Intraarticular injection of magnesium sulphate

Tag : magnesium aspartate
Introduction
Following arthroscopic knee surgery, intraarticular bupivacaine isoften used for pain prevention. The authors hypothesised thatintraarticular magnesium, an N-methyl-D-aspartate receptor blocker,might be effective in producing postoperative analgesia orenhancing the analgesic effect of intraarticular bupivacaine. Theytherefore designed a study to determine whether intraarticularmagnesium sulphate or bupivacaine results in a decrease in visualanalogue scale (VAS) score followed by a decrease in analgesicrequirement, and whether their combination would enhance thereduction in VAS, and subsequently result in less analgesicrequirement, than either drug alone.

Methods
A total of 108 patients undergoing arthroscopic meniscectomy wererandomised blindly into one of four parallel groups. The salineplacebo group received 20 ml of isotonic saline; the magnesiumgroup received 20 ml of isotonic saline containing 1 g magnesiumsulphate; the bupivacaine group received 0.25% (20 ml) bupivacaine;and the magnesium with bupivacaine group received bupivacaine 0.25%and 1 g of magnesium sulphate in 20 ml. Postoperative analgesia wasassessed using VAS recorded after surgery at 1, 2, 4, 6, 8, 12 and24 hours, and patients were evaluated at rest and with movement.

Results

The magnesium with bupivacaine group was found to have asignificantly reduced VAS (both at rest and on movement), asignificantly increased time to first postoperative analgesicrequest and also a significantly reduced total analgesicrequirement than other groups.

Conclusions
The authors conclude that magnesium combined with bupivacaineproduces a reduction in postoperative pain when givenintraarticularly, in comparison with either bupivacaine ormagnesium alone, or to saline placebo.