Delayed post-dialysis recovery times are associated with relative changes in intracellular and extracellular fluid ratios between different body compartments

INTRODUCTION

Hemodialysis patient groups have advocated reducing dialysis fatigue and symptoms. We investigated whether compartmental fluid shifts were associated with peri-dialytic fatigue and symptoms.

METHODS

Sessional dialysis records of patients reporting both a short and delayed recovery (<1 h and ≥1 h) with corresponding bioimpedance measurements were reviewed.

RESULTS

One hundred and twenty-four patients reported both short and delayed recovery times, mean age 66.0 ± 14.8 years, 66.1% male. Differences between sessions included higher distress thermometer [4 (1-6) vs. 3 (0-5)], fatigue [4 (0-9) vs. 2 (0-7)], total symptom scores [20.5 (12.3-34.5) vs. 16 (7-28)], change in extracellular water to total body water ratios between body compartments [right leg/left arm 2.36 (1.23-4.19) vs. 1.28 (0.12-2.01), all p < 0.01] with delayed recovery, and more hemodialysis than hemodiafiltration sessions (χ2 4.6, p = 0.02).

CONCLUSION

Sessions with prolonged recovery times were associated with more peri-dialytic symptoms, psychological distress, and hemodialysis mode, and greater changes in compartmental fluid shifts.

Segmental bioimpedance in pregnant end stage renal failure patient for dry weight titration and volume management (case report)

BACKGROUND

Volume assessment, dry weight titration, and blood pressure control in pregnant kidney failure patients are often challenging, with physiological fluid accumulation in the trunk and lower limbs and an increased risk of preeclampsia. We used segmental bioimpedance in the volume management of our kidney failure patient on haemodialysis.

CASE PRESENTATION

We report a case of a female patient on maintenance haemodiafiltration with no residual kidney function for whom we used segmental bioimpedance to guide dry weight adjustment. At different gestational periods, we targeted a different extracellular to total body water ratio according to body segments. This allowed us to support her high-risk pregnancy, identify her as probably developing preeclampsia and trigger a plan for closer monitoring and delivery during the third trimester when she had rapid weight gain.

CONCLUSION

Segmental bioimpedance is a practical, simple, and non-invasive test that can be performed at the dialysis unit and is useful as an adjunct decision-making tool in the management of pregnant dialysis patients.

Estimation of fluid status using three multifrequency bioimpedance methods in hemodialysis patients

INTRODUCTION

Segmental eight-point bioimpedance has been increasingly used in practice. However, whether changes in bioimpedance analysis components before and after hemodialysis (HD) using this technique in a standing position is comparable to traditional whole-body wrist-to-ankle method is still unclear. We aimed to investigate the differences between two eight-point devices (InBody 770 and Seca mBCA 514) and one wrist-to-ankle (Hydra 4200) in HD patients and healthy subjects in a standing position.

METHODS

Thirteen HD patients were studied pre- and post-HD, and 12 healthy subjects once. Four measurements were performed in the following order: InBody; Seca; Hydra; and InBody again. Electrical equivalent models by each bioimpedance method and the fluid volume estimates by each device were also compared.

FINDINGS

Overall, total body water (TBW) was not different between the three devices, but InBody showed lower extracellular water (ECW) and higher intracellular water (ICW) compared to the other two devices. When intradialytic weight loss was used as a surrogate for changes in ECW (∆ECW) and changes in TBW (∆TBW), ∆ECW was underestimated by Hydra (-0.79 ± 0.89 L, p < 0.01), InBody (-1.44 ± 0.65 L, p < 0.0001), and Seca (-0.32 ± 1.34, n.s.). ∆TBW was underestimated by Hydra (-1.14 ± 2.81 L, n.s.) and InBody (-0.52 ± 0.85 L, p < 0.05) but overestimated by Seca (+0.93 ± 3.55 L, n.s.).

DISCUSSION

Although segmental eight-point bioimpedance techniques provided comparable TBW measurements not affected by standing over a period of 10-15 min, the ECW/TBW ratio appeared to be significantly lower in InBody compared with Seca and Hydra. Results from our study showed lack of agreement between different bioimpedance devices; direct comparison of ECW, ICW, and ECW/TBW between different devices should be avoided and clinicians should use the same device to track the fluid status in their HD population in a longitudinal direction.

