Wound infiltration with local anesthetics for post-operative pain relief in lumbar spine surgery: a systematic review.

BACKGROUND: In this systematic review, we evaluated double-blind, randomized and controlled trials on the effect of wound infiltration with local anesthetics compared with the effect of placebo on post-operative pain after lumbar spine surgery.
METHODS: Medline, the Cochrane Library and Google Scholar were searched for appropriate trials. Qualitative analysis of post-operative effectiveness was evaluated by assessment of significant difference (P < 0.05) between study groups regarding pain relief using pain scores, supplemental analgesic consumption and time to first analgesic request as outcome measures. Data on adverse effects were extracted and evaluated.
RESULTS: Nine trials including 12 comparisons and 529 patients met the inclusion criteria. Ten comparisons presented data on pain scores. In only three of these 10 comparisons (30%), a reduction in pain score using local anesthetic infiltration was observed averaging between 8 and 40 mm on a 100 mm visual analog scale. In six out of 12 comparisons, the local anesthetic infiltration significantly reduced the supplemental opioid consumption after surgery. Observed reductions in analgesic consumption over the first 24 h averaged between 2.5 mg and approximately 15 mg of morphine. Data on opioid-related adverse effects were incomplete and difficult to interpret.
CONCLUSION: Interpretation of the results was difficult because of diversity of the studies. However, clinical significance was in general questionable, with only a few trials showing a small or a modest reduction in pain intensity, which was observed mainly immediately after the operation. Similarly, although more frequently observed, only a minor and probably not clinically relevant reduction in opioid consumption was shown.