Assessment of fluid and nutritional status using multifrequency bioelectrical impedance analysis in peritoneal dialysis patients

Bioimpedance spectroscopy: Is a picture worth a thousand words?

Volume status can be difficult to assess in dialysis patients. Peripheral edema, elevated venous pressure, lung crackles, and hypertension are taught as signs of fluid overload, but sensitivity and specificity are poor. Bioimpedance technology has evolved from early single frequency to multifrequency machines which apply spectroscopic analysis (BIS), modeling data to physics-based mixture theory. Bioimpedance plots can aid the evaluation of hydration status and body composition. The challenge remains how to use this information to manage dialysis populations, particularly as interventions to improve over hydration, sarcopenia, and adiposity are not without side effects. It is therefore of no surprise that validation studies for BIS use in peritoneal dialysis patients are limited, and results from clinical trials are inconsistent and conflicting. Despite these limitations, BIS has clinical utility with potential to accurately evaluate small changes in body tissue components. This article explains the information a BIS plot ("picture") can provide and how it can contribute to the overall clinical assessment of a patient. However, it remains the role of the clinician to integrate information and devise treatment strategies to optimize competing patient risks, fluid and nutrition status, effects of high glucose PD fluids on membrane function, and quality of life issues.

Comparison of hydration and nutritional status between young and elderly hemodialysis patients through bioimpedance analysis

Background

The number of elderly people on dialysis is increasing rapidly. Fluid overload and malnutrition status are serious problems in elderly dialysis patients. We aimed to compare the hydration and nutritional status through bioimpedance analysis (BIA) between young and elderly hemodialysis (HD) patients and to analyze risk factors related to fluid overload and malnutrition status in these patients.

Method

We conducted a cross-sectional study, in which 82 HD (males 42, mean age 58.7±12.9 years) patients were enrolled. We collected different types of data: laboratory data, such as serum creatinine, albumin, total iron-binding capacity, hemoglobin, total cholesterol; anthropometric data, such as hand grip strength (HGS); BIA data, such as intracellular water, skeletal muscle mass, body cell mass, bone mineral content, phase angle (PhA), extra cellular water (ECW)/total body water (TBW) ratio; and malnutrition-inflammation score (MIS), which is a traditional nutritional parameter for dialysis patients. All patients were stratified into two groups according to their age: young (<65 years [n=54]) and elderly (≥65 years [n=28]).

Results

Total iron-binding capacity and HGS were significantly lower in elderly HD patients than in young HD patients (198.9±35.6 vs 221.4±52.1 mcg/dL; and 22.4±10.3 vs 36.4±23.2 kg, respectively) (P<0.05). Also, intracellular water and PhA measured by BIA were significantly lower (18.3±4.0 vs 20.3±4.2 L [P=0.043]; and 4.0±1.0 vs 4.9±1.2° [P=0.002], respectively), and ECW/TBW were higher in elderly HD patients (0.40±0.01 vs 0.39±0.01 [P=0.001]). ECW/TBW was positively associated with age (P<0.001) and the presence of diabetes (P<0.001) and was negatively associated with sex (P=0.001), albumin (P<0.001), urine volume (P=0.042), HGS (P<0.001), and PhA by BIA (P<0.001). MIS was negatively related to sex (P=0.001), albumin (P<0.001), HGS (P=0.001), and PhA (P<0.001) in HD patients. On multivariate analysis, older age (P=0.031), the presence of diabetes (P=0.035), and decreased PhA (P<0.001) were independent risk factors for increased ECW/TBW, representative of fluid overload status, whereas only decreased PhA (P=0.008) was a significant factor for MIS, representative of malnutrition status in these HD patients.

Conclusion

We found that fluid overload and malnutrition status were more common in elderly HD patients compared with young HD patients. PhA was a significant independent factor in fluid overload status and malnutrition in these HD patients. Thus, our results indicated that PhA assessed by BIA might be a clinically useful method for assessing nutritional and hydration status in elderly HD patients.

Improved Effect of Continuous Renal Replacement Therapy in Metabolic Status and Body Composition of Early Phase of Acute Pancreatitis

Objective

To observe the metabolic changes in the early phase of acute pancreatitis (AP) patients induced by continuous renal replacement therapy (CRRT), and to investigate the correlation between the metabolic changes and outcomes of the AP patients.

Methods

We performed a retrospective analysis in the surgical intensive care unit (ICU) of a tertiary teaching hospital. A total of 169 patients diagnosed as AP were divided into 2 groups: CRRT group (n = 71) and non-CRRT group (n = 98), based on whether they received CRRT for more than 24 hours within 7 days from onset of AP. Measured energy expenditure was measured by indirect calorimetry and predicted energy expenditure was determined by specific equations on admission and day 7 (or the closest day to day 7), respectively. Meanwhile, the body composition was measured by multiple-frequency bioelectrical impedance analyzer. Blood test, body weight and vital signs were analyzed daily for both groups.

Results

In this study, we found a significant improvement in the hypermetabolism and fluid distribution of the CRRT group compared with the non-CRRT group. Complications, hospital and ICU length of stays were reduced in CRRT patients.

Conclusions

CRRT is an effective treatment for AP patients. Patients with overhydration and hypermetabolism may get improved outcomes from CRRT.

Control of fluid balance guided by body composition monitoring in patients on peritoneal dialysis (COMPASS): study protocol for a randomized controlled trial

Background

The clinical benefits of bioimpedance spectroscopy (BIS)-guided fluid management in patients on hemodialysis have been widely demonstrated. However, no previous reports have evaluated the effect of regular and serial BIS-guided fluid management on the residual renal function (RRF) in patients on peritoneal dialysis (PD). Therefore, we will evaluate the clinical efficacy of BIS-guided fluid management for preserving RRF and protecting cardiovascular events in patients on PD.

Methods/design

This is a multicenter, prospective, randomized controlled trial. A total of 138 participants on PD will be enrolled and randomly assigned to receive either BIS-guided fluid management or fluid management based only on the clinical information for 1 year. The primary outcome is the change in the glomerular filtration rate (GFR) between months 0 and 12 after starting treatment. The secondary outcomes will include GFR at month 12, time to the anuric state (urine volume <100 ml/day), and fatal and nonfatal cardiovascular events during treatment.

Discussion

This is the first clinical trial to investigate the effect of BIS-guided fluid management on RRF and for protecting against cardiovascular events in patients on PD.

Trial registration

Clinical Trials.gov number NCT01887262, June 24, 2013.