Background

Posterior lumbar interbody fusion surgery (PLIF), a conventional open surgical approach for treating lumbar degenerative diseases1, is associated with significant tissue trauma and severe postoperative pain2. Inadequate acute pain management may substantially impede rehabilitation progress. Within this context, enhanced recovery after surgery (ERAS) protocols demonstrate unique advantages through evidence-based perioperative strategies, particularly in minimizing surgical stress and complications. The anesthesiology-led multimodal analgesia system plays a pivotal role, extending beyond intraoperative management to actively mitigate postoperative pain and facilitate recovery3. While traditional opioid-based analgesia provides potent pain relief, it carries dose-dependent adverse effects, including nausea, constipation, ileus, delirium, pruritus, respiratory depression, and pulmonary infections. Of particular concern is the risk of persistent opioid use disorder with prolonged postoperative administration4. These limitations underscore the critical need for alternative analgesic strategies in spinal surgery.

The innovation of ultrasound-guided regional anesthesia has provided novel solutions in this domain. Erector spinae plane block (ESPB), first described by Forero et al.5, involves depositing a local anesthetic between the erector spinae muscle and the tip of the transverse process. This fascial plane technique achieves analgesia through local anesthetic diffusion within interfascial compartments. Owing to its technical feasibility, adequate postoperative analgesia, and a favorable safety profile, ESPB has expanded clinical applications beyond thoracic procedures to include abdominal and spinal surgeries, significantly enhancing recovery outcomes6,7,8. Anatomic studies utilizing cadaveric dissections and MRI9,10,11 have confirmed the mechanism of action of ESPB through the blockade of dorsal rami and sinuvertebral nerve branches, substantiating its efficacy in posterior spinal surgery analgesia.

Ultrasound-guided quadratus lumborum block at the lateral supra-arcuate ligament (QLB-LSAL) is a regional anesthesia technique that utilizes sonographic identification of the lateral supra-arcuate ligament and quadratus lumborum muscle to deposit local anesthetic into the interfascial compartment between the diaphragm and quadratus lumborum muscle. Bypassing the lateral supra-arcuate ligament barrier, local anesthetic dispersion into the inferior thoracic paravertebral space is facilitated, achieving comprehensive somatic/visceral analgesia coverage12. Characterized by technical accessibility, radiation-free implementation, and a favorable safety profile, QLB-LSAL enables real-time visualization of injectate spread for dynamic dose/needle adjustment. Its clinical efficacy extends to abdominal and pelvic surgeries13,14, demonstrating opioid-sparing effects comparable to those of epidural techniques while mitigating the risks associated with neuraxial interventions.

While both regional techniques are well-established in thoracic and abdominal surgeries, comparative evidence in lumbar surgery remains critically underexplored. This double-blind randomized controlled trial systematically evaluated QLB-LSAL versus the ESPB in posterior lumbar surgery through a standardized multimodal assessment framework.

Methods

Design

This prospective randomized controlled clinical trial was conducted in accordance with the Declaration of Helsinki and reported following the CONSORT guidelines. The protocol received ethical approval from the Medical Ethics Committee of The People’s Hospital of Guangxi Zhuang Autonomous Region (Approval No: KY-IIT-2024-33) and was prospectively registered at the Chinese Clinical Trial Registry (Registration No.: ChiCTR2400084870, accessible at https://www.chictr.org.cn/showproj.html?proj=229297).

This single-center randomized controlled trial, which was conducted at The People’s Hospital of Guangxi Zhuang Autonomous Region from May to August 2024, enrolled 96 patients who underwent initial posterior lumbar interbody fusion after obtaining written informed consent.

Subjects

Inclusion criteria.

  1. 1.

    Age 25–70 years;

  2. 2.

    BMI 18–30 kg/m²;

  3. 3.

    American Society of Anesthesiologists (ASA) Class II -III;

  4. 4.

    Intact communication capacity for pain assessment via the Visual Analog Scale (VAS);

  5. 5.

    Anticipated surgical duration < 4 h;

  6. 6.

    PLIF involving 1–3 vertebral segments;

  7. 7.

    Voluntary participation with signed consent.

Exclusion criteria.

  1. 1.

    BMI ≥ 30 kg/m²15;

  2. 2.

    Body weight < 30 kg/>100 kg;

  3. 3.

    Intracranial hypertension or cerebrovascular accident history;

  4. 4.

    Chronic corticosteroid/analgesic use (> 3 months) or ropivacaine hypersensitivity;

  5. 5.

    Coagulopathy or active anticoagulation;

  6. 6.

