Background: Peripheral nerve blocks provide effective anaesthesia and analgesia for upper limb surgeries while minimising systemic effects of general anaesthesia. Supraclavicular brachial plexus block (SCBPB) is preferred for distal arm and forearm surgeries due to rapid onset and dense sensory-motor blockade. Levobupivacaine, an S-enantiomer of bupivacaine, offers long-acting analgesia with reduced cardiotoxicity. The optimal combination of volume and concentration for SCBPB remains under investigation, particularly regarding block characteristics and phrenic nerve involvement.

Objective: To compare the effects of two different volumes and concentrations of levobupivacaine—15 mL of 0.5% versus 30 mL of 0.25%—on sensory and motor block characteristics, duration of analgesia, and incidence of hemidiaphragmatic paresis in patients undergoing ultrasound-guided SCBPB for elective upper limb surgeries.

Methods: In this prospective randomised controlled study, 66 patients (ASA I–III) scheduled for elective distal arm or forearm surgery were randomly assigned into two groups: Group I received 15 mL of 0.5% levobupivacaine, and Group II received 30 mL of 0.25% levobupivacaine (total dose 75 mg in both groups). Sensory and motor block onset and duration, diaphragmatic movement, postoperative analgesia, rescue analgesic requirement, hemodynamics, and adverse events were recorded. Diaphragmatic excursion was assessed via ultrasound at baseline, 30 minutes, and 4 hours post-block.

Results: Group I demonstrated significantly faster onset of sensory (7.12 ± 1.58 min vs 8.63 ± 1.72 min, p=0.004) and motor block (9.85 ± 1.92 min vs 11.46 ± 2.10 min, p=0.006), longer duration of sensory (585.33 ± 45.67 min vs 552.27 ± 41.42 min, p=0.013) and motor block (524.15 ± 39.52 min vs 498.67 ± 36.84 min, p=0.021), and prolonged analgesia (608.48 ± 47.23 min vs 562.36 ± 42.18 min, p=0.009) compared to Group II. Rescue analgesic requirements were lower in Group I (1.21 ± 0.42 vs 1.48 ± 0.39, p=0.015). The incidence of complete hemidiaphragmatic paresis was higher in Group I (21.2% vs 6.1%, p=0.038). Hemodynamic parameters were stable and comparable in both groups, and adverse events were minimal.

Conclusion: In ultrasound-guided SCBPB, 15 mL of 0.5% levobupivacaine provides faster onset, longer duration, and denser sensory and motor blockade compared to 30 mL of 0.25%, but with a higher incidence of hemidiaphragmatic paresis. Both regimens are safe and hemodynamically stable. Selection of volume and concentration should consider the patient's respiratory status and clinical requirements to balance block quality with diaphragmatic safety.