Effect of adding magnesium sulphate to bupivacaine on the clinical profile of ultrasound-guided thoracic paravertebral block in patients undergoing modified radical mastectomy

Background
Paravertebral block is an effective perioperative analgesic modality in patients undergoing breast or thoracic surgery. Several adjuvants have been reported to improve the clinical profile of local anaesthetic-induced paravertebral block. In the present study, we hypothesized that the addition of magnesium sulphate could potentiate the analgesic effects of paravertebral bupivacaine in female patients undergoing modified radical mastectomy.
Methods
Ninety female patients ASA physical status 1 and 2 patients scheduled for modified radical mastectomy were allocated into 2 groups (45 patients each). Group (B) received bupivacaine 0.25% 0.3 ml/kg in the paravertebral space while group (BM) received 100 mg magnesium sulphate + bupivacaine 0.25% 0.3 ml/kg in the paravertebral space. Both blocks were done guided by ultrasound before induction of standard general anaesthetic technique which was the same in both groups. The two groups were assessed in the first post-operative 24 h for post-operative visual analogue scale (VAS) scores, time to first analgesic request, total 24 h morphine consumption, number of attacks of PONV and any complications from paravertebral block or from the drugs used in the study.
Results
Patients in group (BM) were found to have reduced VAS scores at 30 min, 2, 4, 6, 12, 24 h intervals post-operative. The time to first analgesic request was longer in patients of group (BM) with less amount of post-operative opioid consumption and consequently less number of attacks of PONV in first post-operative 24 h. These results were significant with a value < 0.001.
Conclusion
Adding magnesium sulphate to bupivacaine in ultrasound-guided paravertebral block resulted in more efficient analgesia and opioid-sparing in female patients undergoing modified radical mastectomy.