    Hypovolemia, heart failure, severe respiratory insufficiency, uncontrolled arrhythmias, refractory hypertension, or uncontrolled diabetes;

  7. 7.

    Chronic alcohol abuse, language barrier compromising pain assessment, severe visual impairment, active psychiatric disorders, or severe depression/anxiety;

  8. 8.

    Patients receiving chronic pain management therapy or diagnosed with malignant tumors;

  9. 9.

    Prior lumbar surgery or regional anesthesia;

  10. 10.

    Neuraxial anesthesia contraindications (suspected dural breach, localized infection);

  11. 11.

    Polytrauma;

  12. 12.

    Cognitive impairment (Mini Mental State Examination, MMSE < 24/30).

  13. 13.

    Post-randomization exclusion triggers included perioperative complications requiring protocol deviation, surgical approach modification, or failed nerve block.

Randomization and blinding

This was a randomized controlled trial utilizing a patient- and assessor-blinded design. The randomization sequence was computer-generated by an independent statistician, and 96 participants were allocated in a 1:1:1 ratio to the control, QLB-LSAL, or ESPB groups. Sealed, sequentially numbered envelopes containing group assignments were prepared. Upon entering the operating room, all patients received a unified and standardized anesthetic induction protocol to ensure patient blinding. The same operator opened the sequentially numbered envelope, revealed the group assignment, and performed the corresponding standardized, protocol-defined nerve block procedure. Bilateral ultrasound-guided blocks were performed via a probe for ESPB (20 mL 0.4% ropivacaine/side injected) or QLB-LSAL (20 mL 0.4% ropivacaine/side deposited). All nerve blocks were performed by the same experienced anesthesiologist. All outcome data were collected by assessors who were blinded to group allocation, thereby ensuring assessor blinding.

Anesthesia management

Peripheral intravenous access was established in the preparation area. Upon arrival at the operating room, standard monitoring was applied, including electrocardiography, pulse oximetry, non-invasive blood pressure, bispectral index (BIS), temperature, and end-tidal carbon dioxide (EtCO₂) via a high-flow oxygen mask (3 L/min). Radial arterial cannulation was performed for continuous hemodynamic monitoring following local anesthesia. All three groups received standardized general anesthesia, anesthesia Induction: midazolam (0.05 mg/kg), sufentanil (0.3–0.5 µg/kg), etomidate (0.15–0.3 mg/kg), and cisatracurium besylate (0.15–0.2 mg/kg) were administered. Tracheal intubation was performed once the BIS value dropped below 60. After successful intubation, mechanical ventilation was initiated with an oxygen flow of 1–2 L/min, FiO₂ of 60%, tidal volume of 6–8 ml/kg, and respiratory rate of 10–16 breaths per minute. Anesthesia maintenance: Anesthesia was maintained using propofol (4–12 mg/kg/h) and remifentanil (0.1–0.4 µg/kg/min). Additional boluses of cisatracurium besylate (0.05 mg/kg) were administered as needed. The BIS value was maintained between 40 and 60 in all three groups, and ventilation was adjusted to keep EtCO₂ between 35 and 45 mmHg. Vasoactive agents such as ephedrine and phenylephrine were administered based on hemodynamic parameters, BIS values, and volume status. Atropine (0.3–0.5 mg per dose) was given if heart rate (HR) dropped below 50 bpm; phenylephrine (40–80 µg per dose) was used for decreased mean arterial pressure (MAP) with tachycardia. In the absence of carbon dioxide retention, surgical stimulation, or inadequate muscle relaxation, an increase in MAP of more than 20% above baseline, combined with a BIS value > 65 but with normal or slightly elevated HR, was first considered indicative of inadequate sedation. A bolus of propofol (0.5–1 mg/kg) was administered and observed for 1–2 min. A decrease in blood pressure and BIS with stable HR confirmed the appropriateness of the adjustment. The infusion rate was then incrementally increased by 0.5 mg/kg/h from the current rate and titrated over 5–10 min until MAP was within ± 20% of baseline. If both HR and arterial pressure remained elevated, inadequate analgesia was subsequently considered. A bolus of remifentanil (0.5 µg/kg) was administered and observed for 1–2 min. A decreasing trend in arterial pressure and HR confirmed the correctness of the adjustment. The infusion rate was then gradually increased by 0.05 µg/kg/min from the current rate and adjusted over 5–10 min until HR stabilized and MAP returned to within ± 20% of baseline. If hemodynamics did not improve after deepening anesthesia and analgesia, urapidil (5 mg per bolus) was additionally administered and repeated as necessary to maintain MAP within ± 20% of baseline and HR above 50 bpm. Conversely, if MAP decreased by more than 20% below baseline and the BIS value was excessively low, but HR remained acceptable, oversedation with adequate analgesia was suspected. The propofol infusion rate was reduced by 30–50% from the original rate. Observation over 5–10 min followed; an increase in blood pressure with stable HR confirmed appropriate adjustment, and the BIS was maintained between 40 and 60.If MAP decreased by more than 20% accompanied by significant bradycardia, circulatory depression due to excessive analgesia was considered. The remifentanil infusion rate was reduced by 30–50% from the original rate. Observation over 5–10 min followed; improvement in HR and blood pressure indicated correct adjustment. If blood pressure recovered but HR remained low, remifentanil was further reduced. If blood pressure rebounded excessively, remifentanil was appropriately increased until HR recovered and MAP was stabilized within ± 20% of baseline. If the response remained unsatisfactory after these adjustments, ephedrine (6–12 mg per bolus) was administered. Hemodynamic stability was monitored throughout the procedure. All patients received fluid supplementation (5 ml/kg) during induction. Sevoflurane and cisatracurium were discontinued 30 min before the end of surgery. Intravenous anesthetics were stopped during skin closure, and sufentanil (5–10 µg) was administered at the end of surgery before transfer to the post-anesthesia care unit (PACU) for recovery and connection to a patient-controlled analgesia pump. Tracheal extubation was performed when patients were fully awake, responsive to verbal commands, and had adequate swallowing, cough reflexes, and satisfactory respiratory function. Following anesthetic induction, nerve blocks were performed in the QLB-LSAL and ESPB groups, whereas the control group did not undergo this procedure.

