Spinal surgery is commonly associated with severe postoperative pain due to extensive dissection of the skin, subcutaneous tissues, muscles, bones, and ligaments. Postoperative pain is particularly severe following spinal fusion procedures and, if inadequately managed, may result in delayed mobilization, prolonged hospital stays, poor functional recovery, increased opioid consumption, and progression to chronic pain1. Effective postoperative analgesia after major open spine surgery is therefore of significant clinical importance.2 Because postoperative pain after spinal fusion is multifactorial, single-agent analgesic strategies are often insufficient. Multimodal analgesia (MMA), which combines drugs and techniques acting at different sites in the pain pathway, has gained widespread acceptance.3,4 Evidence from studies on spinal fusion surgery demonstrates that MMA reduces pain intensity and opioid requirements, improves functional outcomes and patient satisfaction, and is cost-effective by reducing length of hospital stay and overall healthcare costs. Consequently, anesthetic protocols incorporating MMA are now routinely used in spine surgery. Regional anesthesia techniques have been included in some MMA regimens.5 Although neuraxial techniques such as epidural or intrathecal analgesia may provide effective pain control, they are associated with potential complications including spinal hematoma, infection, motor blockade, and hemodynamic instability. These risks have encouraged the exploration of alternative regional techniques. The introduction of ultrasound guidance has increased interest in interfascial plane blocks, which are relatively simple to perform and have a favourable safety profile. Among these, the Erector Spinae Plane (ESP) block, first described in 2016, has emerged as a promising option for postoperative analgesia after spine surgery.6 The ESP block targets the dorsal rami supplying posterior spinal structures, has a sound anatomical basis, and is performed at a safe distance from the spinal cord, pleura, and major vessels, making it less invasive than epidural techniques.7 Early evidence, including two randomized controlled trials and subsequent studies, suggested that ultrasound-guided ESP blocks reduce postoperative pain scores and opioid consumption for up to 24 hours following major open spine surgery.8,9 However, most studies compared ESP block with no block or sham block. In contrast, a large retrospective study reported no clinically significant benefit of ESP block after lumbar fusion surgery.10 Given these conflicting results and the absence of randomized trials comparing ESP block with an active standard comparator, this prospective randomized study was undertaken to compare the efficacy of bilateral ESP block with local wound infiltration anesthesia for postoperative analgesia following open lumbar fusion surgery.

Setting and location The study was conducted in Northern Railway Central Hospital, New Delhi. Our institute is a referral centre. The subject sample was drawn from the pool of patients undergoing open lumbar spine fusion surgery. In our institute about 50 to 75 open lumbar fusion surgeries are performed every year. The patients, once posted for surgery, were recruited for the study, provided they fulfilled the inclusion and exclusion criteria [listed below]. Study duration Enrolment of patients, recruitment and intervention was done over 12 months. Multiple interruptions of elective surgical procedures over several months occurred due to the ongoing Covid pandemic. This was followed by data analysis and interpretation of results over the next 1 month. Study design The study is a prospective, randomized trial with an allocation ration of 1:1. There are 2 arms in the study: Intervention arm A: Erector Spinae Plane Block group [ESPB] Intervention arm B: Local Wound Infiltration of Anaesthesia group [LWIA] Patients aged 18 -75 years old, with American Society of Anaesthesiologists (ASA) Physical Status 1-3 scheduled for open lumbar fusion surgery were included in the study. Patients were excluded if they had allergy or intolerance to any of the drugs used in the study; kidney, liver, central or peripheral neurologic disease, coagulopathy, pre-existing neurologic or anatomic deficits in the lower extremities; Severe psychiatric illness, infection in the intervention region, History of narcotic drug use within 24 hours before operation and history of chronic pain, narcotic substance, or alcohol dependence. Approval for our study was first obtained from the institutional ethics committee (Approval of thesis protocol - dated 02/02/2021) and scientific committee (dated 14/12/2020) and we subsequently registered with the clinical trial registry India [CTRI/2021/06/034407 Registered on: 25/06/2021]-Trial registered prospectively. Patients who were admitted for open lumbar fusion surgery and