Patients posted for surgeries requiring general anaesthesia lasting more than 2 hours with endotracheal intubation belonging to the age group of 18-65 years are selected for this study and will be divided into two separate groups, group A and group B consisting of 45 participants each.

The patient will be preoxygenated with a face mask, using 100% oxygen for 3 min followed by intravenous (IV) fentanyl (2 mcg/kg) and propofol (2 mg/kg) for anaesthesia induction. After the loss of consciousness, IV rocuronium (1 mg/kg) will be administered for attaining adequate muscle relaxation. Direct laryngoscopy and endotracheal intubation will be performed by an experienced anaesthesiologist using an appropriately sized endotracheal tube after 1 minute of rocuronium administration.  General anaesthesia is maintained with oxygen, air and sevoflurane to ensure a BIS level of 40–60. Adequate muscle relaxation is ensured during surgery using bolus doses of rocuronium by observing the TOF count.

In both groups, sevoflurane is used intraoperatively as an inhalation anaesthetic to maintain adequate depth of anaesthesia. Patients in Group-A will receive sevoflurane until the end of surgery, while those in Group B will be switched to desflurane 30 minutes before the end of surgery. 

At the end of the surgery, residual neuromuscular blockade will be reversed using IV sugammadex (2-4mg/kg) after assessing TOF count.

The eye-opening time will be measured at 10-s intervals from the point when sevoflurane or desflurane is stopped at the end of the surgery until the patient first open their eyes after verbal instructions from the anaesthesiologist. BIS at the time of eye opening is recorded. The time to removal of endotracheal tube and the time to reach BIS 80 after stopping sevoflurane and desflurane are also noted.