Changes in body composition following haemodialysis as assessed by bioimpedance spectroscopy

BACKGROUND/OBJECTIVES: Patients with chronic kidney disease treated by haemodialysis (HD) are at increased risk of sarcopenia. Bioelectrical impedance spectroscopy (BIS) can be used to determine body composition, and is one of the several potential screening tools for sarcopenia. The newer generation of portable hand-held devices can be readily used in dialysis centres. The results from BIS devices using a two-compartmental model of body composition can be affected by hydration status and so ideally measurements should be made when patients are not overhydrated. More recently BIS devices using a three-compartmental body model, which separate normally hydrated lean tissues from extracellular water (ECW) excess. We wished to determine whether body composition measured using such a BIS device was affected by hydration status. SUBJECTS/METHODS: We performed BISs pre and post HD using a three-body compartmental model. RESULTS: BISs were recorded in 48 patients; 68.8% male; mean age 67.70±14.21 years, weight pre dialysis 70.54±18.07, which fell post to 68.58±17.78 kg, ECW fell 16.92±4.76 vs 15.66±4.43 l, P<0.001, whereas there was no change for intracellular water 14.84±4.27 vs 14.90±4.68 l. Fat-free mass index (FFMI) fell 17.87±3.98 vs 16.78±3.97 kg/m(2), P<0.001, whereas fat mass index (FMI) increased from 7.87±3.98 vs 8.12±3.81 kg/m(2), P=0.002. A fall in FFMI was associated with an increase in FMI (r=0.804, P<0.001). CONCLUSION: FMI and FFMI measured by bioelectrical impedance assessment are both confounded by hydration status. Although pre-dialysis measurements are more convenient, we suggest BIS should preferably be performed post-dialysis when patients are less overhydrated and have less electrolyte imbalances

The prevalence of muscle wasting (sarcopenia) in peritoneal dialysis patients varies with ethnicity due to differences in muscle mass measured by bioimpedance

BACKGROUND/OBJECTIVES: Sarcopenia is associated with increased mortality. European and North American recommended screening for low muscle mass uses gender specific cut points, with no adjustment for ethnicity. We wished to determine whether the prevalence of sarcopenia was altered by ethnicity in peritoneal dialysis (PD) patients. SUBJECTS/METHODS: We measured appendicular lean mass indexed to height (ALMI) in PD patients by segmental bioimpedance and determined sarcopenia using different cut off points for reduced muscle mass. RESULTS: We measured ALMI in 434 PD patients, 55.1% males, mean age 55.3 ± 16.2 years, 32.3% diabetic, 54.1% white, 23.7% Asian, 19.1% black. ALMI was lower in Asian women, compared to white and black women (6.4 ± 1.1 vs. 6.6 ± 1.0 and 6.9 ± 1.4 kg/m2), and lower in Asian men (7.5 ± 1.3 vs. 8.5 ± 1.2 and 8.7 ± 1.3 kg/m2), p < 0.001. Depending on the ALM/ALMI cut point; the prevalence of sarcopenia was greater in Asian patients (25.6–41.2% using North American or European cut points) compared to white (12.3–18.7%) and black patients (3.8–15.7%), p < 0.001, but <11% when using Asian-specific cut points. The prevalence of sarcopenia obesity (BMI ≥ 30 kg/m2) was <3%, for all groups. There was no association with duration of PD, dialysis prescription, residual renal function or small solute clearances. CONCLUSIONS: There is no universally agreed consensus definition for loss of muscle mass (sarcopenia) and current European and North American recommended cut points for screening are adjusted only for gender. As body composition differs also with age and ethnicity, then ideally cut points should be based on age, gender and ethnicity normative values

Do Bioimpedance Measurements of Over-Hydration Accurately Reflect Post-Haemodialysis Weight Changes?

