1. Department of Anesthesiology, Edgardo Rebagliati Martins National Hospital, Lima, Peru
2. Department of Medicine, School of Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru,
3. Clínica Del Dolor, Instituto Nacional de Cancerología, Mexico City, Mexico,
4. Department of Anesthesiology-Critical Care and Pain Medicine, Virgen Macarena University Hospital, Seville, Spain,