Comparative efficacy of two doses of dexmedetomidine as an adjuvant to ropivacaine in paravertebral block for post-mastectomy analgesia: A randomized, double-blind study

Background: Thoracic paravertebral block (TPVB) is a cornerstone for multimodal analgesia following modified radical mastectomy (MRM). This study evaluated the efficacy and safety of two different doses of dexmedetomidine as an adjuvant to ropivacaine in TPVB.Methods: In this prospective, randomized, double-blind trial, 60 female patients (ASA I-II) scheduled for MRM were allocated into three groups (n=20 each). All received a preoperative single-injection TPVB with 20 mL of 0.75% ropivacaine, combined with either saline (Group C), dexmedetomidine 1 µg/kg (Group A), or dexmedetomidine 0.5 µg/kg (Group B), followed by general anaesthesia. Primary outcome was the duration of postoperative analgesia. Secondary outcomes included pain scores (VAS), 24-hour opioid consumption, hemodynamic parameters, and complications.Results: The duration of analgesia was significantly prolonged in both Group A (mean [SD]: 680 [85] min) and Group B (665 [78] min) compared to Group C (310 [65] min) (p < 0.001). However, there was no statistically significant difference between Group A and Group B (p = 0.52). Total tramadol consumption was lower in Groups A and B than in C (p < 0.05). Heart rate and mean arterial pressure were significantly lower in Group A compared to both Group B and Group C at multiple intra- and postoperative time points (p < 0.05). The incidence of clinically significant bradycardia was higher in Group A.Conclusion: The addition of dexmedetomidine (0.5 µg/kg or 1 µg/kg) to ropivacaine for TPVB significantly prolongs postoperative analgesia compared to ropivacaine alone. The lower dose (0.5 µg/kg) provides comparable analgesic benefits to the higher dose (1 µg/kg) while offering a superior hemodynamic stability profile, making it the more favorable adjuvant for this block.