Normalized bioimpedance indices are better predictors of outcome in peritoneal dialysis patients

Bioimpedance spectroscopy: Is a picture worth a thousand words?

Volume status can be difficult to assess in dialysis patients. Peripheral edema, elevated venous pressure, lung crackles, and hypertension are taught as signs of fluid overload, but sensitivity and specificity are poor. Bioimpedance technology has evolved from early single frequency to multifrequency machines which apply spectroscopic analysis (BIS), modeling data to physics-based mixture theory. Bioimpedance plots can aid the evaluation of hydration status and body composition. The challenge remains how to use this information to manage dialysis populations, particularly as interventions to improve over hydration, sarcopenia, and adiposity are not without side effects. It is therefore of no surprise that validation studies for BIS use in peritoneal dialysis patients are limited, and results from clinical trials are inconsistent and conflicting. Despite these limitations, BIS has clinical utility with potential to accurately evaluate small changes in body tissue components. This article explains the information a BIS plot ("picture") can provide and how it can contribute to the overall clinical assessment of a patient. However, it remains the role of the clinician to integrate information and devise treatment strategies to optimize competing patient risks, fluid and nutrition status, effects of high glucose PD fluids on membrane function, and quality of life issues.

Bioimpedance-Guided Fluid Removal in Continuous KRT: The VENUS Randomized Clinical Trial

Key Points

This study, the sole randomized trial of its kind, proposes guidelines for fluid balance management in continuous KRT (CKRT) patients using bioimpedance. Despite this, bioimpedance analysis–guided volume management did not influence the proportion of patients achieving estimated euvolemia at 7 days into CKRT. Further investigation is needed to assess whether bioimpedance analysis guidance can facilitate rapid fluid removal in the early phase of CKRT for patients with AKI.

Background

Ultrafiltration with continuous KRT (CKRT) can be used to manage fluid balance in critically ill patients with AKI. We aimed to assess whether bioimpedance analysis (BIA)–guided volume management was more efficacious than conventional management for achieving estimated euvolemia (e-euvolemia) in CKRT-treated patients.

Methods

In a multicenter randomized controlled trial from July 2017 to July 2020, the patients with AKI requiring CKRT were eligible if the weight at the start of CKRT had increased by ≥5% compared with the weight at the time of admission or total body water (TBW)/height (H)2 ≥13 L/m2. We randomly assigned 208 patients to the control (conventional fluid management; n =103) and intervention groups (BIA-guided fluid management; n =105). The primary outcome was the proportion of attaining e-euvolemia 7 days postrandomization. E-euvolemia was defined as the difference between TBW/H2 D7 and D0 was <−2.1 L/m2, or when TBW/H2 measured on D7 was <13 L/m2. The 28-, 60-, and 90-day mortality rate were secondary outcomes.

Results

The primary outcome occurred in 34 patients in the intervention group and 27 in the control group (47% versus 41%; P = 0.50). The mean value of TBW/H2 measured on D7 was the same at 13.9 L/m2 in both groups. The differences between TBW/H2 D7 and D0 were −1.13 L/m2 in the intervention group and −1.08 L/m2 in the control group (P = 0.84). Patients in the intervention group had a significantly higher proportion of reaching e-euvolemia on D1 than those in the control group (13% versus 4%, P = 0.02). Adverse events did not differ significantly between the groups.

Conclusions

BIA-guided volume management did not affect the proportion of reaching the e-euvolemia at 7 days of the start of CKRT.

Clinical Trial registry name and registration number:

ClinicalTrials.gov , ID: NCT03330626 (Registered on November 6, 2017; seven study participants were retrospectively registered; nonetheless, Institutional Review Board approval of each institution was completed before study participant registration).

Phase angle and standardized phase angle from bioelectrical impedance measurements as a prognostic factor for mortality at 90 days in patients with COVID-19: A longitudinal cohort study

BACKGROUND & AIMS

Severe acute COVID-19 has taken on pandemic proportions with growing interest in identification of prognostic factors for mortality. Standardized bioelectrical impedance (BI) phase angle (SPhA), which is PhA adjusted by age and sex, has been related to mortality in patients with several diseases but never investigated in COVID-19. Inflammation, a consequence of COVID-19 infection, affects fluid status (hydration) and can be identified with PhA. The aim of this study was to determine the predictive role of PhA on 90 days survival of adults with COVID-19.

METHODS

We studied 127 consecutive patients diagnosed with COVID-19. BI measurements determined with a 50 kHz phase-sensitive BI device, body composition parameters and laboratory markers were evaluated as predictors of mortality.

