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.