Estimation of Muscle Mass in the Integrated Assessment of Patients on Hemodialysis.

Assessment of muscle mass (MM) or its proxies, lean tissue mass (LTM) or fat-free mass (FFM), is an integral part of the diagnosis of protein-energy wasting (PEW) and sarcopenia in patients on hemodialysis (HD). Both sarcopenia and PEW are related to a loss of functionality and also increased morbidity and mortality in this patient population. However, loss of MM is a part of a wider spectrum, including inflammation and fluid overload. As both sarcopenia and PEW are amendable to treatment, estimation of MM regularly is therefore of major clinical relevance. Whereas, computer-assisted tomography (CT) or dual-energy X-ray absorptiometry (DXA) is considered a reference method, it is unsuitable as a method for routine clinical monitoring. In this review, different bedside methods to estimate MM or its proxies in patients on HD will be discussed, with emphasis on biochemical methods, simplified creatinine index (SCI), bioimpedance spectroscopy (BIS), and muscle ultrasound (US). Body composition parameters of all methods are related to the outcome and appear relevant in clinical practice. The US is the only parameter by which muscle dimensions are measured. BIS and SCI are also dependent on either theoretical assumptions or the use of population-specific regression equations. Potential caveats of the methods are that SCI can be influenced by residual renal function, BIS can be influenced by fluid overload, although the latter may be circumvented by the use of a three-compartment model, and that muscle US reflects regional and not whole body MM. In conclusion, both SCI and BIS as well as muscle US are all valuable methods that can be applied for bedside nutritional assessment in patients on HD and appear suitable for routine follow-up. The choice for either method depends on local preferences. However, estimation of MM or its proxies should always be part of a multidimensional assessment of the patient followed by a personalized treatment strategy.

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

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

Body composition in dialysis patients: a functional assessment of bioimpedance using different prediction models.

OBJECTIVES: The assessment of body composition (BC) in dialysis patients is of clinical importance given its role in the diagnosis of malnutrition and sarcopenia. Bioimpedance techniques routinely express BC as a 2-compartment (2-C) model distinguishing fat mass (FM) and fat-free mass (FFM), which may be influenced by the hydration of adipose tissue and fluid overload (OH). Recently, the BC monitor was introduced which applies a 3-compartment (3-C) model, distinguishing OH, adipose tissue mass, and lean tissue mass. The aim of this study was to compare BC between the 2-C and 3-C models and assess their relation with markers of functional performance (handgrip strength [HGS] and 4-m walking test), as well as with biochemical markers of nutrition. METHODS: Forty-seven dialysis patients (30 males and 17 females) (35 hemodialysis, 12 peritoneal dialysis) with a mean age of 64.8 ± 16.5 years were studied. 3-C BC was assessed by BC monitor, whereas the obtained resistivity values were used to calculate FM and FFM according to the Xitron Hydra 4200 formulas, which are based on a 2-C model. RESULTS: FFM (3-C) was 0.99 kg (95% confidence interval [CI], 0.27 to 1.71, P = .008) higher than FFM (2-C). FM (3-C) was 2.43 kg (95% CI, 1.70-3.15, P < .001) lower than FM (2-C). OH was 1.4 ± 1.8 L. OH correlated significantly with ΔFFM (FFM 3-C - FFM 2-C) (r = 0.361; P < .05) and ΔFM (FM 3-C - FM 2-C) (r = 0.387; P = .009). HGS correlated significantly with FFM (2-C) (r = 0.713; P < .001), FFM (3-C) (r = 0.711; P < .001), body cell mass (2-C) (r = 0.733; P < .001), and body cell mass (3-C) (r = 0.767; P < .001). Both physical activity (r = 0.456; P = .004) and HGS (r = 0.488; P = .002), but not BC, were significantly related to walking speed. CONCLUSIONS: Significant differences between 2-C and 3-C models were observed, which are partly explained by the presence of OH. OH, which was related to ΔFFM and ΔFM of the 2-C and 3-C models, is therefore an important parameter for the differences in estimation of BC parameters of the 2-C and 3-C models. Both FFM (3-C) and FFM (2-C) were significantly related to HGS. Bioimpedance, HGS, and the 4-m walking test may all be valuable tools in the multidimensional nutritional assessment of both hemodialysis and peritoneal dialysis patients.

Magnetic resonance angiographic assessment of upper extremity vessels prior to vascular access surgery: feasibility and accuracy.

