Kamonwan Tangvoraphonkchai

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.

Immediate Effects of Traditional Thai Massage on Psychological Stress as Indicated by Salivary Alpha-Amylase Levels in Healthy Persons

Background Stress can cause psychological and physiological changes. Many studies revealed that massage can decrease stress. However, traditional Thai massage has not been well researched in this regard. The purpose of this study was to investigate the immediate effects of traditional Thai massage (TTM) on salivary alpha-amylase levels (sAA), heart rate variability (HRV), autonomic nervous system (ANS) function, and plasma renin activity (PRA). Material/Methods Twenty-nine healthy participants were randomly allocated into either a traditional Thai massage (TTM) group or Control (C) group, after which they were switched to the other group with a 2-week wash-out period. Each of them was given a 10-minute mental arithmetic test to induce psychological stress before a 1-hour session of TTM or rest. Results Within-groups comparison revealed that sAA was significantly decreased (p<0.05) in the TTM group but not in the C group. HRV and ANS function were significantly increased (p<0.05) and PRA was significantly decreased (p<0.05) in both groups. However, low frequency per high frequency ratio (LF/HF ratio) and ANS balance status were not changed. Only sAA was found to be significantly different between groups (p<0.05). Conclusions We conclude that both TTM and rest can reduce psychological stress, as indicated by decreased sAA levels, increased parasympathetic activity, decreased sympathetic activity, and decreased PRA. However, TTM may have a modest effect on stress reduction as indicated by a reduced sAA.

Incremental Hemodialysis – A European Perspective

Most patients initiating hemodialysis have residual renal function (RRF). Whereas RRF is monitored prior to commencing hemodialysis, once dialysis is started most centres simply rely on dialyzer urea clearance to determine adequate uremic toxin clearance and disregard the effect of RRF. However sustaining RRF is important for the dialysis patient, as RRF reduces inter‐dialytic weight gains, increases middle molecule and protein bound toxin clearances and is associated with better quality of life assessments. Paradoxically, more frequent dialysis and longer dialysis sessions appear to be associated with more rapid loss of RRF. As such, starting patients with less frequent or shorter dialysis sessions, depending upon individual patient comorbidity, may lead to better preservation of RRF. However to prevent inadequate uremic toxin clearance or volume overload, RRF needs to be regularly monitored. Unfortunately, the 24‐hour urine collection for urea and creatinine clearance remains the mainstay for RRF assessment. This measurement chiefly represents glomerular clearance rather than tubular function, but the latter may be also important for the dialysis patients. Incremental dialysis with less initial dialysis treatment may lower costs and will allow others to dialyze more frequently. The key to start a successful incremental hemodialysis approach is the regular monitoring of the patient, so that as RRF is lost an appropriate decision can be made regarding increasing dialysis session duration and frequency on an individual patient basis or consider switching modalities to hemodiafiltration.

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<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.

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.

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

Background/objectivesSarcopenia 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/methodsWe 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.ResultsWe 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.ConclusionsThere 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.

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.

Enhancing dialyser clearance—from target to development

Products of metabolism accumulate in kidney failure and potentially have toxic effects. Traditionally these uraemic toxins are classified as small, middle-sized and protein-bound toxins, and clearance during dialysis is affected by diffusion, convection and adsorption. As current dialysis practice effectively clears small solutes, increasing evidence supports a toxic effect for middle-sized and protein-bound toxins. Therefore, newer approaches to standard dialysis practice are required to look beyond urea clearance. Current dialysers have been developed to effectively clear small solutes and secondly to increase middle-sized toxin clearances. However, there is no ideal dialyser which can effectively clear all uraemic toxins. Advances in nanotechnology have led to improvements in manufacturing, with the production of smoother membrane surfaces and uniformity of pore size. The introduction of haemodiafiltration has led to changes in dialyser design to improve convective clearances. Both diffusional and convectional clearances can be increased by changing dialyser designs to alter blood and dialysate flows, and novel dialyser designs using microfluidics offer more efficient solute clearances. Adjusting surface hydrophilicity and charge alter adsorptive properties, and greater clearance of protein-bound toxins can be achieved by adding carbon or other absorptive monoliths into the circuit or by developing composite dialyser membranes. Other strategies to increase protein-bound toxins clearances have centred on disrupting binding and so displacing toxins from proteins. Just as the hollow fibre design replaced the flat plate dialyser, we are now entering a new era of dialyser designs aimed to increase the spectrum of uraemic toxins which can be cleared by dialysis.

Effect of Self-Reported Distress Thermometer Score on the Maximal Handgrip and Pinch Strength Measurements in Hemodialysis Patients

Background: Muscle weakness is a risk factor for mortality in hemodialysis (HD) patients. Muscle strength measurements are routinely used as a screening tool but depend on patient cooperation and motivation. We wished to determine whether measuring maximal voluntary muscle strength was affected by patient self-reported distress. Methods: We measured pinch strength (PS) and handgrip strength (HGS) in 382 adult HD patients with a corresponding self-reported distress thermometer (DT) scores. Postdialysis body composition measurements were made using multifrequency bioelectrical assessments and patients assessed for frailty. Results: Mean age was 66.4 ± 14.9 years, with 238 males (62%), 48% diabetic, and dialysis vintage 36 (15–75) months. The mean DT score was 4.4 ± 3.3, with a frailty score of 4.6 ± 1.5. On multivariable analysis, DT scores were associated with frailty (&bgr; = 0.35, P = .003), prescription of aspirin for cardiac disease (&bgr; = 1.0, P = .004), lean body mass (&bgr; = 0.04, P = .004), and negatively with age (&bgr; = −0.05, P < .001), hematocrit (&bgr; = −8.2, P = .004), and maximum PS (&bgr; = −1.4, P = .003). Conclusion: Paradoxically higher self-reported DT scores were associated with younger age and lean body mass. As such, younger healthier, rather than more comorbid, patients may have greater expectations for their health and therefore report more distress. We found no association between DT scores and HGS, and as such, although HGS is a voluntary test, it appears to be a robust test independent of patient stresses. However, PS was lower in patients with higher DT scores, and as such, greater care may be required in interpreting these measurements.

Platelet activation and clotting cascade activation by dialyzers designed for high 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.