Comparison of skin autofluorescence, a marker of tissue advanced glycation end-products in the fistula and non-fistula arms of patients treated by hemodialysis

Advanced glycosylation end-products (AGEs) are reported to be a risk factor for cardiovascular mortality in hemodialysis (HD) patients. As serum AGEs can change with dialysis, measurement of AGEs deposited in the skin by autofluorescence (SAF) is now a recognized method of measuring AGEs. An arteriovenous fistula (AVF) is the preferred way to access blood in HD patients, and as the creation of an AVF changes blood flow distribution in the arm, we wished to determine whether this affected SAF deposition in the skin. SAF was measured using the AGE reader, which directs ultraviolet light at an intensity range of 300-420 nm (peak 370 nm) in the arms of HD patients dialyzing with an AVF. We measured SAF in 267 patients, 60.3% male, 46.1% diabetic, median duration of dialysis 34.7 (15.1-64.2) months with AVF. The median SAF was lower in the AVF arm (median 3.4 (2.9-4.2) vs. 3.7 (3.2-4.5) AU, P < .001), and for the 160 patients with an upper arm AVF (3.5 (2.9-4.3) vs. 3.8 (3.2-4.5) AU, P < .001), but not for the 107 patients dialyzing with a forearm AVF ((3.4 (2.8-4.2) vs. 3.6 (3.0-4.5) AU, P = .085). Blood flow was greater for upper arm AVF compared to forearm AVFs (1190 (770-1960) vs. (930 (653-1250) mL/min, P = .007), but there was no association between blood flow and SAF (P > .05). AVF alters blood flow in the arm, and we found that SAF measurements were lower in the arm with AVF. We suggest that SAF measurements are made in the non-AVF arm.

Evaluation of one year of frequent dialysis on fluid load and body composition using calf bioimpedance technique

OBJECTIVE

The primary aim of this study was to evaluate the effect of increased frequency of dialysis (FHD) on change in fluid status and body composition using segmental bioimpedance.

APPROACH

Twelve stable HD patients were switched from 3 times/week to 6 times/week HD (FHD). Systolic blood pressure (SBP), body mass and body mass index (BMI) were measured pre- and post-HD. Calf resistance (R ₅) at 5 kHz was measured using a multifrequency bioimpedance device (Hydra 4200). Calf resistivity (ρ  =  R ₅ * area/length), normalized resistivity (CNR  =  ρ/BMI) and calf extracellular volume (cECV) were calculated. Fat mass was measured by Futrex body composition analyzers (Futrex 6100, Futrex Tech, Inc.). All measurements were performed at baseline (BL) and monthly for up to one year.

MAIN RESULTS

Nine patients completed one year of FHD. Compared to BL, body weight and cECV decreased, and CNR increased significantly by the first month but did not change thereafter. SBP pre-HD decreased significantly by the end of the first month with further reduction until month 12. Additionally, antihypertensive medication decreased significantly from baseline by month 4 and remained stable from month 6 throughout the rest of the study. The post-HD CNR in five of nine patients reached the range of normal (>18.5 10^-2 * Ohm * m³ kg^-1 for males and  >19.1 10^-2 * Ohm * m³ kg^-1 for females) after 1 year FHD. In patients who returned to 3 times/week dialysis, CNR decreased significantly in the first week, and this was associated with increases in body weight and SBP.

SIGNIFICANCE

Reduction of fluid overload with no alteration of body composition was observed in this study. Accordingly, improving fluid status was confirmed by reducing BP and use of antihypertensive drugs together with increase in CNR. Measurement of fluid status by CNR in hemodialysis patients is a new method to quantitatively assess hydration potentially creating a target for volume of fluid removal.

Body fluid status assessment by bio-impedance analysis in patients presenting to the emergency department with dyspnea

BACKGROUND/AIMS

Fluid retention occurs in patients with heart failure, accounting for dyspnea. We investigated the diagnostic implication of body fluid status, assessed by bio-impedance analysis (BIA), in acute heart failure (AHF) among patients who presented with dyspnea.