A contrast-enhanced magnetic resonance angiography (CE-MRA) protocol for selective imaging of the entire upper extremity arterial and venous tree in a single exam has been developed. Twenty-five end-stage renal disease (ESRD) patients underwent CE-MRA and duplex ultrasonography (DUS) of the upper extremity prior to hemodialysis vascular access creation. Accuracy of CE-MRA arterial and venous diameter measurements were compared with DUS and intraoperative (IO) diameter measurements, the standard of reference. Upper extremity vasculature depiction was feasible with CE-MRA. CE-MRA forearm and upper arm arterial diameters were 2.94 +/- 0.67 mm and 4.05 +/- 0.84 mm, respectively. DUS arterial diameters were 2.80 +/- 0.48 mm and 4.38 +/- 1.24 mm; IO diameters were 3.00 +/- 0.35 mm and 3.55 +/- 0.51 mm. Forearm arterial diameters were accurately determined with both techniques. Both techniques overestimated upper arm arterial diameters significantly. Venous diameters were accurately determined with CE-MRA but not with DUS (forearm: CE-MRA: 2.64 +/- 0.61 mm; DUS: 2.50 +/- 0.44 mm, and IO: 3.40 +/- 0.22 mm; upper arm: CE-MRA: 4.09 +/- 0.71 mm; DUS: 3.02 +/- 1.65 mm, and IO: 4.30 +/- 0.78 mm). CE-MRA enables selective imaging of upper extremity vasculature in patients requiring hemodialysis access. Forearm arterial diameters can be assessed accurately by CE-MRA. Both CE-MRA and DUS slightly overestimate upper arm arterial diameters. In comparison to DUS, CE-MRA enables a more accurate determination of upper extremity venous diameters.

Ionic dialysance and the assessment of Kt/V: the influence of different estimates of V on method agreement.

BACKGROUND: Ionic dialysance was recently introduced as a means to assess Kt/V (K(ID)t/V). With this method, urea distribution volume (V) has to be estimated. The primary aim of the present study was to assess the agreement between equilibrated Kt/V assessed by urea kinetic modelling (eKt/V) with K(ID)t/V taking into account different estimates of V, and to assess the monthly variation in V. Secondly, the mechanisms behind the intra-treatment changes in ionic dialysance and inter-treatment variability of K(ID)t/V were assessed. METHODS: Sixty-six patients were included. eKt/V was estimated using 30 min post-treatment sampling in the second generation Daugirdas equation. V was assessed by the formulae of Watson and Chertow (V(Watson); V(Chertow)), double-pool urea kinetic modelling (V(UKM)) and by ionic dialysance (V(IOD)) [Diascan; Hospal(R)]. RESULTS: The use of V(UKM) or V(IOD) instead of V(Watson) or V(Chertow) improved the relation between eKt/V and K(ID)t/V (both r = 0.93; P < 0.001 vs r = 0.84 and r = 0.81; P < 0.001). Mean values of eKt/V (1.19 +/- 0.21), K(ID)t/V(UKM) (1.19 +/- 0.30) and K(ID)t/V(IOD) (1.21 +/- 0.25) were comparable. Intra-class correlation coefficient of V(IOD) was 0.87 with a 1-month interval and <0.75 after 2 and 3 months. Intra-class correlation coefficient of V(DP) was 0.79 with a 1-month interval and <0.75 after 2 and 3 months. Inter-treatment variation in K(ID)t/V during six consecutive dialysis sessions was 6.1% +/- 0.6%. Changes in blood flow were the main determinant of variations in K(ID)t/V (P < 0.05). During treatment, ionic dialysance decreased by 12 +/- 13 ml/min (P < 0.001). The decline in blood volume was the major determinant of the intra-dialytic change in ionic dialysance (P < 0.05). CONCLUSION: The use of V(IOD) and V(UKM) results in better agreement between eKt/V and K(ID)t/V compared with anthropometric formulae. K(ID)t/V was comparable with eKt/V and thus lower than expected for a single-pool method. V(IOD) and V(UKM), should be assessed at least monthly. K(ID)t/V varies widely between consecutive dialysis sessions, mainly due to differences in blood flow. During treatment, ionic dialysance decreases, which is related to the relative decline in blood volume.

An evaluation of blood volume changes during ultrafiltration pulses and natriuretic peptides in the assessment of dry weight in hemodialysis patients.

