Bioimpedance and brain natriuretic peptide in peritoneal dialysis patients

Assessment of ideal body weight in peritoneal dialysis (PD) patients is important for clinical practice. Fluid overload may produce hypertension, reduced arterial distensibility, left ventricular hypertrophy. All these are risk factors for mortality in PD patients: cardio- and cerebrovascular events are the main causes of morbidity and mortality in PD population. Nowadays, a clear and widely accepted definition of ideal body weight in PD patients does not exist. Probably the ideal body weight is the weight at which the extra cellular volume is normal. Many different tools have been used to assess the hydration status in dialysis patients. Ultrasonic evaluation of inferior vena cava diameter only assesses intravascular volume, and is also influenced by diastolic dysfunction and is thus a reflection of preload and not of tissue hydration. Direct measurement of extra cellular and total body water by dilution methods is considered as the golden standard, but these techniques are laborious and expensive. Parameters, such as brain natriuretic peptide (BNP) or NT-proBNP can reflect changes in hydration status and may help the nephrologist to estimate it. Natriuretic peptides are influenced both by preload and ventricular abnormalities and in patients with renal failure accumulation can occur. Bioimpedance is an accurate, reproducible, not expensive and not invasive technique that permits a good evaluation of hydration status in PD and can drive the nephrologist in his clinical choices. Clinical evaluation, strict control of body weight, diuresis, sodium and fluids intakes, bioimpedance monitoring and serum levels of natriuretic peptides may all together help us to maintain the PD patient euvolemic.