who met the requirements of inclusion and exclusion criteria were approached and the details of the study were described to them. Those who consented were recruited. After the expected risks and possible benefits were explained in detail, a written informed consent was taken from those who were willing to participate. The eligible patients included in the study were then randomised into 2 groups by an online randomisation system prior to surgery in the pre-anaesthetic (PA) clinic. The randomization numbers were computer-generated and stored in sealed opaque envelopes. Participants were randomized in a 1:1 ratio to receive either ultrasound-guided bilateral ESP block (ESPB group) or local wound infiltration (control group). The anaesthesiology residents providing post-operative care, nursing staff, and the patients were blinded to patient group allocation throughout the study. All eligible patients were familiarised with the verbal numeric rating scale (vNRS) preoperatively. The 11-point verbal numeric rating scale (vNRS) involves patients rating their pain on a scale of 0–10, with 10 being the worst possible pain. [see annexure] Peri operative anaesthesia management was according to our hospitals routine protocol. Group A patients of this group were allocated to receive bilateral ESP block by the method described by Tulgar et al. 11 (modified for the lumbar region) using 15 ml of 0.375% ropivacaine on each side prior to surgery [Thus the total dose of ropivacaine was 112.5mg] Group B patients of this group were allocated to receive local infiltration using 22.5 ml of 0.5% ropivacaine at the end of surgery [Thus the total dose of ropivacaine was also 112.5mg] All eligible patients were taken to the OT 30 minutes before surgery. Standard monitoring pulse oximetry, non-invasive arterial blood pressure measurement and electrocardiogram were applied. The erector spinae plane (ESP) block was performed after induction of general anesthesia and after placement of the patient in prone position for surgery. The lumbar ESP block was performed in the manner as described by Tulgar et al.11 A curvilinear probe [Sonosite M- Turbo 2-5 Hz] was used to provide the blocks as in the lumbar region, as in the majority of cases, the lumbar transverse processes in our population was at a depth of 4-5 cm or greater. The ultrasound probe was initially placed in the midline over the sacrum; the desired lumbar vertebral level of injection was identified by counting spinous processes, while sliding the probe upwards. Keeping the probe in the sagittal axis in the midline at the desired lumbar vertebral level, the spinous processes were first well visualised, after which the probe was slide laterally and the transverse processes and the erector spinae muscle visualised approximately 3-4 cm lateral to the midline. A 100-mm 21-gauge(G) nerve plexus needle [Vygon Stimuplex] was inserted from the cranial to the caudal portion using the in-plane technique. The needle tip was advanced between the transverse process and the deep fascia of the erector spinae muscle. The location of the needle was confirmed with 2 ml saline solution, after which 15 ml of 0.375% ropivacaine was administered. The same procedure was also performed on the opposite side. [See FIGURE 1] After the block performance, cleaning and draping was repeated and surgical procedure was carried out in the usual manner. Open (lumbar laminectomy and fusion at 2 or 3 levels) was performed by the same surgical team on all patients. Patients of Group B – the control group, received Local Wound Infiltration of Local Anaesthesia [LWIA] using 22.5 ml of 0.5% Ropivacaine at the incision site with a 22-gauge needle, after the surgery. In both groups crystalloid infusion was started at 6 ml/kg with a 20-gauge intravenous catheter. Induction of anaesthesia was done in the standard manner with 2 mg/kg iv Propofol, 0.6mg/kg iv Rocuronium and 2 mcg/kg iv Fentanyl. Lumbar spine surgery was performed by the same surgical team, using the same technique, on all patients. In the intraoperative period, when necessary, 0.1 mg/kg Rocuronium was administered for muscle relaxation during operation. In addition, all patients received inj. Dexamethasone 0.02 mg/kg intravenously. Maintenance of anaesthesia was established with 1% - 2% Sevoflurane, 50% N2O, 50% O2, and Fentanyl if required, was titrated to maintain blood pressure and heart rate within 20% of baseline values. By the end of surgery, all patients received Paracetamol 1gm IV, Diclofenac 1mg/kg IV (maximum of 75 mg) and Ondansetron 4 mg IV, the muscle relaxant was antagonized using 2.5 mg Neostigmine and 1 mg Atropine. Once all extubation criteria was met, patients were extubated. All patients were then transferred to the post anaesthesia care unit. Post-operative pain management was treated with regular doses of Paracetamol (PCM) 1gm IV around the clock (four