Intervention

All procedures adhered to the posterior lumbar surgical protocol. Under standardized general anesthesia, bilateral ultrasound-guided regional blocks (ESPB/QLB-LSAL) were executed via a low-frequency ultrasound transducer (1–5 MHz, Sonosite Edge II system, Bothell, DC, USA).

Following induction, patients were positioned prone with standard aseptic preparation. With the use of a low-frequency ultrasound transducer in a sterile sleeve, longitudinal scanning commenced 3–4 cm lateral to the midline at the surgical level. Under real-time ultrasound guidance, a 22G Quincke needle was advanced in-plane through the erector spinae muscle until it contacted the osseous interface between the transverse process and the lamina. After negative aspiration, 20 mL of 0.4% ropivacaine was injected into the fascial plane between the erector spinae and transverse process, with successful deposition confirmed by cephalocaudal spread along the paraspinal compartment (≥ 3 vertebral segments). The contralateral blockade was performed using identical topographic landmarks (Fig. 1. Ultrasound image of an ultrasound-guided erector spinae plane block).

Fig. 1
Fig. 1
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Ultrasound image of an ultrasound-guided erector spinae plane block.

Patients were positioned prone with a lumbar support pillow to accentuate the thoracolumbar curvature. Following the standard aseptic protocol, sagittal scanning was performed via the L1 transverse process vanishing technique. After the T12 rib and L1 transverse process were identified, the transducer was caudally angulated until dynamic pleural sliding (“curtain sign”) adjacent to the T12 rib and diaphragmatic apposition (“double-track sign”) were visualized. A 22G echogenic needle was advanced in-plane through sequential tissue planes (skin, subcutaneous tissue, latissimus dorsi, quadratus lumborum) until it penetrated the lateral arcuate ligament. Following confirmation of needle tip placement via the hydrodissection technique, 0.4% ropivacaine (20 mL) was administered through slow incremental injection after confirming negative aspiration for blood and air. Contralateral blockade was used to replicate the protocol via mirrored sonographic landmarks (Fig. 2. Ultrasound image of an ultrasound-guided quadratus lumborum block over the arcuate ligament).

Fig. 2
Fig. 2
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Ultrasound image of an ultrasound-guided quadratus lumborum block over the arcuate ligament.

Perioperative pain management

All patients received identical multimodal analgesia. Upon PACU arrival, patient-controlled intravenous analgesia (PCIA) was initiated with the following formulation: sufentanil (2 µg/kg) + flurbiprofen axetil (4 mg/kg) + tropisetron hydrochloride (0.2 mg/kg) in 200 mL of normal 0.9% saline. The PCIA parameters were set as follows: 4 mL loading dose, 4 mL/h basal infusion, and 0.5 mL bolus on-demand with a 15-minute lockout interval. Rescue analgesia (nalbuphine hydrochloride 10 mg IV) was administered if the VAS score was ≥ 4 within 24 h postoperatively. Ward-based analgesia included cobratide injection (140 µg IM bid), citrus bioflavonoid tablets (0.5 mg PO bid), and pregabalin capsules (150 mg PO bid).

