Bioimpedance Spectroscopy Research Articles

Natriuretic peptides, extracellular volume, and subclinical cardiovascular changes in chronic kidney disease stages 1–3: a pilot study

Natriuretic peptide levels are elevated in persons with chronic kidney disease (CKD) stages 1–3, but it remains unclear whether this is associated with extracellular volume excess or early cardiovascular changes....

Serum Osteoprotegerin Is an Independent Marker of Left Ventricular Hypertrophy, Systolic and Diastolic Dysfunction of the Left Ventricle and the Presence of Pericardial Fluid in Chronic Kidney Disease Patients.

Background: Osteoprotegerin (OPG) is a molecule which belongs to the tumor necrosis factor receptor superfamily. OPG concentration is elevated in patients with left ventricle hypertrophy, heart failure and acute myocardial infarction. OPG concentrations rise in chronic kidney disease (CKD). The aim of this study was to investigate the association between OPG concentrations and cardiovascular complications, such as left ventricle hypertrophy, systolic and diastolic dysfunction of left ventricle and dysfunction of right ventricle in chronic kidney disease patients not treated with dialysis. The relation between OPG and the amount of pericardial fluid was also examined. Methods: One hundred and one men with CKD stage 3–5 not treated with dialysis were included in the study. Overhydration, body fat mass and lean body mass were measured using bioimpedance spectroscopy (BIS). Echocardiography was performed to evaluate the amount of pericardial fluid and to measure the thickness of the interventricular septum (IVS), systolic and diastolic function of left ventricle, as well as systolic function of right ventricle. Results: We observed a significant positive association between OPG and the thickness of the interventricular septum, the size of the left atrium (LA) and the presence of pericardial fluid. A negative relationship was observed between OPG and ejection fraction (EF). Conclusions: Our results suggest that OPG can be an independent marker of left ventricular hypertrophy, systolic and diastolic dysfunction of left ventricle and the presence of pericardial fluid in chronic kidney disease patients.

A Wearable Wideband Analog Bio-Impedance Analyzer for Real-Time Monitoring of Human Physiology.

Continuous monitoring of electrophysiological activities of the human body is a significant step toward the effective prognosis, diagnosis, and management of functional disorders and cardiovascular diseases. This paper presents the development of a wireless system for the real-time acquisition of hemodynamics data and ambulatory monitoring of body composition based on electrical bio-impedance (Bio-Z) analysis. The developed system is composed of a low-power wearable unit and a stationary unit connected to a computer. The system conducts the non-radiative non-invasive Bio-Z analysis over a wide bandwidth of 1 MHz through four independent channels. The proposed analog approach detects the physiological activity by extracting the magnitude of the mixed Bio-Z signal, in real-time. A graphical user interface was designed for monitoring, analysis, and storage of the processed data. Moreover, the amplitude and frequency of the electrical excitation signals can be instructed through the user interface, wirelessly. Bench-top validation of the system demonstrated the delivery of current signals over a wide frequency range of 1 kHz - 1 MHz and peak-to-peak amplitude of up to 20 mA. Besides, the system was able to detect the magnitude of the envelope of the mixed signal with amplitude modulation depths as low as 0.1 %. Clinical Relevance- The system provides the real-time monitoring of cardiac activity and blood pulsation in human arteries. In addition, due to the configurability of the frequency and amplitude of the current injection circuit, the system is an excellent candidate to be utilized for real-time medical imaging through electrical bio-impedance tomography as well as electrical bio-impedance spectroscopy.

Risk factors for breast cancer-related lymphedema in patients undergoing 3 years of prospective surveillance with intervention.

BackgroundTo evaluate risk factors (treatment‐related, comorbidities, and lifestyle) for breast cancer–related lymphedema (BCRL) within the context of a Prospective Surveillance and Early Intervention (PSEI) model of care for subclinical BCRL.MethodsThe parent randomized clinical trial assigned patients newly diagnosed with breast cancer to PSEI with either bioimpedance spectroscopy (BIS) or tape measurement (TM). Surgical, systemic and radiation treatments, comorbidities, and lifestyle factors were recorded. Detection of subclinical BCRL (change from baseline of either BIS L‐Dex ≥6.5 or tape volume ≥ 5% and < 10%) triggered an intervention with compression therapy. Volume change from baseline ≥10% indicated progression to chronic lymphedema and need for complex decongestive physiotherapy. In this secondary analysis, multinomial logistic regressions including main and interaction effects of the study group and risk factors were used to test for factor associations with outcomes (no lymphedema, subclinical lymphedema, progression to chronic lymphedema after intervention, progression to chronic lymphedema without intervention). Post hoc tests of significant interaction effects were conducted using Bonferroni‐corrected alphas of .008; otherwise, an alpha of .05 was used for statistical significance.ResultsThe sample (n = 918; TM = 457; BIS = 461) was female with a median age of 58.4 years. Factors associated with BCRL risk included axillary lymph node dissection (ALND) (p < .001), taxane‐based chemotherapy (p < .001), regional nodal irradiation (RNI) (p ≤ .001), body mass index >30 (p = .002), and rurality (p = .037). Mastectomy, age, hypertension, diabetes, seroma, smoking, and air travel were not associated with BCRL risk.ConclusionsWithin the context of 3 years of PSEI for subclinical lymphedema, variables of ALND, taxane‐based chemotherapy, RNI, body mass index >30, and rurality increased risk.

