Intraoperative use of methadone improves control of postoperative pain in morbidly obese patients: a randomized controlled study - Machado, Felipe Chiodini; Palmeira, Claudia Carneiro de Araujo; Torres, Joao Nathanael Lima; Vieira, Joaquim Edson; Ashmawi, Hazem Adel (Journal of pain research, 2018)