Changes in blood volume (BV) during dialysis as well as plasma levels of brain natriuretic peptide (BNP) and N-terminal (NT) pro-BNP levels are possible tools to assess dry weight in hemodialysis (HD) patients. The aim of the study was to compare these parameters with other non-invasive techniques used to assess dry weight in HD patients, and to study their relation with intradialytic hypotension (IDH) and the presence of cardiovascular disease BV changes during HD, both during regular dialysis and during an ultrafiltration pulse, plasma levels of NT pro-BNP and BNP, and vena cava diameter index (VCDI) were assessed in a cohort of 66 HD patients, which was subdivided according to tertiles of total body water (TBW) corrected for body weight, assessed by bioimpedance analysis. Parameters were also related to the presence of IDH and history of cardiovascular disease. The decline in BV during regular dialysis and during an ultrafiltration pulse, as well as VCDI and BNP were significantly different between the tertiles of normalized TBW, but refill after the ultrafiltration pulse and NT pro-BNP were not. Only VCDI and the decline in BV during regular dialysis were significantly different between patients with or without IDH. Vena cava diameter index, BNP, and NT pro-BNP were significantly higher in patients with cardiovascular disease. Using bioimpedance as the reference method, changes in BV, either during regular dialysis or during an ultrafiltration pulse, as well as VCDI and BNP are all indicative of hydration state in dialysis patients, but refill after an ultrafiltration pulse is not. Only VCDI and BV changes were related to IDH. The presence of cardiovascular disease appears to influence both VCDI as well as BNP.

Effect of ultrafiltration on thermal variables, skin temperature, skin blood flow, and energy expenditure during ultrapure hemodialysis.

The cause of the increase in core temperature (CT) during hemodialysis (HD) is still under debate. It has been suggested that peripheral vasoconstriction as a result of hypovolemia, leading to a reduced dissipation of heat from the skin, is the main cause of this increase in CT. If so, then it would be expected that extracorporeal heat flow (Jex) needed to maintain a stable CT (isothermic; T-control = 0, no change in CT) is largely different between body temperature control HD combined with ultrafiltration (UF) and body temperature control HD without UF (isovolemic). Consequently, significant differences in DeltaCT would be expected between isovolemic HD and HD combined with UF at zero Jex (thermoneutral; E-control = 0, no supply or removal of thermal energy to and from the extracorporeal circulation). During the latter treatment, the CT is expected to increase. In this study, changes in thermal variables (CT and Jex), skin blood flow, energy expenditure, and cytokines (TNF-alpha, IL-1 receptor antagonist, and IL-6) were compared in 13 patients, each undergoing body temperature control (T-control = 0) HD without and with UF and energy-neutral (E-control = 0) HD without and with UF. CT increased equally during energy-neutral treatments, with (0.32 +/- 0.16 degrees C; P = 0.000) and without (0.27 +/- 0.29 degrees C; P = 0.006) UF. In body temperature control treatments, the relationship between Jex and UF tended to be significant (r = -0.51; P = 0.07); however, there was no significant difference in cooling requirements regardless of whether treatments were done without (-17.9 +/- 9.3W) or with UF (-17.8 +/- 13.27W). Changes in energy expenditure did not differ among the four treatment modes. There were no significant differences in pre- and postdialysis levels of cytokines within or between treatments. Although fluid removal has an effect on thermal variables, no single mechanism seems to be responsible for the increased heat accumulation during HD.

Assessment of fluid status in peritoneal dialysis patients.

OBJECTIVES: To assess the influence of abnormalities in fluid status and body composition on agreement between multifrequency bioimpedance analysis (MF-BIA), segmental BIA (sigmaBIA), the Watson formula, and tracer dilution techniques. DESIGN: Cross-sectional. SETTING: Multicenter. PATIENTS: 40 patients (29 males, 11 females) on peritoneal dialysis (PD). MAIN OUTCOME MEASURES: Agreement between the various techniques used to assess total body water (TBW) [MF-BIA, deuterium oxide (D2O), and the Watson formula] and extracellular water (ECW) [MF-BIA, bromide dilution (NaBr), and sigmaBIA], also in relation to the relative magnitude of the body water compartments [ECW (NaBr):body weight (BW) and TBW (D2O):BW] and body composition (DEXA). Second, the relation between body water compartments with echocardiographic parameters. RESULTS: Wide limits of agreement were observed between tracer dilution techniques and MF-BIA [TBW (D2O - MF-BIA) 2.0 +/- 3.9 L; ECW (NaBr - MF-BIA) -2.8 +/- 3.9 L], which were related to the relative magnitude of the body water compartments: r = 0.70 for ECW and r = 0.40 for TBW. sigmaBIA did not improve the agreement [ECW (NaBr-sigmaBIA): 3.7 +/- 2.9 L]. Also, wide limits of agreement were observed between D2O and the Watson formula (-2.3 +/- 3.3 L). The difference between D2O and Watson was related to hydration state and to percentage of fat mass (r = 0.70 and r = -0.53, p < 0.05). Both ECW and TBW as assessed by BIA and tracer dilution were related to echocardiographic parameters. CONCLUSION: Wide limits of agreement were found between MF-BIA and sigmaBIA with dilution methods in PD patients, which were related to hydration state itself. The disagreement between the Watson formula and dilution methods was related to both hydration state and body composition.