Predictors and prognostic significance of persistent fluid overload: A longitudinal study in Chinese peritoneal dialysis patients.

Cross-sectional studies showed that fluid overload (FO) measured by bioimpedance spectroscopy (BIS) predicted adverse outcomes in patients on peritoneal dialysis (PD). We aimed to describe the longitudinal change in volume status in Chinese PD patients and determine its relation with clinical outcomes. We performed a single-centre, retrospective analysis of all PD patients who underwent repeated BIS from 2010 to 2015. FO was defined by relative hydration index (RHI; volume of overhydration adjusted by extracellular water >7%). Variability of volume status (VVS) was denoted by the standard deviation of all RHI. The association of time-averaged RHI and VVS on patient and technique survival was explored by a competing risk model. A total of 269 patients were followed for a median of 47.1 months. Mean time-averaged RHI was 17.6 ± 10.2%. Multivariable mixed linear regression revealed that RHI was significantly associated with diabetes, time-varying systolic blood pressure, and inversely with time-varying albumin level, lean tissue index and fat tissue index (p <0.0001 for all). Time-averaged RHI independently predicted patient survival (subdistribution hazard ratio (SHR) 1.05, 95% CI 1.03-1.07, p <0.0001) and technique survival (SHR 1.04, 95% CI 1.02-1.06, p <0.0001), whereas VVS did not. The mortality risk for patients with persistent FO was consistently higher than the corresponding risk estimated from baseline FO of the same extent. Persistent FO was a strong predictor of patient and technique failure. Repeated bioimpedance measurements to monitor volume status may provide additional prognostic information in PD patients.

Moderating Effect of the Lean Tissue Index on the Relationship between the Trabecular Bone Score and Augmentation Index in Dialysis Naïve Patients with Stage 5 Chronic Kidney Disease.

Osteopenia, sarcopenia, and increased vascular stiffness are common in patients with chronic kidney disease-mineral bone disorder (CKD-MBD) with protein energy wasting and can lead to worse clinical outcomes. We investigated the potential moderating role of the lean tissue index (LTI) in the relationship between bone microarchitecture and vascular stiffness in dialysis naïve patients with stage 5 CKD. Bioimpedance spectroscopy for evaluating LTI, lumbar spine dual energy X-ray absorptiometry for determining the trabecular bone score (TBS), and arterial applanation tonometry measurements for the central augmentation index, at a heart rate of 75 beats/minute (cAIx75), were simultaneously performed in 117 consecutive patients. A hierarchical regression analysis was conducted to assess the moderating effect of LTI on the relationship between TBS and cAIx75 after adjusting for age and sex. The effect of the interaction between LTI and TBS on cAIx75 was statistically significant (p = 0.030), demonstrating that the cAIx75 tends to decrease more, with the joint effect of LTI and TBS. In the separate analyses, the interaction effect was significant only in women (p = 0.048) and the group of diabetes (p = 0.042). Our study suggests that the evaluation of changes in body composition, bone health, and vascular stiffness needs to be performed simultaneously in patients with advanced-stage CKD. Further research in patients with different stages of CKD warranted to generalize and apply our results to patients in other stages.

Dual Fluorescent Tracers for Surgical Guidance: Preventing Donor-site Lymphedema in Vascularized Lymph Node Transfer.

