@article{fonseca_guimarães_pontes_azi_de ávila oliveira_2023,  title={Safety and effectiveness of adding fentanyl or sufentanil to spinal anesthesia: systematic review and meta-analysis of randomized controlled trials},  volume={73},  ISSN={2352-2291},  url={https://doi.org/10.1016/j.bjane.2021.10.010},  DOI={10.1016/j.bjane.2021.10.010},  number={2},  journal={Brazilian Journal of Anesthesiology},  publisher={Sociedade Brasileira de Anestesiologia (SBA)},  author={Fonseca, Neuber Martins and Guimarães, Gabriel Magalhães Nunes and Pontes, João Paulo Jordão and Azi, Liana Maria Tores de Araujo and de Ávila Oliveira, Ricardo},  year={2023},  month={Mar},  pages={198–216} }