Effect of Postoperative Analgesia on Major Postoperative Complications: A Systematic Update of the Evidence

BACKGROUND: Few individual clinical trials have had sufficient subject numbers to definitively determine the effects of postoperative analgesia on major outcomes. METHODS: We systematically searched the Medline and the Cochrane Library databases for the past decade and focused on meta-analyses and large, randomized, controlled trials. RESULTS: Eighteen meta-analyses, 10 systematic reviews, 8 additional randomized, controlled trials, and 2 observational database articles were identified for review or comment. Epidural analgesia with local anesthetics has the greatest theoretical potential to affect major outcomes and has been the most thoroughly investigated technique. The majority of evidence favors an ability of epidural analgesia to reduce postoperative cardiovascular and pulmonary complications only after major vascular surgery or in high-risk patients. This finding may become irrelevant because of rapid conversion of major surgery to minimally invasive techniques (e.g., endoluminal abdominal aortic repair) that carry less risk of complications. There is also consistent evidence that epidural analgesia with local anesthetics is associated with faster resolution of postoperative ileus after major abdominal surgery. Again, this finding may also become irrelevant with the adoption of laparoscopic techniques and multimodal fast-track programs for abdominal surgery. There is no current evidence that perineural analgesia, continuous wound catheters using local anesthetics, IV patient-controlled analgesia with opioids, or addition of multimodal systemic analgesics have any clinically significant beneficial effect on postoperative complications. CONCLUSIONS: Overall, there is insufficient evidence to confirm or deny the ability of postoperative analgesic techniques to affect major postoperative mortality or morbidity. This is primarily due to typically insufficient subject numbers to detect differences in currently low incidences of postoperative complications.