Different Analgesic Routes of Magnesium Sulfate: Intravenous versus Pectoralis II Interfascial Plane Block for Breast Cosmetic Surgeries

PURPOSE: The purpose of the study is to evaluate the most effective analgesic route of magnesium sulfate (MgSO(4)) either intravenous (i.v.) or pectoralis interfascial plane block. PATIENTS AND METHODS: Fifty adult female patients were divided into two equal groups: i.v. MgSO(4) and Pecs II block MgSO(4) (Pecs MgSO(4)) group. After general anesthesia, in i.v. MgSO(4) group, the local anesthetic (LA) for Pecs II block was prepared by adding 3 mL saline to 57 mL bupivacaine 0.25% divided equally for each side. A bolus i.v. solution of MgSO(4) 10% 0.5 mL.kg(-1) diluted in saline in a total volume of 100 mL was given over 15 minutes. Then, the solution for continuous i.v. infusion; 30 mL MgSO(4) 10% and 70 mL saline was infused at the rate of 0.5 mL.kg(-1).h(-1) intraoperatively. For PecsMgSO(4) group, LA formed of 3 mL MgSO(4) 10% added to 57 mL bupivacaine 0.25%. Whereas, 100 mL saline was given as bolus i.v. followed by continuous infusion of 100 mL normal saline at the rate of 0.5 mL.kg(-1).h(-1). RESULTS: In the group received MgSO(4)-bupivacaine Pecs II block, there was a nonsignificant decrease in postoperative morphine consumption compared to i.v. administration of MgSO(4). The two groups were comparable in the intensity of pain and sedation scores. CONCLUSION: The use of bupivacaine Pecs II block enhanced with addition of MgSO(4) to pectoralis interfascial plane block or intravenously in patients underwent breast cosmetic surgeries under general anesthesia was associated with comparable results of the postoperative morphine requirements, intensity of postoperative pain, and extension of the duration of postoperative analgesia. The intraoperative hemodynamic effects i.v. MgSO(4) were superior to the pectoralis interfascial plane route of administration.