RESULTS

Non-surviving COVID-19 patients had significantly lower PhA and SPhA values (p < 0.001) and increased hydration (p < 0.001) compared to surviving patients. Patients in the lowest SPhA quartile had increased (p < 0.001) mortality and hospital stay, hyperhydration (p < 0.001), increased inflammation biomarkers [CRP (p < 0.001)], decreased nutritional parameters: body mass cell index [BCMI (p < 0.001) albumin (p < 0.001)], and reduced other biomarkers [D-dimer (p = 0.002)]. Multivariate analysis (Cox regression) revealed that PhA and hydration status, adjusted for age, sex, BMI, diabetes, hypertension, dyslipidaemia or heart disease, were associated (p < 0.001) with increased mortality. The hazard ratio was 2.48 (95% CI, 1.60-3.84, p < 0.001) for PhA and 1.12 (95% CI, 1.04-1.20, p = 0.003) for hydration percentage. PhA <3.95° was the cut-off for predicting mortality in acute COVID-19 with 93.8% sensitivity and 66.7% specificity. PhA offers greater sensitivity as a predictive prognostic test at admission, compared to the established analytical parameters of poor prognosis (CRP, lymphocytes, prealbumin).

CONCLUSIONS

Low PhA (<3.95°), independent of age, sex, BMI, and comorbidities, is a significant predictor of mortality risk in COVID-19. These findings suggest that the evaluation of body composition with single-frequency phase-sensitive BI measurements should be included in the routine clinical assessment of COVID-19 patients at hospital admission to identify patients at increased mortality risk.

Application of DSM–BIA in dry weight assessment in continuous ambulatory peritoneal dialysis

Objectives

Dry weight assessment (DWA) is an important part of dialysis and fluid management in patients receiving renal replacement therapy. With the development of bioimpedance analysis (BIA), the development of the direct segmental multi-frequency BIA (DSM–BIA) has provided a more convenient measure for DWA of dialysis patients, but its accuracy remains unclear. This study was designed to evaluate the application of DSM–BIA in DWA of continuous ambulatory peritoneal dialysis (CAPD) patients.

Design

This is a cross-sectional study. Using the conventional BIA as a reference, we examined the accuracy of the DSM–BIA technique for assessing dry weight in CAPD patients and analyzed the potential factors influencing their fluid volume status.

Setting and participants

A total of 31 patients with end-stage renal disease receiving CAPD and 310 healthy volunteers were recruited for this study.

Methods

The intraclass correlation coefficients (ICC) and Bland–Altman plots were used to assess the consistency between DSM–BIA and the conventional BIA for DWA. Univariate and multivariate linear regression analyses were used to explore the influencing factors associated with the edema index.

Results

DSM–BIA and the conventional BIA technology were consistent in DWA in CAPD patients (ICC female 0.972, ICC male 0.882, ICC total 0.960). Similarly, Bland–Altman plots showed good agreements between the two methods in DWA for both genders. Univariate and multivariate linear regression analysis showed both eGFR level (P = 0.04) and serum NT-pro BNP concentration (P = 0.007) were positively correlated with the ratio of extracellular water to total body water (ECW/TCW).

Conclusions

DSM–BIA in DWA has good accuracy in clinical applications and has potential application value for fluid volume management in CAPD patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-022-03281-7.

Bioimpedance Guided Fluid Management in Peritoneal Dialysis: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Bioelectrical impedance analysis (BIA) devices can help assess volume overload in patients receiving maintenance peritoneal dialysis. However, the effects of BIA on the short-term hard end points of peritoneal dialysis lack consistency. This study aimed to test whether BIA-guided fluid management could improve short-term outcomes in patients on peritoneal dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A single-center, open-labeled, randomized, controlled trial was conducted. Patients on prevalent peritoneal dialysis with volume overload were recruited from July 1, 2013 to March 30, 2014 and followed for 1 year in the initial protocol. All participants with volume overload were 1:1 randomized to the BIA-guided arm (BIA and traditional clinical methods) and control arm (only traditional clinical methods). The primary end point was all-cause mortality and secondary end points were cardiovascular disease mortality and technique survival.

RESULTS

A total of 240 patients (mean age, 49 years; men, 51%; diabetic, 21%, 120 per group) were enrolled. After 1-year follow-up, 11(5%) patients died (three in BIA versus eight in control) and 21 patients were permanently transferred to hemodialysis (eight in BIA versus 13 in control). The rate of extracellular water/total body water decline in the BIA group was significantly higher than that in the control group. The 1-year patient survival rates were 96% and 92% in BIA and control groups, respectively. No significant statistical differences were found between patients randomized to the BIA-guided or control arm in terms of patient survival, cardiovascular disease mortality, and technique survival (P>0.05).

