Opioid-free anesthesia versus opioid-based anesthesia on postoperative delirium incidence: A systematic review
The use of opioids as anesthetic agents is associated with multiple adverse effects, such as delirium. Patients with postoperative delirium (POD) have a higher risk of mortality or major complications. Recently, a multimodal anesthetic technique known as opioid-free anesthesia (OFA) has been developed to minimize or eliminate the use of opioids during anesthesia, which is hypothesized to reduce the incidence of POD. This systematic review aims to compare OFA and opioid-based anesthesia (OBA) to the incidence of POD. Literature searches were conducted electronically without time restrictions across six databases: PubMed, Cochrane Central Register for Controlled Trials, ProQuest, ScienceDirect, Springer Nature, and PMC Europe. Additional studies were obtained through electronic searches on Google. The inclusion criteria were human studies involving participants aged ≥18 years, interventions of OFA and OBA, and POD as an outcome. Study selection was performed using Rayyan QCRI, and risk of bias was assessed using the Cochrane Risk of Bias 2 (RoB 2) and Risk of Bias in Non-randomized Studies - of Interventions (ROBINS-I). Six studies met the inclusion criteria; three randomized controlled trials (RCTs), two cohort studies, and one case-control study. Five studies demonstrated no significant difference in the incidence of POD between the OFA and OBA groups; one study reported no occurrence of POD in either group. Several factors influencing POD included advanced age, type and duration of surgery, and the pharmacological effects of anesthetic agents such as dexmedetomidine, lidocaine, midazolam, and regional analgesic agents. OFA has not been shown to clearly reduce the incidence of POD. The occurrence of POD is multifactorial.