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.