Abstract
<title>Abstract</title> <p> <bold>Background:</bold> Unilateral biportal endoscopy (UBE) has become a minimally invasive and effective decompression treatment for the elderly with lumbar spinal stenosis (LSS). Commonly used general anesthesia protocol poses a higher risk for some elderly patients. We propose a combined subarachnoid anesthesia (SA) and monitoring anesthesia care (MAC) approach to reduce perioperative risks for elderly and provide benefits to the surgeons. <bold>Methods:</bold> This single‑center retrospective cohort study enrolled 248 elderly patients (≥65 years) undergoing UBE for LSS between June 2024 and June 2025. Patients received either SA (n=124) or SA+MAC (n=124). After 1:1 propensity score matching (PSM, caliper 0.2), 98 patients per group were successfully matched. Perioperative hemodynamics, surgical field quality (modified Leiden scale), train‑of‑four (TOF) monitoring for objective motor block assessment (both groups), BIS monitoring for sedation depth (SA+MAC group), postoperative delirium assessed by 3‑Minute Diagnostic Interview for CAM (3D‑CAM),as well as patient and surgeon satisfaction were compared. Bonferroni correction was applied for multiple comparisons. Non‑inferiority testing (margin Δ=0.5 for surgical field score) was performed for the primary efficacy outcome. VAS and ODI were evaluated preoperatively and at 3 months. <bold>Result:</bold> After PSM, both groups (n=98 each) were well balanced (all SMD<0.2). Both achieved significant VAS/ODI improvements (p<0.001). SA+MAC showed more stable perioperative hemodynamics (p<0.01 after Bonferroni) and superior surgical field visibility (p<0.05). Non‑inferiority was confirmed (mean difference 0.53, 95% CI 0.40–0.66, lower bound > –0.5). TOF‑derived lowest motor ratio was comparable (28%±13% vs 31%±14%, p=0.29), confirming similar objective motor block. BIS values in SA+MAC were maintained at 72±7 (target 65–80). The incidence of postoperative delirium (3D‑CAM positive) was significantly lower in SA+MAC (3.1% vs 12.2%, p=0.004 after Bonferroni). Patient satisfaction (93.9% vs 67.3%, p<0.001) and surgeon satisfaction (95.9% vs 70.4%, p<0.001) were higher in SA+MAC. Total severe complication rates were lower in SA+MAC (4.1% vs 14.3%, p=0.005). <bold>Conclusion:</bold> SA combined with MAC provides better surgical conditions, higher doctor-patient satisfaction, more stable hemodynamics, delirium prevention, and less postoperative pain in elderly patients undergoing UBE. This protocol is a feasible and safe anesthetic option without comparison to general anesthesia. </p>