Journal: Anesth Analg 106(5):1548-1552, 2008
Reprint: Dept of Anesthesiology and Intensive Care, Faculty of Medicine, Ain-shams University, Cairo, Egypt (NM Elsharnouby, MD)
Faculty Disclosure: Abstracted by L. Easley, who has nothing to disclose.
Intraarticular local anesthetics are often used for pre¬vention of pain after arthroscopic knee surgery. Recent evidence suggests that N-methyl-D-aspartate (NMDA) receptors located in the peripheral somatic and visceral pain pathways play an important role in nociception. This randomized, prospective double-blind study investigated whether magnesium sulfate or bupivacaine results in a decrease in visual analog scale (VAS) scores followed by a reduction in analgesic requirement, and whether their combination would provide more reduction in VAS, and subse¬quently less analgesic requirement, than either drug alone.
One hundred and eight patients, ASA PS 1-2, under¬going arthroscopic meniscectomy were included in this randomized prospective study. Patients were randomized using a computer-generated randomiza¬tion list into one of four groups: placebo saline group (group S), magnesium group (group M), bupivacaine group (group B), and magnesium with bupivacaine group (group MB). Group M received 20 mL of isotonic saline containing 1 g magnesium sulfate, group B received 0.25% bupivacaine; group MB received 0.25% bupivacaine and 1 g of magnesium sulfate in 20 mL saline, whereas group S received 20 mL of saline.
VAS was recorded after surgery at 1, 2, 4, 6, 8, 12, and 24 hr. Patients were evaluated at rest and with movement. At 1, 2, 4, 6, 8, 12, and 24 hr, pain scores were significantly lower in group MB, and group B compared with either group M or group S. Pain scores were significantly lower in group MB com¬pared with those in group B at rest and on movement, respectively, at 1, 2, 4, 6, and 8 hr, whereas there was no significant difference in pain scores at 12 hr and 24 hr. Pain scores were significantly reduced in group M compared with group S only at 1 hour post¬operatively. The duration of analgesia was signifi¬cantly different among the groups. The 24-hr con¬sumption of ketorolac was significantly different among groups. Group MB used less than group B, group M and group S.
This study revealed a significant analgesic benefit from the intraarticular administration of combined magnesium and bupivacaine for postoperative anal¬gesia after arthroscopic knee surgery. Patients in the group receiving intraarticular magnesium and bupiva¬caine had reduced postoperative pain scores, a longer analgesic duration, and lower 24-hr analgesic use compared with the other groups receiving intra¬articular bupivacaine, magnesium, or saline. In this study, the analgesic effect of magnesium alone was significantly less than bupivacaine alone, suggesting local anesthetic action as a mechanism for this analgesic effect.
Intraarticular bupivacaine has a long safety record of effective intraarticular use after arthroscopic knee surgery with significant reduction in postoperative analgesic consumption and increasing the time to first analgesic dose demanded, which was confirmed in this study. It was concluded that magnesium com¬bined with bupivacaine produces a reduction in post¬operative pain when given intraarticularly in com¬parison to either bupivacaine or magnesium alone, or to saline placebo. |
