Pain Severity: pain will be assessed by the second anesthetist blinded to the study drug used. Pain score will be evaluated on arrival to recovery room (T0), 1, 2, 4, 6, 8, 12 and 24 hours using the FLACC pain scale (Face, Legs, Activity, Cry and Consolability scale). If FLACC score ≥ 3, IV nalbuphine 0.1 mg/kg will be given for supplemental analgesia.