Data collection and outcomes

The primary outcome was intraoperative remifentanil consumption (µg).

The secondary outcomes included the following: (1) intraoperative hemodynamics (MAP; HR) and vasopressor requirements; (2) anesthetic consumption (sufentanil, propofol, sevoflurane); (3) C-reactive protein levels; (4) pain intensity assessed by a visual analog scale (VAS, 0 = no pain to 10 = worst pain) at rest/movement; (5) number of patients requiring postoperative rescue analgesia; (6) PCIA satisfaction according to a Likert scale (1 = completely satisfied to 5 = completely dissatisfied); (7) Bruggrmann Comfort Scale(BCS: 0 = persistent pain at rest; 1 = pain-free at rest with severe pain during deep breathing/coughing; 2 = pain-free in the supine position but mild pain during respiratory maneuvers; 3 = complete pain relief during deep breathing (or mild cough-related discomfort); and 4 = complete comfort during coughing.); (8) Richmond Agitation and Sedation Scale (RASS, -5 = unarousable to + 4 = combative); (9) Mini-Mental State Examination (MMSE) for postoperative cognitive dysfunction (POCD: 25–27 = mild, 19–24 = moderate, ≤ 18 = severe); (10) Self-Rating Anxiety Scale (SAS: <50 = normal, 50–59 = mild, 60–69 = moderate, > 69 = severe); (11) Pittsburgh Sleep Quality Index (PSQI, 0–21, higher = worse); (12) recovery milestones: time to emergence, extubation, PACU discharge, first oral intake, flatus, and ambulation; (13) 15-item Quality of Recovery (QoR-15); (14) intraoperative adverse events.

The assessment timelines were standardized with the VAS recorded at emergence, and at 6, 12, 24, and 48 h postoperatively; the BCS and RASS were evaluated at emergence, and at 6, 12, and 24 h postoperatively; and the MMSE, SAS, and QoR-15 were administered on preoperatively day 1and on postoperative days 1 (POD1) and 3(POD3).

Sample size

The sample size was determined on the basis of preliminary observational data from our institution, with the primary outcome being intraoperative remifentanil consumption16. Pretrial estimates indicated mean consumption values of 913 µg, 1206 µg, and 1577 µg for the ESPB, QLB-LSAL, and control groups, respectively, with standard deviations (σ) of 404, 387, and 772. With a 1:1:1 balanced design (g = 3 groups), two-sided α = 0.05, 80% power (β = 0.2), and PASS 15.0 software for ANOVA-based sample size calculation, the estimated required sample size was 27 per group. To account for a 10% attrition rate, 30 participants per group (total N = 90) were enrolled to ensure adequate statistical power for the final analysis17,18.

Statistical analysis

Statistical analyses were performed via SPSS 25.0 with visualization in R 4.4.1. Normally distributed continuous variables are expressed as the means ± standard deviations and were analyzed by one-way ANOVA with least significant difference (LSD) post hoc tests for intergroup comparisons. Nonnormally distributed data are presented as medians (interquartile ranges) [M(IQRs)] and were compared via Kruskal-Wallis tests followed by Nemenyi pairwise testing. Categorical variables were summarized as counts (percentages) with χ² or Fisher’s exact tests for group comparisons, employing Bonferroni correction for multiple testing. Missing data were excluded from the statistical analysis. Statistical significance of overall intergroup differences was defined as P < 0.05 after adjustment for multiple comparisons in post hoc pairwise testing: aP<0.05 vs. the control Group; bP<0.05 vs. the control Group; cP<0.05 vs. the ESPB group.

Results

The study screened 96 eligible patients, excluding 3 with a BMI > 30 kg/m², and observed postoperative complications in 3 patients (one with fever, one with cerebrospinal fluid leakage, one with incisional exudate), with all groups completing follow-up (n = 30 each; Fig. 3. Flow diagram of the study). The baseline characteristics, including age, gender distribution, height, weight, body mass index (BMI), ASA classification, and surgical parameters (anesthetic time, operative time, medical costs) showed no intergroup differences (all p > 0.05, Table 1).

Fig. 3
Fig. 3
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Flow diagram of the study.

