Dynamic Preload Dependence Indices in Laparoscopic Surgery

The measurements of pulse pressure variation, plethysmographic waveform of pulse oximetry variation and stroke volume variation will be performed before pneumoperitoneum at the beginning of the surgery, and will be repeated after pneumoperitoneum insufflation applying each time modification of preload conditions (applying reverse Trendelenburg position followed by Trendelenburg position). The responses will be appreciated by the measurements of the stroke volume.