Relationship between bioimpedance-determined body composition and peritoneal transport in peritoneal dialysis

PURPOSE

In peritoneal dialysis (PD) patients, body fluid homeostasis is dependent on peritoneal elimination of water and solutes. Patients with less favorable peritoneal transport parameters should be more overhydrated. Despite this, the association between faster transport and overhydration (OH) is weak, and the factors that influence hydration status are still poorly characterized. Modified peritoneal equilibration tests (PET) offer us new parameters that might correlate better with hydration status, like free water transport (FWT). The aim of this study was thus to establish the relationships between new peritoneal transport parameters and body composition parameters estimated by bioimpedance spectroscopy (BIS).

METHODS

Prospective observational study on incident PD patients with a baseline and 1-year follow-up evaluation.

RESULTS

61 patients were included in the baseline evaluation, 19 of whom had a 1-year follow-up evaluation; 67.2% were fluid overloaded. There was a negative correlation between D/P creatinine and FWT (r = -0.598, p = 0.000). The fraction of FWT was negatively correlated with OH (r = -0.302, p = 0.018). Peritoneal protein losses (PPL) were also correlated with OH (r = 0.287, p = 0.028). There were no significant differences in OH according to small-solute transport status or fluid output parameters. After 1 year, we observed a significant worsening of renal function and an improvement in 24-hour ultrafiltration (UF) and hydration status, but we detected no differences in peritoneal transport of water or solutes that could explain these changes.

CONCLUSIONS

There is a poor relationship between kidney/peritoneal function parameters and body composition parameters. The fraction of FWT and PPL may be underestimated markers of peritoneal health and of its contribution to the hydration status.

Extracellular volume expansion and the preservation of residual renal function in Korean peritoneal dialysis patients: a long-term follow up study

INTRODUCTION

In chronic peritoneal dialysis patients, preservation of residual renal function (RRF) is a major determinant of patient survival, and maintaining sufficient intravascular volume has been hypothesized to be beneficial for the preservation of RRF. The present study aimed to test this hypothesis using multifrequency bioimpedence analyzer (MFBIA), in Korean peritoneal dialysis patients.

METHODS

A total of 129 patients were enrolled in this study. The baseline MFBIA was checked, and the patients were divided into the following two groups: group 1, extracellular water per total body water (ECW/TBW) < median, group 2, ECW/TBW > median. We followed up the patients, and then we analyzed the changes in the urine output (UO) and the solute clearance (weekly uKt/V) in each group. Data associated with patient and technical survivor were collected by medical chart review. The volume measurement was made using Inbody S20 equipment (Biospace, Seoul, Korea). We excluded the anuric patients at baseline.

RESULT

The median value of ECW/TBW was 0.396. The mean patient age was 49.74 ± 10.01 years, and 62.1 % of the patients were male; most of the patients were on continuous ambulatory peritoneal dialysis (89.1 %). The mean dialysis vintage was 26.20 ± 28.71 months. All of the patients were prescribed hypertensive medication, and 48.5 % of the patients had diabetes. After 25.47 ± 6.86 months of follow up, ΔUO and Δweekly Kt/V were not significantly different in the two groups as follows: ΔUO (-236.07 ± 185.15 in group 1 vs -212.21 ± 381.14 in group 2, p = 0.756); Δ weekly Kt/v (-0.23 ± 0.43 in group 1 vs -0.29 ± 0.49 in group 2, p = 0.461). The patient and technical survivor rate was inferior in the group 2, and in the multivariable analysis, initial hypervolemia was an independent factor that predicts both of the patient mortality [HR 1.001 (1.001-1.086), p = 0.047] and the technical failure [HR 1.024 (1.001-1.048), p = 0.042].

CONCLUSIONS

Extracellular volume expansion, measured by MFBIA, does not help preserve residual renal function, and is harmful for the technical and patient survival in Korean peritoneal dialysis patients.

Pneumatic compression devices during hemodialysis: a randomized crossover trial

BACKGROUND

Maintenance of central blood volume (CBV) is essential for hemodynamic stability during hemodialysis (HD), though preservation of CBV is poorly understood. Pneumatic compression devices (PCDs) during HD may help maintain CBV.

