This study is going to be conducted in accordance with the Helsinki Declaration and has been approved by Eskisehir Osmangazi University Ethics Committee. Forty consecutive patients, aged 18-65, who will undergo elective major abdominal operations will be enrolled in the study after obtaining informed consent. All patients will receive adequate postoperative pain management with the Pain Buster ® system and patient-controlled intravenous analgesia (PCA). The patients will be randomly assigned to either the experimental group or the control group. The control group will receive the usual care. The patients in the experimental group will be screened in the side-rooms where normally the patients who either have infections or are at risk of infection, are nursed. The study intervention will include dimming the lights to 40 lux and closing the doors of the side-room to decrease the noise level below 40 decibels (dB) between 11:00 p.m.-5:00 a.m.