Comparison of block characteristics and outcomes in opioid-free and opioid-based thoracic continuous spinal anaesthesia in patients undergoing major abdominal surgery: A double-blinded randomised controlled trial.

Background and aims: Thoracic continuous spinal anaesthesia (TCSA) is emerging as the sole anaesthetic for major abdominal surgery due to its better perioperative outcomes. This study was designed to evaluate block characteristics and outcomes in 'opioid-free' and 'opioid-based' TCSA.

Methods: After ethical approval, trial registration and written informed consent, 50 adult patients undergoing major abdominal surgery were randomised into 'opioid-free' (bupivacaine alone) and 'opioid-based' (bupivacaine with fentanyl) groups. After confirmation of T4-L1 dermatome level of spinal anaesthesia, sedation by intravenous (IV) midazolam (0.02-0.05 mg/kg), ketamine (0.25 mg/kg) and dexmedetomidine (bolus dose of 1 µg/kg IV over 10 min followed by 0.2-0.7 µg/kg/h infusion) were started. The primary outcome measured was postoperative pain scores for 72 h in both groups. The secondary objectives were rescue opioid requirement, and the dose of bupivacaine required to achieve T4 level. Data were compared using the two-sided Student t-test, Mann-Whitney and Fisher's exact tests.

Results: The 'opioid-based' group performed significantly better compared with the 'opioid-free' group concerning pain scores at rest at 0 h (P = 0.023), 18 h (P = 0.023) and 24 h (P = 0.016) postoperatively, decreased intrathecal bupivacaine requirement [(induction (P = 0.012) and maintenance (P = 0.031)], postoperative rescue fentanyl requirement (P = 0.018) and patient satisfaction (P = 0.032) at the cost of increased postoperative nausea and vomiting (P = 0.049).

Conclusion: The 'opioid-based' TCSA provided better postoperative analgesia with significantly lesser postoperative pain scores when compared to the 'opioid-free' group in patients undergoing major abdominal surgery.