Feasibility of subarachnoid combined with monitoring anesthesia care for unilateral biportal endoscopic decompression in elderly with lumbar spinal stenosis:A Propensity-Matched Analysis

Technical Summary: Feasibility of Subarachnoid Combined with Monitoring Anesthesia Care for Unilateral Biportal Endoscopic Decompression in Elderly Patients

Problem Statement
Unilateral biportal endoscopy (UBE) has emerged as a minimally invasive standard for treating lumbar spinal stenosis (LSS) in elderly patients. However, the optimal anesthetic protocol remains a subject of debate. General anesthesia (GA) carries risks of intraoperative nerve root injury and higher medical costs, while regional anesthesia alone (specifically subarachnoid anesthesia, SA) may fail to provide adequate muscle relaxation or sedation, leading to intraoperative pain, patient movement, and hemodynamic instability (tachycardia/hypertension). These factors can compromise surgical field clarity, increase surgical risk, and exacerbate postoperative complications such as delirium in the elderly. The study addresses the need for an anesthetic strategy that balances surgical conditions with patient safety and enhanced recovery.

Methodology
This single-center, retrospective cohort study analyzed 248 elderly patients (≥65 years) undergoing UBE for LSS between June 2024 and June 2025. Patients were divided into two groups: those receiving Subarachnoid Anesthesia (SA) alone (n=124) and those receiving SA combined with Monitored Anesthesia Care (SA+MAC) (n=124).

• Propensity Score Matching (PSM): To mitigate selection bias, a 1:1 nearest-neighbor PSM was performed (caliper 0.2) using covariates including age, gender, ASA classification, preoperative hemodynamics, and comorbidities (hypertension, diabetes). This resulted in 98 matched patients per group.
• Anesthetic Protocols:
  • SA Group: Received hyperbaric 0.5% ropivacaine (11 mg) and fentanyl (25 µg) via L3-4 or L4-5 puncture.
  • SA+MAC Group: Received the same SA block followed by continuous intravenous dexmedetomidine (loading 0.5 µg/kg over 10 min, maintenance 0.2–0.5 µg/kg/h) and low-dose fentanyl. Sedation depth was titrated to maintain a Modified Observer's Assessment of Alertness/Sedation (MOAA/S) score of 3–4 and a Bispectral Index (BIS) between 65–80.
• Outcome Measures:
  • Primary Efficacy: Surgical field clarity (Modified Leiden scale, 1–5) tested for non-inferiority (margin Δ = -0.5).
  • Secondary Outcomes: Perioperative hemodynamics (HR, BP, incidence of severe hypotension), objective motor block (Train-of-Four/TOF monitoring), postoperative delirium (3D-CAM), patient and surgeon satisfaction, and complication rates.
  • Statistical Analysis: Bonferroni correction was applied for multiple comparisons (α = 0.01). Non-inferiority testing was conducted for the primary outcome.

Key Contributions
The study introduces a combined anesthetic approach (SA+MAC) specifically tailored for elderly UBE patients, distinguishing itself by:

1. Objective Motor Assessment: Utilizing TOF monitoring to quantitatively confirm that the addition of MAC does not alter the depth or duration of motor blockade compared to SA alone.
2. Delirium Prevention: Focusing on the incidence of postoperative delirium as a critical outcome in the elderly, utilizing the high-sensitivity 3D-CAM tool.
3. Hemodynamic Stability: Isolating the circulatory benefits of dexmedetomidine-based sedation within a purely spinal anesthetic framework, rather than comparing against general anesthesia.

Results
After PSM, baseline characteristics were well-balanced (SMD < 0.2).

• Surgical Field Quality: The SA+MAC group demonstrated superior surgical field clarity (mean score 3.77 vs. 3.44, p < 0.001). Non-inferiority was confirmed, with the lower bound of the 95% CI (0.40) exceeding the pre-specified margin (-0.5), indicating statistical superiority over SA alone.
• Hemodynamics: The SA+MAC group exhibited more stable intraoperative heart rates and blood pressures. The incidence of severe hypotension requiring vasopressors was significantly lower in the SA+MAC group (7.1% vs. 23.5%, p_adj = 0.002).
• Motor Block: TOF monitoring showed comparable objective motor block intensity between groups (lowest TOF ratio 28% vs. 31%, p = 0.29), confirming that MAC did not induce additional paralysis.
• Postoperative Delirium: The incidence of delirium was significantly lower in the SA+MAC group (3.1% vs. 12.2%, p = 0.004 after Bonferroni correction).
• Satisfaction and Complications: Patient satisfaction (88.9% vs. 70.66%) and surgeon satisfaction (92.3% vs. 70.8%) were significantly higher in the SA+MAC group. The total severe complication rate was lower in the SA+MAC group (4.1% vs. 14.3%, p = 0.005).
• Functional Outcomes: Both groups showed significant improvement in VAS and ODI scores at 3 months, with no significant difference between groups.

Significance and Claims
The authors conclude that combining subarachnoid anesthesia with MAC is a feasible and safe anesthetic option for elderly patients undergoing UBE. The study claims that this protocol offers a synergistic effect, providing:

• Better surgical conditions (clarity and stability) without compromising motor function.
• Enhanced hemodynamic stability, likely due to the central sympatholytic effects of dexmedetomidine.
• A significant reduction in postoperative delirium.
• Higher satisfaction rates for both patients and surgeons.

The paper posits that this combined protocol represents a cost-effective, patient-centered enhancement to perioperative care. However, the authors maintain a modest tone regarding the generalizability of these findings, acknowledging the study's retrospective, single-center design and the need for prospective, multicenter randomized trials to confirm the results before universal recommendation.