Introduction:Vascularized lymph node transfer (VLNT) restores physiological lymphatic function. Although effective, postoperative impairment of donor-site lymphatic function and iatrogenic lymphedema following lymph node transfer remains a pressing concern.Methods:Prospective analysis of VLNT patients undergoing dual fluorescent tracers-assisted harvest was performed at our institution from September 2013 to April 2022. Reverse lymphatic mapping of the lower extremity was performed with indocyanine green (ICG). Blue dye was utilized in both white light and near-infrared spectra for visualization of donor-site lymphatic structures. Demographics, intraoperative details, and surgical outcomes were recorded.Results:Twenty-five patients were included. Median age was 52.9 years with a body mass index of 29.1 kg/m2 and mean follow-up of 44 months (range 24 to 90 months). Lymphedema stage ranged from Campisi 2 to 4. Inguinal VLNT was performed in 13 patients, and 12 patients received combined VLNT and free flap breast reconstruction. No patients required change in lymph node donor site intraoperatively. All ICG stained nodes were preserved in situ. No cases of iatrogenic lower extremity lymphedema were observed. Postoperative bioimpedance spectroscopy, circumferential, and volumetric measurements of the donor-site limb did not show evidence of subclinical or clinical lymphedema. The donor site healed appropriately in 92% of patients; one patient developed methylene blue-induced skin necrosis.Conclusion:Reverse lymphatic mapping and surgical guidance with dual ICG and blue dye fluorescent tracers provides surgeons with real-time surgical guidance without radioisotope, improves surgical visualization in both white light and near-infrared spectra, and avoids iatrogenic lymphatic dysfunction in the donor limb.

Preliminary study on parameterization of raw electrical bioimpedance data with 3 frequencies

This study tests the geometrical parameterization method for Electrical Bio-Impedance Spectroscopy (EBIS) readings previously proposed by one of the authors. This method uses the data of just three frequencies (therefore called 3P method). The test was carried out by the analysis of parameterization from 26 spectra (selected from 13 data sets) by the non-linear square (NLS) method, the 3P method and a combination of the two (3P-NLS). Additionally, the behaviour of the 3P method for 4 levels of noise and 3 different ways of segmenting the spectra were also explored with a MATLAB simulation of 400 spectra. Finally, a system for the classification of EBIS readings is presented, based on deviations of the raw data from the semi-circle obtained by the parameterization methods. Overall, the results suggest a very good performance of the 3P method when compared with the other two. The 3P method performs very well with levels of noise of 1 and 2%, but performs poorly with levels of noise of 5% and 10%. The results support the idea that the 3P method could be used with confidence for the parameterization of EBIS spectra, after the selection of three adequate frequencies according to specific applications.

Relationship of Adjuvant Radiation and the Lymphedema Index: A Valuable Trend to Follow Subclinical Lymphedema in Patients After Immediate Lymphatic Reconstruction.

Immediate lymphaticovenular bypass (immediate lymphatic reconstruction [ILR]) at the time of axillary lymph node dissection has emerged as a preventative paradigm to decrease the incidence of breast cancer-related lymphedema in high-risk patients. These patients are often treated with adjuvant therapies, including radiation. Bioimpedance spectroscopy is a validated tool for trending breast cancer-related lymphedema and identifying subclinical disease. Lymphedema Index (LDEX) values are commonly obtained in ILR patients; however, postoperative trends and relationships with adjuvant treatments are yet to be reported in the literature. After International Review Board approval, 100 consecutive patients underwent axillary lymph node dissection with axillary reverse lymphatic mapping and ILR at a tertiary cancer center. These patients were then followed prospectively in a multidisciplinary lymphedema clinic at 3-month intervals with clinical examination, circumferential limb girth measurements and bioimpedance spectroscopy (LDEX). Seventy-two patients met inclusion for analysis at 3 months, 60 at 6 months, 51 at 9 months, 45 at 12 months, 41 at 15 months, and 22 at 18 months. A majority of the patients included underwent adjuvant radiation. Average LDEX score for patients who developed lymphedema was 3.02 at 3 months, at 29.1 months, 17.8 at 9 months, 15.05 at 12 months, 18.75 at 15 months, and 7.7 at 18 months. Patients who went on to develop lymphedema had a higher LDEX score at 6 months (29.1 vs 3.20, P = 0.1329), which reached a significant difference beginning at 9 months (17.8 vs 3.19, P = 0.0004). All patients who went on to develop lymphedema received adjuvant radiation. These data provide valuable insight guiding follow-up after ILR. Six-month LDEX is much higher in patients who developed lymphedema, all of which underwent adjuvant radiation therapy, which correlates with the time of completion of their treatment. Average LDEX value after this remains significantly higher in this population. Patients who demonstrate this increase in LDEX and received adjuvant radiation are at highest risk to develop lymphedema despite ILR. All patients who developed lymphedema despite ILR had adjuvant radiation, and this is likely a contributing factor. Injury from adjuvant radiation and its impact after ILR is not insignificant and warrants further studies.

Overhydration in acute kidney injury: Is it always a menace to critically ill patients? A survival study using bioimpedance spectroscopy.