CONCLUSIONS

Although BIA-guided fluid management improved the fluid overload status better than the traditional clinical method, no significant effect was found on 1-year patient survival and technique survival in patients on peritoneal dialysis.

Effect of bioimpedance-defined overhydration parameters on mortality and cardiovascular events in patients undergoing dialysis: a systematic review and meta-analysis

OBJECTIVE

To evaluate the role of bioimpedance-defined overhydration (BI-OH) parameters in predicting the risk of mortality and cardiovascular (CV) events in patients undergoing dialysis.

METHODS

We searched multiple electronic databases for studies investigating BI-OH indicators in the prediction of mortality and CV events through 23 May 2020. We assessed the effect of BI-OH indexes using unadjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Sensitivity analysis was used for each outcome.

RESULTS

We included 55 studies with 104,758 patients in the meta-analysis. Extracellular water/total body water (ECW/TBW) >0.4 (HR 5.912, 95% CI: 2.016-17.342), ECW/intracellular water (ICW) for every 0.01 increase (HR 1.041, 95% CI: 1.031-1.051), and OH/ECW >15% (HR 2.722, 95% CI: 2.005-3.439) increased the risk of mortality in patients receiving dialysis. ECW/TBW >0.4 (HR 2.679, 95% CI: 1.345-5.339) and ECW/ICW per increment of 10% (HR 1.032, 95% CI: 1.017-1.047) were associated with an increased risk of CV events in patients undergoing dialysis. A 1-degree increase in phase angle was a protective factor for both mortality (HR 0.676, 95% CI: 0.474-0.879) and CV events (HR 0.736, 95% CI: 0.589-0.920).

CONCLUSIONS

BI-OH parameters might be independent predictors for mortality and CV events in patients undergoing dialysis.

Association of Phase Angle, but Not Inflammation and Overhydration, With Physical Function in Peritoneal Dialysis Patients

Introduction: Muscle mass depletion, overhydration, and inflammatory state have been related to impaired physical function in chronic kidney disease patients. The relationship between bioelectrical impedance analysis (BIA) parameters, such as hydration status and phase angle (PhA), with physical function in peritoneal dialysis (PD), is still not well-established. Therefore, the objective was to evaluate the association of BIA parameters (overhydration index and PhA) and inflammatory markers with physical function in patients on PD.

Methods: The present cross-sectional study enrolled PD patients. Multifrequency BIA was performed to obtain overhydration index and PhA. The Short Physical Performance Battery (SPPB) test battery was applied to assess physical function. The time to complete the 4-m gait test and sit-to-stand test was also considered for physical function assessment. The inflammatory markers tumor necrosis factor-alpha and C-reactive protein levels were determined. Multiple linear regression models were performed, with the physical function variables as dependent variables, adjusted for age, diabetes, and sex.

Results: Forty-nine PD patients were enrolled, 53.1% (n = 26) women; mean age, 55.5 ± 16.3 years. There were significant correlations between PhA and SPPB (r = 0.550, p < 0.001), time of 4-m gait test (r = −0.613, p < 0.001) and sit-to-stand test and (r = −0.547, p < 0.001). Overhydration index was significantly correlated with SPPB, 4-m gait test (r = 0.339, p = 0.017), and sit-to-stand test (r = 0.335, p = 0.019). Inflammatory markers were not significantly correlated with physical function parameters. In the multiple linear regression analysis, PhA was associated with physical function parameters, even after adjustments. Overhydration index was associated with all physical function tests only in the models with no adjustments.

Conclusion: PhA was independently associated with physical function in PD patients. Inflammatory markers and overhydration index were not associated with physical function.

Lower Phase Angle Measured by Bioelectrical Impedance Analysis Is a Marker for Increased Mortality in Incident Continuous Ambulatory Peritoneal Dialysis Patients

OBJECTIVE

Phase angle (PA) determined by bioelectrical impedance analysis has been suggested to be a predictor of death in a variety of disease conditions, but its associations with outcomes have not yet been assessed in a large continuous ambulatory peritoneal dialysis (CAPD) patient cohort. The aim of the present study was to examine the association of PA with risks for all-cause and cardiovascular death in patients treated with CAPD.

METHODS

Incident CAPD patients were enrolled from January 1, 2010 to December 31, 2015 and were followed until December 31, 2017. Multifrequency bioelectrical impedance analysis was conducted in the morning with patients in a fasting state. Multivariable linear regression analyses were performed to study the relationships between PA and other variables. Cox proportional hazard models were used to evaluate the association between PA and mortality.

