Double-injection technique assisted by a nerve stimulator for ultrasound-guided supraclavicular brachial plexus block results in better distal sensory-motor block: A randomised controlled trial.

BACKGROUND: To evaluate the efficacy of a nerve stimulator when used with ultrasound-guided double injection in supraclavicular brachial plexus block. OBJECTIVES: We hypothesised that targeting the inferior trunk of the plexus guided by a nerve stimulator would obtain a higher success rate of ulnar nerve blockade than the traditional double-injection technique. DESIGN: A blinded randomised controlled study. SETTING: Conducted at the University Hospital from October 2015 to January 2016. PATIENTS: Ninety patients undergoing upper extremity surgery were randomised into two equal groups. INTERVENTIONS: Patients were randomly allocated to a modified double-injection group (MDI group) or a traditional double-injection group (DI group). All patients received 23 ml of a 1 : 1 mixture of 2% lidocaine and 1% ropivacaine during ultrasound-guided supraclavicular brachial plexus block. In the MDI group (n = 45), half the volume was deposited within the brachial plexus sheath guided by ultrasound, next to the inferior trunk and verified by nerve stimulation; the remaining volume was deposited in the main neural cluster. In the double-injection group (n = 45), the first half volume was deposited on ultrasound guidance alone. Sensory-motor blockade of the musculocutaneous, median, radial, ulnar nerves and surgical anaesthesia, performance time, number of needle passes and complications were recorded. MAIN OUTCOME MEASURES: The success rate of complete sensory block of the ulnar nerve within 15 min after local anaesthetic injection. RESULTS: Compared with the DI group the MDI group had higher success rates of complete sensory block of the ulnar nerve (93 vs 67%, P = 0.002) and complete anaesthesia (80 vs 56%, P = 0.014) at 15 min, whereas the average performance time was significantly longer (5.08 +/- 1.41 vs 4.10 +/- 0.64 min, P

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