Background & objective: Traditionally, analgesia after heart surgery is obtained with the use of intravenous opioids (particularly morphine). Continuous infusion of narcotic analgesics results in a more constant level of analgesia, but slow accumulation may cause excessive sedation. The caudal epidural narcotics, alone or with local anesthetics have been advocated following lower abdominal and thoracic surgery in children. We compared the analgesic effect and safety of caudal epidural morphine (CEM) after heart surgery with intravenous morphine infusion. Methodology: Sixty children, aged 6 months to 5 y, undergoing elective cardiac surgery under general anesthesia were enrolled in the study. The patients were randomly allocated to one of the two groups to receive either 0.06 mg/kg CEM at induction of anesthesia (study group or CEM group) or postoperative morphine infusion at a rate of 0.025 mg/kg/h intravenously (control group or PIVM group). Postoperative pain scores were assessed according to the COMFORT behavior scale. Two patients were excluded from the study after randomization and 58 patients completed the study. Results: Time from pediatric intensive care unit (PICU) admission to the need of intravenous morphine boluses was significantly longer in the CEM group compared with the control group (16-20 h vs 38 min; P < 0.0001). In CEM group, 68.97% of patients did not require additional morphine and the total intravenous morphine consumption over the 48 h postoperatively was lower (P < 0.0001). Moreover, the use of CEM resulted in earlier extubation and earlier discharge from the PICU (P = 0.011). Over-sedation was recorded in the control group on the first postoperative day. The incidence of adverse events was low in both groups. Respiratory depression was not seen in CEM group patients. Conclusion: A single dose of morphine 0.06 mg/kg in caudal epidural, preoperatively in pediatric cardiac surgery, had a significant intravenous morphine sparing effect as compared to a postoperative morphine infusion at a rate of 0.025 mg/kg/h, and was associated with a low incidence of adverse events after pediatric cardiac surgery. Effective analgesia was achieved for 16-20 h after surgery. Key words: Caudal epidural morphine; COMFORT behavior scale; Opioid–related adverse events; Pediatric cardiac surgery; Analgesia, Postoperative Citation: Nguyen TD, Ngo D, Pham NH, Jantzen T. Caudal epidural morphine versus intravenous morphine for postoperative analgesia in pediatric cardiac surgery. Anaesth. pain intensive care 2022;26(4):514-522. DOI: 10.35975/apic.v26i4.1959 Received: August 15, 2022; Reviewed: January 02, 2022; Accepted: July 07, 2022