Table 1 Baseline characteristics of the study Patients.
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Intraoperative hemodynamic parameters

Post-hoc analyses following significant omnibus tests revealed that, compared with control, ESPB demonstrated superior hemodynamic control at T6 [ΔMAP − 1.0 (-6.0,0.0) vs. 2.3 (-6.0,7.0); p < 0.05] and T4 [ΔHR -1.0 (-5.0,7.0) vs. 8.0 (1.0,15.0); p < 0.05]; moreover, compared with control, QLB-LSAL presented enhanced stability at T4-T6 [ΔHR4 -0.5 (-7.0,4.0) vs. 8.0 (1.0,15.0), p < 0.05; ΔHR5 0.0 (-3.0,4.0) vs. 9.0 (4.0,15.0), p < 0.05; ΔHR6 0.5 (-2.0,3.0) vs. 5.5 (2.0,13.0), p < 0.05], while outperforming ESPB in early-phase MAP control [ΔMAP1 -5.0 (-10.0,-3.0) vs. -17.5 (-23.0,-12.0); p < 0.05]. No significant differences emerged in the intraoperative vasoactive requirements (p > 0.05), with detailed comparative statistics shown in Table 2.

Table 2 The magnitude of intraoperative changes in mean arterial pressure (MAP) and heart rate (HR).
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Intraoperative anesthetic administration and postoperative analgesic efficacy

As shown in Table 3, significant differences were observed among the three groups in terms of intraoperative analgesic consumption, postoperative pain scores, and comfort assessments. Intraoperative analysis revealed that the ESPB group required significantly lower opioid doses than the control group did, with reductions in remifentanil [820.0 (640.0–1120.0) vs. 1120.0 (960.0–1778.0) µg; p < 0.05] and sufentanil [30.0 (25.0–35.0) vs. 35.0 (30.0–40.0) µg; p < 0.05], while the QLB-LSAL group also showed reduced remifentanil use versus the control [920.0 (800.0–1060.0) vs. 1120.0 (960.0–1778.0) µg; p < 0.05]. Postoperative assessments demonstrated superior analgesia in both block groups: the ESPB group presented lower resting VAS scores (emergence, 12 h, 24 h, 48 h postoperatively; all p < 0.05), activity VAS scores (emergence, 6 h, 24 h postoperatively; all p < 0.05), and higher BCS scores (emergence, 6 h, 24 h postoperatively; all p < 0.05) than the control group did. The QLB-LSAL group further displayed sustained analgesic benefits, with reduced resting VAS (emergence, 24 h, 48 h postoperatively) and activity VAS (6 h, 12 h, 24 h postoperatively; all p < 0.05), improved BCS scores at all timepoints (p < 0.05), and fewer rescue analgesia requests [4 (13.3%) vs. 16 (53.3%); p < 0.05]. Direct comparison between the blocks groups highlighted the advantages of the QLB-LSAL at 12 h post surgery, as the VAS score [2.0 (1.0–2.0) vs. 2.0 (2.0–3.0); p < 0.05] and BCS score [2.0 (2.0–3.0) vs. 2.0 (1.0–2.0); p < 0.05] were greater than those of the ESPB group.

Table 3 Intraoperative and postoperative analgesic Efficacy.
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Postoperative recovery profile

Postoperative recovery assessments revealed significant intergroup differences in neuropsychiatric and somatic functional recovery (Table 4). For neuropsychiatric outcomes, the ESPB group demonstrated reduced RASS scores compared with the control group during emergence [0.0 (0.0–0.0) vs. 1.0 (0.0–2.0); p < 0.05] and at 24 h postop [0.0 (0.0–1.0) vs. 1.0 (0.0–1.0); p < 0.05]. The QLB-LSAL group exhibited superior performance across all timepoints: RASS scores were lower at emergence [0.0 (0.0–0.0) vs. 1.0 (0.0–2.0)], 6 h [0.0 (0.0–0.0) vs. 1.0 (0.0–1.0)], 12 h [0.0 (0.0–0.0) vs. 0.0 (0.0–1.0)], and 24 h [0.0 (0.0–0.0) vs. 1.0 (0.0–1.0)] (all p < 0.05 vs. control). MMSE in the QLB-LSAL group surpassed that in the control group at postoperative day 1 (POD1) [28.5 (26.0–30.0) vs. 27.0 (24.0–28.0)] and postoperative day 1 (POD3) [29.5 (28.0–30.0) vs. 28.0 (25.0–29.0)] (both p < 0.05), with concurrently reduced SAS [POD1: 27.5 (25.0–28.8) vs. 30.6 (27.5–36.3); POD3: 25.0 (25.0–27.5) vs. 27.5 (26.3–31.3)] and PSQI [POD1: 7.5 (5.0–9.0) vs. 12.5 (7.0–15.0); POD3: 5.5 (5.0–9.0) vs. 8.5 (6.0–13.0)] (all p < 0.05). Compared with ESPB, QLB-LSAL achieved better RASS at 12 h [0.0 (0.0–0.0) vs. 0.5 (0.0–1.0)] and higher MMSE at POD3 [29.5 (28.0–30.0) vs. 27.5 (25.0–29.0)] (both p < 0.05).In terms of somatic recovery, compared with the control, ESPB accelerated the first flatus time by 7.5 h [12.5 (8.0–19.0) vs. 20.0 (14.0–25.0) h; p < 0.05] and improved the POD1 QoR-15 score [125.0 (121.0–130.0) vs. 120.5 (116.0–125.0); p < 0.05]. QLB-LSAL demonstrated exceptional perioperative efficiency: reduced emergence time [26.0 (24.0–30.0) vs. 36.0 (25.0–75.0) min], extubation time [28.5 (26.0–33.0) vs. 39.5 (27.0–65.0) min], and PACU stay [58.5 (52.0–65.0) vs. 76.0 (55.0–98.0) min] (all p < 0.05 vs. control). Additionally, QLB-LSAL further shortened the first flatus [12.5 (6.0–17.0) vs. 20.0 (14.0–25.0) min; p < 0.05], first ambulation [52.5 (48.0–66.0) vs. 67.0 (53.0–70.0) min; p < 0.05], and enhanced the QoR-15 scores at POD1 [128.0 (126.0–130.0) vs. 120.5 (116.0–125.0)] and POD3 [137.0 (135.0–139.0) vs. 132.5 (129.0–136.0)] (both p < 0.05). Notably, compared with ESPB, QLB-LSAL reduced the PACU duration by 11 min [58.5 (52.0–65.0) vs. 69.5 (60.0–75.0) min; p < 0.05].

