Brain natriuretic peptide and impedance cardiography to assess volume status in peritoneal dialysis patients

Assessment of volume status in patients with end-stage renal disease has long been a problem. Objective tools for estimating dry weight are necessary. The present study was designed to determine if better assessment of volume status could be achieved by measuring brain natriuretic peptide (BNP) and thoracic fluid content (TFC) by bioimpedance. We prospectively surveyed 51 medically stable peritoneal dialysis (PD) patients during their routine visits to our PD facility. There were no exclusion criteria. Clinical volume status was assessed by the attending nephrologist as hypovolemic, euvolemic, or hypervolemic. Once the clinical assessment was complete, plasma BNP concentration was measured. The TFC was determined by bioimpedance cardiography measured in the supine position. Of 51 patients, 19 (37.3%) were considered hypervolemic, 30 (58.8%) euvolemic, and 3 (5.9%) hypovolemic by clinical assessment. As defined by systolic blood pressure > or = 130 mmHg or diastolic pressure > or = 80 mmHg (or both), 57% were hypertensive. The hypovolemic group was excluded from the statistical analysis because of the small sample size. Logistic regression analysis did not show a significant correlation between clinical assessment of volume and BNP (p = 0.76) or TFC (p = 0.39). Our data demonstrate the limitations of BNP and thoracic impedance in helping with the clinical evaluation of volume status in a cohort of chronic PD patients.