The effect of passive leg raising (PLR) test application on hemodynamic parameters in patients ventified with low tidal volume under general anesthesia

Aim: The primarily aim of the study is to suggest the specificity, sensitiviy, cutt-off values and effectiveness of the Passive Leg Raising (PLR) Test in predicting fluid responsiveness in patients ventilated with low tidal volume under general anesthesia and mechanical ventilation. Materials and methods: The study was completed with 38 patients following the approval of the Ethics Committee and informed consent of the patients. Patients' heart rate (KTA), mean arterial pressure (MAP), stroke volume (SV), stroke volume index (SVI) and stroke volume variation (SVV) values were recorded first time after general anesthesia induction - before PLR test, second time after 1st minute of PLR, third time 3 minutes after PLR in supine position and finally fouth time after 500 ml fluid loading. Patients whose SVI value increased more than 15% after fluid loading were defined as volume responses. Data received during PLR were re-evaluated in light of the volume responsiveness information obtained after fluid loading. Results: Seventeen (44%) patients were volume responder. After PLR test, increase percentage in SVI was 10.7 ± 3.9% and 5.5 ± 3.1% in responder and non-responder respectively (P<0.001). After fluid loading, the change percentage in SVI was 18.7 ± 3.1 % and 7.9 ± 5.5% in responders and non-responders, respectively. A positive correlation was found between increase percentage in SVI during PLR (Δ%SVIPLR) and increase percentage in SVI after fluid loading (Δ%SVISY) (p<0.001 R2 = 0.540). The area under ROC (receiver operating characteristics) curves generated to predict fluid responsiveness for increase percentage in SVI during PLR 0.832 (95% CI: 0.698 – 0.966), for PPV and SVV 0.723 (95% CI: 0.554-0.892) and 0.706 (95% CI: 0.539 – 0.873). The area under the ROC curve was similar between the PLR test and PPV and SVV. Best cut-off values of increase percentage in SVI during PLR was 8.3% with 82% sensitivity and 81% specificity. Conclusion: The percentage of SVI change occurring after PLR test performed in patients with low tidal volume under general anesthesia has higher specificity and sensitivity values than SVV and PPV with 82% sensitivity and 81% specificity at 8.3% cut-off value. Although not statistically different from SVV and PPV, the PLR test, which has higher sensitivity and specificity values, is a preferable method for evaluating fluid responsiveness in the clinic.