Introduction: Bioelectrical impedance spectroscopy (BIS) devices are being used to determine ultrafiltration requirements to achieve target weight for haemodialysis (HD) patients. Pre-dialysis measurements are more convenient for both patients and staff. We wished to compare the changes in pre- and post-dialysis hydration measured by BIS with actual weight loss. Methods: We compared paired BIS measurements made pre and post HD using a BIS device based on a 3-compartmental model, designed to provide information on extracellular water (ECW) excess. Results: BIS was measured in 49 HD patients, 35 male (71.4%) with mean age 67.6 ± 14.2. Weight fell significantly from 69.2 ± 17.8 to 67.6 ± 17.4 kg, and BIS over hydration (OH) from 4.5 ± 3.3.4 to 3.4 ± 2.9 litres, and ECW from 16.8 ± 4.8 to 15.5 ± 4.4 litres, but there was no change in the amount of intracellular water. Weight loss correlated positively with the change in ECW, but exceeded the fall in OH; mean bias -0.58 (95% confidence limits -3.6 to 4.8 kg). Summary: We measured OH pre and post HD, but did not find that the change in OH correlated with changes in body weight. Although there was a correlation between changes in OH and ECW, there was none for weight. Our findings do not support total reliance on pre-dialysis BIS alone for assessing volume status in HD patients, but rather BIS should be considered an aid to clinical assessment of volume status

Increasing Haemodialytic Clearances as Residual Renal Function Declines: An Incremental Approach

Many patients with chronic kidney disease start undergoing thrice-weekly haemodialysis (HD), aiming for an HD sessional dialyzer urea clearance target, irrespective of whether they have residual renal function (RRF). While increasing sessional dialyzer urea clearance above a target of 1.2 has not been shown to improve patient survival, it has been shown that the preservation of RRF improves patient self-reported outcomes and survival. Observational studies have suggested that initiating twice-weekly HD schedules leads to greater preservation of RRF. This has led to the concept of following an incremental approach to initiating HD, steadily increasing the amount of weekly dialyzer clearance as RRF decreases. Incremental dialysis practice requires the regular assessment of RRF to prevent inadequate delivery of dialysis treatment. Once RRF is lost, then the dialysis schedule and modality need to be adjusted to try to increase the middle-sized solute clearance and protein-bound toxins

Differences in Prevalence of Muscle Weakness (Sarcopenia) in Haemodialysis Patients Determined by Hand Grip Strength Due to Variation in Guideline Definitions of Sarcopenia

BACKGROUND: Muscle weakness is associated with increased mortality, and hemodialysis (HD) patients are at an increased risk for muscle loss. There is no agreed definition for muscle weakness, so we determined whether using different cut‐off criteria recommended by guideline groups altered the prevalence in HD patients. METHODS: We measured hand grip strength (HGS) in HD outpatients, comparing HGS with clinical guideline cut‐offs (European Working Group on Sarcopenia in Older People [EWGSOP] and North American Foundation for the National Institutes of Health Sarcopenia Project [FNIH]) used to define muscle wasting (sarcopenia) with age‐matched and gender‐matched normative data. RESULTS: We studied 459 patients, 61.4% male, 47.3% diabetic. The prevalence of muscle weakness was significantly different when measuring HGS; 84.5% using the EWGSOP cut‐off and 73.2% with FNIH criteria, and 75.2% using North American normative data and 56.6% U.K. normative data (P < .01). On logistic regression, muscle weakness was associated with age (odds ratio [OR] 1.05, P < .001), weight (OR 0.96, P < .001), serum albumin (OR 0.89, P = .007), and being nondiabetic (OR 0.31, P = .001). Of patients with no comorbidity, 66.7% were weak when compared with 93.8% with the highest comorbidity scores (P < .001). CONCLUSION: There is currently no agreed universal definition for sarcopenia, but the EWGSOP and FNIH advocate HGS cut‐offs as part of their definition. The prevalence of muscle weakness varies according to cut‐off and whether age‐matched and gender‐matched normative data are used. In addition, patient characteristics in terms of age and comorbidity determine the prevalence of muscle weakness

Reduction in Aortic Pulse Wave Velocity Is Associated with a Short-Term Reduction in Dual-Energy X-Ray Absorptiometry Lumbar Spine Bone Mineral Density T Score

