CONGRESS ABSTRACT

The passive leg raising (PLR) manoeuvre is an accepted method for assessing fluid responsiveness without the risks associated with direct fluid infusion. The present study aimed to investigate whether two consecutive PLR manoeuvres could influence fluid response, measured in terms of the diameter and collapsibility of the inferior vena cava (IVC). A cohort of thirteen healthy subjects (five men and eight women, age of 27 ± 9.5 years) participated. The assessment of each manoeuvre was structured around three key events: the pre-manoeuvre (baseline) state, the PLR interventions, and the immediate post-manoeuvre assessments. To evaluate the hemodynamic changes associated with the PLR, segmentation of the IVC was conducted utilizing specialized software developed by VIPER s.r.l. This segmentation process enabled the detailed analysis of various parameters indicative of the hemodynamic behaviour, including IVC diameter and caval index (CI). During the first manoeuvre, the mean diameter of the IVC, averaged over all subjects, was observed to increase from a baseline measurement of 14.4 ± 4.7 mm to 16.6 ± 4.1 mm during PLR. Coming back to the initial posture, there was a subsequent decrease in the IVC diameter to 14.9 ± 5.1 mm. The CI decreased from 0.35 ± 0.13 (baseline) to 0.26 ± 0.01 (PLR phase), before returning to 0.34 ± 0.12 upon removing the manoeuvre. In the second manoeuvre, the initial mean IVC diameter, between all subjects, was 13.7 ± 5.0 mm. This measurement increased significantly to 16.8 ± 5.3 mm during the PLR phase, followed by a reduction to 13.3 ± 4.4 mm afterward. The CI decreased from 0.33 ± 0.13 to 0.26 ± 0.01 during PLR, with a subsequent recovery to 0.34 ± 0.13 post-manoeuvre. Two-sample t-tests revealed significant differences between parameters measured during both PLR manoeuvres and their respective baseline values, as well as between measurements taken immediately following the manoeuvres. However, no significant differences were identified between parameters recorded during the two PLR manoeuvres themselves. In conclusion, these findings suggest that the PLR manoeuvre does not induce physiological adaptation, reinforcing its status as a consistent and reliable assessment tool.