The arrow of bioimpedance

Peritoneal-Membrane Characteristics and Hypervolemia Management in Peritoneal Dialysis: A Randomized Control Trial

Excessive bodily-fluid retention is the major cause of hypertension and congestive heart failure in patients with end-stage renal disease. Compared to hemodialysis, peritoneal dialysis (PD) uses the abdominal peritoneum as a semipermeable dialysis membrane, providing continuous therapy as natural kidneys, and having fewer hemodynamic changes. One major challenge of PD treatment is to determine the dry weight, especially considering that the speed of small solutes and fluid across the peritoneal membrane varies among individuals; considerable between-patient variability is expected in both solute transportation and ultrafiltration capacity. This study explores the influence of peritoneal-membrane characteristics in the hydration status in patients on PD. A randomized control trial compares the bioimpedance-assessed dry weight with clinical judgment alone. A high peritoneal membrane D/P ratio was associated with the extracellular/total body water ratio, dialysate protein loss, and poor nutritional status in patients on PD. After a six-month intervention, patients with monthly bioimpedance analysis (BIA) assistance had better fluid (−1.2 ± 0.4 vs. 0.1 ± 0.4 kg, p = 0.014) and blood-pressure (124.7 ± 2.7 vs. 136.8 ± 2.8 mmHg, p < 0.001) control; however, hydration status and blood pressure returned to the baseline after we prolonged BIA assistance to a 3-month interval. The dry-weight reduction process had no negative effect on residual renal function or peritoneal-membrane function. We concluded that peritoneal-membrane characteristics affect fluid and nutritional status in patients on PD, and BIA is a helpful objective technique for fluid assessment for PD.

The effect of "xanthan gum-based fluid thickener" on hydration, swallowing functions and nutritional status in total maxillectomy patients

PURPOSE

Swallowing functions are affected after total maxillectomy operations and adjuvant chemoradiotherapy. The purpose of our study is to assess the role of xanthan gum based thickening agents on swallowing and hydration of maxillectomy patients on a randomized controlled fashion.

METHODS

12 of the 22 patients diagnosed with maxillary carcinoma and planned to undergo total maxillectomy was identified as study group and 10 of them were identified as control group. The study group used "xantham based liquid thickener" for liquid foods up to 3 months postoperatively and the control group did not use. Dysphagia-related quality of life, bioimpedance analysis, EAT-10 scores, swallowing functions were evaluated both preoperative and postoperative period.

RESULTS

The mean age of the study group was 56 ± 9.87, and 41.6% were women. The mean age of control group was 60 ± 15.63, and 50% were women. Postoperative EAT-10 scores were statistically significant higher than preoperative scores in both groups (p < 0.05). In both of the study and control groups, a statistically significant reduction in dysphagia related quality of life was detected postoperatively (p < 0.05). Intracellular water, extracellular water and total body water detected statistically significant higher in study group at postoperative month three.

CONCLUSION

Swallowing functions are affected due to total maxillectomy and radiotherapy. With this study, it has been shown that, total maxillectomy and radiotherapy reduce dysphagia-related quality of life. Swallowing dysfunction and dehydration has been shown to affect total maxillectomy patients. Using of 'xanthan gum-based fluid thickener' helps to maintain intracellular water, extracellular water, and total body water.

Integration of Blood Volume, Blood Pressure, Heart Rate and Bioimpedance Monitoring for the Achievement of Optimal Dry Body Weight during Chronic Hemodialysis

Background

Achieving optimal dry body weight in hemodialysis is challenging. Clinical assessment alone is inadequate, and methods such as bioimpedance monitoring may be impractical for every patient treatment. Continuous blood volume monitoring, blood pressure and heart rate variability inform clinical decision-making, but integrated use of multiple methodologies to achieve dry weight and understand patient factors has not yet been described.

Methods

Nineteen chronic hemodialysis patients underwent thrice-weekly treatments for two weeks. Baseline hydration status and target weight were determined by bioimpedance. During subsequent treatments, ultrafiltration was adjusted and relative blood volume, blood pressure and pulse were recorded non-invasively Bioimpedance was repeated to assess hydration. Response of variables to progressive change in weight was assessed and selected patients underwent additional autonomic function testing.

Results

Four distinct hemodynamic patterns emerged. Profile A: 4 patients demonstrated overhydration at baseline. With decreasing target, pulse and blood pressure remained stable while blood volume and bioimpedance demonstrated achievement of dry weight. Profile B: 8 patients demonstrated overhydration at baseline. With decreasing target, blood pressure remained stable while pulse increased. Profile C: 5 patients were overhydrated, but as weight decreased, blood pressure became unstable and heart rate failed to compensate. Further testing confirmed autonomic dysfunction. Profile D: 2 patients were dehydrated, and with increasing target demonstrated stable pulse and pressure, while blood volume and bioimpedance revealed achievement of dry weight.

