Intrathecal morphine use in total knee arthroplasty in patients over 50 years old.: A single-center experimental study. Actas Médicas (Ecuador), [S. l.], v. 33, n. 1, p. 27–31, 2023. DOI: 10.61284/59. Disponível em: https://actasmedicas.ec/index.php/am/article/view/59.. Acesso em: 30 may. 2026.