The hydration status is a predictor of survival in critically ill patients. However, it is unclear whether this association depends on the patient clinical condition. This study was designed to analyze the impact of hydration status on survival of critically ill patients with acute kidney injury (AKI) with or without sepsis. A prospective cohort study following critically ill patients with AKI consecutively admitted over a one-year period to a teaching hospital intensive care unit (ICU). All patients with AKI stage three or higher of the KDIGO score were included. The hydration status was evaluated through the overhydration (OH) parameter of spectroscopy bioimpedance and sepsis was defined according Sepse-3 criteria. The survival analysis used adjusted competing-risks regression. Forty-eight patients were included, 27 (56%) with a sepsis diagnosis. The main negative predictors of survival among sepsis patients, adjusted by SAPS3 score, were higher OH (SHR 1.1, 95% CI 1.0-1.2, p=0.02), mechanical ventilation (SHR 6.9, 95% CI 1.0-47.8, p=0.04) and older age (SHR 1.1, 95% CI 1.0-1.1, p=0.005). The predictors in non-sepsis patients were lower OH (SHR 0.82, 95% CI 0.71-0.95, p=0.008) and mechanical ventilation (SHR 12, 95% CI 2.4-6.6, p<0.001). This finding suggests that extracellular overhydration is an independent predictor of survival in critically ill patients with sepsis, but it seems to have opposite effect in non-sepsis patients.

Adipose and serum zinc alpha-2-glycoprotein (ZAG) expressions predict longitudinal change of adiposity, wasting and predict survival in dialysis patients

There were limited data on adipose and serum zinc alpha-2-glycoprotein (ZAG) expression and its association with body composition in patients with advanced chronic kidney disease (CKD). This study aimed to quantify adipose and serum ZAG expression and evaluate their association with body composition and its longitudinal change, together with mortality in incident dialysis patients. We performed a single-center prospective cohort study. Patients who were planned for peritoneal dialysis were recruited. ZAG levels were measured from serum sample, subcutaneous and pre-peritoneal fat tissue obtained during peritoneal dialysis catheter insertion. Body composition and functional state were evaluated by bioimpedance spectroscopy and Clinical Frailty Scale respectively at baseline and were repeated 1 year later. Primary outcome was 2-year survival. Secondary outcomes were longitudinal changes of body composition. At baseline, the average adipose and serum ZAG expression was 13.4 ± 130.0-fold and 74.7 ± 20.9 µg/ml respectively. Both adipose and serum ZAG expressions independently predicted adipose tissue mass (ATM) (p = 0.001, p = 0.008, respectively). At 1 year, ATM increased by 3.3 ± 7.4 kg (p < 0.001) while lean tissue mass (LTM) remained similar (p = 0.5). Adipose but not serum ZAG level predicted change in ATM (p = 0.007) and LTM (p = 0.01). Serum ZAG level predicted overall survival (p = 0.005) and risk of infection-related death (p = 0.045) after adjusting for confounders. In conclusion, adipose and serum ZAG levels negatively correlated with adiposity and predicted its longitudinal change of fat and lean tissue mass, whilst serum ZAG predicted survival independent of body mass in advanced CKD patient.

Compact CMOS Wideband Instrumentation Amplifiers for Multi-Frequency Bioimpedance Measurement: A Design Procedure

The design of an instrumentation amplifier (IA), based on indirect current feedback and suited to electrical bioimpedance spectroscopy, is presented. The IA consists of two transconductors and a summing stage, featuring a single-stage configuration process that allows the maximum achievable bandwidth to be extended. The transconductors are linearized by means of resistive source degeneration, whereas the use of super source followers allows a reduction in the values of the source degeneration resistors. This fact leads to a decrease in the overall noise and the silicon area, thus resulting in a compact implementation. A thorough analysis of the proposed solution, accompanied by a design procedure and verified by means of electrical simulations, is also provided. Two versions of the IA, i.e., a single-ended (SE) and a pseudo-differential (PD) structure, were designed and fabricated using 180 nm CMOS technology to operate with a 1.8 V supply. The experimental results, including a BW of 5.2 MHz/8.0 MHz, a CMRR higher than 72 dB/80 dB, a DC current consumption of 139.0 μA/219.3 μA and a silicon area equal to 0.0173 mm2/0.0291 mm2 for the SE/PD implementation, validate the suitability of the approach.

