Modified Passive Leg‐Raising Maneuver to Predict Fluid Responsiveness by Transthoracic Ultrasound Guidance in Healthy Pigs Under Sevoflurane Anesthesia

ABSTRACT Objective To evaluate whether the velocity–time integral of aortic blood flow (VTI Ao ) assessed by transthoracic echocardiography is increased after the passive leg‐raising maneuver (PLRM) in anesthetized and mechanically ventilated, fluid‐responder pigs. Design Prospective laboratory study. Setting University teaching hospital. Animals Eight healthy Landrace pigs. Interventions Pigs were anesthetized, mechanically ventilated, and subjected to the PLRM. Ultrasound‐guided VTI Ao measurements were compared before and after the PLRM to assess changes. A fluid challenge was then performed, and changes in VTI Ao were assessed again to classify pigs as fluid responders or nonresponders. Measurements and Main Results Seven of the eight animals were responders, and one was a nonresponder. After the PLRM, fluid responders exhibited an increase in VTI Ao compared with baseline ( p = 0.017). An optimal cutoff of 11.2% for changes in ultrasound‐guided VTI Ao was calculated for predicting fluid responsiveness after the PLRM, with an area under the receiver operating characteristic curve of 1.00 (95% confidence interval [CI]: not estimated), sensitivity of 100% (95% CI: 59–100), specificity of 100% (95% CI: 2.5–100), positive predictive value of 100% (95% CI: 59–100), and negative predictive value of 100% (95% CI: 2.5–100). Conclusions Despite limitations, this study demonstrates the potential of using ultrasound‐guided VTI Ao measurements associated with the PLRM to predict fluid responsiveness in anesthetized pigs. An ultrasound‐guided VTI Ao cutoff of ≥11.2% could serve as a reference for identifying fluid‐responsive pigs under anesthesia and mechanical ventilation, and offer a noninvasive alternative to fluid challenges.