Bilateral ultrasound-guided erector spinae plane block versus surgical site infiltration for post-operative analgesia in patients undergoing complex spinal surgeries: A randomized controlled trial

INTRODUCTION

Complex spinal surgeries often result in substantial tissue trauma and prolonged operative times, leading to significant post-operative pain. Effective analgesia is vital for patient comfort, early mobilization, shorter hospital stays, and prevention of chronic pain syndromes. Although multimodal analgesia has evolved, the ideal strategy for managing post-operative pain in such cases remains under active investigation.^[1]

Opioids and their derivatives have long served as the primary agents for managing pain following surgery. However, their side effects – including nausea, vomiting, constipation, respiratory depression, and the potential for dependence – highlight the need for safer, opioid-sparing alternatives.^[2,3] In this context, regional anesthesia techniques such as the erector spinae plane (ESP) block and surgical site infiltration (SSI) have gained increasing attention.

The ESP block is a fascial plane technique where local anesthetic is administered between the erector spinae muscle and the vertebral transverse processes.^[4] The block offers analgesia by affecting both the dorsal and ventral rami of the spinal nerves. It is considered a safe technique with a low complication rate and has shown effectiveness across thoracic, abdominal, and spinal procedures.^[5] Bilateral ESP blocks, in particular, are advantageous for surgeries involving midline incisions, such as complex spinal operations.^[6] However, the need for ultrasound guidance and skilled operators may limit its accessibility, especially in resource constrained settings.

SSI, on the other hand, involves the direct administration of local anesthetic into the incision site or surrounding tissues. It is simple, cost-effective, and does not require ultrasound guidance, making it suitable for low-resource environments.^[7]Despite its convenience, its analgesic duration is often shorter than that of ESP blocks, and additional analgesics may be needed postoperatively.^[8]

Choosing between ESP blocks and SSI involves weighing efficacy against practicality. While the ESP block may provide extended and bilateral analgesia, most supporting data are from small case series or observational studies.^[9] Direct comparative data, particularly in the setting of complex spinal surgery, are scarce. Some studies suggest that ESP blocks reduce pain scores and opioid consumption more effectively than conventional methods,^[10,11] but larger randomized controlled trials (RCTs) are needed to confirm these benefits.

Patient variability in pain perception, surgical technique, and response to analgesia complicates post-operative pain management. Therefore, high-quality RCTs are essential to inform evidence-based practice.^[12,13] Ultrasound guidance enhances the safety and precision of ESP blocks by enabling real-time visualization of anesthetic spread,^[14] an advantage not afforded by SSI.

This study aims to compare the efficacy of bilateral ultrasound-guided ESP blocks with SSI for post-operative pain relief in patients undergoing complex spinal surgeries. The primary endpoint will be post-operative pain scores and opioid consumption; secondary outcomes include patient satisfaction, duration of analgesia, and incidence of side effects. By filling a significant gap in current literature, this study hopes to contribute to safer, more effective, and opioid-sparing analgesic protocols for spine surgery patients.

MATERIALS AND METHODS

This prospective, randomized controlled trial was conducted to compare the analgesic efficacy of bilateral ultrasound-guided ESP block versus SSI in patients undergoing complex spinal surgeries. After obtaining Institutional Ethical Clearance (IEC Regd No. 38/23) and registering with the Clinical Trials Registry of India (CTRI/2023/03/012234), the study was carried out over 18 months (May 2023–December 2024) at the Department of Anesthesiology and Critical Care, Army Hospital (R&R), Delhi Cantt – a high-volume tertiary referral center for spine surgery.

Fifty adult patients (aged 18–60 years), classified as American society of anesthesiologists (ASA) Physical Status I–II, scheduled for complex spinal procedures – such as posterior lumbar interbody fusion, transforaminal lumbar interbody fusion, multi-level discectomy or laminectomy, and spinal tumor resection were recruited. Exclusion criteria included allergy to bupivacaine, coagulopathy, infection at block site, cognitive impairment, chronic pain conditions, or refusal to participate. Following informed consent, patients were randomized into two groups (Group E or Group S) using a computer-generated sequence. Due to the nature of the interventions, blinding of the care team was not feasible; however, outcome assessors and data analysts remained blinded to allocation.