Body composition is associated with tacrolimus pharmacokinetics in kidney transplant recipients

PurposeA population pharmacokinetic (popPK) model may be used to improve tacrolimus dosing and minimize under- and overexposure in kidney transplant recipients. It is unknown how body composition parameters relate to tacrolimus pharmacokinetics and which parameter correlates best with tacrolimus exposure. The aims of this study were to investigate which body composition parameter has the best association with the pharmacokinetics of tacrolimus and to describe this relationship in a popPK model.MethodsBody composition was assessed using bio-impedance spectroscopy (BIS). Pharmacokinetic analysis was performed using nonlinear mixed effects modeling (NONMEM). Lean tissue mass, adipose tissue mass, over-hydration, and phase angle were measured with BIS and then evaluated as covariates. The final popPK model was evaluated using goodness-of-fit plots, visual predictive checks, and a bootstrap analysis.ResultsIn 46 kidney transplant recipients, 284 tacrolimus concentrations were measured. The base model without body composition parameters included age, plasma albumin, plasma creatinine, CYP3A4 and CYP3A5 genotypes, and hematocrit as covariates. After full forward inclusion and backward elimination, only the effect of the phase angle on clearance (dOFV = − 13.406; p < 0.01) was included in the final model. Phase angle was positively correlated with tacrolimus clearance. The inter-individual variability decreased from 41.7% in the base model to 34.2% in the final model. The model was successfully validated.ConclusionThe phase angle is the bio-impedance spectroscopic parameter that correlates best with tacrolimus pharmacokinetics. Incorporation of the phase angle in a popPK model can improve the prediction of an individual’s tacrolimus dose requirement after transplantation.

Investigation of the Relationship between Lean Muscle Mass and Erythropoietin Resistance in Maintenance Haemodialysis Patients: A Cross-Sectional Study.

Each patient undergoing maintenance haemodialysis (MHD) has a different response to erythropoiesis-stimulating agents (ESAs). Haemodilution due to fluid overload has been shown to contribute to anaemia. Body mass index (BMI) has been shown to influence ESA response in dialysis patients; however, BMI calculation does not distinguish between fat and lean tissue. The association between lean muscle mass and erythropoietin hyporesponsiveness is still not well-known among MHD patients. We designed a cross-sectional study and used bioimpedance spectroscopy (BIS) to analyse the relationship between body composition, haemoglobin level, and erythropoietin resistance index (ERI) in MHD patients. Seventy-seven patients were enrolled in the study group. Compared with patients with haemoglobin ≥ 10 g/dL, those with haemoglobin < 10 g/dL had higher serum ferritin levels, malnutrition–inflammation scores (MIS), relative overhydration, ESA doses, and ERIs. In multivariate logistic regression, higher ferritin levels and MIS were the only predictors of lower haemoglobin levels. The ERI was significantly positively correlated with age, Kt/V, ferritin levels, and MIS and negatively correlated with albumin levels, BMI, and lean tissue index (LTI). Multivariate linear regression analysis revealed that ferritin levels, BMI, and LTI were the most important predictors of ERI. In MHD patients, using BIS to measure body composition can facilitate the development of early interventions that aim to prevent sarcopenia, support ESA responsiveness, and, consequently, improve anaemia management.

MO893: The Prognostic Value of Dysvolemia, Cardiac Biomarkers and Echocardiographic Parameters in Chronic Haemodialysis Patients

Abstract BACKGROUND AND AIMS Hypervolemia is one of the important risk factors for mortality in haemodialysis (HD) patients. The aim of this study is to determine the prognostic significance of volemia determined by bioimpedance spectroscopy (BIS), as well as cardiac biomarkers and echocardiographic (ECHO) measurements. METHOD A prospective single-centre observational study included 73 (42 m) chronic HD patients. The BIS and cardiac biomarkers were measured before the second weekly HD procedure. In addition, to overcome the problem of possible different pre-HD and post-HD fluid volume levels (`overhydration’, OH and post-HD or `dehydration’, DH, respectively) on different HD sessions of the week, the concept of Average Weekly hypervolemia (AVOH) or hypovolemia (AVDH) was implemented—the remaining two OH and DH values were calculated from pre-HD and post-HD weights and normal weight as suggested by BIS measurement. ECHO was performed 1 day after aforementioned measurements (i.e. 1 day after HD). RESULTS During observation period 11 subjects died (15%): seven (64%) directly due to cardiovascular (CV), two due to infective and due to malignant causes. Three-year cumulative survival was significantly lower (by Kaplan–Meier analysis) in those who had: 1) AVOH &amp;gt;13% extracellular fluid (ECV) (survival rate 73% versus 92% (P &amp;lt; 0.05); 2) average AVDH&amp;gt; -3% ECV (survival 69% versus 94%; P &amp;lt; 0.01); 3) value of serum N-terminal prohormone of brain natriuretic peptide (NT-proBNP)&amp;gt; 7350 pg/mL (survival 76% versus 93%; P &amp;lt; 0.05); 4) troponin T (TnT) value &amp;gt;0.067 ng/mL, (survival rate 68% versus 94%; P &amp;lt; 0.01). In addition, regarding just CV mortality, left ventricular ejection fraction according to Simpson (LVEF) &amp;lt;40% (survival rate 80% versus 93%; P &amp;lt; 0.05) and global longitudinal strain (GLS) &amp;lt;–8.5 (survival rate 81% versus 95%, P &amp;lt; 0.05) were markers of pure survival. CONCLUSION Determination of volemia by BIS, cardiac biomarkers and echocardiography has prognostic significance in HD patients. Further studies will show how much correction of dysvolemia affects their better survival.

