A dose-finding randomised controlled trial of magnesium sulphate as an adjuvant in ultrasound-guided supraclavicular brachial plexus block.

BACKGROUND AND AIM

Magnesium sulphate (MgSO) has been used as an adjuvant in brachial plexus block with encouraging results; however, there is no consensus regarding its optimal dose. Thereby, we compared the efficacy of two doses of MgSO as an adjuvant in ultrasound (USG) guided supraclavicular brachial plexus block.

METHODS

Ninety patients, aged 20-60 years, belonging to American Society of Anesthesiologists physical status 1 or 2, were given USG-guided supraclavicular block. Group B ( = 30) received 20 ml of 0.5%bupivacaine + 5 ml normal saline (NS), Group BM( = 30) received 20 ml of 0.5%bupivacaine + 3.75 ml NS and 125 mg MgSO (1.25 ml) and Group BM( = 30) received 20 ml of 0.5%bupivacaine + 2.5 ml NS and 250 mg MgSO (2.5 ml). The primary outcome of study was the duration of post-operative analgesia. The normally distributed data were analysed using analysis of variance and categorical data analysed using Chi-square test.

RESULTS

Duration of post-operative analgesia was prolonged in Groups BM and BM (665.13 ± 97.874, 475.10 ± 53.294) min respectively as compared to Group B (272.03 ± 40.404 min: = 0.00). The onset times of sensory and motor block were shorter in Group BM (5.17 ± 2.2 min) as compared to Groups BM and B (8.9 ± 2.3 and 17.7 ± 5.1 min: = 0.00) respectively. Sensory and motor block durations were prolonged in Group BM as compared to BM and B ( = 0.00).

CONCLUSIONS

MgSO as adjuvant in brachial plexus block increases the duration of post-operative analgesia. MgSO in the dose of 250mg has greater efficacy as compared to 125 mg.