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).
