Throughout the induction of anaesthesia and the surgery, standard monitoring procedures were utilised to pay close attention to the vital parameters such as non-invasive arterial pressure (BP), heart rate (HR), standard electrocardiography (ECG) II, arterial oxygen saturation (SaO2), fraction of inspired oxygen in the gas mixture (FiO2), facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), exhaled carbon dioxide concentration (etCO2), minimal alveolar concentration of sevoflurane (MAC).