This study investigates whether two simple bedside tests - the Passive Leg Raising (PLR) test and the Pleth Variability Index (PVI) - can predict a drop in blood pressure that sometimes occurs during a lung-opening procedure called an Alveolar Recruitment Maneuver (ARM).
ARM is routinely performed during general anesthesia to prevent lung collapse and improve oxygen levels. However, in some patients - particularly those with low fluid levels - ARM can cause a temporary but significant drop in blood pressure (hypotension), which may require immediate treatment.
In this prospective observational study, adult patients scheduled for elective non-cardiac, non-thoracic surgery under general anesthesia will be enrolled. Before each ARM is performed, PLR test and PVI values will be measured. We will then evaluate how well these measurements predict whether the patient will develop ARM-induced hypotension.
If PLR and PVI can reliably identify patients at risk, clinicians may be able to take preventive steps before performing ARM, making the procedure safer for vulnerable patients.
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Single group
Alveolar Recruitment Maneuver (ARM)
DeviceARM is performed using a stepwise increase in positive end-expiratory pressure (PEEP) in pressure-controlled ventilation mode until peak inspiratory pressure reaches 40 cmH₂O, then stepwise decrease back to baseline. Hemodynamic parameters are continuously monitored throughout the maneuver.
Passive Leg Raising (PLR) Test
BehavioralWith the patient in supine position under general anesthesia, both legs are raised to 45 degrees for 60 seconds. The change in mean arterial pressure (ΔMAP) is recorded as an indicator of preload responsiveness. The test is performed immediately before each ARM.
Prediction of ARM-Induced Hypotension by PLR Test and PVI
Area under the ROC curve (AUC) of pre-ARM passive leg raising test (PLR-ΔMAP) for predicting ARM-induced hypotension (defined as MAP decrease ≥20% from baseline or MAP \<65 mmHg during ARM).
AUC of PVI for Predicting ARM-Induced Hypotension
Area under the ROC curve (AUC) of pre-ARM pleth variability index (PVI) for predicting ARM-induced hypotension (defined as MAP decrease ≥20% from baseline or MAP \<65 mmHg during ARM)
Correlation Between ARM-Induced ΔMAP% and Post-ARM Fluid Responsiveness
Pearson or Spearman correlation coefficient between the maximum MAP decrease during ARM (ΔMAP%) and fluid responsiveness after ARM. Fluid responsiveness is defined as MAP increase ≥10% following 250 mL crystalloid bolus.
Comparative Diagnostic Accuracy of PLR Test versus PVI for Predicting ARM-Induced Hypotension
The difference in AUC values between PLR-ΔMAP and PVI will be compared using the DeLong method.
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