RESULTS

A total of 760 incident CAPD patients were enrolled in this study. Patients have a median PA value of 4.59° ranging from 2.30° to 7.22°. Aging, presence of diabetes mellitus, and fluid overload were independently associated with lower PA, whereas male sex, higher body mass index, higher serum levels of albumin and creatinine, and better residual renal function were independently associated with higher PA in a multivariable linear regression model. A total of 125 (16.4%) patients died during a median follow-up of 42 months. In the Cox model with adjustment for confounders, PA was significantly associated with all-cause and cardiovascular mortality in incident CAPD patients (hazard ratio, 0.584; 95% confidence interval, 0.403 to 0.844, P = .004; hazard ratio, 0.597; 95% confidence interval, 0.359 to 0.993, P = .047, respectively).

CONCLUSIONS

PA reflected a combined dimension of the illness including deranged hydration status and nutritional status. Lower PA was associated with both all-cause and cardiovascular death in patients with CAPD.

Bioimpedance analysis and physical functioning as mortality indicators among older sarcopenic people

OBJECTIVES

To assess the prognostic significance of various characteristics and measurements of sarcopenia and physical functioning on all-cause mortality among home-dwelling older people with or at-risk of sarcopenia.

DESIGN

Cross-sectional and longitudinal analyses.

SETTING

Porvoo sarcopenia trial in open care.

PARTICIPANTS

Community-dwelling people aged 75 and older (N = 428, of which 182 were re-examined at one year) with four years of follow-up.

MEASUREMENTS

Body mass index (BMI), physical functioning (physical component of the RAND-36) and physical performance tests (Short Physical Performance Battery (SPPB)), hand grip strength, walking speed, Charlson Comorbity Index, bioimpedance-based surrogates for muscle mass: Single Frequency Skeletal Muscle Index (SF-SMI), and Calf Intracellular Resistance Skeletal Muscle Index (CRi-SMI). Date of death was retrieved from central registers. Survival analyses were performed using Life-Table analyses and Cox models.

RESULTS

Most test variables (except BMI) were associated with four-year mortality in a dose-dependent fashion. After controlling for age, gender and co-morbidity, physical performance and functioning (both SPPB and RAND-36), muscle strength (hand grip strength) and CRi-SMI appeared to be independent mortality risk indicators (p < 0.001) whereas SF-SMI was not. When CRi-SMI values were grouped by gender-specific cut-off points, the probability of surviving for four years decreased by 66% among the older people with low CRi-SMI (HR = 0.34, 95%CI 0.15-0.78, p = 0.011). When low CRi-SMI was further controlled for SPPB, the prognostic significance remained significant (HR = 0.55, 95%CI 0.33-0.92, p = 0.021). After controlling for age, gender, comorbidity, and CRi-SMI, the physical component of the RAND-36 (p = 0.007), SPPB (p < 0,001) and hand grip strength (p = 0.009) remained significant mortality predictors. Twelve-month changes were similarly associated with all-cause mortality during the follow-up period.

CONCLUSION

CRi-SMI, muscle strength, physical performance and physical functioning are each strong independent predictors of all-cause mortality among home-dwelling older people. Compared to these indicators, BMI seemed to be clearly inferior. Of two bioimpedance-based muscle indices, CRi SMI was better predictor of mortality than SF-SMI. In this regard, muscle mass, muscle strength and physical performance are all suitable targets for the prevention of sarcopenia-related over-mortality.

Clinical value of body composition monitor to evaluate lean and fat tissue mass in peritoneal dialysis

BACKGROUND/OBJECTIVES

Bioimpedance analysis is often routinely performed in any dialysis unit to guide fluid management but can provide a reproduceable assessment of fat and muscle mass. We wished to determine the clinical significance of low muscle or high fat mass and the determinants that influence their change.

SUBJECTS/METHODS

We performed retrospective analysis of 824 patients on peritoneal dialysis who underwent routine repeated bioimpedance analysis measurements using the body composition monitor (BCM).

RESULTS

Lean tissue index (LTI) was an independent predictor of mortality when sex, age, PD vintage and diabetes status were included in the models (HR 0.93; 95% CI 0.86-1.00, p < 0.05) and when baseline serum albumin was included in a separate model (HR 0.86; 95% CI: 0.79-0.93, p < 0.001). High fat tissue index (FTI) was an independent predictor of mortality when demographic factors were included (HR 0.87; 95% CI: 0.78-0.97, p < 0.02), but not with the addition biochemical parameters. Changes in body composition of 206 patients over a 2-year follow-up period could not be predicted by baseline demographics, functional or biochemical assessments. However, there was a strong inverse relationship between changes in LTI and FTI. There were no associations between changes in body composition with prescribed dialysate glucose.

