Laminectomy is a routine procedure for patients with lumbar spinal stenosis, offering significant benefits such as reduced low back pain, alleviation of radiculopathy, and improved motor strength 1 23. Despite these advantages, postoperative pain remains a challenge for anesthesiologists. According to Davin et al., approximately 80% of patients undergoing lumbar laminectomy experience postoperative discomfort, with 20% developing persistent postsurgical pain (PPSP). The application of erector spinae plane (ESP) block in lumbar laminectomy surgery significantly reduces postoperative pain and hospital length of stay. However, ESP block without adjuvants has limitations in duration. Adjuvants are thus required to optimize the effects of ESP block 4.

Dexamethasone is a glucocorticoid that is widely used in the perioperative setting. Interfascial administration of dexamethasone has been shown to prolong the duration of analgesia provided by the peripheral nerve blocks. Pehora et al (2017) reported that perineural dexamethasone with local anesthetics prolongs sensory blockade, effectively reducing postoperative pain intensity and opioid consumption. Its analgesic effects likely stem from anti-inflammatory mechanisms, including supression of proinflammatory cytokines, induction of anti-inflammatory cytokines, reduced prostaglandin synthesis, and decreased neuronal excitability 5 6. Adjuvant dexamethasone provides additional benefits, including prolonged analgesia, reduced pain scores, lower postoperative opioid requirements, and decreased inflammation in patients undergoing lumbar laminectomy.

Prior literature has not examined the benefits of dexamethasone as an adjuvant for lumbar ESP block, nor measured and compared inflammatory biomarkers with its use. Therefore, this study investigates the efficacy of dexamethasone adjuant in ESP block for lumbar laminectomy surgery by assessing postoperative prostaglandin E2 levels, analgesia duration, pain scores (VAS) at 8, 12, 16, and 24 hours postoperatively, and patient-controlled analgesia (PCA) fentanyl requirements at the same intervals.

This study is a single-center, double-blind randomized controlled trial conducted in the Central Surgical Installation operating room at Ngoerah General Hospital, Denpasar, Indonesia, from March to August 2025, following ethical approval (No. 0326/UN14.2.2.VII.14/LT/2025). Participants were patients undergoing lumbar laminectomy during the study period. Consecutive sampling was employed. Inclusion criteria were age 18-65 years, American Society of Anesthesiologists (ASA) physical status I-III, and body mass index (BMI) 18-30 kg/m2. Exclusion criteria included contraindications to regional anesthesia, puncture site infection, type 2 diabetes mellitus, drug allergy, chronic opioid use, laminectomy involving >2 segments, or inability to assess Visual Analog Scale (VAS) pain or inability to use paient-controlled analgesia (PCA). Dropout criteria were hypotension >30% from baseline requiring continuous vasopressors or postoperative mechanical ventilation.

Sample size calculation determined 36 participants, randomized 1:1 into two groups using computer-generated simple randomization: Group P1 (n=18) received erector spinae plane (ESP) block with dexamethasone adjuvant, and Group P2 (n=18) received ESP block without dexamethasone. The study flowchart is shown in Figure 1.

All participants provided written informed consent. Upon arrival in the operating room, blood samples were collected for baseline prostaglandin E2 measurement. General anesthesia was induced with standard monitoring (SpO2, ECG, respiratory rate, noninvasive blood pressure) using propofol (2-3 mg/kg), fentanyl (1-2 mcg/kg), and rocuronium (0.6 mg/kg). Patients were then positioned prone for ESP block. Group P1 received 20 mL of 0.375% ropivacaine with 5 mg dexamethasone per side; Group P2 received 20 mL of 0.375% ropivacaine per side.

Anesthesia was maintained with sevoflurane, adjusted to achieve a minimum alveolar concentration of 1.2. Intraoperative analgesia included Paracetamol 1 g. Ondansetron 8 mg was administered for postoperative nausea and vomiting prophylaxis. Postoperative analgesia consisted of fentanyl PCA, oral paracetamol 500 mg every 6 hours, and oral ibuprofen 400 mg every 8 hours. Postoperative assessments were performed by the Acute Pain Service team, with blood sampling for Prostaglanin E2 at 24 hours postoperatively.

Primary outcome were postoperative prostaglandin E2 levels, analgesia duration, VAS pain score at 8, 12, 16, and 24 hours postoperatively, and fentanyl PCA requirements at the same intervals.

Descriptive data are presented as mean ± standard deviation. Normality was assessed using the Shapiro-Wilk test. Between-group comparisons used the independent t-test for normally distributed data or Mann-Whitney U test for non-normal data. Clinical interpretability was evaluated using 95% CI of the Difference. Analyses were performed using IBM SPSS Statistics for Windows, version 20.0 (IBM Corp., Armonk, NY, USA).

Inclusion Criteria:

• Patients aged between 18 - 65 years
• ASA physical status I-III
• Patients with a BMI of 18 - 30 kg/m2

Exclusion Criteria:

• Patients with contraindications to regional anesthesia
• Infection at the puncture site
• Type 2 Diabetes Mellitus (T2DM)
• Hypersensitivity or allergy to the medications used
• Prolonged or chronic opioid use
• Laminectomy involving more than two segments
• Inability to be assessed using the Visual Analogue Scale (VAS) or to operate the PCA device

The informed consent signed by participants does not include permission for the sharing of individual-level data with third parties. Protecting participant anonymity is our primary priority

"This is a double-blind study designed to ensure that both the investigators and the participants are unaware of the group assignments. To maintain blinding, the investigator responsible for data collection and analysis is different from the operator performing the Erector Spinae Plane (ESP) block procedure. Participants are provided with a standardized explanation and informed consent; since the procedure is identical for both groups and only the adjuvant (dexamethasone or none) differs, the participants remain blinded to their specific treatment allocation.