RESUMEN
PURPOSE: Postoperative pain is a common consequence of surgery. Pre-emptive analgesia involves the initiation of analgesics prior to surgical incision. This has been proposed as a simple method to help reduce postoperative pain, which may be more effective in higher-risk populations such as cervical spine surgery. A previous meta-analysis has demonstrated that pre-emptive acetaminophen may be effective in reducing postoperative pain although the certainty of evidence was limited. This present paper is an updated meta-analysis comparing pre-emptive acetaminophen versus postincision acetaminophen in adult patients undergoing surgery. DESIGN: Systematic review and meta-analysis with the inclusion of an unpublished randomized, placebo-controlled, double-blind trial. METHODS: An updated meta-analysis was conducted which searched electronic databases to identify randomized controlled trials with the same interventions. FINDINGS: We included 845 participants and 12 studies in the updated meta-analysis. The meta-analysis (including our trial) found reduced 24-hour morphine consumption in the pre-emptive group (mean difference -2.42 mg; 95% confidence interval -4.26 to -0.59 mg), as well as reduced postoperative vomiting (risk ratio 0.56; 95% confidence interval 0.36 to 0.88). There was no difference between pre-emptive acetaminophen and control groups for time to analgesic request, pain scores at 6 and 24 hours or pruritis. For all outcomes assessed, there was very low certainty of evidence. CONCLUSIONS: This meta-analysis found pre-emptive acetaminophen reduced 24-hour opioid consumption and postoperative vomiting.