Based on prior studies reporting significant differences in opioid consumption between ESP and SSI groups, a minimum sample size of 44 (22 per group) was required for 95% power at α = 0.05. To accommodate potential dropouts, 50 patients were enrolled, with 25 per group.

• Group E: ESP Group: Patients received bilateral ultrasound- guided ESP blocks at the T8 level, using 20 mL of 0.25% bupivacaine on each side, administered under strict asepsis after patient was placed in the prone position (post intubation).

• Group S: SSI Group: The operating surgeon infiltrated 20 mL of 0.25% bupivacaine into the surgical wound before closure.

General anesthesia was standardized across both groups. Induction was achieved with propofol (1.5–2.5 mg/kg) and fentanyl (1.5–2.0 µg/kg), followed by atracurium (0.5 mg/kg) for muscle relaxation. Anesthesia was maintained with a 50:50 mix of oxygen and air with sevoflurane (minimum alveolar concentration (MAC) 0.8–1.2). Monitoring included non invasive blood pressure (NIBP), pulse oximetry (Spo2), electrocardiography (ECG), capnography, and temperature. All patients received fentanyl boluses through patient controlled analgesia (PCA) pump (20 µg boluses, 15-min lockout), IV paracetamol (1 g every 8 h), and IV ondansetron (4 mg every 12 h). Post-operative assessments were performed at 1, 4, 6, 12, and 24 h.

Outcomes considered were as follows:

1. Primary outcome: Pain scores using the Visual Analog Scale (VAS) at rest and movement.

2. Secondary outcomes: Total opioid (fentanyl) consumption within the first 24 h, measured in micrograms, patient satisfaction (rated on a 3-point scale), and incidence of nausea/vomiting or allergic reactions.

Data were recorded using a structured pro forma covering demographic, intraoperative, and post-operative parameters. Statistical analysis was performed using the Statistical Package for the Social Sciences v21. Continuous variables were compared using t-tests or analysis of variance, and categorical data using the Chi-square test. Multivariate regression was conducted to control for confounders. p < 0.05 was considered statistically significant.

The study was conducted in accordance with the Consolidated Standards of Reporting Trials guidelines. Confidentiality was maintained by anonymizing patient data. Patients were informed of their rights and allowed to withdraw at any stage without affecting their medical care.

RESULTS

Demographic profile of the patients

A total of 72 patients were assessed for eligibility. Twenty-two were excluded: Eight did not meet inclusion criteria, seven declined to participate, and seven were lost due to intraoperative changes or technical failure. The final analysis included 50 patients, with 25 each in the ESP (Group E) and SSI (Group S) groups [Figure 1]. The groups were comparable in terms of demographic variables and comorbidities [Table 1]. Mean age was 46.3 ± 12.1 years in Group E and 48.5 ± 11.4 in Group S (p = 0.41). ASA physical status distribution and gender ratio were also similar between groups (p = 0.94). Common comorbidities included hypertension (22%), diabetes mellitus (16%), and chronic obstructive pulmonary disease (COPD) (18%) with no significant intergroup differences [Table 1].

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Figure 1: Consolidated standards of reporting trials flow diagram. ESP: Erector spinae plane, SSI: Surgical site infiltration.

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Table 1: Demographics and surgical characteristics.

Variable	Group ESP (n=25)	Group SSI (n=25)	p-value
Age (years)	46.3±12.1	48.5±11.4	0.41
Sex (M/F)	15/10	14/11	0.79
BMI (kg/m2)	25.6±3.2	26.1±2.8	0.54
ASA grade (I/II/III)	5/16/4	4/17/4	0.94
Duration of surgery (min)	172±36	180±40	0.48
Number of levels fused	2.4±1.1	2.6±1.0	0.36
Surgical procedure performed
Laminectomy with instrumentation	10 (40%)	11 (44%)	0.79
Posterior lumbar interbody fusion	8 (32%)	7 (28%)	0.76
Revision spine surgery	3 (12%)	2 (8%)	0.64
Discectomy with decompression	2 (8%)	3 (12%)	0.67
Other complex spinal procedures	2 (8%)	2 (8%)	1.00

BMI: Body mass index, ASA: American society of anesthesiologists, M: Male, F: Female, ESP: Erector spinae plane, SSI: Surgical site infiltration. p-value < 0.05 was considered as significant

DISCUSSION

This study aimed to compare the analgesic efficacy of bilateral ultrasound-guided ESP block with SSI in patients undergoing complex spinal surgeries. The primary outcomes assessed included pain relief at rest and during movement, total opioid consumption, and patient satisfaction within the first 24 post-operative h.

