Methods
postoperative pain
Sixty-six patients were enrolled and randomly allocated into three groups: group B1 (butorphanol 0.03 mg/kg), group B2 (butorphanol 0.04 mg/kg) and group N (control group). The primary outcome was postoperative pain scores evaluated by a Visual Analogue Scale (VAS) at 2 h (T1), 8 h (T2), 24 h (T3) and 48 h (T4) after surgery. Secondary outcome was postoperative sleep quality measured using Subjective Sleep Quality Value (SSQV).