METHODS

A total of 100 patients who presented with dyspnea and suspected with AHF were analyzed in this study. We enrolled 50 AHF and 50 non-AHF patients discriminated through echocardiographic analysis and Framingham criteria and were matched by age and sex. Body composition was analyzed using a multifrequency BIA.

RESULTS

AHF patients demonstrated higher extracellular water (ECW)/total body water (TBW) compared with non-AHF patients (0.412 ± 0.017 vs. 0.388 ± 0.023, p < 0.001). A significant difference of ECW/TBW between AHF patients and nonAHF patients was noted when the upper extremities, trunk, and lower extremities were analyzed (all p < 0.001, respectively). ECW/TBW was not different between patients with reduced ejection fraction (EF) and preserved EF along body compartments. The best cut-off value to predict AHF was > 0.412 at lower extremities with sensitivity and specificity of 0.780 and 0.960. The ECW/TBW of the lower extremities (ECW/TBWL) was correlated with log B-type natriuretic peptide (BNP) levels (r = 0.603, p < 0.001) and also improved the net reclassification improvement and integrated discriminated improvement when added to log BNP level. Multivariate analysis revealed that ECW/TBWL > 0.412 had an independent association with AHF patients (p = 0.011).

CONCLUSION

The ECW/TBWL was higher in patients with dyspnea caused by AHF than their counterparts and demonstrated an independent diagnostic implication. It may be a promising marker to diagnose AHF at bedside.

Differences in the prevalence of sarcopenia in peritoneal dialysis patients using hand grip strength and appendicular lean mass: depends upon guideline definitions

BACKGROUND

Peritoneal dialysis (PD) patients with sarcopenia have increased risk of mortality. There is consensus that sarcopenia should combine assessments of muscle function and mass. We wished to determine the effect of using different operational definitions in PD patients.

METHODS

Hand grip strength (HGS) and segmental bioimpedance derived appendicular lean mass (ALM) were measured and the prevalence of sarcopenia determined using the Foundation for the National Institutes of Health Sarcopenia Project (FNIH), European Working Group on Sarcopenia Older Persons (EWGSOP), and Asian Working Group on Sarcopenia (AWGS) definitions.

RESULTS

We studied 155 PD patients, 95 men (61.3%), mean age 63.0 ± 14.9 years, 37.4% diabetic, treated by PD 9 (3-20) months with a HGS of 22.5 (15.5-30.2) kg, weight 73.6 ± 16.6 kg, % body fat 31.4 ± 4.2, and ALM index 7.52 ± 1.40 kg/m². More patients were defined with muscle weakness using the EWGSOP compared to the FNIH criteria (X² = 6.8, p = 0.009), whereas fewer patients met the EWGSOP criteria for muscle wasting compared to FNIH body mass index adjustment (X² = 7.7, p = 0.006). However, when combining both criteria, there was no difference in the prevalence of sarcopenia between the different recommended definitions (11-15.5%).

CONCLUSION

We report a much lower prevalence of sarcopenia compared to studies in haemodialysis patients. Although there may be an element of patient selection bias, PD patients are not subject to changes in hydration and electrolytes with haemodialysis, which can affect HGS and muscle mass measurements. Using HGS and segmental bioimpedance we found similar prevalence of sarcopenia using EWGSOP, FNIH, AWGS definitions.

Prediction of hemodialysis vascular access failure using segmental bioimpedance analysis parameters

PURPOSE

Segmental bioimpedance analysis (BIA) can identify fluid volume changes in the arms of patients on hemodialysis (HD) after vascular access surgery. We investigated whether the difference in fluid volumes between the arms of the patients using segmental BIA is associated with vascular access outcome.

METHODS

Body composition measurements were taken for 127 patients on HD with segmental, multi-frequency BIA equipment (InBody 1.0, Biospace Co. Ltd, Seoul, Korea). The difference in fluid volume between the arms of the patients was calculated from the fluid volume of the arm with the vascular access minus that of the other. The primary outcome was the loss of vascular access patency within 3 months of BIA measurement.

