This randomized controlled trial compares periarticular vasoconstrictor infiltration (PVI) versus erector spinae plane block (ESP) to reduce bleeding and postoperative pain in adults undergoing lumbar fusion surgery (up to 3 levels). Patients are randomly assigned 1:1 to receive ultrasound-guided ropivacaine 0.2% + epinephrine 1:200,000: PVI (150-200mL bilateral in retrolaminar, thoracolumbar fascia, supraspinous ligament, subcutaneous planes) or ESP (20mL/side at transverse processes). Both groups receive standardized general anesthesia (TIVA), multimodal analgesia (dexamethasone, paracetamol, dexketoprofen/metamizole, ketamine, magnesium), and tranexamic acid. Multicenter study: Hospital de la Santa Creu i Sant Pau (Barcelona, 32 patients) and Hospital Quirón Salud Murcia (30 patients). Primary outcome: intraoperative blood loss (surgical aspirate minus irrigation + gravimetric gauze weight). Secondary outcomes: Fromme surgical field scale, pain (NRS at REA discharge/24h/48h), opioid consumption (morphine equivalents), PONV/antiemetic use, drain output, hospital stay, patient satisfaction. N=62 patients (31/arm). Blinded outcome assessment.