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 < 0.001) and the number of needle passes was significantly higher (4.40 ± 1.14 vs 2.87 ± 0.79, P < 0.001).
Conclusion: The MDI technique has a higher success rate for complete sensory block of the ulnar nerve within 15 min of local anaesthetic injection. The time needed to perform the block is about 1 min longer than the traditional technique.
Trial registration: http://www.chictr.org.cn with the registration number of ChiCTR-IOR-15007588.