RESULTS

The median absolute and relative inter-arm fluid volume differences were 150 ml [interquartile range (IQR) 90-250 ml] and 9.6% (IQR 4.9-14.4%), respectively. Within 3 months of BIA measurement, 38 patients (30.0%) experienced vascular access failure. When the patients were divided into three groups based on the tertiles of relative inter-arm fluid volume differences (lowest tertile: < 6.8%; middle tertile: 6.8-12.7%; highest tertile: > 12.7%), greater difference in relative inter-arm fluid volume differences was associated with higher vascular access failure rates (14 vs. 28 vs. 48%, p value for trend across tertiles = 0.003).

CONCLUSIONS

We conclude that segmental BIA may be used as a tool that can predict vascular access failure in patients on HD by calculating the relative difference in fluid volume between the arms of the patients with and without vascular access.

The Body Composition Monitor: a flexible tool for routine fluid management across the haemodialysis population

Bioimpedance measurements with the Body Composition Monitor (BCM) have been shown to improve fluid management in haemodialysis. However, there is a lack of a sufficiently robust evidence-base for use of the BCM outside of standard protocols. This study aims to characterise BCM measurement variation to allow users to make measurements and interpret the results with confidence in a range of clinical scenarios. BCM measurements were made in 48 healthy controls and in 48 stable haemodialysis patients before and immediately after dialysis. The effect of utilising alternative measurement paths was assessed using mixed effects models and the effect of measuring post-dialysis was assessed by comparing changes in BCM-measured overhydration (OH) with weight changes over dialysis. The data from healthy controls suggest that there is no difference in BCM-measured OH between all the whole-body paths other than the foot-to-foot measurement. Dialysis patients showed similar results other than having higher BCM-measured OH when measured across the site of a vascular access. There was good agreement between BCM-measured OH and change in weight, suggesting post-dialysis measurements can be utilised. These results suggest BCM protocols can be flexible regarding measurement paths and timing of measurement to ensure as many patients as possible can benefit from the technology.

Does the presence of an arteriovenous fistula alter changes in body water following hemodialysis as determined by multifrequency bioelectrical impedance assessment?

Multifrequency bioelectrical impedance assessments (MFBIAs) aid clinical assessment of hydration status for hemodialysis (HD) patients. Many MFBIA devices are restricted to whole body measurements and as many patients dialyze using arteriovenous fistulas (AVFs), we wished to determine whether AVFs affected body water measurements. We reviewed pre- and post-HD segmental MFBIA measurements in 229 patients attending for midweek HD sessions. Up to 144 were dialyzed with a left arm AVF (L-AVF), 42 with a right arm AVF (R-AVF), and 43 by central venous access catheter (CVC). Water content and lean tissue were greater in the left compared to right arm in those patients with L-AVFs both pre and post dialysis (pre 2.1 ± 0.7 vs. 2.0 ± 0.7 L, and post 1.9 ± 0.6 vs. 1.8 ± 0.6 L and pre 2.65 ± 0.9 vs. 2.56 ± 0.8 kg, and post 2.34 ± 0.8 vs. 2.48 ± 0.8 vs. 2.34 ± 0.8 kg, respectively) and were also greater in the right compared to left arm for those patients dialyzing with R-AVFs (pre-HD 1.92 ± 0.5 vs. 1.86 ± 0.6 L and post-HD 1.79 ± 0.5 vs. 1.7 ± 0.5 L, and pre-HD 2.47 ± 0.6 vs. 2.38 ± 0.7 kg and post-HD 2.3 ± 0.74 vs. 1.28 ± 0.7 kg, respectively), all Ps < 0.05. There were no significant differences in arm volumes or composition pre or post dialysis in those dialyzing with CVCs. Segmental MFBIA detects differences in arm water and lean mass in patients with AVFs. The presence on an AVF increases the water content in the ipsilateral arm both pre and post HD. This increased water content of the fistula arm will not be detected by whole body bioimpedance devices.

Are serum to dialysate sodium gradient and segmental bioimpedance volumes associated with the fall in blood pressure with hemodialysis?

INTRODUCTION

A fall in blood pressure is the most common complication of outpatient hemodialysis. Several factors have been implicated, including serum sodium to dialysate gradient, ultrafiltration rate, and the amount of fluid to be removed during dialysis.

METHODS

We prospectively audited 400 adult patients attending for their routine midweek hemodialysis session, and recorded changes in mean arterial blood pressure (MAP).

