Effect of Magnesium Sulphate as an Adjuvant to Bupivacaine in Interscalene Brachial Plexus Block for Postoperative Analgesia

Abstract

Introduction: Ultrasound guided interscalene block is used for the upper limb surgeries. Various adjuvants have been used for prolonging the local anaesthetic action, without increasing the drug dosage. Aim: To evaluate the effect of magnesium sulphate (MgSO4 ) as an adjuvant to bupivacaine on onset and duration of interscalene block, haemodynamic parameters, and requirement of postoperative analgesics. Materials and Methods: A total of 60 ASA I and II patients of age group 20-60 years were scheduled for shoulder and arm surgeries. The patients received 20 mL of 0.5% bupivacaine with 0.5 mL of MgSO4 (50%) in Group I and 20 mL of bupivacaine with 0.5 mL saline in Group II for ultrasound guided interscalene block. Onset and duration of sensory and motor block was noted. VAS score, time to first rescue analgesic and total analgesic used in 24 hour were recorded. Results: The demographic profile was comparable (p>0.05). The mean onset of sensory blockade and motor blockade was comparable in both the groups (p>0.05). The duration of sensory blockade was significantly prolonged in Group I (759.93 min) as compared to Group II (568.37 min) (p<0.001). The duration of motor blockade was 350.17 minutes in group I and 300.27 minutes in Group II and the difference was significant (p<0.001). The VAS scores were significantly lower in Group I as compared to Group II (p<0.05). The time to first rescue analgesic and total analgesic used in 24 hours were significantly less in group I (p<0.001). Conclusion: MgSO4 as an adjuvant to ultrasound guided interscalene block significantly improves the quality and duration of the block.

Keywords

• motor block
• sensory block
• ultrasound guided
• upper limb surgery