Table 4 Postoperative recovery Profile.
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Discussion

In recent decades, there has been a marked increase in the number of lumbar decompression and fusion surgeries for treating spinal disorders19,20. Spinal fusion has become a routine technique in neurosurgical practice and is widely applied to treat degenerative lumbar pathologies, disc injuries, cervical instability, and spinal deformities19. However, patients who undergo decompressive fusion frequently experience moderate-to-severe postoperative pain, with suboptimal analgesia remaining a critical challenge21. While lumbar instrumentation effectively alleviates nerve root compression in degenerative conditions, inadequate acute pain management combined with prolonged immobilization and functional decline often precipitates chronic postsurgical pain—a complication that severely compromises quality of life while imposing substantial psychological and economic burdens22. The integration of ERAS protocols23 has elevated the role of regional anesthesia within multimodal analgesic strategies. Ultrasound-guided nerve block techniques, particularly ESPB and QLB-LSAL, are now extensively utilized in spinal procedures24,25. This randomized trial compared the ESPB and QLB-LSAL techniques in PLIF surgery with 40 mL of 0.4% ropivacaine (within safety thresholds) via a combined regional-general anesthesia strategy. The study assessed opioid consumption, analgesia quality, and functional recovery to optimize technique selection.

For ESPB, current evidence indicates blockade of posterior rami of spinal nerves with cephalocaudal spread, potentially leading to the anesthetization of lumbar cutaneous and deep muscular structures26. Studies have additionally documented anterior-medial dispersion of the injectate into the paravertebral and epidural compartments11. The primary mechanism of QLB-LSAL may involve local anesthetic diffusion along the endothoracic fascia to paravertebral spaces, blocking somatic nerves and thoracic sympathetic trunks27. Studies have revealed alternative pathways in which the solution permeates through the lumbar plexus roots between the intervertebral foramina and psoas major, anesthetizing the subcostal, iliohypogastric, and ilioinguinal nerves traversing the proximal/lateral psoas before coursing ventral to the quadratus lumborum into the fascia transversalis28. Additionally, emerging evidence suggests that QLB-LSAL may exert analgesia through peripheral sympathetic nerve blockade combined with the modulation of nociceptors and mechanoreceptors embedded within thoracolumbar fascial fiber networks29.

QLB-LSAL and ESPB outperformed general anesthesia alone in terms of hemodynamic stability (reduced HR/MAP fluctuations during extubation /post-extubation) and analgesia. Both techniques lowered intraoperative remifentanil use and achieved superior postoperative analgesia (lower resting/movement VAS, higher BCS scores) with increased patient comfort, while maintaining comparable satisfaction (Likert). These regional blocks demonstrate enhanced synergy with general anesthesia, optimizing perioperative pain control and hemodynamic profiles—these findings align with the outcomes reported in prior studies30,31,32,33,34. ESPB/QLB-LSAL analgesia involves two mechanisms: (1) nociceptive pathway blockade suppresses surgical stress-induced sympatho-adrenullary hyperactivation, stabilizing hemodynamics while reducing opioid needs; (2) prolonged neural blockade synergizes with general anesthesia for multimodal analgesia, preventing central sensitization. This mechanistic synergy drives improved VAS/BCS outcomes.