Conclusions

Integrating existing non-invasive, continuous monitoring during hemodialysis enabled achievement of dry weight and identified distinct profiles of the patients, some with autonomic dysfunction. This strategy may contribute to achieving optimum dry weight while improving cardiovascular tolerability of hemodialysis.

Extracellular fluid management and hypertension in urban dwelling versus rural dwelling hemodialysis patients

BACKGROUND

Rural-dwelling hemodialysis patients have less frequent contact with nephrologists than urban-dwelling patients, and are known to have higher mortality. We hypothesized that rural-dwelling hemodialysis patients would have more evidence of poorly controlled extracellular fluid volume (ECVF) than otherwise similar urban-dwellers.

METHODS

We studied prevalent hemodialysis patients within a single renal program in Alberta, Canada and assessed ECFV using bioimpedance spectroscopy (BIS). Our primary outcome was impedance vector length (ohm/m) as assessed by BIS using the Xitron Hydra 4200 device, where shorter vector length indicated poorer ECFV control. Because poor ECFV control can lead to hypertension, we also assessed pre- and post-dialysis blood pressure. We measured outcomes at baseline.

RESULTS

We studied 228 hemodialysis patients, of whom 115 (50.4 %) and 113 (49.6 %) were urban- and rural-dwelling, respectively. There were no differences in volume control in urban versus rural participants; odds ratio (OR) for vector length in the lowest sex-specific quartile of vector length was 0.93 (95 % CI 0.54, 1.59) after adjusting for age, sex, diabetic status, years since dialysis initiation and phase angle. The odds of very poor blood pressure control (pre-dialysis blood pressure ≥180/100) did not differ between urban and rural participants [fully adjusted OR 0.96 (0.36, 2.60)].

CONCLUSIONS

Differences in ECFV control do not appear to explain higher mortality among remote- and rural- dwelling hemodialysis patients, compared to urban-dwellers.

Impedance ratio: a novel marker and a powerful predictor of mortality in hemodialysis patients

PURPOSE

Impedance ratio (Imp-R) obtained by multifrequency bioimpedance analysis (BIA) has been shown to be associated with volume and nutrition status. In this prospective study, the predictive role of Imp-R for mortality in hemodialysis (HD) patients was investigated.

METHODS

Multifrequency (5-50-100-200 kHz) BIA was applied to 493 prevalent HD patients in March-April 2006. Imp-R was defined as the ratio of 200-5 kHz impedance values. Demographical, clinical and laboratory data at the time of the analysis were recorded. All-cause and cardiovascular (CV) mortality were assessed during 3 years of follow-up.

RESULTS

Mean age was 57.7 ± 13.9 years, HD duration 52.1 ± 42.6 months and prevalence of diabetes 21.7 %. Imp-R was negatively correlated with nutritional markers including albumin, creatinine and hemoglobin levels. In addition, there was a positive correlation between Imp-R and age, ratio of extracellular water to total body water and high-sensitive C-reactive protein. Over a mean follow-up period of 27.9 ± 11.1 months, 93 deaths (52 from CV reasons) were observed. In the multivariate analysis, Imp-R was significantly associated with all-cause and CV mortality after adjustments [HR 1.13, 95 % CI (1.04-1.23); p = 0.004 and HR 1.15, 95 % CI (1.03-1.27); p = 0.01, respectively]. The risk of all-cause mortality was 3.4 times higher in the fourth quartile of Imp-R (>83.5 %) compared to the first Imp-R quartile (<78.8 %) as reference. Cutoff value of Imp-R for all-cause mortality was 82.0 % with a sensitivity of 65.5 % and specificity of 64 %.

CONCLUSION

Impedance ratio measured by multifrequency in standardized conditions BIA is an independent and powerful predictor of both all-cause and CV mortality in hemodialysis patients.

Effects of three times weekly eight-hour nocturnal hemodialysis on volume and nutritional status

BACKGROUND

This prospective cohort study compared the changes in body water composition and nutritional parameters measured with multifrequency bioimpedance analysis between 8-hour three times weekly nocturnal hemodialysis (NHD) and 4-hour conventional hemodialysis (CHD) patients.

PATIENTS AND METHODS

55 patients on CHD and 57 patients on NHD were included in the study. Multifrequency bioimpedance analysis was performed at baseline and at the 12th month. The primary outcomes of the study were changes in extracellular water (ECW), fat mass, dry lean mass and phase angle. Secondary outcomes of the study included changes in blood pressure and biochemical parameters related to nutrition and inflammation.

