P3.N261: Increased fluid intake can lower blood pressure in healthy children. The SPAII Project.

Background: Sodium (Na) intake is known to contribute to the development of hypertension, thus the reduction of its intake is a cornerstone in the prevention and management of hypertension. The increase in renal Na excretion might represent a further potential preventive and/or therapeutic opportunity.
The present study was aimed at exploring the working hypothesis that an increased fluid intake can decrease blood pressure (BP) in healthy children by increasing Na excretion.

Methods: The SPA Project is a multicenter, prospective, controlled, randomized study investigating if an increased fluid intake for 1 year can lower BP in healthy children. At baseline and again after 1 year, BP was determined by means of multiple office blood pressure measurements (mOBPM) and fluid intake was estimated by measuring urine dilution (mean urinary creatinine of different days). Subjects were randomized in 2 groups: one was actively motivated to drink more water than usual, particularly during school hours, while the other group served as control. Urinary Na and K were also measured.

Results: One hundred and seventy-five healthy children (89 females, 54.9%) with a median age of 8.6 years (IQR: 8.4-8.9) were enrolled but only 152 successfully completed the study (baseline and final mOBPM and coefficient of variation of BP less than 15%). Compared with controls, children addressed to introduce more fluids showed a lower systolic BP (-0.87 and -0.69 SDS; p: 0.07) and diastolic BP (+0.12 and +0.31 SDS; p: 0.02) at 12 mos. The recorded difference in SDS is equivalent to 1.7 and 2.4 mmHg on systolic and diastolic BP, respectively.

Conclusion: An increased fluid intake can lower BP. It is speculated that this is due to an increased efficiency in sodium handling (excretion) by kidneys. This simple, highly acceptable, inexpensive, and harmless measure might have a role in preventing and/or minimizing the epidemics of hypertension and of its related morbidities both in children and in adults.