Our comparative analysis revealed distinct clinical‒anatomical profiles between ESPB and QLB-LSAL: QLB-LSAL combines anterior quadratus lumborum and lumbosacral lateral blocks to achieve multisegmental nociceptive blockade spanning T10-S1. This anatomical advantage—simultaneously covering anterior abdominal (T10-L1), inguinal (L1-L2), and pelvic (L4-S1) innervation. This multisegmental coverage may be particularly advantageous for pelvic or lower abdominal procedures (e.g., colorectal/gynecological surgeries), potentially attenuating central sensitization and pain memory engram formation through extended nociceptive pathway inhibition35. Intraoperative remifentanil dosage variations across groups did not affect postoperative pain scoring because of the rapid metabolism of remifentanil. Compared with ESPB, QLB-LSAL demonstrated superior analgesia, with a significantly lower 12-h postoperative visual analog scale (VAS) score (movement) and higher BCS, which is consistent with its multisegmental nociceptive blockade mechanism. However, this contrasts sharply with the findings of laparoscopic nephrectomy studies36 favoringthat favor ESPB, a discrepancy attributable to the surgical context: the thoracic incisions (T8-T10) of nephrectomy align with the reliable paravertebral/epidural spread of ESPB. The underlying mechanism likely involves differential local anesthetic distribution patterns in QLB-LSAL37, where intraoperative disruption of the fascia transversalis may permit drug extravasation, thereby reducing its analgesic efficacy. In contrast, ESPB achieves superior pain control through diffusion into the thoracic paravertebral space, epidural space, and dorsal rami26, collectively blocking nociceptive pathways. This study assessed nerve block-general anesthesia combinations for posterior lumbar surgery. Given that procedure-specific block efficacy varies, its clinical applicability may differ from that reported in the literature.

This study not only confirms the perioperative analgesic advantages of ESPB and QLB-LSAL in posterior lumbar surgery but also, more critically, reveals their multidimensional impacts on early postoperative holistic recovery through an innovative assessment framework: RASS (sedation-agitation), MMSE (cognition), SAS (psychological distress), PSQI (sleep), and QoR-15 (global recovery). The integrated protocol enables cross-domain neuropsychological evaluation, establishing standardized metrics for comparative analysis of the mental health impacts of regional anesthesia. This design paradigm aligns rigorously with ERAS consensus guidelines23.

Compared with the controls, the ESPB patients presented significantly lower RASS scores during the emergence phase and at 24 h postoperatively, whereas the QLB-LSAL group presented superior RASS stability across all observations. This divergence aligns with established µ-opioid receptor (MOR) neuropharmacology38: systemic opioids induce central nervous system depression through MOR agonism, exacerbating sedation-related complications. Both ESPB and QLB-LSAL attenuated these effects via localized analgesia, resulting in reductions in postoperative opioid requirements and minimizing MOR-mediated disruption. This opioid-sparing mechanism directly correlates with improved neurobehavioral outcomes, as evidenced by the superior RASS profiles of the regional block groups. Mechanistic investigations further revealed that postoperative pain-induced physiological stress responses impair cognitive function through multisystem interactions. Nociceptive signaling activates both the hypothalamic‒pituitary‒adrenal axis and the sympathetic nervous system, increasing the levels of inflammatory mediators and disrupting blood-brain barrier integrity39, permitting neurotoxic infiltration that impairs cognitive function. The superior MMSE scores of the QLB-LSAL group at POD1 and POD3 validate the clinical relevance of this pathway, which confirmed the protective effect of nerve block on cognitive function by blocking nociceptive signal transduction and reducing the inflammatory response. Notably, there may be a synergistic effect between this protective effect and its improvement in the psychological status of patients. The QLB-LSAL group demonstrated dual superiority in both SAS and PSQI values at POD1 and POD3, substantiating its multidimensional benefits. As evidenced by Su et al.40, a 10% improvement in postoperative sleep efficiency correlated with a 2.3-point reduction in anxiety scores, highlighting a self-perpetuating pain-sleep-anxiety triad. QLB-LSAL’s sustained analgesic efficacy directly enhanced sleep architecture by reducing arousal thresholds and REM sleep fragmentation. This mechanism interrupts the pain→anxiety→sleep disturbance→cognitive decline pathway. This systematic improvement may explain why this group of patients had better results in MMSE cognitive assessment, highlighting the overall protective value of the regional block technique on perioperative neurocognitive function. Our study further revealed that patients who received QLB-LSAL presented significantly lower RASS scores at 12 h postoperatively and higher MMSE scores at POD3 than did those who received QLB-LSAL. These findings suggest that, compared with ESPB, QLB-LSAL may provide superior sedative stability and early cognitive recovery, underscoring its potential advantages in multimodal postoperative analgesia regimens. The reduced RASS scores in the QLB-LSAL group align with evidence demonstrating that QLB-LSAL effectively modulates nociceptive signaling and minimizes postoperative stress41. These findings may be attributed to the broader sensory blockade achieved by QLB-LSAL42, in contrast to ESPB’s predominant targeting of posterior ramus innervation, which provides less comprehensive visceral analgesia43. QLB-LSAL has been shown to reduce surgery-induced cytokine release, thereby mitigating blood-brain barrier disruption and subsequent cognitive decline; therefore, the MMSE score is greater. Furthermore, the enhanced analgesic efficacy of the QLB-LSAL reduces sleep fragmentation—a modifiable risk factor for delirium and early POCD—by preserving REM sleep continuity44.