MO741: Poor Agreement between Physical Examination and Bioimpedance Spectroscopy in the Detection of Hypervolemia in Haemodialysis Patients

Abstract BACKGROUND AND AIMS Assessment of dry-weight among patients on haemodialysis is challenging in the absence of reliable markers to define overhydration (OH) [1, 2]. This study aimed to explore the value of two simple clinical signs, the presence of pedal oedema and crackles at pulmonary auscultation, in diagnosing hypervolemia, using the bioimpendence spectroscopy as a more objective method. METHOD In a cohort of 107 asymptomatic dialysis patients, the volume status was assessed with physical examination and bioimpedance spectroscopy shortly before the mid-week dialysis session [3]. Patients were also asked to perform home blood pressure (BP) monitoring with a validated, automatic device (HEM-705, Omron, Healthcare) [4] for 1 week in order to determine their BP control status. RESULTS Patients within the high tertile of pre-dialysis OH had longer dialysis vintage, lower serum albumin and higher home systolic BP, despite the more aggressive treatment with a higher average number of antihypertensives daily. In receiver-operating-characteristic (ROC) curve analysis, pedal oedema [area under curve (AUC): 0.534, 95% confidence interval (95% CI) 0.416–0.651] and pulmonary crackles (AUC: 0.551; 95% CI 0.432–0.671) had limited accuracy in the diagnosis of pre-dialysis OH &amp;gt; 2.2 L. The agreement of pedal oedema (Cohen's k-coefficient: 0.065) and pulmonary crackles (Cohen's k-coefficient: 0.122) with bioimpedance spectroscopy in the detection of hypervolemia was poor. In multivariate linear regression analysis, longer dialysis vintage (β: 0.306; P&amp;lt;0.001) and higher home systolic BP (β: 0.287; P&amp;lt;0.01) were the two factors that were independently associated with pre-dialysis OH. CONCLUSION This diagnostic-test study showed that among asymptomatic hemodialysis patients, pedal oedema and pulmonary crackles in physical examination had limited discriminatory power in the detection of hypevolemia, as assessed more objectively with the method of bioimpedance spectroscopy.

MO102: Lean Tissue, as Assessed by Bioimpedance Spectroscopy, Is Dependent on Renal Function in Patients with HFREF

Abstract BACKGROUND AND AIMS Despite impressive improvements in treatment strategies, heart failure (HF) morbidity and mortality remain substantially high worldwide. Muscle wasting is common and is associated with increased morbidity and mortality in patients with HF. The aim of the study was to determine muscle mass, by bioimpedance spectroscopy (BIS), and to identify factors associated with decreased muscle mass in this population. METHOD This was a prospective observational study of outpatient adults referred for clinically indicated transthoracic echocardiograms at an academic hospital between 2016 and 2018. A left ventricular ejection fraction below 45% was required for inclusion (HFrEF). Muscle mass was assessed using BIS (with the body composition monitor—BCM® device). RESULTS Our study included 151 patients. The mean age and eGFR values of the population at baseline were 67.1 years and 66.5 mL/min/1.73 m2. The median levels for lean tissue index (LTI, lean tissue mass/height2) were 11.3 (IQR 9.4–12.9) kg/m2. LTI was positively associated with eGFR and negatively associated with uric acid, ST-2 and galectin-3 levels. Including all these variables in a stepwise multivariable regression only eGFR and ST-2 remained independently associated with LTI (see Table 1). Based on the LTI median value, we also divided the patients into two groups—group 1 (LTI ≤ 11.3 kg/m2) and group 2 (LTI &amp;gt; 11.3 kg/m2). In the univariable logistic regression age, using the haemoglobin, eGFR and ST-2 levels predicted the group appurtenance. Including all these variables in a stepwise multivariable logistic regression, only eGFR and eGFR remained independently associated with LTI groups (see Table 2). CONCLUSION A better understanding of the factors associated with decreased muscle mass is needed to develop preventive strategies for muscle wasting in patients with HF. Muscle mass, as measured by the BCM and expressed as the LTI, is strongly associated with eGFR.

