Modified Passive Leg-Raising Maneuver to Predict Fluid Responsiveness by Transthoracic Ultrasound Guidance in Healthy...

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.

Prospective laboratory study.

University teaching hospital.

Eight healthy Landrace pigs.

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.

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).

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.