The effect of combining lidocaine and ropivacaine on the duration and onset time of an ultrasound-guided infraclavicular brachial plexus nerve block

BACKGROUND: The combination of short- and long-acting local anaesthetics is traditionally associated with reduced block duration, though evidence remains inconsistent. OBJECTIVES: To investigate the effects of a fixed or reduced dose of a long-acting local anaesthetic (ropivacaine) mixed with a short-acting agent (lidocaine-epinephrine) on duration of analgesia and sensory onset time in lateral infraclavicular blocks. DESIGN: Randomised, blinded, active-controlled superiority trial. SETTING: A tertiary hospital in the Capital Region of Denmark, from 18 April to 23 November 2024. PATIENTS: Seventy-eight patients undergoing hand surgery under lateral infraclavicular brachial plexus nerve block. INTERVENTION: Patients were allocated to three groups: R150: 30 ml ropivacaine 5 mg ml -1 , R100-L200: 20 ml ropivacaine 5 mg ml -1 + 10 ml lidocaine-epinephrine 20 mg ml -1 + 5 μg ml -1 and R150-L200: 20 ml ropivacaine 7.5 mg ml -1 + 10 ml lidocaine-epinephrine 20 mg ml -1 + 5 μg ml -1 . MAIN OUTCOME MEASURES: The primary outcome was duration of analgesia, and secondary outcomes included sensory onset time. RESULTS: The duration of analgesia was 847 (152) min in the R150 group, 536 (198) min in the R100-L200 group, and 671 (234) min in the R150-L200 group. Compared with that in the R150 group, the mean duration of analgesia was reduced by 311 min (95% confidence interval [CI], 212 to 411; P < 0.001) in the R100-L200 group and by 177 min (95% CI, 64 to 289; P = 0.003) in the R150-L200 group. The difference between the R100-L200 and R150-L200 groups was not statistically significant after adjustment for multiple testing (135 min; 95% CI, 13 to 257; P = 0.031). Sensory onset times ranged insignificantly from 17 to 18 min across groups. CONCLUSION: Mixing lidocaine-epinephrine with ropivacaine significantly shortened the duration of analgesia by up to 5 h without affecting the sensory onset time. This effect was independent of the ropivacaine dose. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT06381622.