Intraoperative Ketamine for Chronic Postoperative Pain After Open-Heart Surgery

The goal of this interventional study is to determine whether a single intraoperative IV dose of ketamine can reduce postoperative chronic and acute pain and postoperative opioid requirements in adult patients undergoing open-heart surgery under general anesthesia. The main questions it aims to answer are: Primary outcome: Does a single-dose intraoperative IV ketamine reduce the presence and severity of pain at 3 and 6 months after surgery ? Secondary outcomes: Does it reduce acute postoperative pain scores, opioid consumption, and other recovery-related outcomes in the early postoperative period ? Researchers will compare a single-dose IV ketamine arm to a placebo arm to see if ketamine decreases chronic pain incidence at 3 and 6 months and improves acute pain/opioid-related outcomes. Participants will: Be randomized to receive either a single IV bolus of ketamine or placebo during surgery. Undergo standard general anesthesia and open cardiac surgery per protocol. Have postoperative pain assessed using Numeric Rating Scale (NRS) at extubation, 0, 3, 6, 12, 24, and 48 hours. Have opioid and additional analgesic use recorded, time to first rescue analgesic noted, and ICU/hospital length of stay tracked. Be evaluated for ICU delirium (CAM-ICU) and complete Quality of Recovery-15, Brief Pain Inventory-Short Form, and Pain Self-Efficacy questionnaires. Be followed up at 3 and 6 months for assessment of chronic postoperative pain.