times daily). Pain was rated by an observer blinded to the pain procedure employed; The 11-point verbal numeric rating scale (vNRS) involves patients rating their pain on a scale of 0–10, with 10 being the worst possible pain. If pain management on the PACU was inadequate, defined as a verbal numeric rating scale (vNRS) of 3 or more, boluses of 1-mg/kg Tramadol was administered. If pain management with Tramadol remained inadequate after 30 minutes, of Tramadol administration; IV diclofenac1mg/kg was administered appropriately diluted in normal saline. All additional analgesic drugs given were noted, and the vNRS was noted at the appropriate intervals. All relevant data were collected by assessors blinded to the pain procedure employed; these were accurately filled up and subsequently rechecked by the principal investigator within 24 hours DATA COLLECTION AND DATA MANAGEMENT Primary end point: Analgesic consumption [measured in terms of oral morphine equivalents in mg] during the first 24 hours post operatively. Secondary end points: 1. Pain scores assessed at rest by the verbal numeric rating scale (vNRS) at following intervals- 0, 1, 6, 12 hours and 24 hours after arrival in PACU. 2. Pain scores assessed in motion by the verbal numeric rating scale (vNRS) at following time intervals-12 hours and 24 hours after arrival in PACU. 3. Comparison of Postoperative Nausea and Vomiting: The incidence and severity of postoperative nausea vomiting was noted and graded by a PONV Impact Scale. 4. Comparison of Quality of Recovery [QoR-40] score between the 2 groups (calculated from responses to a standard questionnaire) at postoperative day 2 scored at 48 hours SAMPLE SIZE The sample size calculation was based on on an average 24-hour morphine consumption of 7 mg ± 2mg as assessed by Singh et al who conducted a randomized controlled study, involving Indian patients, undergoing elective lumbar spine surgery. 8 A 30% reduction in 24-hour morphine consumption was considered clinically significant, with a confidence level of 95% and a statistical power of 80%. STATISTICAL ANALYSIS The following baseline information prior to randomisation was collected: age, sex, BMI, ASA physical status, and preoperative pain [using verbal numeric rating scale (vNRS)]. For categorical variables, frequencies and percentages were reported. Continuous variables were summarised as mean with standard deviation or median with interquartile range as appropriate. Comparisons of demographic and baseline characteristics between the treatment groups were conducted to assess the effectiveness of randomisation. Statistical analysis was performed by the SPSS program for Windows ver. 17.0 (SPSS, Chicago, Illinois). Continuous variables are presented as mean ± SD, and categorical variables are presented as absolute numbers and percentage. Data was checked for normality before statistical analysis. We compared normally distributed continuous variables compared using the Students unpaired t test and the Mann-Whitney U test was used for those variables that were not normally distributed. For categorical variables inter-group differences were assessed for significance using either the chi square test or the Fisher’s exact test, as appropriate. For all statistical tests, a p value less than 0.05 was taken to indicate a significant difference.

Demographic and clinical characteristics The study included a total of 46 patients, with 23 patients in the ESP block group (Group A) and 23 patients in the Local wound infiltration anaesthesia group (Group B). The demographic and clinical characteristics of the participants are summarized in Table 1. There were no significant differences between the groups in terms of sex, age, or body weight wise distribution. Postoperative pain scores Postoperative pain intensity was assessed via the verbal numeric rating scale (VNRS) at various time points. The results, summarized in Table 2, revealed that there was statistically significant differences in the mean vNRS scores between the ESP block and LWIA groups at any of the assessed time points (0 min, 1 h, 6 h, 12 h, and 24 h postoperatively). These findings suggest that ESPB technique is more effective in managing postoperative pain during the first 24 h. Additional outcomes Postoperative outcomes, including postoperative nausea and vomiting (PONV), QoR score at 48 hours and total analgesic consumption of morphine equivalents are summarized in Table 3. The mean PONV impact score in 24 hrs postoperative period in group A was 0.57±0.95 and in group B was 0.83±1.03. The p-value is 0.273and so there is no significant difference between the two groups with respect to post operative nausea and vomiting. The mean QoR score at 48 hrs postoperative period in group A was 161.04±9.38 and in group B was 130.35±9.46. Thus, there was a difference in the quality of recovery scores which reached statistical