Introduction: Increased vascular stiffness is a risk factor for mortality. We wished to determine whether changes in vascular stiffness are associated with changes in bone mineral density (BMD) in peritoneal dialysis patients. Methods: We measured vascular stiffness by aortic pulse wave velocity (aPWV) and BMD by dual electron absorptiometry (DXA) scanning and compared T scores to compensate for differences in patient ages and gender. Results: Twenty-four patients had repeat aPWV measurements and DXA scans, median 12.4 months apart. aPWV decreased in 15 and increased in 9. As there were more women in the group with an increase in aPWV, we used gender-adjusted DXA T scores Total body T scores fell in both groups, but median T scores remained positive for those with an increase in aPWV, whereas negative T scores on both scans for those with a decrease in or stable aPWV. Lumbar spine T scores fell in those with a reduction in aPWV (–1.6 [–2.4 to 0.6] to –2.1 [–2.4 to 0.3], p < 0.05), whereas there was no significant decrease in those with an increase in aPWV (–0.5 [–1.1 to 0.15] to –0.7 [–1.7 to 0.6]). There were no changes in femoral neck T scores. Conclusions: Our study reinforces the hypothesis of a link between bone disease and vascular disease in dialysis patients. Lumbar spine DXA includes imaging of the aorta and will include aortic calcification, and as such a reduction in lumbar spine T score without a change in femoral neck T score suggests a reduction in aortic calcification. Although our study requires additional confirmation, our data would suggest that changes in aPWV could be used as a surrogate for changes in vascular calcification in the investigation of interventions designed to reduce vascular calcification

Platelet activation and clotting cascade 3 activation by dialyzers designed for high AQ1 4 volume online hemodiafiltration

INTRODUCTION: Hemodialysis patients are pro-thrombotic. Higher volume online postdilutional hemodiafiltration (OL-HDF), with increasing hematocrit increases the risk of clotting in the extracorporeal circuit (ECC). We wished to determine whether OL-HDF increased platelet activation and ECC clotting. METHODS: Coagulation parameters, platelet, white cell, and endothelial activation markers were measured at the start and end of dialysis sessions in 10 patients and also pre- and post-dialyzer after 15 minutes using two different dialyzers designed for high volume OL-HDF; cellulose triacetate (TAGP) and polysulphone (PS), and polyvinylpyrrolidone (PVP). Patients were anticoagulated with a heparin bolus. FINDINGS: At the start of OL-HDF, D dimers, thrombin antithrombin complexes (TATs), and soluble adhesions molecules (sICAM-1 and sVCAM-1) were increased. Post-treatment soluble P selectin (PS/PVP 26.7 ± 7.1 versus 36.6 ± 9.9; TAGP 28.7 ± 7.2 versus 43.5 ± 8.4 ng/ml, P < 0.001), and soluble CD40 ligand (PS/PVP 297 ± 228 versus 552 ± 272, TAGP 245 ± 187 versus 390 ± 205 ng/ml, P < 0.05) increased. Post-dialyzer concentrations increased versus pre-dialyzer for tissue factor (PS/PVP 117 ± 12 versus 136 ± 16, TAGP 100 ± 25 versus 128 ± 40 ng/ml, P < 0.05), factor VIIIc (PS/PVP 174 ± 54 versus 237 ± 83, TAGP 163 ± 60 versus 247 ± 102 IU/ml, P < 0.01), sVCAM-1 (PS/PVP 782 ± 64 versus 918 ± 140, TAGP 722 ± 121 versus 889 ± 168 ng/ml, P < 0.01), and D-dimers (PS/PVP 292 ± 132 versus 355 ± 167, TAGP 300 ± 129 versus 391 ± 171 ng/ml, P < 0.001). There was no macroscopic thrombus noted in the ECC, and no increase in microparticles, platelet factor-4, or TATs. DISCUSSION: Despite being pro-thrombotic, with activation of platelets, and lymphocytes during passage through ECC, no macroscopic clotting, or increased TATs were noted during OL-HDF, and no major differences between cellulosic and polysulphone dialyzers

Aortic Pulse wave velocity is greater in peritoneal dialysis patients with lower dual energy X-ray absorptiometry (DXA) femoral neck bone mineral density