CONCLUSIONS

We showed body composition changes are common and complex. LTI was an independent predictor of survival. Changes in LTI and FTI could not be predicted by baseline parameters. BCM may be a sensitive and accurate tool to monitor changes in body composition during dialysis treatment.

VolumE maNagement Under body composition monitoring in critically ill patientS on CRRT: study protocol for a randomized controlled trial (VENUS trial)

Background

Despite recent technical advances in the management of acute kidney injury (AKI), such as continuous renal replacement therapy (CRRT), intensive care unit mortality is still high, at approximately 40 to 50%. Although several factors have been reported to predict mortality in AKI patients, fluid overload (FO) during CRRT is a well-known predictor of patient survival. However, FO has been mostly quantified as an arithmetical calculation and determined on the basis of the physicians’ perception. Even though such quantification and assessment provides an easy evaluation of a patient’s fluid status and is a simple method, it is not applicable unless a detailed record of fluid monitoring is available. Furthermore, the method cannot differentiate excess water in individual water compartments but can only reflect excess total body water. Bioimpedance analysis (BIA) has been used to measure the nutritional component of body composition and is a promising tool for the measurement of volume status. However, there has been no prospective interventional study for fluid balance among CRRT-treated AKI patients using BIA. Therefore, we will investigate the usefulness of fluid management using the InBody S10 (InBody®, Seoul, Korea), a BIA tool, compared with that of generally used quantification methods.

Methods/design

This will be a multicenter, prospective, randomized controlled trial. A total of 244 patients undergoing CRRT treatment will be enrolled and randomly assigned to receive either to InBody S10-guided management or to fluid management based only on clinical information for 7 days. The primary outcome is to compare the rate of euvolemic status 7 days after the initiation of CRRT, with a secondary outcome being to compare the 28-, 60-, and 90-day mortality rates between the two groups.

Discussion

This will be the first clinical trial to investigate the effect of using BIA-guided fluid management to achieve euvolemia in CRRT-treated AKI patients.

Trial registration

ClinicalTrials.gov, ID: NCT03330626. Registered on 6 November 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3056-y) contains supplementary material, which is available to authorized users.

Bioimpedance-defined overhydration predicts survival in end stage kidney failure (ESKF): systematic review and subgroup meta-analysis

Both overhydration and comorbidity predict mortality in end-stage kidney failure (ESKF) but it is not clear whether these are independent of one another. We undertook a systematic review of studies reporting outcomes in adult dialysis patients in which comorbidity and overhydration, quantified by whole body bioimpedance (BI), were reported. PubMed, EMBASE, PsychInfo and the Cochrane trial database were searched (1990-2017). Independent reviewers appraised studies including methodological quality (assessed using QUIPS). Primary outcome was mortality, with secondary outcomes including hospitalisation and cardiovascular events. Of 4028 citations identified, 46 matched inclusion criteria (42 cohorts; 60790 patients; 8187 deaths; 95% haemodialysis/5% peritoneal dialysis). BI measures included phase angle/BI vector (41%), overhydration index (39%) and extra:intracellular water ratio (20%). 38 of 42 cohorts had multivariable survival analyses (MVSA) adjusting for age (92%), gender (66%), diabetes (63%), albumin (58%), inflammation (CRP/IL6-37%), non-BI nutritional markers (24%) and echocardiographic data (8%). BI-defined overhydration (BI-OH) independently predicted mortality in 32 observational cohorts. Meta-analysis revealed overhydration >15% (HR 2.28, 95% CI 1.56-3.34, P < 0.001) and a 1-degree decrease in phase angle (HR 1.74, 95% CI 1.37-2.21, P < 0.001) predicted mortality. BI-OH predicts mortality in dialysis patients independent of the influence of comorbidity.

Advanced wasting in peritoneal dialysis patients

AIM

To identify patients with end-stage renal disease treated by peritoneal dialysis (PD) who had zero body fat (BF) as determined by analysis of body composition using anthropometric formulas estimating body water (V) and to compare nutritional parameters between these patients and PD patients whose BF was above zero.

METHODS

Body weight (W) consists of fat-free mass (FFM) and BF. Anthropometric formulas for calculating V allow the calculation of FFM as V/0.73, where 0.73 is the water fraction of FFM at normal hydration. Wasting from loss of BF has adverse survival outcomes in PD. Advanced wasting was defined as zero BF when V/0.73 is equal to or exceeds W. This study, which analyzed 439 PD patients at their first clearance study, used the Watson formulas estimating V to identify patients with V_Watson/0.73 ≥ W and compared their nutritional indices with those of PD patients with V_Watson/0.73 < W.