significance. For consistency and ease of comparison across studies, presenting total opioid consumption in morphine equivalents is a common and effective approach. This standardization allows the reader to better interpret the opioid-sparing effects of the interventions (ESPB vs. LWIA), as different types of opioids (such as tramadol, fentanyl, or morphine) have varying potencies. To convert tramadol (the opioid used in this study) and diclofenac into morphine equivalents, the typical conversion factor is:10 mg of tramadol ≈10 mg of Diclofenac ≈ 1 mg of morphine (approximately a 10:1 ratio). Therefore, the total morphine equivalent consumption in the ESPB group was (11.94 ± 4.26 mg) and in LWIA group was (25.63 ± 5.26 mg). and the difference between the two groups was statistically significant. Postoperative outcomes, including postoperative nausea and vomiting (PONV), QoR score at 48 hours and total analgesic consumption of morphine equivalents FIGURE 1 Table 1: The demographic and clinical characteristics of the participants Variable ESP block (n=23) LWIA (n=23) p value Female,n 11 10 0.767 Male,n 12 13 Age, years, Mean 50.78 57.22 0.184 Body weight 62.17 67.18 0.27 ASA grade 1 12 9 0.261 grade 2 4 9 grade 3 7 5 Table 2: Comparison of the mean NVRS static and dynamic scores at different time points between groups Time point ESP block(n=23) mean(s.d) LWIA(n=23) mean(sd) p value NVRS static 0 min 1.09 (1.2) 2.48(2.48) 0.004 NVRS static 1 hr 1.48(1.38) 2.26(0.86 ) 0.017 NVRS static 6 hr 2.35(1.19) 4.30(1.15 ) <0.001 NVRS static 12 hr 2.48(0.99) 4.78(1.13 ) <0.001 NVRS static 24 hr 1.45(1.07 ) 4.35(1.06 ) <0.001 NVRS dynamic 12 hr 2.96(0.93) 6.09(1.00 ) <0.001 NVRS dynamic 24 hr 1.91(1.04) 1.41(1.3 ) 0.004 Table 3 Outcome ESP block(n=23) Mean (s.d) LWIA(n23) Mean (s.d) p value Post op PONV 0.57 0.83 0.273 QoR score at 48 hrs 161.04 130.35 <0.001 Total analgesic (ME)(mg) consumption 11.94 25.63 <0.001

The present prospective randomized study was undertaken to compare the postoperative analgesic efficacy of ultrasound-guided bilateral single-shot erector spinae plane block (ESPB) with standard local wound infiltration anesthesia (LWIA) in patients undergoing open lumbar spine fusion surgery. Effective pain control following major spine surgery remains a critical component of perioperative care, as severe postoperative pain may impair early mobilization, prolong hospitalization, increase opioid consumption, and predispose patients to the development of chronic pain. In recent years, several studies have explored the role of ESPB as part of multimodal analgesia strategies for spine surgery, with varying results. The findings of the present study add to this evolving body of literature by providing a direct comparison between ESPB and an active standard comparator. In the current study, patients who received ultrasound-guided bilateral ESPB demonstrated significantly lower total postoperative analgesic consumption within the first 24 hours following surgery compared with those who received LWIA. This opioid-sparing effect is consistent with the findings reported in earlier randomized controlled trials by Singh et al. and Yayik et al.8,9 both of which demonstrated reduced opioid requirements and improved analgesia following ESPB in open spine surgery. Singh et al. studied 40 patients undergoing spine surgeries and found significantly lower 24-hour morphine consumption with ESP block compared to controls. Their lower opioid use compared to our study may reflect routine postoperative diclofenac use and a higher pain score threshold for rescue Morphine. In addition to reduced analgesic consumption, the present study demonstrated significantly lower pain scores at rest and during movement in the ESPB group during the first 24 postoperative hours. These findings align with previous studies that reported improved pain scores following ESPB, particularly in the early postoperative period. Zhu et al. conducted a randomized controlled trial in 40 patients undergoing posterior lumbar fusion, comparing ultrasound-guided ESP block with ropivacaine to a sham block. Postoperative analgesia included patient-controlled intravenous oxycodone along with routine opioid and NSAID(flurbiprofen) administration, resulting in lower pain scores than observed in our study.12 Similarly, Zhang et al. reported reduced 24-hour opioid consumption with ESP block compared to sham, with fentanyl requirements translating to morphine-equivalent doses comparable to our findings when adjunctive NSAID use was considered.13 Although both studies reported lower absolute pain scores, likely due to more intensive postoperative analgesic regimens, the mean differences in static and dynamic pain scores between ESP and control groups were comparable to those observed in our study, supporting the consistency of ESP block analgesic benefit. The ability of ESPB to provide