Comparison of oral water ingestion and intravenous fluid infusion on fluid responsiveness in healthy volunteers, a prospective, randomized trial

The primary goal of fluid therapy is to optimize cardiac output in preload-dependent patients. However, all types of fluid solutions can have side effects. Oral water intake regulates fluid absorption, leading to an appropriate adaption of volemia. The study aimed to compare intravenous fluid challenge versus oral fluid challenge on fluid responsiveness. We conducted a prospective, randomized, open-label, single-center study on healthy volunteers aged between 18 and 30 years from April 2022 to May 2022. The intervention consisted of administering 500 ml of intravenous 0.9% sodium chloride over 5 min or 500 ml of oral water intake over 5 min according to the group allocation. After ethical approval, healthy subjects were randomized into two groups (“oral water” or “saline” group). The main endpoint was the rate of fluid responsiveness at 30 min after the end of fluid administration. Fluid responsiveness was defined by a 15% increase in stroke volume (SV) after the intervention. Sixty subjects were randomly assigned to either the “oral water” group (n = 30) or the “saline” group (n = 30). The fluid responsiveness rate did not differ significantly between the saline group (16.7%) and the oral water group (26.7%): absolute risk difference 10.0 percentage points (95% CI − 10.7 to + 30.7), p = 0.35. Within the responders, the temporal pattern of stroke volume increase differed between groups. In young, healthy volunteers, no statistically significant difference was detected in the proportion of fluid responders between the two groups (“saline” and “oral water” groups). Clinical trial identifier: NCT05153837.