Ultrasound-Guided Erector Spinae Plane Block Versus Intravenous Nalbuphine

2.1. Study population and setting: This prospective, randomized, controlled clinical trial will be conducted at the thoracic surgery operation room, cardiothoracic surgery building, Zagazig University Hospitals, from July 2025 to December 2025. Our study included 102 patients who are planned for video-assisted thoracoscopy. Cases will randomly divided into two groups: Erector Spinae Plane Block (ESPB) and the control group, comprising 51 patients each. Inclusion criteria also include: American Society of Anesthesiologist (ASA) status of II and III, age between 21 years and 60 years, and BMI (body mass index) between 30 and 40 kg/ m2. Patients who will be excluded from the present study included: BMI \ 40 kg/ m2, chronic pain with regular use of either opioids or gabapentinoids during the 2 weeks before surgery, history of thoracic surgery on the same side, anticipated high risk of conversion to thoracotomy, taking anticoagulation, suffering from any bleed¬ing disorders, known allergy to local anesthetics, nalbuphine or fentanyl, active infection at the injection site, pre-existing neurological or psychiatric illness, severe cardiovascular disease, liver failure, renal failure (estimated glomerular filtration rate less than 15 ml min), and pregnancy. Patients will be also excluded after randomiza¬tion if they have converted to thoracot¬omy, severe intra- or postoperative blood loss \>1000cc, required postoperative mechanical ventilation, or a technical difficulty in the ESPB performance. 2.2. Randomization and allocation Patients will be randomized in a one-to-one ratio and assigned to either the ESPB (group A) or control group (group B) (Fig. 1). Randomization allocations will be kept in sealed opaque covers and only opened by the investigator immediately prior to the ESPB, which will be performed in a holding area before entry into the block rooms. All blocks will be performed by the same anesthetist using the linear probe of an Ultrasound machine (GE V