Current status of pre-emptive analgesia

Abstract

The controversy over preemptive analgesia continues unabated, with studies both supporting and refuting its efficacy. The timing of an analgesic intervention and presence of a placebo control may have significant impact on the interpretation of results and may have led to the premature conclusion that preemptive analgesia is of limited clinical utility. A review of the recent literature using strict definitions of preemptive and preventive analgesia is required in order to clarify the broader issue of the benefits of perioperative analgesia. A total of 27 studies, published from April 2001 to April 2002, were found to evaluate preemptive (n = 12) or preventive analgesia (n = 15). Evidence for a benefit of preventive analgesia was strong, with 60% of studies finding reduced pain or analgesic consumption beyond the clinical duration of action of the analgesic intervention. Evidence for a benefit of preemptive analgesia was equivocal, with 41.7% of studies demonstrating that preincisional treatment reduces pain or analgesic consumption to a greater extent than does postincisional treatment. Studies that used a preventive design had a greater likelihood of finding a beneficial effect. The application of preventive perioperative analgesia (not necessarily preincisional) is associated with a significant reduction in pain beyond the clinical duration of action of the analgesic agent, in particular for the N-methyl-D-aspartate antagonists. The classical definition of preemptive analgesia should be abandoned in favor of preventive analgesia. This will broaden the scope of inquiry from a narrow focus on preincisional versus postincisional interventions to one that aims to minimize postoperative pain and analgesic requirements by reducing peripheral and central sensitization arising from noxious preoperative, intraoperative and postoperative inputs.