BACKGROUND: Increased vascular stiffness is associated with low bone mineral density (BMD) in the general population, and both are risk factors for mortality. We wished to determine whether vascular stiffness is associated with BMD in peritoneal dialysis (PD) patients. // METHODS: We measured vascular stiffness by aortic pulse wave velocity (aPWV), BMD by dual electron absorptiometry (DXA) scanning, and body composition using bioimpedance. // RESULTS: We reviewed DXA scans in 125 PD patients, 56.8% male, mean age 64.4 ± 15.3 years, mean aPWV, 10.2 ± 2.6 m/s. We divided patients by aPWV ( 10 m/s), and there were no statistical differences in patient demographics, body composition, PD adequacy, peritoneal and urinary calcium losses. On univariate analysis aPWV was negatively associated with total body T score (r = − 0.20, p = 0.037). On multivariable logistic regression patients with higher aPWV were prescribed fewer non-calcium containing phosphate binders, odds ratio (OR) 0.83, 95% confidence interval (CI) 0.70–0.99, p = 0.039, more had lower 25 hydroxy-vitamin D3 concentrations < 50 ng/L (OR 0.34, CI 0.12–0.93, p = 0.035, and lower femoral BMD OR 0.03 (CI 0–0.3.4), p = 0.029, but there was no association with total or lumbar spine BMD. // CONCLUSIONS: Our study reinforces the hypothesis of a link between bone disease and vascular disease in dialysis patients. As patients with higher aPWV were prescribed fewer non-calcium containing phosphate binders and fewer had higher 25 hydroxy-vitamin D3 concentrations, then this raises the possibility that differences in clinical practice and drug prescribing may help to reduce vascular stiffness, which will require testing in future trials

Pre-dialysis and post-dialysis hydration status and N-terminal pro-brain natriuretic peptide and survival in haemodialysis patients

PURPOSE: Many dialysis centres have no formal program for assessing and adjusting post-haemodialysis (HD) target weight. Apart from clinical assessment, there are bioimpedance devices and natriuretic peptides that could potentially aid clinical management. We wished to determine whether pre- or post-HD bioimpedance assessment of extracellular water (ECW) or N terminal probrain natriuretic peptide (NT-proBNP) affected patient outcomes. METHODS: Multi-frequency bioimpedance assessments (MFBIA) were made before and after the midweek dialysis session, along with a post-dialysis NT-proBNP measurement. RESULTS: Data from 362 patients, median age of 63 (50-76) years, 59.7% male, 41.2% Caucasoid, with a median dialysis vintage of 31.4 (13.5-61.7) months were available for review. During a median follow-up of 49.6 (21.9-50.2) months there were 110 (30.4%) deaths. Patients who died had significantly increased ECW, as % over-hydrated both pre-HD 6.6 (5.8-7.6)% vs. survivors 5.1 (4-6.6)%, and post-HD 5.1 (4-6.6)% vs. 0.5 (-1-2.2.0, p&lt;0.001, respectively. They also had higher NT-proBNP 325 (122-791) vs. 102 (48-342) pmol/l, p = 0.002. Using an adjusted Cox model, pre-HD ECW overhydration remained an independent factor associated with mortality (overhydration %: hazard ratio 1.15, 95% limits 1.03-1.28, p = 0.013), with a receiver operator curve (ROC) value of 0.7. CONCLUSIONS: ECW excess is associated with increased mortality for HD patients, with ECW excess pre-dialysis being the strongest association, although these patients also had increased ECW post dialysis. Future trials are required to determine whether achieving euvolaemia as determined by bioimpedance improves patient survival

Magnesium and Cardiovascular Disease

Magnesium is the most abundant intracellular divalent cation and essential for maintaining normal cellular physiology and metabolism, acting as a cofactor of numerous enzymes, regulating ion channels and energy generation. In the heart, magnesium plays a key role in modulating neuronal excitation, intracardiac conduction, and myocardial contraction by regulating a number of ion transporters, including potassium and calcium channels. Magnesium also has a role in regulating vascular tone, atherogenesis and thrombosis, vascular calcification, and proliferation and migration of endothelial and vascular smooth muscle cells. As such, magnesium potentially has a major influence on the pathogenesis of cardiovascular disease. As the kidney is a major regulator of magnesium homeostasis, kidney disorders can potentially lead to both magnesium depletion and overload, and as such increase the risk of cardiovascular disease. Observational data have shown an association between low serum magnesium concentrations or magnesium intake and increased atherosclerosis, coronary artery disease, arrhythmias, and heart failure. However, major trials of supplementation with magnesium have reported inconsistent benefits and also raised potential adverse effects of magnesium overload. As such, there is currently no firm recommendation for routine magnesium supplementation except when hypomagnesemia has been proven or suspected as a cause for cardiac arrhythmias