RESULTS

Mean age 58.4 ± 16.6 years, 60.9% male, 30.7% diabetic, 36.8% Caucasoid, single pool Kt/V 1.57 ± 0.4, and median percentage change in MAP -6.7% (-14.1 to + 2.8). The percentage fall in MAP was greatest for those starting with higher MAPs (β 0.448 , F 67.5, p<0.001), greater serum sodium to dialysate sodium gradient (β 0.676, F 5.59, p = 0.019), and age (β 0.163, F 5.15, p = 0.024). In addition, the percentage fall in MAP was greater in those with the lowest segmental extracellular water/total body water (ECW/TBW) ratios in the right arm prior to dialysis (β -477.5, F 7.11, p = 0.008).

CONCLUSIONS

Falls in blood pressure are common during dialysis, and greater for those starting dialysis with the highest systolic pressures, greater dialysate to serum sodium concentration gradient, and also those with the least ECW in the arm. As such, segmental bioimpedance may be useful in highlighting patients at greatest risk for a fall in blood pressure with dialysis.

The association between arterial stiffness and fluid status in peritoneal dialysis patients

OBJECTIVES

In this study our aim was to evaluate the relationship between degree of fluid status and arterial stiffness measured by pulse wave velocity (PWV) in peritoneal dialysis (PD) patients. Fluid status was determined by different methods including fluid overload measured by bioimpedance (Body Composition Monitor, BCM), calf normalized resistivity (CNR), plasma N-terminal fragment of B-type natriuretic peptide (NT-proBNP) and extracellular to intracellular water ratio (ECW/ICW).

METHODS

Sixty PD patients were evaluated. They were stratified into normo- and hypervolemic groups according to their fluid overload (FO). CNR was calculated from resistance at 5 kHz using calf bioimpedance spectroscopy. Arterial stiffness was assessed by PWV. Additionally, all patients underwent transthoracic echocardiography and had levels of NT-proBNP measured.

RESULTS

PWV was higher in the hypervolemic compared to normovolemic patients (9.99 ± 2.4 m/sec vs 7.48 ± 2.3 m/sec, p < 0.001). Hypervolemic patients had higher NT-proBNP levels (3065 ± 981 pg/mL vs 1095 ± 502 pg/mL, p < 0.001), a higher ratio of ECW/ICW; (0.93 ± 0.11 vs 0.81 ± 0.08, p < 0.001) and lower CNR (13.7 ± 2.4 vs 16.0 ± 3.3 W m(3)/kg(*)10(-2), p = 0.005). NT-pro BNP level, ECW/ICW ratio, relative FO, and left ventricular (LV) mass index were positively and CNR negatively correlated with PWV. Relative FO and CNR independently predicted PWV in multivariate analysis adjusted for age, duration of PD, body mass index and mean arterial pressure.

CONCLUSIONS

Arterial stiffness is increased in fluid-overloaded PD patients. Our results indicated that fluid status is an independent predictor of PWV.

Noninvasive techniques for prevention of intradialytic hypotension

Episodes of hypotension during hemodialysis treatment constitutes an important clinical problem which has received considerable attention in recent years. Despite the fact that numerous approaches to reducing the frequency of intradialytic hypotension (IDH) have been proposed and evaluated, the problem has not yet found a definitive solution--an observation which, in particular, applies to episodes of acute, symptomatic hypotension. This overview covers recent advances in methodology for predicting and preventing IDH. Following a brief overview of well-established hypotension-related variables, including blood pressure, blood temperature, relative blood volume, and bioimpedance, special attention is given to electrocardiographic and photoplethysmographic (PPG) variables and their significance for IDH prediction. It is concluded that cardiovascular variables which reflect heart rate variability, heart rate turbulence, and baroreflex sensitivity are important to explore in feedback control hemodialysis systems so as to improve their performance. The analysis of hemodialysis-related changes in PPG pulse wave properties hold considerable promise for improving prediction.

Haemodiafiltration results in similar changes in intracellular water and extracellular water compared to cooled haemodialysis

BACKGROUND/AIMS

Intradialytic hypotension is the most common complication of modern day haemodialysis (HD). Convective modalities, including haemodiafiltration (HDF) are reported to result in greater cardiovascular stability compared to standard HD, which has been suggested to be due to improved solute transport between compartments. We therefore investigated the effect of treatment on body water by bioimpedance.

