A STUDY ON EFFICACY OF VARIABLE CONCENTRATIONS OF BUPIVACAINE IN ULTRASOUND-GUIDED ANTERIOR SCIATIC NERVE BLOCK FOR PATIENTS UNDERGOING LOWER LIMB SURGERIES

Abstract

Background: Ultrasound-guided peripheral nerve blocks have become an integral component of multimodal perioperative analgesia. Sciatic nerve block provides effective anaesthesia and postoperative analgesia for lower limb surgeries while reducing systemic opioid requirements. The optimal concentration of bupivacaine for anterior sciatic nerve block remains a subject of clinical interest. Aim: To compare the efficacy of 0.25% bupivacaine and 0.5% bupivacaine, both combined with dexamethasone, in ultrasound-guided anterior sciatic nerve block for lower limb surgeries. Methods: A prospective randomized study was conducted on 60 patients of American Society of Anaesthesiologists (ASA) physical status I and II, aged 18–75 years, undergoing lower limb surgeries at Sri Balaji Medical College and Hospital (SBMC&H), Tirupati, between November 2025 and April 2026. Patients were randomly allocated into two groups of 30 each. Group A received 15 mL of 0.25% bupivacaine with dexamethasone (4 mg/mL), while Group B received 15 mL of 0.5% bupivacaine with dexamethasone (4 mg/mL). Ultrasound-guided anterior sciatic nerve block was performed using the anterior approach. Parameters assessed included onset of sensory block, onset of motor block, duration of analgesia, time to rescue analgesia, quality of analgesia, and adverse effects. Statistical analysis was performed using Student’s t-test and Chi-square test. Results: Results: Demographic characteristics were comparable between the groups. The onset of sensory block was significantly faster in Group B (17.93 ± 2.18 min) compared with Group A (24.17 ± 2.90 min) (p<0.001). Similarly, motor block onset occurred earlier in Group B (28.43 ± 2.46 min vs 35.93 ± 3.23 min; p<0.001). Duration of analgesia was significantly prolonged in Group B (678.43 ± 34.12 min vs 449.50 ± 17.37 min; p<0.001), and time to first rescue analgesia was also longer (758.07 ± 41.24 min vs 525.20 ± 16.66 min; p<0.001). No major adverse effects or neurological complications were observed in either group. Conclusion: Ultrasound-guided anterior sciatic nerve block using 0.5% bupivacaine with dexamethasone provides faster sensory and motor blockade, prolonged postoperative analgesia, and delayed rescue analgesic requirement compared with 0.25% bupivacaine, while maintaining a favourable safety profile.