The adjustment of post-dialysis dry weight based on non-invasive measurements in children.

BACKGROUND: The clinical criteria to assess hydration status are not always reliable. Hence, the development of techniques to estimate more accurately post-dialysis dry weight (DW) remains a major challenge. The present study evaluates the value of the inferior vena cava (IVC) diameter, plasma concentration of atrial natriuretic peptide (ANP), and plasma renin activity (PRA) in determining the DW in chronic haemodialysis children.

METHODS: Twelve overhydrated haemodialysis patients (4 girls, 8 boys) with a mean age of 12.8 were admitted to the study. Clinical, electrocardiographic, telecardiographic and echocardiographic findings, IVC and collapsibility indices and plasma concentrations of ANP and PRA were investigated before and after ultrafiltration (UF) therapy. Twelve age-matched normal children were studied as controls. Analysis of variance and Dunnett's test were applied for comparisons between patients and controls.

RESULTS: Following UF therapy the patients' mean IVC collapsibility index was increased from 42.3 to 53.6% and IVC index was decreased from 1.08 to 0.81 cm/m2, both statistically significant. The pre-UF therapy collapsibility and IVC indices of the patient group were significantly different from those of the control group (56.9% and 0.70 cm/m2 respectively). The patients' mean plasma concentrations of ANP were 171 +/- 47.4 pg/ml before UF, 129 +/- 51.3 pg/ml after UF and 102 +/- 38.7 pg/ml in the control group. The ANP levels of the patients showed a significant decrease following the UF therapy. PRA was measured as 0.82 ng/ml/h before UF and 1.08 ng/ml/h after UF, but the increase was not statistically significant.

CONCLUSIONS: Our findings revealed increased diameter of the IVC and plasma ANP concentrations and decreased collapsibility due to overhydration. Echography of IVC may be a promising non-invasive tool to estimate the DW in haemodialysis children. Further studies providing normative values for the IVC indices in both haemodialysis and normal children are required.