ONSD According to the Position During Laparoscopy

"Anesthesia with desflurane in both Group 1 and Group 2~\- adjust MAC to maintain BIS between 40-60"

"Adjuvant continuous administration~\- adjust effect site concentration to maintain changes of vital sign below 20%"

Patients were placed in the supine position with their eyes closed, and a thick gel layer was applied to the closed upper eyelid. The 7.5-MHz linear probe was placed on the gel without excessive pressure and adjusted to the proper angle for displaying the entry of the optic nerve into the globe. The intensity of the ultrasound was adjusted to display optimal contrast between the retrobulbar echogenic fat tissue and the vertical hypoechoic band. An ultrasound beam was focused on the retrobulbar area (4 cm deep) using the lowest possible acoustic power that could measure ONSD. The ONSD was measured 3 mm behind the optic disc. Measurements were performed in the transverse and sagittal planes of both eyes, and the final ONSD value was calculated by averaging 4 measured values.

After tracheal intubation, the lungs of the patients were then ventilated with oxygen in air (1:2) using a tidal volume of 8-10 mL/kg and a respiratory rate of 10-12/min, and the ventilation rate was adjusted to maintain the end-tidal carbon dioxide partial pressure between 35 and 40 mmHg and peak inspiratory pressure below 30 cmH2O.

Trendelenburg position - 30 degree

Reverse Trendelenburg position - 30 degree