Sodium and potassium levels in hypertensive children

In a baseline survey of 4,936 school children aged 6-16 years, 199 children with systolic blood pressure (SBP) values equal or greater than the 95-th percentiles for age and sex were chosen as the hypertensive group (HBP), and were matched for age and sex with 197 children with SBP from the 5-th through the 50-th percentiles as the control (normotensive) group (NBP). For both groups the intra-RBC and plasma sodium and potassium contents, 8-hour night urinary sodium, potassium and creatinine excretions for three days, and an oral saline-water load test were performed. The results show that (1) intra-RBC potassium level in the HBP was lower than that in NBP. The level in those with positive hypertension family history (FH+) was lower than that with negatives (FH-). The intra-RBC potassium contents correlated inversely with diastolic BP. No correlation between intra-RBC sodium and BP was found; (2) Plasma sodium concentration in HBP was much lower than that in NBP. No difference was found between the FH+ and FH- in the plasma sodium concentrations; (3) Mean 8-hour night urinary potassium excretion expressed as mmol/g creatinine, was lower in HBP than in NBP; (4) After the saline load test the 4-hour urinary sodium excretion was significantly higher in HBP. Of those children with FH- the 4-hour sodium excretion in HBP was higher than that in NBP, but no significant difference was found between HBP and NBP of the FH+ children in the 4-hour urinary sodium excretions.(ABSTRACT TRUNCATED AT 250 WORDS)