Fluid balance in patients with chronic renal failure assessed with N-terminal proatrial natriuretic peptide, atrial natriuretic peptide and ultrasonography

The N-terminal proatrial natriuretic peptide (proANP) has become an importa nt parameter for assessing the prognosis of patients with cardiac disease. Its use for evaluating the hydration status in patients with chronic renal failure, however, is still under investigation. The present study comprised 12 haemodialysis (HD) and 17 pre-dialysis patients. In the HD patients, th e inferior vena cava diameter during quiet expiration (IVCe) was estimated by ultrasonography and plasma concentrations of N-terminal proANP, atrial n atriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) were mea sured before and 4 h after termination of HD. In the pre-dialysis patients venous blood samples were taken during rest to measure plasma N-terminal pr oANP and ANP and serum creatinine. Normal values for N-terminal proANP and ANP were obtained from 18 healthy volunteers. The plasma concentrations of N-terminal proANP and ANP in healthy volunteers were 328 +/- 92 and 11.4.0 +/- 3.1 pM L-1, respectively. In pre-dialysis patients, serum creatinine ra nged from 110 to 447 muM L-1 and was significantly correlated to plasma N-t erminal proANP (r=0.60, P < 0.05) but not to ANP. This may indicate that N- terminal proANP is more dependent on renal function for its clearance than ANP, which is probably cleared by extrarenal mechanisms as well. In HD pati ents, IVCe was significantly correlated to the three hormones before HD, mo st strongly to N-terminal proANP. After dialysis, IVCe was significantly co rrelated to ANP and cGMP but was not correlated to N-terminal proANP. This may suggest that proANP takes a longer time than other hormones to reflect changes in intravascular volume. In conclusion, N-terminal proANP is a horm one closely related to degree of renal function. Furthermore, it is a sensi tive marker reflecting the interdialytic hydration status in HD patients, a s indicated by its high correlation to IVCe, a standard method which is use d frequently nowadays to assess the body hydration. However N-terminal proA NP could not reflect the acute changes in fluid volume induced by HD, proba bly because it is slowly metabolized.