METHODS

We performed a randomized, crossover trial to determine the effect of PCDs on CBV during HD. Patients underwent two consecutive mid-week HD sessions, randomized to begin the first session either with or without PCDs [stratified by intradialytic hypotension (IDH)-prone status]. The primary outcome was change in CBV during HD. The secondary outcomes were change in other hemodynamic and volume status parameters.

RESULTS

Fifty-one patients (median age 65 years, 75% male, 22% IDH-prone) were randomized; forty-six completed the study. During HD, the median change in CBV for PCD and control sessions was -0.08 versus -0.05 L (P = 0.62). There was no difference in the change in cardiac output (CO) (-0.63 versus -0.49 L/min, P = 0.78) or systemic vascular resistance (SVR) (+1.30 versus +1.55 mmHg/L/min, P = 0.67) for PCDs versus control. Based on the bioimpedance measurements, patients were not volume overloaded pre-dialysis. There was a greater reduction in total body water (TBW) (-2.6 versus -2.3 L, P = 0.05) and intracellular fluid (ICF) volume (-1.3 versus -1.1 L, P = 0.03), and no difference in change in the extracellular fluid (ECF) volume (1.3 versus 1.2 L, P = 0.09) with PCDs versus control. Similar results were observed in IDH-prone patients.

CONCLUSIONS

Compared with standard of care, PCDs have no effect on intradialytic hemodynamic parameters, including CBV, although they may allow greater capacity for fluid removal. Further studies are required to better understand physiological and hemodynamic changes in patients during HD.

Assessment of fluid status in CAPD patients using the body composition monitor

AIMS AND OBJECTIVES

To assess the degree of overhydration in our peritoneal dialysis patients and to examine the factors contributing to overhydration.

BACKGROUND

Volume control is critical for the success of peritoneal dialysis, but dry weight has been difficult to ascertain accurately. Chronic fluid overload and hypertension are among the leading causes of mortality in dialysis patients.

DESIGN

A cross-sectional observational study.

METHODS

The body composition monitor (Fresenius Medical Care, Bad Homburg, Germany) is a bioimpedance spectroscopy device that has been validated for the assessment of overhydration. We used this body composition monitor device on all patients on continuous ambulatory peritoneal dialysis at our institution who met the inclusion criteria to assess their degree of overhydration.

RESULTS

Thirty four (17 men, 17 women; mean age 44·5 ± 14·2 years) of a 45 continuous ambulatory peritoneal dialysis patients were enrolled. The mean overhydration was 2·4 ± 2·4 l. Fifty per cent of the patients were ≥2 l overhydrated. Overhydration correlated with male gender, low serum albumin, increasing number of antihypertensive agents and duration of dialysis. There was no difference in overhydration between diabetic and non-diabetic patients. Men were more overhydrated than women, had lower Kt/V and were older. Although, there was no difference in blood pressure between the genders, men had a trend towards a higher usage of antihypertensive agents.

CONCLUSION

Our study demonstrates that overhydration is common in peritoneal dialysis patients. Blood pressure should ideally be controlled with adherence to dry weight and low salt intake rather than adding antihypertensive agents even in the absence of clinical oedema.

RELEVANCE TO CLINICAL PRACTICE

Body composition monitor is a simple, reliable and inexpensive tool that can be routinely used in the outpatient clinic setting or home visit to adjust the dry weight and avoid chronic fluid overload in between nephrologists review.

The Stoke contribution to peritoneal dialysis research

The Stoke Renal Unit has been at the forefront of peritoneal dialysis (PD) research for much of the past two decades. Central to this work is the PD cohort study, which was started in 1990 and is based on regular outpatient measurements of peritoneal and clinical function, correlating these with long-term outcomes. It has provided a wealth of information on risk factors for morbidity and mortality in patients on PD, the most significant being demonstration of the effects of time and dialysate glucose exposure on changes to the peritoneal membrane, as evidenced by increases in small solute transport. Early on, the study confirmed the adverse relationship between high small-solute transport status and outcome but more recently suggested that this relationship no longer held with modern techniques for managing patients on PD. Central themes of the PD research in Stoke have included evaluation of euvolemia, the importance of ultrafiltration and how best to achieve it, and detailed assessments of transmembrane water movement. The work has included the study of sodium removal and the use of novel low sodium dialysates. More recently, attention has turned to the significance of impaired ultrafiltration capacity in patients on PD as a sign of structural membrane damage. It is hoped that further work in this area will identify preventive strategies.

