Mild dehydration and atrial natriuretic peptide in young and elderly subjects

Atrial natriuretic Peptide in young and elderly children with mild gastroenteritis

Objective. Atrial Natriuretic Peptide (ANP) has natriuretic and diuretic effects, synthesized and stored in the atrial cells, released in response to stretch of the atrial muscle during increase venous return. Acute gastroenteritis (AGE) causes dehydration. We intend to determine whether the decrease in venous return due to dehydration would lead to a decrease in ANP levels. Patients and Methods. This is a prospective observational controlled study. Blood collected from 30 children with AGE and ANP's levels were compared with 25 controls. ANP levels were determined by radioimmunoassay. Results. The study group was in mild dehydration. As a significant difference was found in ANP levels between children in the 3mo–3y group and older children 3y–14y. We analyzed the results according to age. No difference was found between children with AGE and control, in the 3mo–3y, ANP was 12.1 ± 11 pg/ml versus 13.4 ± 12 pg/ml respectively, and 3 ± 2 versus 3.8 ± 3 pg/ml in the 3y–14y groups, respectively. Conclusion. Dehydration due to AGE does not change the ANP's plasma levels. A weak positive correlation between sodium levels and ANP was found r = 0.29. The significant finding of our study is the difference in ANP levels related to age, in the control as well as the GE group.

24-h hydration status: parameters, epidemiology and recommendations

Hydration of individuals and groups is characterised by comparing actual urine osmolality (Uosm) with maximum Uosm. Data of actual, maximum and minimum Uosm in infants, children and adults and its major influencing factors are reviewed. There are remarkable ontogenetic, individual and cultural differences in Uosm. In the foetus and the breast-fed infant Uosm is much lower than plasma osmolality, whereas in children and adults it is usually much higher. Individuals and groups may show long-term differences in Uosm. In industrialised countries, the gender difference of Uosm is common. There are large intercultural differences of mean 24-h Uosm ranging from 860 mosm/kg in Germany, 649 mosm/kg in USA to 392 mosm/kg in Poland. A new physiologically based concept called 'free-water reserve' quantifies differences in 24-h euhydration. In 189 boys of the DONALD Study aged 4.0-6.9 y, median urine volume was 497 ml/24-h and median Uosm 809 mosm/kg. Considering mean-2 s.d. of actual maximum 24-h Uosm of 830 mosm/kg as upper level of euhydration and physiological criterion of adequate hydration in these boys, median free-water reserve was 11 ml/24-h. Based on median total water intake of 1310 ml/24-h and the third percentile of free-water volume of -156 ml/24-h, adequate total water intake was 1466 ml/24-h or 1.01 ml/kcal. Data of Uosm in 24-h urine samples and corresponding free-water reserve values of homogeneous groups of healthy subjects from all over the world might be useful parameters in epidemiology to investigate the health effects of different levels of 24-h euhydration.