TY  - JOUR 
T1  - Safety and effectiveness of adding fentanyl or sufentanil to spinal anesthesia: systematic review and meta-analysis of randomized controlled trials
JO  - Brazilian Journal of Anesthesiology
A1  - Fonseca, Neuber Martins
A1  - Guimarães, Gabriel Magalhães Nunes
A1  - Pontes, João Paulo Jordão
A1  - Azi, Liana Maria Tores de Araujo
A1  - de Ávila Oliveira, Ricardo
SN  - 2352-2291
UL  - 10.1016/j.bjane.2021.10.010
VL  - 73 
Y1  - 2023
PB  - Brasil 
ER  -