Comparing the effects of peripheral nerve block and general anesthesia with general anesthesia alone on postoperative delirium and complications in elderly patients: a retrospective cohort study using a nationwide database.

Introduction: The difference between the effects of peripheral nerve block (PNB) with general anesthesia (GA) and GA alone on the patients' postoperative clinical outcomes remains unknown. We assessed whether there is a difference in postoperative delirium and composite morbidity between patients receiving GA with PNB and GA alone using a national clinical database in Japan.

Methods: We compared the outcomes of patients receiving GA with PNB and GA alone from April 2016 to October 2019. The primary outcome was postoperative delirium, defined as a status requiring newly prescribed antipsychotic drugs or that given the code of a reimbursable disease after the surgery date. The secondary outcome was morbidity incidence as the occurrence of at least one of any of the following life-threatening complications. We conducted propensity score-matched analyses using covariates for patients who underwent any surgical procedure. We used instrumental variables and restricted the definition of postoperative delirium and subgroup for sensitivity analyses.

Results: Of 653,759 patients, 90,358 received GA-PNB and 563,401 received only GA. After 1:4 propensity score matching, 89,754 patients were included in the GA-PNB and 359,015 in the GA. The adjusted ORs for postoperative delirium and composite morbidity were 0.96 (95% CIs 0.94 to 0.99; p<0.01), 0.80 (95% CIs 0.76 to 0.83; p<0.001), respectively, for the GA-PNB concerning the GA. For sensitivity analyses, findings were also consistent with instrumental variables and subgroup analyses.

Discussion: This retrospective, nationwide cohort study demonstrated that GA-PNB was associated with a small reduction in the likelihood of postoperative delirium and a moderate reduction in the likelihood of composite morbidity.