Evaluation of Magnesium as an Adjuvant in Ropivacaine Induced Interscalene Brachial Plexus Block: A Prospective, Double-Blinded, Randomized Controlled Study

Abstract

Background: Interscalene block is a commonly performed procedure for surgery of shoulder and upper arm, however very few studies have studied the effect of magnesium sulphate when added in interscalene block.
 Aims: The primary aim was to compare block characteristics along with postoperative analgesia and the secondary aim was to study the side effect profile and postoperative analgesic requirements.
 Methods: We randomly recruited 60 American Society of Anaesthesiologists (ASA) physical status I and II patients, undergoing surgeries of the shoulder to receive ultrasound-guided interscalene block with 1 mL normal saline or 150 mg Magnesium sulphate added to 20ml of 0.5% ropivacaine.
 Statistical analysis used: Statistical Package for Social Sciences (SPSS version 21.0) was used for analysing the data. Chi-square test or Fisher’s exact probability test were used for categorical variables; while the continuous variables were compared by unpaired t-test or Mann-Whitney U test.
 Results: With the addition of magnesium sulphate, onset of sensory (10.03 ± 1.03 vs 12.73 ± 1.14 min) and motor block (15.17 ± 2.02 min vs 17.87 ± 1.41) was hastened. The duration (sensory 528.00 ± 14.98 min vs 376.83 ± 13.16 min, motor 429.83 ± 11.57 min vs 319.97 ± 6.800 min) and postoperative analgesia (527.77 ± 21.96 min vs 402.97 ± 12.83 min) (p < 0.001) were all prolonged by magnesium sulphate, with resultant decrease in requirement of postoperative analgesic dosage.
 Conclusion: Magnesium when added to local anaesthetics in interscalene block, effectively improves all characteristics of block and provides better postoperative analgesia.