Background <p>Opioids were considered the main analgesics for pain management during and after cardiac surgery. There are many complications associated with the use of opioids. Paravertebral block (PVB) is injecting Anaesthetics into the paravertebral space. We designed a randomised controlled trial to investigate whether PVB-based opioid-free general Anaesthesia, as compared to traditional low-dose opioid-based fast-track anaesthesia, can reduce opioid consumption within 24 h after thoracotomy incision cardiac surgery with cardiopulmonary bypass (CPB) in paediatric patients.</p> Methods <p>This is a single-centre, single-blinded, randomised controlled trial with a 1:1 allocation ratio. Patients will be randomised into two groups (control group and PVB group); 20 children will be enrolled in this trial, with 10 subjects in each group. Block randomisation will be performed. Patients aged 1–6 years, with the diagnosis of atrial and/or ventricular septal deficient And scheduled for cardiac surgery via a right thoracotomic incision, will be eligible for enrolment. The primary outcome is opioid consumption during the first 24&#xa0;h after surgery. The main secondary outcomes include the perioperative stress response, inflammatory level, and intraoperative haemodynamics.</p> Discussion <p>This is the first randomised clinical study investigating opioid-free anaesthesia based on PVB for paediatric congenital thoracotomy surgery with CPB. If the OPTION trial proves that opioid-free anaesthesia based on PVB is safe for children undergoing thoracotomic cardiac surgery, we would be glad to provide an OPTION for the perioperative management of these children, especially in the era of ERAS.</p> Trial registration <p>Chinese Clinical Trial Registry: ChiCTR2200066517 (<a href="http://www.chictr.org.cn">www.chictr.org.cn</a>), Registered on December 7, 2022.</p>