METHODS

We measured the change in extracellular water (ECW) and intracellular water (ICW) in 263 outpatients attending for HD using cooled dialysate and 134 patients for HDF.

RESULTS

Patient cohorts were matched for demographics, dialysate composition, ultrafiltration rate, and session duration. The fall in systolic blood pressure following HD was -11.8 mm Hg (-25.3 to 2.3) and not different from that following HDF -12 mm Hg (-27 to 6). Similarly there were no differences in pretreatment serum sodium and dialysate sodium gradient [HD 1 mmol/l (-1 to 3) vs. HDF 2 mmol/l (1 to 4)], or change in serum sodium posttreatment [HD 0 mmol/l (-2 to 2) vs. HDF 1 mmol/l (-1 to 3)]. There were no differences in ICW or ECW pretreatment, and following treatment the reduction in ICW and ECW did not differ [ICW HD -3.5% (-5.7 to -1.8) vs. -4.1% (-6.0 to -1.7), ECW HD -7.1% (-9.4 to -4.7) vs. HDF -7.1% (-9.7 to -4.9)].

CONCLUSION

We were unable to demonstrate any advantage for HDF over HD using cooled dialysate in terms of changes in blood pressure during a treatment session, or differences in the relative changes in ICW or ECW volumes.

Is there a role for N-terminal probrain-type natriuretic peptide in determining volume status in haemodialysis patients?

BACKGROUND/AIMS

Natriuretic peptides have been reported to be a valuable biomarker for predicting cardiac events and mortality for haemodialysis patients. However, there has been a debate as to whether these biomarkers can be used to assess volume overload and help determine dry weight.

METHODS

We measured the N-terminal probrain natriuretic peptide (NTproBNP) in 366 stable haemodialysis outpatients with a corresponding pre- and post-dialysis multifrequency bioimpedance assessment of extracellular water (ECW)/total body water (TBW).

RESULTS

Median age was 61 years (46-73); 58.5% were male, 28.5% diabetic, and 37.7% Caucasoid; 71.1% had a history of hypertension, 8.4% of myocardial infarction, and 9.3% of coronary artery bypass surgery; dialysis vintage was 54 months (22-85.5), and urea reduction ratio was 73.4 ± 7.6%. Median post-dialysis NTproBNP was 179 pmol/l (68-535), pre-dialysis ECW/TBW was 0.393 ± 0.014, and post-dialysis ECW/TBW was 0.385 ± 0.015. On multivariate analysis log NTproBNP was associated with post-dialysis ECW/TBW (β 9.09, 95% CI 3.22-14.95, p = 0.003), mean arterial pressure (β 0.0087, 95% CI -0.0045 to -0.013, p = 0.000), and ultrafiltration rate (ml/kg · h; β 0.038, 95% CI 0.01-0.06, p = 0.001).

CONCLUSION

In this study postdialysis NTproBNP values were correlated with direct assessments of volume status in haemodialysis patients, i.e. by ECW/TBW, or indirect measures of volume overload, i.e. ultrafiltration rate and post-dialysis mean arterial blood pressure. This suggests that serial NTproBNP values may aid clinical assessments of volume status in dialysis patients.

Changes in upper limb extracellular water content during hemodialysis measured by multi-frequency bioimpedance

INTRODUCTION

Hemodialysis patients are at risk of chronic volume overload, with consequent increased cardiovascular morbidity and mortality. Multifrequency bioimpedance allows assessment of body fluid volumes. Devices vary from two paired electrodes which measure bioimpedance down one side of the body to four paired electrodes which measure both sides of the body. As arteriovenous fistulae may cause arm swelling, we investigated whether the presence of a fistula affected bioimpedance limb measurements. 


METHODS

We audited the change in extracellular water (ECW) and total body water (TBW) in the arms following hemodialysis in 414 adult patients attending for routine mid-week hemodialysis session 
by multifrequency bioimpedance using a four-paired electrode bioimpedance device (InBody 720; Biospace, Seoul, South Korea). 