RESULTS

ECW/height values decreased in the NHD group, while they increased in the CHD group. Fat mass, dry lean mass, and serum albumin increased and high sensitive CRP decreased in the NHD group but did not change in the CHD group. When changes in parameters from baseline to the 12th month between the groups were compared, NHD was associated with improvement in volume parameter including ECW/height (difference -0.44 l/m, p < 0.001). Change in blood pressure was not different between the groups, however requirement for antihypertensive medication decreased from 26.5 to 8.5% in the NHD group (p = 0.002). NHD was also associated with increases in fat mass (difference 1.8 kg, p < 0.001), dry lean mass (difference 0.6 kg, p = 0.006), serum albumin (difference 0.19 g/dl, p < 0.001) and cholesterol (difference 18.8 mg, p < 0.001). Phase angle values decreased in the CHD group but did not change in the NHD group (difference between the groups 0.37°, p = 0.04).

CONCLUSION

This study revealed that longer HD facilitates volume control and improves nutritional status.

Volume excess in chronic haemodialysis patients--effects of treatment frequency and treatment spacing

BACKGROUND

The main objective of this study was to theoretically quantify the fluctuations of fluid volume excess for different modes of intermittent ultrafiltration schedules and to compare the prediction for the typical and asymmetric thrice-weekly schedule to clinical, physiological and biophysical markers of volume expansion in a group of stable haemodialysis patients.

METHODS

Overall volume excess (V(OVE)) was described as the sum of a time-independent (V(0)) and a time-dependent component (V). An exact relationship was developed to relate V to variable treatment frequency, treatment spacing and net volume accumulation rate. In a single-centre haemodialysis population, body mass profiling was combined with volume state evaluation by bioimpedance analysis, N-terminal pro-B-type natriuretic peptide (NT-pro BNP) levels, clinical signs, a volume questionnaire and blood pressure levels.

RESULTS

In 23 patients following the typical thrice-weekly schedule, the time-averaged volume excess (V) during the whole week (1.1 ± 0.5 L) was significantly larger than that during the midweek interval (0.9 ± 0.4 L) (P < 0.002) by a factor comparable to that of 1.21 obtained from the theoretical analysis. V(OVE) was 1.3 ± 1.7 L and significantly related to pre- (P < 0.001) and post-dialysis levels of NT-pro BNP (P < 0.001).

CONCLUSION

Asymmetric treatment spacing such as with the typical thrice-weekly treatment schedule leads to a significant increase in time-averaged volume excess. The theoretical analysis allows for comparison of time-averaged volume excess in treatments varying with regard to treatment frequency and regularity and could be helpful to prescribe post-treatment volume (target weight) for such variable treatment modes.

Development and Validation of Bioimpedance Analysis Prediction Equations for Dry Weight in Hemodialysis Patients

BACKGROUND

Accurate assessment of hydration status and specification of dry weight (DW) are major problems in the clinical treatment of hemodialysis (HD) patients. Bioelectrical impedance analysis (BIA) has been recognized as a noninvasive and simple technique for the determination of DW in HD patients.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This study was designed to develop and validate BIA prediction equations for DW in HD patients. It included white adults (1540 disease-free adults with normal body mass index [BMI] and 456 prevalent and 27 incident HD patients). All participants underwent at least one single-frequency BIA measurement (800 muA and 50 kHz alternating sinusoidal current with a standard tetrapolar technique). The BIA variable measured was resistance (R). Data of 1463 (95% of the cohort) disease-free individuals with normal BMI (prediction sample) were used to establish best-fitting BIA prediction equations of body weight. The latter were cross-validated in the residual 5% subset (77 individuals) of the same cohort (validation sample).

RESULTS

Multiple regression analysis showed a significant relationship among body weight, R, age, and height in 739 men (R(2) = 0.82, P < 0.0001) and among body weight, R, and height in 724 women (R(2) = 0.68, P < 0.0001) in the prediction sample. The Bland Altman analysis showed a mean difference between predicted and measured body weight of 0.3 +/- 1.0 kg (95% confidence interval +/- 2.0 kg) in the validation sample. The BIA prediction equations that were obtained in disease-free individuals with normal BMI were applied to a cohort of 456 prevalent HD patients: The mean difference between achieved and estimated DW was 0.1 +/- 1.0 kg (P = 0.53) in men and -0.3 +/- 1.0 (P = 0.76) in women. Finally, BIA prediction equations were tested in a cohort of 27 incident HD patients. The mean difference between predicted and achieved DW was -0.6 +/- 1.0 kg (P = 0.76) in men and 0.6 +/- 1.0 (P = 0.50) in women.

CONCLUSIONS

This study was able to develop and validate BIA prediction equations for DW in HD patients. They seem to be a promising tool; however, they still need external validation.