The aim of this study is to investigate the effect of bilateral erector spinae plane (ESP) block application on postoperative chronic pain in patients undergoing on-pump open-heart surgery. At 3 months post-discharge, patients will be contacted by phone to assess their chronic pain status. Pain intensity and status will be evaluated using the Brief Pain Inventory, and the character of pain will be assessed using the Douleur Neuropathique 4 (DN4) score. Additionally, the patient's anxiety and depression status will be evaluated using the Hospital Anxiety and Depression Scale.

Acute or chronic pain following cardiac surgery is a common issue that significantly impacts quality of life. The reported incidence of moderate to severe acute pain post-cardiac surgery varies widely in the literature, ranging from less than 5% to over 80%. Factors contributing to severe postoperative pain after median sternotomy include vasospasm, increased inflammatory response, soft tissue and bone injury during dissection, and chest tube placement. While pain typically decreases after the first 24 hours post-surgery, inadequate pain management can prolong this period. Chronic pain syndrome following sternotomy has been reported in 7% to 66% of patients undergoing open-heart surgery.

Initially, neuraxial anesthesia techniques such as thoracic epidural or thoracic paravertebral blocks were recommended for postoperative pain control in minimally invasive cardiac surgery. However, debates exist due to technical and patient-related challenges such as procedural difficulties, coagulation disorders, complete heparinization, hemodynamic instability, and pneumothorax. Fascial plane chest wall blocks involving serratus anterior and erector spinae have gained popularity for managing postoperative pain after minimally invasive cardiac surgery and thoracotomy/sternotomy, especially in patients receiving antiplatelet and anticoagulant therapy. An alternative approach, ultrasound-guided erector spinae plane block (ESPB), was introduced by Forero and colleagues in 2016 for treating thoracic neuropathic pain.

Inadequate pain control post-surgery can lead to persistent postoperative pain, high opioid consumption, and opioid-related morbidity. Theoretically, in patients receiving an erector spinae plane (ESP) block, the local anesthetic spreads both cranio-caudally and anteriorly through the costotransverse foramina, blocking the ventral/dorsal branches of spinal nerves, dorsal root ganglion, and rami communicantes at multiple levels. In patients undergoing sternotomy for cardiac surgery, bilateral thoracic ESP catheters or a single injection technique have reduced opioid use and pain scores.

This study is planned as a prospective, randomized controlled, double-blind, parallel-group trial.

Patients will be divided into two groups:

ESP Group: General anesthesia + ESP Block + Patient-Controlled Analgesia (PCA) Group K: General anesthesia + PCA

Inclusion Criteria:

• Patients aged 18-80 undergoing elective on-pump open-heart surgery via median sternotomy.
• American Society of Anesthesiologists (ASA)classification II-III patients.
• Patients who can use PCA.
• Patients who will sign the informed consent form.

Exclusion Criteria:

• History of opioid use for more than four weeks
• Chronic pain syndromes
• Patients with a history of local anesthetic or opioid allergy, hypersensitivity
• Alcohol and drug addiction
• Conditions where regional anesthesia is contraindicated
• Failure in the dermatomal examination performed after the block
• Emergency surgeries and redo surgeries.
• Individuals with obstructive sleep apnea.
• Left ventricular ejection fraction less than 30%.
• Patients with severe psychiatric illnesses (such as psychosis, dementia) that limit cooperation with verbal numerical pain scales.
• Pregnant and breastfeeding patients.
• Hematological disorders.
• Significant impairment in the function of a major organ (e.g., severe hepatic or renal disease).
• Patients who cannot be extubated within the first 6 hours postoperatively.

Sealed opaque envelopes containing study participation numbers will be used to assign each patient. A researcher not involved in patient follow-up will use the web-based "Research Randomizer" (Urbaniak and Plous 2013) tool to give each participation number to a random group with a 1:1 ratio. A nurse not an active investigator in the study will have each participant choose an envelope containing the study participation number. They will inform the anesthetist administering the block/blocks about which group the patient is in immediately before administration. Researchers, surgeons, and nurses will not be aware of the randomization of groups.