RESULTS

The study identified at the first clearance study two male patients with V_Watson/0.73 ≥ W among 439 patients on PD. Compared to 260 other male patients on PD, the two subjects with advanced wasting had exceptionally low body mass index and serum albumin concentration. The first of the two subjects also had very low values for serum creatinine concentration and total (in urine and spent peritoneal dialysate) creatinine excretion rate while the second subject had an elevated serum creatinine concentration and high creatinine excretion rate due, most probably, to non-compliance with the PD prescription.

CONCLUSION

Advanced wasting (zero BF) in PD patients, identified by the anthropometric formulas that estimate V, while rare, is associated with indices of poor somatic and visceral nutrition.

Design of a randomized controlled clinical trial assessing dietary sodium restriction and hemodialysis-related symptom profiles

Aim

In hemodialysis patients, the need to have intercurrent sodium and water intake removed by ultrafiltration increases disease burden through the symptoms and signs that occur during hemodialysis (HD). This added burden may be mitigated by reduction of dietary sodium intake. The National Kidney Foundation (NKF) recommends 2400 mg of dietary sodium daily for patients on HD, and the American Heart Association (AHA) suggests 1500 mg, evidence is lacking, however, to support these recommendations in HD. Moreover, little is known about the relationship of specific levels of dietary sodium intake and the severity of symptoms and signs during ultrafiltration. Our goal will be to determine the effects of carefully-monitored levels of sodium-intake as set forth by the NKF and AHA on symptoms and signs in patients undergoing (HD).

Methods

We designed a three-group (2400 mg, 1500 mg, unrestricted), double blinded randomized controlled trial with a sample of 42 HD participants to determine whether 1. Symptom profiles and interdialytic weight gains vary among three sodium intake groups; 2. The effect of HD-specific variables on the symptom profiles among the three groups and 3. Whether total body water extracellular volume and intracellular volume measured with bioimpedance varies across the three groups. We will also examine the feasibility of recruitment, enrollment, and retention of participants for the five-day inpatient stay.

Conclusion

Curbing dietary sodium intake may lead to improvement in intradialytic symptom amelioration and potential for better long-term outcomes. Generating empirical support will be critical to ascertain, and espouse, the appropriate level of sodium intake for patients receiving HD.

Volume-Based Peritoneal Dialysis Prescription Guide to Achieve Adequacy Targets

♦

BACKGROUND

The use of automated and continuous ambulatory peritoneal dialysis (APD and CAPD) prescriptions (Rxs) to achieve adequate uremic toxin and fluid removal targets is important for attaining optimal patient outcomes. One approach for predicting such Rxs is the use of kinetic modeling. ♦

METHODS

Demographic data and peritoneal membrane characteristics derived from a peritoneal equilibration test (PET) were available from 1,005 patients in North American centers who participated in a national adequacy initiative in 1999. Twelve patient subgroups were identified according to peritoneal membrane transport type and tertiles of total body water, assumed equal to urea distribution volume (Vurea). Each patient was then modeled using PD Adequest 2.0 to be treated by 12 CAPD and 34 APD Rxs using both glucose and icodextrin solutions to achieve adequacy targets of weekly urea Kt/V of 1.7 and 1 L of daily ultrafiltration (UF). Residual kidney function (RKF) was assumed to be 0, 2, 4, and 6 mL/min. Feasible peritoneal dialysis (PD) Rxs were identified where: 1) the 95% confidence limit achieved the goal of meeting the targets for urea Kt/V, daily UF, and both in 85%, 75%, and 70% of patients, respectively; 2) average PD solution dextrose concentration was < 2.5%; and 3) the number of daytime exchanges was minimized. ♦

RESULTS

Feasible PD Rxs were similar when RKF was ≥ 2 mL/min, allowing condensed recommendations based on RKF ≥ 2 mL/min or < 2 mL/min. Individuals with lower or slower membrane transport required relatively greater 24-h solution volumes to achieve adequacy targets when RKF fell below 2 mL/min. With increasing Vurea, there was disproportionately greater dependence on RKF to achieve targets. While multiple Rxs achieving urea Kt/V and daily UF goals were identified for all membrane transport types, use of icodextrin in the long dwell reduced the need for a midday exchange in APD, glucose exposure, required fill and 24-h dwell volumes, irrespective of RKF and Vurea. While these benefits were most notable in high and high-average transporters, similar results were also seen in low and low-average transporters. ♦

CONCLUSIONS

Kinetic modeling identified multiple APD and CAPD Rxs that achieved adequate uremic solute and fluid removal for patients, irrespective of RKF and Vurea. Use of icodextrin rather than glucose in the long dwell reduced the complexity of the PD regimen, total glucose exposure, and 24-h total treatment solution volumes. Irrespective of modeling, adequacy of any PD prescription should be based upon individual clinical evaluation both for volume and solute removal.