Significant differences emerged in pain scores at rest, particularly at 1, 12, and 24 h postoperatively. Group E consistently reported lower VAS scores than the Group S (ρ = 0.003), suggesting a more sustained analgesic effect. These results are consistent with studies by Zhang et al.,^[15]Yayik et al.,^[16] and Wahdan et al.,^[17] all of whom reported prolonged post-operative analgesia with ESP blocks in spinal surgeries. The findings also support observations by Singh et al.,^[18] highlighting effective pain relief from ESP with 0.25% bupivacaine. Thus, ESP appears superior for resting pain, especially in the later post-operative period.

In contrast, VAS scores during movement showed no statistically significant difference between the two groups at any time point (ρ > 0.05). These results corroborate findings by Fiorelli et al.^[19] and Ciftci et al.,^[20] who reported limited benefits of ESP for dynamic pain. While some studies, such as Gişi and Öksüz,^[21] observed improved movement-related pain control with ESP, variability in block technique and surgical type may explain the inconsistencies in the results. Therefore, ESP may require adjunctive measures to manage pain during mobilization.

Although not statistically significant (ρ = 0.841), fentanyl consumption over 24 h was lower in the Group E (276.80 ± 117.14 µg) than the Group S (336.00 ± 121.66 µg). This trend aligns with prior research by Jiao et al.^[22] and Melvin et al.,^[23] which demonstrated also demonstrated reduced opioid needs with ESP. The non-significant trend toward reduced opioid use supports the equality in the opioid-sparing potential of both ESP and SSI within multimodal analgesia.

Satisfaction scores were comparable between groups, with no significant difference (ρ = 0.258). Slightly more patients in the Group E reported high satisfaction, though not enough to be statistically relevant. These findings are similar to the earlier reports by Qiu et.al.^[24] who associated ESP with higher patient satisfaction in spinal surgeries when compared with standard (opioid-based) analgesia. Similarly, Yeşiltaş et.al.^[25] also reported better patient satisfaction score when they compared ESP with intercostal nerve block for thoracic surgeries. The similarity in satisfaction levels reflects that both ESP and SSI are equally acceptable to patients.

This study highlights the clinical utility of ultrasound-guided ESP block and SSI in managing post-operative pain following complex spinal surgeries. ESP demonstrated sustained analgesia at rest and reduced opioid consumption, supporting its role as a valuable component of multimodal analgesia protocols. While ESP and SSI yielded similar outcomes for movement-related pain and patient satisfaction, the benefit of ESP in pain at rest makes it preferable in settings aiming to minimize opioid use. In resource-limited environments where ultrasound is unavailable, SSI remains a practical and effective alternative.

The randomized controlled design, standardized protocols, and comprehensive outcome evaluation strengthen the study’s credibility. However, limitations include a small sample size, single-center setting, short follow-up period (24 h), and potential bias due to lack of blinding. Cost-effectiveness and block placement time were not assessed, both of which are relevant in high-volume centers with limited time and resources.

CONCLUSION

This study evaluated the efficacy of bilateral ultrasound-guided ESP block versus SSI for post-operative analgesia in patients undergoing complex spinal surgeries. The findings demonstrated that both techniques are effective, with ESP showing slight advantages in certain parameters. However, for resource constrained settings without the facilities of USG, SSI should be utilized for its effectiveness and opioid sparing effects.

Future research should involve multicenter trials with larger cohorts to validate these findings. Long-term outcomes, cost-benefit analyses, and studies exploring ESP in other surgical contexts or in combination with other analgesic techniques are warranted. Personalizing analgesia through patient-specific factors and leveraging advanced imaging for block precision represent promising directions for advancing postoperative pain management.