postdialysis volume depletion. We also demonstrate the relationship between IDWG, volume overload and predialysis serum sodium concentration, and comment on salt intake. Discriminating between volume overload and IDWG will likely lead to a more appropriate management of fluid withdrawal during dialysis. Consensually, the present authors agree that this discrimination should be among the primary goals for dialysis caretakers today. In consequence, we recommend objective measures of volume status beyond mere evaluations of IDWG.

Clinical audit improves hypertension control in hemodialysis patients

BACKGROUND

In patients on hemodialysis (HD), hypertension is a risk factor for cardiovascular disease. In this study we tested the effectiveness of a clinical audit in improving blood pressure (BP) control in HD patients. 


METHODS

177 adult, prevalent patients undergoing dialysis in NephroCare centers in Italy were audited. At the conclusion of the audit, individual strategies were developed in order to improve BP control. Patient data was collected and examined at months -1 (Pre), 0 (the date of the audit- Audit), and +1 and +6 after the audit (Post-1 and Post-6, respectively).
We recorded BP, information on factors affecting BP, and anti-hypertensive drug regimen. The primary outcome of the study was to decrease prevalence of hypertension (BP ≥ 140/90 mmHg). Secondary outcomes were a reduction in average BP in hypertensive patients and/or a decrease in drug delivery associated with lower or unchanged BP.


RESULTS

104 patients out of 177 (58.7%) were hypertensive at Audit. BP levels were directly related to comorbidity and male sex, and inversely related to dialysate sodium concentration. The announcement of the audit alone was associated with a decreased prevalence of hypertension (Pre 64.4% to Audit 58.7%); a further decrease followed the audit (Post-1 51.1%, Post-6 47.6%, p<0.05 vs. Audit). Systolic BP in hypertensive patients also decreased (mean decrease was -8.5 and -14.1; p = 0.007 and p<0.001 at Post-1 and Post-6). Number of drugs assumed was significantly lower at Post-1 and Post-6 vs. Audit (p = 0.005 and p<0.001, respectively).


CONCLUSIONS

A clinical audit is an effective tool to improve BP control in HD patients.

Treatment of posthemorrhagic hydrocephalus in premature infants with subcutaneous reservoir drainage

AIMS

To investigate the effectiveness of subcutaneous reservoir drainage as a treatment for the different types of posthemorrhagic hydrocephalus in premature infants.

METHODS

11 premature infants with posthemorrhagic hydrocephalus underwent subcutaneous reservoir embedment surgery, and cerebrospinal fluid (CSF) was drained via the reservoir intermittently for 8 weeks. During the period of drainage, ultrasound and computerized tomography were used to measure ventricle size. CSF examinations were performed routinely to assess the presence of intraventricular hemorrhage (IVH) and/or infection.

RESULTS

(1) Five infants were diagnosed as having obstructive hydrocephalus; 2 had nearly normal ventricle sizes with treatment and drainage was stopped after 8 weeks, 2 had nearly normal ventricle sizes after 4 more weeks of drainage, and 1 underwent ventriculoperitoneal shunt (V-P shunt) surgery due to failure of ventricle size reduction. (2) Six infants were diagnosed as having communicating hydrocephalus; 4 had further enlarged ventricle size after 8 weeks and underwent V-P shunt surgery, 1 had treatment aborted at week 8 of drainage, and only 1 had moderate reduction of ventricle size after 8 weeks. (3) None of the 11 infants had progressive IVH and/or intracranial infection during drainage.

CONCLUSIONS

Subcutaneous reservoir drainage is a suitable and safe treatment for posthemorrhagic hydrocephalus in premature infants. It is more effective for obstructive hydrocephalus than for communicating hydrocephalus.