Interscalene brachial plexus block for shoulder arthroscopic surgery: Prospective randomised controlled study of effects of 0.5% ropivacaine and 0.5% ropivacaine with dexamethasone

BACKGROUND AND AIMS: Various adjuvants have been used to prolong the duration of local anaesthetic action after peripheral and regional nerve blocks. We evaluated the effect of dexamethasone on the duration of pain relief in shoulder arthroscopic surgeries performed under interscalene brachial plexus using ropivacaine as local anaesthetic. METHODS: After Ethical Committee approval and informed consent from patients we performed a prospective, randomised, comparative study on patients scheduled for arthroscopic shoulder surgery under interscalene block (ISB). Patients in ropivacaine group (Group R) received 30 ml of 0.5% ropivacaine plus 2 ml normal saline (n = 50) and dexamethasone-ropivacaine (Group RD) received 0.5% ropivacaine 30 ml plus 8 mg dexamethasone (4 mg/ml) (n = 50). Duration of analgesia, onset of sensory and motor block, success and failure of block, and complications were recorded and compared. Computer software SPSS version-16 (SPSS Inc., Chicago, Illinois, USA) was used for statistical analysis. Chi-square test and Student's t-test were used and P < 0.05 was considered as significant. RESULTS: The mean duration of analgesia in Group RD was 1103.72 ± 296.027 min and in Group R it was 551.54 ± 166.92 min (P = 0.0001). Onset of sensory block in Group RD was 12.24 ± 1.88 min and in Group R was 13.48 ± 1.81 min (P = 0.5170). Onset of motor block in Group RD was 16.24 ± 2.04 min and in Group R was 17.76 ± 2.21 min (P = 0.2244). Onset of surgical anaesthesia in Group RD was19.46 ± 1.86 min and in Group R was 20.84 ± 1.71 min (P = 0.0859). CONCLUSION: Dexamethasone significantly prolonged duration of analgesia of ropivacaine during ISB used for arthroscopic surgeries of shoulder. Dexamethasone when mixed with ropivacaine had no effect on the onset of sensory and motor effects of ISB with ropivacaine.