Association of peripheral nerve block plus general anesthesia with MMSE-Defined early postoperative cognitive decline in older orthopedic patients: A prospective observational pilot study.

BackgroundPostoperative cognitive dysfunction (POCD) frequently affects older surgical patients. Neuroinflammation, anesthetic neurotoxicity, and impaired cerebral oxygenation contribute to its pathogenesis. Clinical evidence on combined peripheral nerve block plus general anesthesia for prevention of POCD remains limited and methodologically heterogeneous.ObjectivesTo explore whether adding peripheral nerve block to general anesthesia was associated with differences in POD7 MMSE-defined early postoperative cognitive decline, cognitive recovery trajectories, cerebral oxygenation, and perioperative biomarkers in older patients undergoing elective orthopedic surgery.MethodsThis prospective observational pilot study included 89 patients aged ≥65 years undergoing elective orthopedic surgery at a tertiary teaching hospital. Patients received general anesthesia alone (GA; n=49) or general anesthesia plus peripheral nerve block (GA+Block; n=40), according to routine clinician-selected anesthetic planning. Cognitive function was assessed using the Mini-Mental State Examination before surgery and through postoperative day 7. The primary endpoint was POD7 MMSE-defined early postoperative cognitive decline, defined pragmatically as a >2-point decrease from baseline MMSE. Secondary outcomes included MMSE recovery trajectories, regional cerebral oxygen saturation, and neuronal/stress biomarkers, including NSE, MBP, cortisol, and ACTH. Analyses included Fisher's exact test, Haldane-Anscombe correction, mixed-effects modelling, and exploratory sensitivity analyses.ResultsPOD7 MMSE-defined early postoperative cognitive decline occurred in 5/49 GA patients (10.2%) and 0/40 GA+Block patients. The absolute risk difference was -10.2 percentage points, but the primary comparison did not reach conventional statistical significance (Fisher exact p=0.062). The corrected relative risk was 0.11, with a wide 95% confidence interval (0.006-1.95). Cognitive recovery slopes were similar between groups (p=0.79). Cerebral oxygenation remained stable and comparable, and postoperative biomarker changes did not differ significantly.ConclusionFewer POD7 MMSE-defined early cognitive-decline events were observed with GA+Block than with GA alone. However, this non-randomized pilot study was underpowered, statistically imprecise, and hypothesis-generating only. Larger randomized multicenter studies are needed.