Comparing lung ultrasound with bioimpedance spectroscopy for evaluating hydration in peritoneal dialysis patients

BACKGROUND

Bioimpedance spectroscopy (BIS), ultrasound lung comets (ULC) and serum biomarkers (N-terminal pro-brain natriuretic peptide, NT-proBNP) have all been used to assist clinicians to determine hydration status in dialysis patients.

METHODS

We performed simultaneous BIS, ULC and NT-proBNP measurements in 27 peritoneal dialysis patients to determine the concordance of the three methods.

RESULTS

Patients with evidence of increasing lung congestion (as determined by ultrasound) were more likely to be diabetic, have systolic hypertension and have higher NT-proBNP (r = 0.65, P < 0.0005). Although there was a trend for patients with high ULC to be overhydrated as determined by BIS, this did not reach statistical significance. Moreover, the correlation between BIS and NT-proBNP (though statistically significant at r = 0.47, P < 0.02) appeared to be weaker.

CONCLUSION

BIS and ULC may be complementary, providing different information, whereas BIS may be more specific to hydration. ULC and NT-proBNP may indicate left ventricular failure coexisting with overhydration.

Use of Multifrequency Bioimpedance Analysis in Male Patients with Acute Kidney Injury Who Are Undergoing Continuous Veno-Venous Hemodiafiltration

Introduction

Fluid overload is a well-known predictor of mortality in patients with acute kidney injury (AKI). Multifrequency bioimpedance analysis (MF-BIA) is a promising tool for quantifying volume status. However, few studies have analyzed the effect of MF-BIA-defined volume status on the mortality of critically ill patients with AKI. This retrospective medical research study aimed to investigate this issue.

Methods

We retrospectively reviewed the medical records of patients with AKI who underwent continuous veno-venous hemodiafiltration (CVVHDF) from Jan. 2013 to Feb. 2014. Female patients were excluded to control for sex-based differences. Volume status was measured using MF-BIA (Inbody S20, Seoul, Korea) at the time of CVVHDF initiation, and volume parameters were adjusted with height squared (H²). Binary logistic regression analyses were performed to test independent factors for prediction of in-hospital mortality.

Results

A total of 208 male patients were included in this study. The mean age was 65.19±12.90 years. During the mean ICU stay of 18.29±27.48 days, 40.4% of the patients died. The in-hospital mortality rate increased with increasing total body water (TBW)/H² quartile. In the multivariable analyses, increased TBW/H² (OR 1.312(1.009-1.705), p=0.043) and having lower serum albumin (OR 0.564(0.346-0.919, p=0.022) were independently associated with higher in-hospital mortality. When the intracellular water (ICW)/H² or extracellular water (ECW)/H² was adjusted instead of the TBW/H², only excess ICW/H² was independently associated with increased mortality (OR 1.561(1.012-2.408, p=0.044).

Conclusions

MF-BIA-defined excess TBW/H² and ICW/H² are independently associated with higher in-hospital mortality in male patients with AKI undergoing CVVHDF.

Can Bioimpedance Measurements of Lean and Fat Tissue Mass Replace Subjective Global Assessments in Peritoneal Dialysis Patients?

OBJECTIVE

Malnutrition and protein energy wasting (PEW) determined by Subjective Global Assessment (SGA) is associated with increased mortality. There is an inverse relationship between body mass and overhydration in dialysis patients. Is the predictive accuracy of SGA (for death) independent of hydration status? Can bioimpedance spectroscopy analysis of lean tissue index (LTI) and fat tissue index (FTI) accurately identify dialysis patients with protein energy wasting and increased mortality?

METHODS

We report an observational study of 455 peritoneal dialysis (PD) patients.

RESULTS

We found that 96 patients (21%) were malnourished (SGA score between 1 and 5), and 192 (42%) had LTI values below 10th centile (age, gender adjusted). FTI was significantly lower in the SGA-defined malnourished cohort. By contrast, there was an inverse relationship between LTI and FTI. Malnourished (by SGA) patients were significantly more overhydrated (P < .0001), but SGA remained highly predictive of survival in multivariate analysis that included hydration status (hazard ratio: 3.12, 95% confidence interval 1.86-5.23, P < .0001). Obesity (patients with the highest 20% FTI) predicted survival (hazard ratio of death was 0.47, 95% confidence interval 0.16-0.85, P < .02) on univariate but not multivariate analysis.