RESULTS

Patients with right-sided brachial fistulae had a greater percentage ECW/TBW in the fistula arm both prior to and post dialysis compared to those dialyzing with catheters (pre 39.6 ± 3.5 vs. 38.4.3 ± 1.6 and post 38.5 ± 1.3 vs. 37.8 ± 1.1, p<0.01), but there was no difference in the ECW/TBW in the non-fistula arm, pre dialysis between those dialyzing with fistulae compared to catheters, but the ECW/TBW was greater post dialysis with both brachial (38.4 ± 1.1) and radial fistulae (38.1 ± 1.3) compared to those with catheters (37.7 ± 0.9, p<0.05 respectively). 


CONCLUSIONS

Although absolute and also relative extracellular fluid volumes are increased in the fistula arm of hemodialysis patients, particularly right-sided and with brachial fistulae, the amount of fluid is unlikely to be of clinical significance when making bioimpedance measurements in the non-fistula side of the body to determine volume status.

Does peritoneal dialysate affect body composition assessments using multi-frequency bioimpedance in peritoneal dialysis patients?

BACKGROUND/OBJECTIVES

Multi-frequency bioelectrical impedance analysis (MFBIA) is increasingly being used to assess peritoneal dialysis patients. Protein energy wasting (PEW) is a recognised complication of peritoneal dialysis. Although MFBIA can be used to assess body composition, measurements can be affected by fluid overload, and we wished to determine whether the presence of peritoneal dialysate in the peritoneal cavity equally could affect MFBIA-derived body composition assessments.

SUBJECTS/METHODS

Fifty consecutive adult patients had MFBIA made with 2l 22.7 g/l dextrose dialysate instilled into the peritoneal cavity and then after draining out.

RESULTS

When full, extracellular water (ECW) and the ratio of ECW to total body water (TBW) were greater compared with when empty: 13.9 ± 3.0l versus 13.4 ± 3.0, and 0.393 ± 0.01 versus 0.391 ± 0.01, P<0.001, respectively. Segmental ECW/TBW was only different for the trunk, 0.395 ± 0.01 full versus 0.392 ± 0.01 empty, P<0.0001. Body composition changed with a fall in skeletal muscle mass from 26.1 ± 6.3 to 25.2 ± 6.1 kg, P<0.001, and a smaller reduction in body fat from 19.3 ± 8.4 to 19.1 ± 8.0 kg, P=0.0104.

CONCLUSION

MFBIA measurements made in peritoneal dialysis patients with peritoneal dialysate instilled can overestimate body composition, including muscle mass, and as such potentially delay the recognition of PEW. Thus, for more accurate MFBIA in peritoneal dialysis patients, the dialysate should be drained out.

Changes in N-terminal pro-brain natriuretic peptide correlate with fluid volume changes assessed by bioimpedance in peritoneal dialysis patients

BACKGROUND/AIMS

Both brain natriuretic peptide (BNP) and volume overload are reported to be powerful predictors of survival for peritoneal dialysis patients. The usefulness of single BNP determinations in helping determine volume status in peritoneal dialysis patients remains controversial, so we reviewed serial BNP and multifrequency bioimpedance measurements to determine whether changes in BNP reflected changes in volume status.

METHODS

Prospective measurements of fluid volume by multifrequency bioimpedance and serum N-terminal pro-BNP (NTproBNP) were conducted in stable adult peritoneal dialysis outpatients attending for routine assessments of peritoneal dialysis adequacy and transport status.

RESULTS

A total of 189 serial measurements were made in 92 patients, and NTproBNP increased from a median of 162.5 pmol/l (interquartile range 82-385.4) to 195 pmol/l (interquartile range 101.9-348.6; p < 0.05). Changes in NTproBNP correlated with changes in extracellular water (ECW), total body water (TBW) and ECW/TBW (r = 0.38, 0.31 and 0.45, respectively; all p < 0.0001). Patients were divided into quartiles depending upon NTproBNP changes; those with the greatest fall in NTproBNP had significant falls in ECW (p < 0.001), TBW (p = 0.001) and ECW/TBW (p < 0.001) compared to the quartile with the greatest increase in NTproBNP, who also had an increase in systolic blood pressure from 133.5 ± 22.7 to 142.7 ± 28.8 mm Hg (p = 0.0078), whereas it fell in the quartile with the greatest fall in NTproBNP (143.8 ± 24.6 vs. 136.5 ± 18.7 mm Hg).