MO671: Should We Undergo Peritoneal Dialysis in Malnourished Chronic Kidney Disease Patients?

Abstract BACKGROUND AND AIMS The implementation of peritoneal dialysis (PD) in end-stage renal disease has been associated with various long-term pathophysiologic changes, which result in adverse consequences, such as malnutrition, occurring in 30–50% of patients. Specific factors to PD might be associated with poor oral intake as continuous absorption of glucose from PD solutions and abdominal fullness induced by the dialysate can suppress appetite. There are several accepted strategies for stratifying malnutrition in PD, such as laboratory markers [serum albumin and normalized protein catabolic ratio (nPCR)] and the recent use of bioimpedance spectroscopy (BIS) (with low lean tissue index). We aimed to evaluate if PD patients with a poor nutritional status at the beginning of the technique had worse outcomes (peritonitis, PD failure, hospitalizations, and death). METHOD We studied a cohort of incident patients from a single PD unit between 1 July 2011 and 31 August 2021, who had one BIS measurement and a peritoneal equilibration test in the first 3 months after the start of PD. We also collect laboratory data within 6 months from the BIS evaluation (serum albumin). Besides demographic parameters, we evaluated established endpoints (peritonitis, PD failure, hospitalizations and death). RESULTS There were included 91 PD patients. The mean age of patients was 65.40 $ \pm $ 13.88 years with a median dialysis vintage of 24 (IQR 14–31.61) months; 59.3% were male and 28% had diabetes. During the follow-up period, 5.5% of the cohort died, 56% were hospitalized and 47.3% had at least one episode of peritonitis. Furthermore, the transfer to hemodialysis occurred in 18 cases (19.8%) and 15 (16.5%) received a renal transplant. There was no difference in nutritional markers median in patients that had clinical endpoints versus those who had not (Table 1). In a multivariable analysis, neither nPCR, nor albumin nor lean tissue index were predictors of peritonitis, PD failure or hospital admissions. CONCLUSION In this study, we found that malnourished patients, prevalent in PD, did not have worse clinical endpoints (higher rate of infections, hospital admissions and PD failure). Although adequate nutrition has been deemed vital to the success of PD, this modality of renal replacement therapy did not result in worse outcomes, despite the malnutrition markers at the beginning of PD. Further studies are warranted to evaluate the positive impact of PD in nutrition status.

MO689: Relationship between Peritoneal/Renal Function and Nutritional Status in Peritoneal Dialysis Patients

Abstract BACKGROUND AND AIMS The positive impact of nutritional status on the health and treatment adequacy of peritoneal dialysis (PD) patients has been well established. There are several accepted strategies for stratifying malnutrition in PD, such as laboratory markers [serum albumin and normalized protein catabolic ratio (nPCR)] and the recent use of bioimpedance spectroscopy (BIS). The aim of this study was to assess the nutritional status of PD patients upon the start of the therapy. We also aimed to establish a potential relationship between peritoneal/renal function, obtained by a peritoneal equilibration test (PET), and nutritional markers. METHOD We studied a cohort of patients from a single PD unit between 1 July 2011 and 31 August 2021, who had one BIS measurement and a PET in the first 3 months after the beginning of PD. We also collect laboratory data within 6 months from the BIS reading (albumin, C-reactive protein and phosphorus). Demographic parameters (age, dialysis vintage, presence or absence of diabetes mellitus) and body mass index were also evaluated. RESULTS The study included 91 incident PD patients. The mean age of patients was 65.40 $ \pm $ 13.88 years, 59.3% were male and 28% had diabetes. Regarding baseline renal and peritoneal parameters, weekly total kt/v median was 1.99 (IQR 0.99–2.59) residual renal function (eGFR) median 3.2 (IQR 2.12–7.75) mL/min/1.73 m2 daily diuresis median 1500 (IQR 1000–2100), fluid removal (FR) median 2.23 (IQR 1.86–2.65) L/day and 41.8% had a dialysate/plasma (D/P) creatinine higher than 0.77. Lean tissue index was low in 36.3% and fat tissue index was high in 52.2%. Serum albumin median was 3.7 (IQR 3.3–4) g/dL and nPCR median 0.84 (IQR 0.72–1.04) g/kg/day. Hypervolemic patients had significantly lower lean tissue index (13.77 ± 3.25 versus 16.87 ± 3.82, P = 0.003). In a univariate analysis, patients with nPCR &amp;lt; 1.2 g/kg/day (79.1% from the complete cohort with no age difference) had lower baseline weekly total kt/v (2.17 ± 0.43 versus 6.62 ± 4.45, P &amp;lt; 0.001, lower daily diuresis (1261 ± 753 versus 1687 ± 958, P = 0.047), lower FR (2.05 ± 0.57 versus 2.40 ± 0.80, P = 0.043), and also significantly lower D/P creatinine (0.74 ± 0.1 versus 0.97 ± 0.27, P &amp;lt; 0.001). Furthermore, patients with serum albumin &amp;lt;3.8 g/dL had a lower ultrafiltration proof (326 ± 192 versus 511 ± 267, P = 0.028) and those with low lean tissue index had a lower daily diuresis (1405 ± 825 versus 1823 ± 1025, P = 0.045). In a multivariate analysis, patients with nPCR &amp;lt; 1.2 g/kg/day were older [exp (B) 0.19, 95% CI 0.8–0.9, P = 0.012] and had lower weekly total kt/v [exp (B) 0.18, 95% CI 0.6–0.9, P = 0.017]. CONCLUSION This study showed some relationships between kidney/peritoneal function parameters and body composition parameters. The level of nPCR, a measure of nutritional status, was significantly and positively associated with indicators of dialysis adequacy (kt/v), daily diuresis and, also with transport type. Further research regarding nutrition must be undertaken to help improve health outcomes in PD patients.

