A ward-based procedure for assessment of fluid status in peritoneal dialysis patients using bioimpedance spectroscopy

This study was carried out to evaluate a procedure for converting bioimpedance spectroscopy (BIS) data to a clinically useful measure of fluid status that is easily interpreted by nursing staff and patients.

The ratio of extracellular water (ECW) to total body water (TBW) in a cohort of peritoneal dialysis (PD) patients was compared with the distribution for normal control subjects. The result was expressed as the difference between the measured ECW/TBW ratio and the mean ratio for age- and sex-matched controls divided by the standard deviation for the controls (the "hydration score"). Where possible, interventions were made to reduce the target weight in patients with a hydration score greater than +2.0.

This clinical study was carried out in the nurse-led outpatient PD unit at St. James's University Hospital. BIS measurements were carried out during routine clinic visits. The data for the control subjects were obtained in a range of settings in the UK and the Czech Republic.

31 PD patients (21 M, 10 F; aged 19 - 78 years) who came to the PD unit for routine procedures during the study participated.

The mean hydration score for PD patients was significantly higher than for the control subjects (+1.3 vs 0.0, p < 0.0001). 11 (35%) patients had a hydration score greater than +2.0, compared with only 2.5% of the controls; systolic blood pressure was greater than 130 mmHg in only two of these patients. After a 3-month follow-up, a weight reduction of 3.6 +/- 2.3 kg had been achieved in 7 patients through modality change and implementation of prescription changes, with no adverse effects.

Although this was a small study, all the data collected indicated that the hydration score provides a reliable indication of fluid status in PD patients. BIS measurements are now carried out at 6-month intervals and are used to monitor the effect of interventions.