effective dynamic pain relief is of particular clinical relevance, as pain during mobilization is a major limiting factor in early postoperative rehabilitation after spine surgery. An important distinction between the present study and many previous trials is the use of LWIA as an active comparator rather than no block or sham block. While earlier studies primarily demonstrated superiority of ESPB over no regional intervention, the current study demonstrates that ESPB provides superior analgesia even when compared with a commonly used standard technique. This finding is clinically significant, as LWIA is widely employed in routine practice and represents a more realistic benchmark for evaluating the added value of ESPB. We opted to use the Quality of Recovery (QoR-40) scoring system. The reliability and validity of the QoR-40 questionnaire has been well established. 14 The QoR-40 scores are commonly reported measures of patient-assessed quality of recovery after surgery .14The improved analgesic outcomes observed in this study translated into significantly higher Quality of Recovery (QoR-40) scores in the ESPB group. Although QoR-40 has not been uniformly assessed in all prior ESPB studies, similar improvements in patient satisfaction and functional recovery have been reported in studies evaluating multimodal analgesia protocols that include ESPB.15 This finding suggests that the benefits of ESPB extend beyond pain control alone and contribute to a more favourable overall postoperative recovery experience. In contrast, studies that failed to demonstrate significant analgesic benefits with ESPB have generally not reported improvements in broader recovery outcomes, highlighting the importance of comprehensive assessment tools such as QoR-40. Qiu et al. reviewed 11 studies of ESPB in lumbar surgery and found reduced pain with good safety, though improved patient satisfaction was studied and shown in only one study5. They recommended bilateral ESPB using 20 ml of 0.375% ropivacaine per side, with no reported adverse events. Notably, the findings of the present study differ from those of a large retrospective study by Soffin et al., which concluded that ESPB had no clinically meaningful impact on 24-hour opioid consumption or pain scores following lumbar fusion surgery.10 Several factors may account for these discrepancies. The retrospective design of that study may have introduced selection bias and limited control over confounding variables. Additionally, variations in surgical technique, anesthetic protocols, timing of block administration, and the experience of the practitioners performing the blocks may have influenced outcomes. In contrast, the prospective randomized design of the present study, along with standardized anesthetic and analgesic protocols, strengthens the internal validity of the findings. The anatomical and physiological basis for the efficacy of ESPB observed in this and other similar studies probably lies in the blockade of the dorsal rami supplying the posterior spinal structures. Compared with LWIA, which provides localized and relatively short-lived analgesia, ESPB allows wider cranio-caudal spread of local anesthetic and more sustained pain relief. Furthermore, unlike neuraxial techniques, ESPB has consistently demonstrated a favorable safety profile across studies, with a low incidence of complications when performed under ultrasound guidance. Despite the encouraging results, it is important to acknowledge that variability in study designs, outcome measures, and ESPB techniques across the literature has contributed to inconsistent findings. Differences in local anesthetic dosing, block level, unilateral versus bilateral administration, and timing relative to surgery may all influence analgesic efficacy. These factors underscore the need for standardized protocols in future research.

The present study demonstrates that ultrasound-guided bilateral single-shot erector spinae plane block provides superior postoperative analgesia compared with local wound infiltration anesthesia following open lumbar spine fusion surgery. The findings are largely consistent with earlier randomized controlled trials and supportive observational studies, while addressing limitations of prior research through the use of an active comparator. ESPB was associated with reduced postoperative analgesic consumption, lower pain scores at rest and during movement, and improved quality of recovery in the first 24 hours postoperatively. Although some studies have reported conflicting results, differences in study design and methodology may account for these discrepancies. Larger multicentre randomized trials are warranted to further validate these findings and to establish ESPB as a standard component of multimodal analgesia protocols for open lumbar spine fusion surgery.

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