Background and Objectives: The Pleth Variability Index (PVI) is a noninvasive dynamic parameter to assess fluid responsiveness. It is often utilised in the perioperative period for goal-directed fluid therapy and is believed to be superior to static parameters. This study aims to demonstrate the impact of fasting on baseline and passive leg raising (PLR)-induced changes in PVI in healthy volunteers. This challenges the conventional thinking of substituting fluid for the duration of fasting before a surgical procedure.
Methods: Forty healthy adult volunteers were enrolled and divided into: Group 1 (n = 20, fasted overnight) and Group 2 (n = 20, fed). PVI was recorded using a Masimo Radical-7® Pulse CO-Oximeter® in two scenarios: baseline in the supine position (PVI 1) and post-PLR (PVI 2). The difference between PVI 1 and PVI 2 was calculated. Patient demographics were noted, and a comparative analysis between the groups was performed. Statistical significance was set at p < 0.05.
Results: The mean PVI 1 in Group 1 was significantly higher (26.6 ± 3.2) compared to Group 2 (18.2 ± 2.8), p = 0.0016. Similarly, the mean PVI 2 was significantly higher in Group 1 (20.9 ± 2.9) than in Group 2 (13.9 ± 2.3), p = 0.0012. The PLR-induced changes in PVI were more pronounced in Group 1, indicating greater fluid responsiveness in the fasted state. Box-and-whisker plots demonstrated clear distinctions between the groups.
Conclusion: Fasting significantly impacts PVI readings, with higher baseline and post-PLR values observed in fasted individuals. This underscores the importance of interpreting PVI measurements for fluid responsiveness assessment. Responsiveness does not often translate to deficit.