MO651: The Blood to Extracellular Volume Relationship is Stable and in the Physiologic Range in Chronic Haemodialysis Patients

Abstract BACKGROUND AND AIMS Blood volume (BV) is tightly controlled by the kidneys and the interstitial space plays an important role in this control. The interstitial space serves as a volume buffer in case of volume excess or volume depletion. It is the purpose of this buffer to maintain adequate circulatory and diastolic filling pressures, and thereby to maintain a functional circulation of the blood. BV is approximately one-third of the extracellular volume (ECV) under physiologic conditions. In haemodialysis patients without renal function, ECV is expanded because fluid is accumulated in the interdialytic period. This volume excess has to be removed during dialysis by ultrafiltration (UF) of blood. The question therefore arises, i) how is this volume excess distributed between intra-and extravascular compartments in dialysis patients and ii) how is this distribution affected by UF? METHOD Blood and extracellular volumes were measured in 79 stable chronic haemodialysis patients with moderate volume overload (1.85 ± 1.22 L). Immediately before treatment, ECV and volume overload were evaluated by bioimpedance spectroscopy using the body composition monitor [BCM, Fresenius Medical Care (FMC), Bad Homburg, Germany]. ECV at the end of treatment was calculated by subtracting the intra-dialytic weight loss from pre-dialysis ECV. The actual BV at the beginning of dialysis was determined by indicator dilution, using an online infusate bolus of 240 mL which was administered immediately after the beginning of the dialysis session and subsequent calculation using the data of the relative BV monitor integrated into the haemodiafiltration machine 5008 [Fresenius Medical Care (FMC), Bad Homburg, Germany]. BV at the end of the dialysis session was calculated from the measurement of BV at the beginning and the relative BV at the end of dialysis. RESULTS The relationship of BV (5.76 ± 1.54 L) to ECV (17.91 ± 3.90 L) was 0.321 ± 0.039 at dialysis start and 0.319 ± 0.040 at the end (BV 5.20 ± 1.41 L, ECV 16.22 ± 3.57 L). The mean deviation between pre- and post-dialysis was −0.002 ± 0.018. There were strong correlations (P &amp;lt; .001) between BV and ECV both at the beginning (r = 0.88) and at the end (r = 0.88) of dialysis. CONCLUSION These data show that i) the blood to extracellular volume ratio in haemodialysis patients is close to one-third assumed under physiologic conditions and that ii) this ratio remains unchanged in spite of UF. The constant relationship between the two compartments is maintained under conditions of haemodialysis with the rapid volume removal by UF. This confirms previous findings that the vascular refilling volume is only about 70% of UF volume during dialysis. Despite the lack of kidney function, the mechanisms to adequately distribute volume excess between intra- and extravascular appear to be maintained. The volume shift between plasma and interstitial volume prevents both an inter-dialytic cardio-vascular burden and intra-dialytic hypotension. Therefore, haemodialysis patients with moderate volume overload are likely to be adequately protected from volume-related complications. To the best of our knowledge, this is the first time that these relationships are reported in dialysis patients.