Ropivacaine and magnesium sulfate in sciatic nerve block at the popliteal level: randomized double-blind study

Following surgical procedures, over 80% of patients experience acute pain, with half of them expressing dissatisfaction with pain relief. The modern approach to surgical treatment and pain management increasingly relies on implementing multimodal analgesia, which includes the use of adjuvants in addition to long-acting local anesthetics (such as ropivacaine). This double-blind randomized study evaluated the analgesic effect of magnesium sulfate added to ropivacaine in the sciatic nerve block at the popliteal level for bunion correction surgery.

In this double-blind study, fifty patients were enrolled and randomized in a 1:1 ratio to receive ropivacaine and MgSO4 200 mg or ropivacaine and physiological solution. The primary endpoint was the duration of sensory block.

A statistically significant difference was observed in the onset time for sensory block (9.2 minutes vs. 21.8 minutes, P<0.001) and its duration (18.2 hours vs. 13.9 hours, P<0.001) between the two groups. Between 12 and 24 hours postoperatively, the maximum NRS pain scores in the magnesium group were lower than those in the control group (IQR [range]) 2 (2-3.8 [0-6.5]) vs. 6.7 (5.6-7.9 [2.7-9.2], P<0.001). The need for additional opioids after 12-24 hours was significantly higher in patients in the physiological solution group compared to those in the magnesium group.

Our results suggest that magnesium added to the local anesthetic extends sensory block duration, reduces postoperative pain, improves the quality of analgesia, decreases the need for additional opioids. Further studies are needed to confirm these preliminary findings.