Analgesic Effect of Dexmedetomidine or Magnesium Sulphate Added to Bupivacaine in Interscalene Brachial Plexus Block During Shoulder Arthroscopy

Abstract
Background: Shoulder surgery is accompanied with sig-nificant post-operative pain. Interscalene block is one of regional techniques which is effective and safe to control this pain. Magnesium Sulphate (MgSO4) & dexmedetomidine as adjuvants to bupivacaine is expected to prolong the block with minimal undesirable systemic effects.
Aim of Study: The aim of this work was to evaluate the post-operative analgesic effects of ultrasound guided intersca-lene brachial plexus block in elective shoulder surgeries under general anesthesia using either bupivacaine, bupivacaine-magnesium sulphate or bupivacaine-dexmedetomidine.
Material and Methods: This double blind RCT was carried out on 45 patients of both sexes, 18-60y, ASA I or II and scheduled for elective arthroscopic shoulder surgeries under GA. US guided interscalene block with total volume 20ml was done to all patients who randomly allocated into 3 equal groups: Group I (control group): 0.25% bupivacaine 18ml, Group II (Mg group): 0.25% bupivacaine 18ml + 2ml 10% MgSO4 200mg and Group III (Dex group): 0.25% bupivacaine 18ml + 2ml dexmedetomidine (100m g). HR & MAP at baseline, skin incision, 30, 60, 90 & 120min after skin incision and at 2h, 4h, 6h & 8h post-operative, onset & duration of sensory block, (VAS & sedation score) at 2, 4, 6, 8 & 12hrs post-operative, onset of 1st and total dose of meperidine and complications were measured.
Results: Our results showed no significant difference as regard to age, sex, ASA, duration & type of surgery, sedation score but there was significant decrease in HR, MAP, VAS, onset of sensory block & 1st analgesic requirements, total dose of rescue analgesic and prolongation in sensory block in Mg group & Dex group as compared to control group & also Dex group was superior to Mg group.
Conclusion: Dexmedetomidine 100μg was better than MgSO4 200mg when they added to bupivacaine 0.25% in US guided interscalene brachial plexus block as evidenced by prolongation of sensory block, improved quality of post-operative analgesia, decreased requirements of rescue analge-sics and providing desirable sedation without side effects.