This work aimed to evaluate the
analgesic efficacy of
intra-articular injection of
magnesium sulphate (4%) compared with equivalent volume of
bupivacaine (0.5%) after outpatient knee
arthroscopic meniscectomy. Forty patients were randomly assigned to two groups. Group M (n = 20) received intra-articular
magnesium sulphate 4%, group B (n = 20) received
bupivacaine (0.5%).
Analgesic effect was evaluated by
analgesic duration, and by measuring
pain intensity at 1, 2, 4, 6, 12, 24 h both at rest and on knee movement to 90°. The primary outcome variable was
pain intensity on the VAS at 1, 2, 4, 6, 12, 24 h post arthroscopy at rest and on movement (flexion of knee to 90°), although the
magnesium group had lower time weighted averages (TWAs) at rest and on movement, these TWAs were not statistically significant. The median duration of postoperative
analgesia was significantly longer in the patients treated with
magnesium sulphate (528 min) than in the
bupivacaine group (317 min) (p < 0.0001), with less number of patients needing supplementary
analgesia in
magnesium group (8/20) than those of the
bupivacaine group (16/20) (p < 0.022). Also
analgesic consumption was significantly lower in the
magnesium sulphate group (p < 0.002). We concluded that the use of
magnesium sulphate is rational and effective in reducing
pain, and is more physiological and shortens
convalescence after outpatient
arthroscopic meniscectomy, however our hypotheses that
analgesic efficacy of intra-articular isotonic
magnesium sulphate would be superior to intra-articular local anaesthetic cannot be supported with this study.