Effects of dehydration on the Inferior Vena Cava

Currently, the hydration status of human subjects is assessed through either invasive techniques, e.g. the blood sample analysis or time-consuming laboratory methods such as the analysis of urine. The aim of this study is to assess, with ultrasound, whether the diameter and the pulsatility of the inferior venca cava (IVC) can use as indicators of the hydration status. The pulsatility is expressed by the caval index (CI), which is the variation of the diameter in relation to the maximum one. The parameters were extracted with VIPER s.r.l. software using longitudinal section ultrasound videos of IVC. The software automatically tracks the IVC, allowing for parameter extraction from each frame. An experimental protocol was designed to induce dehydration in the participants through physical activity by 10-minute walk repeated for five times. Ultrasound images and weight were taken at the beginning of the protocol and after each trial, approximately in 3 minutes. Finally, participants were rehydrated, and the hydration status was assessed through ecographic imaging conducted at 2, 4, and 6 minutes later. The sample consisted of 37 healthy subjects (18 females and 19 males), aged 24.24 ± 1.92 years. The results show a significant decrease in the diameter (&#8710;D) after 50 minutes of activity in comparison to the initial diameter (&#8710;D = 2.02 mm, p-value < 0.02) and a significant increase during the rehydration phase (&#8710;D = 1.86 mm, p-value < 0.03). No notable differences were identified in the caval index between the baseline and the 50-minute post-activity measurement (p-value = 0.93). Furthermore to verify whether the results were not the consequence of possible acquisition errors by the operator, an evaluation of both inter-operator repeatability and software was performed, resulting in a standard deviation = 0.94 mmand an ICC (Intraclass Correlation Coefficient) > 0.9.