Fluid status in peritoneal dialysis patients: the European Body Composition Monitoring (EuroBCM) study cohort

BACKGROUND

Euvolemia is an important adequacy parameter in peritoneal dialysis (PD) patients. However, accurate tools to evaluate volume status in clinical practice and data on volume status in PD patients as compared to healthy population, and the associated factors, have not been available so far.

METHODS

We used a bio-impedance spectroscopy device, the Body Composition Monitor (BCM) to assess volume status in a cross-sectional cohort of prevalent PD patients in different European countries. The results were compared to an age and gender matched healthy population.

RESULTS

Only 40% out of 639 patients from 28 centres in 6 countries were normovolemic. Severe fluid overload was present in 25.2%. There was a wide scatter in the relation between blood pressure and volume status. In a multivariate analysis in the subgroup of patients from countries with unrestricted availability of all PD modalities and fluid types, older age, male gender, lower serum albumin, lower BMI, diabetes, higher systolic blood pressure, and use of at least one exchange per day with the highest hypertonic glucose were associated with higher relative tissue hydration. Neither urinary output nor ultrafiltration, PD fluid type or PD modality were retained in the model (total R² of the model = 0.57).

CONCLUSIONS

The EuroBCM study demonstrates some interesting issues regarding volume status in PD. As in HD patients, hypervolemia is a frequent condition in PD patients and blood pressure can be a misleading clinical tool to evaluate volume status. To monitor fluid balance, not only fluid output but also dietary input should be considered. Close monitoring of volume status, a correct dialysis prescription adapted to the needs of the patient and dietary measures seem to be warranted to avoid hypervolemia.

Body composition, hydration, and related parameters in hemodialysis versus peritoneal dialysis patients

AIMS

Maintaining euvolemia is an important goal in patients on renal replacement therapy. However, adequate assessment of volume status in clinical practice is hampered by a lack of accurate measuring tools. A new multifrequency bioimpedance tool has recently been validated. This study compares volume status in peritoneal dialysis (PD) and hemodialysis (HD) patients in a single center.

METHODS

Body Composition Monitoring (BCM; Fresenius Medical Care, Bad Homburg, Germany) was performed in all patients on PD or HD without contraindication. PD patients were measured with a full abdomen; HD patients were measured at the midweek session, once immediately before and once 20 minutes after dialysis. Clinical overhydration was defined as an overhydration-to-extracellular water ratio of >0.15.

RESULTS

Total body water, extracellular water, and intracellular water were 33.7 +/- 6.9 L versus 31.8 +/- 8.1 L vs 33.9 +/- 6.7 L, 16.4 +/- 3.9 L vs 15.3 +/- 4.9 L vs 16.8 +/- 3.3 L, and 17.1 +/- 6.2 L vs 16.5 +/- 4.6 L vs 17.2 +/- 3.9 L in the pre-HD, post-HD, and PD patients, respectively (p = NS). In the pre-HD and the PD patients, overhydration was 1.9 +/- 1.7 L and 2.1 +/- 2.3 L, whereas post-HD this was only 0.6 +/- 1.7 L (p < 0.001). Clinical overhydration was more prevalent in pre-HD and PD patients compared to post-HD patients (24.1% vs 22.3% vs 10%, p < 0.001). In multivariate models, overhydration was related to age, male gender, and post-HD status.

CONCLUSION

Although much clinical attention is paid to volume status, 24% of patients still have clinically relevant volume overload. Implementation of a reliable and clinically applicable tool to assess volume status is therefore necessary. It is possible to obtain comparable volume status in PD and HD patients.