Efeitos da ingestão de água sobre o sistema nervoso autônomo

Abstract

The water intake is associated with changes in the autonomic nervous system (ANS) specifically in parasympathetic branch. However, the actual hemodynamic and autonomic changes in the SNA are not well established, as well as the optimum amount of water intake to reflect changes. For this purpose, two studies were developed: an original study in order to compare the effect of sudden intake of 250 and 500 mL of water on the initial transient heart rate (TIFC), heart rate variability (HRV) and heart rate rest (resting HR) in young healthy subjects, and the other, in order to verify through a systematic review, the effects of water intake on SNA and hemodynamic variables in adults. In the first, they evaluated 26 men, aged between 18 and 30 years undergoing two days of evaluation with 24-hour interval. The protocol consisted of the intake 250 or 500 mL of water, in random order. To assess the TIFC in dynamic exercise we used the cardiac vagal index (CVI) obtained through the 4-second exercise test in the pre and post-ingestion (5, 10, 20 and 30 minutes). To evaluate the autonomic modulation at home was used HRV for 30 minutes after ingestion, which was also recorded HR rest. After 5 minutes the water intake there was an increased TIFC (p = 0.02), with no difference in function of the ingested volumes of water (p = 0.8). HRV there was no difference between the intake volumes in both the time domain and the frequency domain. Regarding HR at rest, there were differences after 20 minutes when compared to other times (p <0.05). These results show that there was no difference in TIFC, HRV and HR at rest when compared to intake were 250 and 500 ml of water at room temperature in healthy individuals. However, TIFC and the resting HR demonstrated difference between the analyzed moments. The second study examined only controlled and randomized clinical trials (RCTs) published between 2000 and 2015 in the MedLine database. It was used for the preparation of this review the systematization PRISMA. They were part of the review 10 RCTs involving 246 volunteers aged 19-64 years, 35% male. Changes commonly observed were: increased cardiac vagal activity, decreased heart rate, and increased peripheral vascular resistance as well as conflicting results regarding blood pressure.