CONCLUSIONS

Serial measurements of NTproBNP correlated with changes in volume assessments made by multifrequency bioimpedance in peritoneal dialysis outpatients. As multifrequency bioimpedance measures total ECW, rather than effective plasma volume, serial NTproBNP determinations may prove an adjunct to the clinical assessment of volume status in peritoneal dialysis patients.

Comparison of volume status in asymptomatic haemodialysis and peritoneal dialysis outpatients

BACKGROUND

The majority of haemodialysis (HD) patients gain weight between dialysis sessions and thereby become volume overloaded, whereas peritoneal dialysis (PD) is a more continuous technique. Cardiovascular mortality and hypertension is increased with both treatment modalities. We therefore wished to compare volume status in PD and HD to determine whether PD patients are chronically volume overloaded, as a risk factor for cardiovascular mortality. Study Design, Setting and Participants:We retrospectively audited 72 healthy HD patients and 115 healthy PD patients attending a university hospital dialysis centre for routine outpatient treatment, who had multi-frequency bioimpedance measurements of extracellular water to total body water (ECW/TBW).

RESULTS

The groups were well matched for age, sex, weight and ethnicity, PD patients had greater urine output [1,075 (485-1,613) vs. 42.5 (0-1,020) ml/day, p < 0.001], but there was no difference in antihypertensive prescription (63.5 vs. 76.4%), mean arterial blood pressure (post-dialysis 101.6 ± 1.5 mm Hg vs. pre-dialysis 102 ± 2.4 mm Hg), although post-dialysis arterial blood pressure was lower than in PD patients (96.4 ± 3.1 mm Hg, p < 0.05). The ratio of ECW/TBW fell after HD (pre-dialysis 0.394 ± 0.001 vs. post-dialysis 0.389 ± 0.004, p < 0.001) and was similar in the PD group to the group before HD (0.393 ± 0.001), and greater than that in the group after HD (p < 0.001). ECW/TBW was greater than the normal reference range in 30% PD patients, 28% patients before HD and 20% patients after HD.

CONCLUSIONS

Overhydration is common in healthy stable PD outpatients, and ECW volumes in PD patients are not dissimilar to those of pre-dialysis HD patients. The role of chronic volume overload as a risk factor for cardiovascular disease needs further investigation.

Estimation of normal hydration in dialysis patients using whole body and calf bioimpedance analysis

Prescription of an appropriate dialysis target weight (dry weight) requires accurate evaluation of the degree of hydration. The aim of this study was to investigate whether a state of normal hydration (DW(cBIS)) as defined by calf bioimpedance spectroscopy (cBIS) and conventional whole body bioimpedance spectroscopy (wBIS) could be characterized in hemodialysis (HD) patients and normal subjects (NS). wBIS and cBIS were performed in 62 NS (33 m/29 f) and 30 HD patients (16 m/14 f) pre- and post-dialysis treatments to measure extracellular resistance and fluid volume (ECV) by the whole body and calf bioimpedance methods. Normalized calf resistivity (ρ(N)(,5)) was defined as resistivity at 5 kHz divided by the body mass index. The ratio of wECV to total body water (wECV/TBW) was calculated. Measurements were made at baseline (BL) and at DW(cBIS) following the progressive reduction of post-HD weight over successive dialysis treatments until the curve of calf extracellular resistance is flattened (stabilization) and the ρ(N)(,5) was in the range of NS. Blood pressures were measured pre- and post-HD treatment. ρ(N)(,5) in males and females differed significantly in NS. In patients, ρ(N)(,5) notably increased with progressive decrease in body weight, and systolic blood pressure significantly decreased pre- and post-HD between BL and DW(cBIS) respectively. Although wECV/TBW decreased between BL and DW(cBIS), the percentage of change in wECV/TBW was significantly less than that in ρ(N)(,5) (-5.21 ± 3.2% versus 28 ± 27%, p < 0.001). This establishes the use of ρ(N)(,5) as a new comparator allowing a clinician to incrementally monitor removal of extracellular fluid from patients over the course of dialysis treatments. The conventional whole body technique using wECV/TBW was less sensitive than the use of ρ(N)(,5) to measure differences in body hydration between BL and DW(cBIS).