Efficacy of Two Doses of Dexmedetomidine as an Adjuvant to Intrathecal Hyperbaric Ropivacaine in Lower Limb Surgeries: A Randomised Controlled Trial

Introduction: Regional anaesthesia techniques are widely used for lower limb surgeries, offering superior postoperative pain relief and faster recovery. Dexmedetomidine, a highly selective α2-adrenergic agonist, has emerged as a promising adjuvant to local anaesthetics in intrathecal anaesthesia, providing prolonged analgesia without significant adverse effects. Aim: To compare the efficacy of two different doses of dexmedetomidine (5 mcg versus 10 mcg) as an adjuvant to intrathecal hyperbaric ropivacaine in patients undergoing lower limb surgeries. Materials and Methods: This double-blinded, randomised controlled trial was conducted at the Department of Anaesthesia and Critical Care, Pradyumna Bal Memorial Hospital (PBMH), Kalinga Institute of Medical Science, Bhubaneswar, Odisha, India, from May 2023 to September 2025. The study included 76 American Society of Anaesthesiologists (ASA) physical status I-II patients aged 18-60 years undergoing elective lower limb surgeries. Patients were randomly allocated into two groups. Group A (n=38) received 3 mL of 0.75% hyperbaric ropivacaine with 5 mcg dexmedetomidine, and Group B (n=38) received 3 mL of 0.75% hyperbaric ropivacaine with 10 mcg dexmedetomidine intrathecally. Primary outcomes included postoperative Visual Analogue Scale (VAS) scores and duration of analgesia. Secondary outcomes encompassed haemodynamic parameters, onset of sensory and motor blocks, sedation scores, and adverse effects. Data analysis was performed using IBM Statistical Package for Social Sciences (SPSS) software version 25.0 with the Mann-Whitney U test for continuous variables and the Chi-square test for categorical variables. A p-value <0.05 was considered statistically significant. Results: Both groups were comparable regarding demographic variables, including age (group A: 41.0±10.5 years vs group B: 38.5±11.2 years, p-value=0.28), gender distribution, Body Mass Index (BMI), and ASA physical status. Group B demonstrated significantly lower VAS scores at 2, 4, 6, and 8 hours postoperatively compared to Group A (p-value <0.05). At 2 hours, mean VAS was 1.5±1.2 in group B versus 3.2±1.5 in group A (p-value=0.01). The requirement for rescue analgesia was significantly delayed in group B, with 71.05% of group A patients requiring tramadol at 6 hours versus only 2.63% in group B (p-value <0.001). Group B achieved faster sensory block onset to T8 level (mean time: 4.5±0.8 minutes) compared to group A (mean time: 5.8±1.2 minutes, p-value=0.01). Haemodynamic parameters remained stable in both groups with no significant differences. No cases of postoperative nausea and vomiting were observed in either group. Conclusion: Intrathecal dexmedetomidine 10 mcg provides superior postoperative analgesia, faster sensory block onset, and reduced rescue analgesic requirements compared to the 5 mcg dose, while maintaining a comparable haemodynamic safety profile. This higher dose represents an optimal balance between enhanced analgesic efficacy and safety in lower limb surgeries.