This study revealed that both ESPB and QLB-LSAL can effectively promote the postoperative physical rehabilitation of patients, but there are significant differences in terms of recovery efficiency and sustained effects. Compared with the control group, both intervention cohorts demonstrated statistically significant advantages in terms of core recovery metrics, including time to first flatus and QoR-15 scores on POD1. Notably, the QLB-LSAL group exhibited enhanced perioperative efficiency through significantly shorter emergence times, extubation times, and PACU discharge times. Furthermore, the first ambulation of the QLB-LSAL group occurred 14.5 h earlier than that of the control group did, reflecting optimized functional recovery trajectories. This observation aligns with prior investigations31,34,45 demonstrating that regional anesthesia enhances postoperative gastrointestinal motility through opioid-sparing effects, substantiating the dual role of neural blockade in analgesia and gastrointestinal recovery optimization. The sustained recovery advantage of the QLB-LSAL method was evidenced by persistently higher QoR-15 scores at POD3, which was attributable to dual synergistic mechanisms: (1) blockade of nerve conduction reduces noxious stimulation, thereby improving the patient’s physiological recovery process and (2) improving the subjective recovery experience by downregulating central sensitization. Further study revealed that patients who received the QLB-LSAL block had a significantly shorter time to leave the PACU than did those in the ESPB group. This result may be attributed to the more comprehensive blocking effect of the QLB-LSAL technique on nociceptive conduction. The QLB-LSAL technique not only improves patient outcomes but also may improve the overall efficiency of the perioperative healthcare system.

Both ESPB and QLB-LSAL were safely implemented under ultrasound guidance. The advantages of ESPB include the following: (1) clear transverse process landmarks that enhance puncture safety, (2) bony barriers that prevent pleural/organ injury, and (3) minimal cardiorespiratory interference. However, fascial tissue variability may limit anesthetic spread. QLB-LSAL has clinical advantages such as rapid onset, hemodynamic stability, and prolonged analgesia. However, it requires advanced ultrasound skills and carries risks including pleural puncture and perirenal hematoma, particularly when respiratory motion obscures imaging.

Our study limitations include (1) A key limitation of this study is its relatively short postoperative observation period. While the findings provide meaningful short-term insights into the efficacy and safety of the intervention, longer-term functional outcomes, durability, and potential complications require further investigation through extended follow-up studies; (2) potential sensory evaluation confounders from post-induction blocks; (3) residual observer bias in subjective measures; (4) Despite successful blinding of both patients and outcome assessors, this study has an inherent limitation: the operator could not be blinded. This was due to the distinct anatomical targets required for the QLB and ESP blocks under ultrasound guidance. The operator’s awareness of group assignment may theoretically introduce performance bias; for instance, knowledge of the group may have subconsciously motivated the operator to invest more effort in the technique perceived as more effective or to pursue more optimal spread of local anesthetic. To mitigate this potential bias, the following measures were implemented: first, all nerve blocks were performed by the same experienced anesthesiologist; second, postoperative analgesic management followed a standardized preset protocol, thereby limiting individual discretion. Most importantly, outcome assessment was conducted by blinded team members, which provided crucial protection for the objectivity of the study results; (5) restricted generalizability due to the single-center design and small sample size. Multicenter trials with extended follow-up and diverse cohorts are needed for validation. No nerve block-related complications were observed among the patients postoperatively.

Conclusions

In summary, both the QLB-LSAL and ESPB improved hemodynamics, decreased opioid use, and facilitated postoperative recovery after lumbar surgery under general anesthesia. Compared with ESPB, QLB-LSAL exhibited enhanced analgesia and expedited recovery.