CONCLUSIONS

We have confirmed that SGA is an accurate predictor of mortality in PD patients, and its predictive value is independent of the hydration status. Predictive power of SGA was not affected when LTI and FTI were included in multivariate analysis. Patients with low LTI were different from patients with low SGA (associated with high FTI). Sensitivity and specificity of Body Composition Monitor to diagnose patients with low SGA readings were poor (area under the curve for receiver operator characteristics analysis 0.66). The phenomenon of reverse epidemiology (high FTI predicting a survival advantage) was found in our PD cohort.

Clinical significance of multi-frequency bioimpedance spectroscopy in peritoneal dialysis patients: independent predictor of patient survival

BACKGROUND

It is becoming increasingly evident that the accurate assessment of hydration status is critical to care of a dialysis patient. Using the Body Composition Monitor, different parameters (overhydration (OH), extra-cellular water/total body water (ECW/TBW) or OH/ECW) have been proposed to indicate hydration status. We wished to determine which parameter (if any) was most predictive of all-cause mortality, and if this was independent of nutritional indices.

METHODS

We performed a single-centre retrospective analysis of prospectively collected data of all peritoneal dialysis (PD) patients between 1 January 2008 and 30 March 2012. Record review was undertaken to establish patient survival, clinical and demographic data. Follow-up was continued even after PD technique failure (transfer to haemodialysis) and transplantation.

RESULTS

The study included 529 patients. OH index (OH and OH/ECW) was the independent predictor of mortality in multi-variate analysis. ECW/TBW as a continuous variable was not associated with increased risk of death. In contrast, patients that were severely overhydrated (highest 33%) had hazard ratios (HRs) that were statistically significant irrespective of the parameter used to define hydration. Using OH, severely overhydrated patients had an HR of 1.83 [95% confidence interval (CI) 1.19-2.82, P < 0.01], OH/ECW: 2.09 (95% CI 1.36-3.20, P < 0.001) and ECW/TBW: 2.05 (95% CI 1.31-3.22, P < 0.005).

CONCLUSIONS

Our results also indicated that there was no influence of body mass index (BMI) on the hydration parameter OH/ECW. OH/ECW remained an independent predictor of mortality when the BMI and lean tissue index were included in multivariate model. However, it remains to be determined if correcting the OH status of a patient will lead to improvement in mortality.

Intraperitoneal fluid overestimates hydration status assessment by bioimpedance spectroscopy

BACKGROUND

Bioimpedance spectroscopy (BIS) is a valuable tool to assess nutrition and volume status in peritoneal dialysis (PD) patients. However, data about the influence of intraperitoneal fluid on body composition measures are conflicting, and there is no clear consensus about whether the abdomen should be drained before the procedure. We designed a comparison study to detect the influence of intra-abdominal fluid on BIS results.

METHODS

We performed 73 pairs of BIS measurements in 34 stable PD patients, first with the peritoneum filled with a 1.36% glucose dialysate solution and then after the solution was drained. Patients stayed in the supine position for 10 minutes before the BIS procedure, and the electrodes were not moved between measures. Clinical and demographic data were collected, as were analytic parameters of nutrition and volume status.

RESULTS

Fluid overload is overestimated when BIS is performed with a full abdomen (1.82 ± 1.73 L vs 1.64 ± 1.68 L, p = 0.043). We also found a spurious overestimation in extracellular water (16.40 ± 3.21 L vs 16.24 ± 3.16 L, p < 0.001) and in relative overhydration (8.29% ± 6.96% vs 7.14% ± 6.79%, p = 0.017). No differences in intracellular water or parameters of nutrition were found. We observed negative correlations for the extracellular water overestimation with age (r = -0.245, p = 0.037), serum B-type natriuretic peptide (r = -0.366, p = 0.036), body mass index (r = -0.248, p = 0.035), and lean tissue index (r = -0.427, p = 0.001). The difference in extracellular water correlated only with body mass index (r = -0.259, p = 0.039). We also found that, assessed at 50 KHz, whole-body impedance (-4.52 ± 8.37, p = 0.001) and phase angle (-0.08 ± 0.23 degrees, p = 0.002) were both lower when BIS was performed in patients with a full abdomen.

CONCLUSIONS

Fluid overload is overestimated by BIS when performed in patients with dialysate in the peritoneum. The observed differences are greater in younger, more poorly nourished, or less overhydrated patients. If more precise results are required, we suggest that the abdomen be drained before BIS is performed.