The study aims to shed light about the potential role of Erector Spinae Block in the management of postoperative pain following vertebral fixation surgery via posterior approach. Patients will be randomized, the block will be performed before inducing general anesthesia, intraoperative management will be uniformed, while postoperative analgesia will compare cases (patients who received the block) versus controls (usual care with endovenous morphine infusion only).

The study is a single-centre, interventional, prospective, case-control study. After being informed about the study and potential risks during preoperative anaesthetic evaluation, all patients giving written informed consent will be enrolled in the study.

Inclusion criteria will be: patients undergoing vertebral fixation via posterior approach both for degenerative or traumatic causes, age 18-85, American Society of Anesthesiologists (ASA) I-III, written informed consent signed. Exclusion criteria will be: patients outside the 18-85 year old range, allergies or contraindications to the use of local anaesthetics and erector spinae block, skin infections at the puncture site, body-mass index above 40.

The initial estimate of patients needed to detect statistically significant results has been estimated in 30 (15 cases versus 15 controls). Considering the surgical activity in the organising centre, the study should be completed before the end of 2021. Randomization will be made with a random sequence informatically produced. The study will be double-blinded, with the patient, the nurse doing the postoperative pain assessment and the statisticians not knowing the type of anaesthesia performed (only the anesthesist in the operating theatre is unblinded).

Erector spine plane (ESP) block will be performed after general anaesthesia (GA) induction, with the patient already in prone position. It will be made at the vertebral level of surgical fixation, bilaterally, with Ropivacaine 0.4% and dexamethasone 4 mg in 20 mL of sodium chloride (NaCl) 0.9% per side. GA will be induced with propofol, fentanyl and rocuronium to all patients, while GA maintenance will be performed with total-intravenous anaesthesia (TIVA) with propofol and boluses of fentanyl as required. Basic blood pressure, pulse-oximetry, electrocardiogram, train-of-four, body temperature and bispectral index monitoring will be applied to every patient. At the end of the surgery all the patients will receive a bolus of acetaminophen 1 g and morphine 4 mg.

Post-operative analgesia in controls will be performed by patient-controlled analgesia (PCA) pumps infusing boluses-at-request of morphine 1 mg (maximum once every 15 minutes) with no background infusion, plus acetaminophen 1 g every 8 hours for the first 48 hours.

Post-operative analgesia in cases will be performed with PCA only releasing boluses-at-request (maximum 1 mg every 15 minutes) and acetaminophen 1 g every 8 hours during the first 48 hours.

Postoperative pain will be assessed by a trained physician blinded to the anaesthetic technique employed. Numerical rating scale (NRS) and Richmond agitation-sedation scale (RASS) will be performed at 2-6-12-24-36-48 hours after the end of the surgery.

The primary outcome is postoperative morphine consumption. Secondary outcomes are intraoperative opioid use, postoperative NRS scores, in-hospital length-of-stay and final patient satisfaction.

Statistical analysis will be performed by trained professionals with STATA 14.2 for Windows.

Inclusion Criteria:

• ASA I-II-III
• written informed consent signed
• traumatic or degenerative disease
• adult age (18-65 year old)

Exclusion Criteria:

• allergies to local anesthetics
• contraindications to ESP block execution
• congenital or drug-induced coagulopathies
• infections at the puncture site
• BMI > 40

All data.

5 years, after publication.

Corresponding author email, upon reasonable request.

Care provider (anaesthetist) will know the type of anaesthesia performed. Outcome assessor (physician visiting the patient postoperatively) and investigator (study design and data analysis) will not know the type of anaesthesia performed.