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Transmission of pain signals evoked by tissue damage leads to sensitization of the peripheral and central pain pathways. Pre-emptive analgesia is a treatment that is initiated before the surgical procedure in order to reduce this sensitization. Owing to this 'protective' effect on the nociceptive system, pre-emptive analgesia has the potential to be more effective than a similar analgesic treatment initiated after surgery. Theoretically, immediate postoperative pain may be reduced and the development of chronic pain may be prevented. Although some clinical studies have demonstrated significant effects on acute postoperative pain, no major clinical benefits of pre-emptive analgesia have been documented. The only way to prevent sensitization of the nociceptive system might be to block completely any pain signal originating from the surgical wound from the time of incision until final wound healing. Other pharmacological interventions, including 'antihyperalgesic' drugs such as NMDA-receptor antagonists and gabapentin, may interfere with the induction and maintenance of sensitization. Future studies will investigate the analgesic effect of prolonged multimodal combinations of different classes of 'traditional' analgesics and 'antihyperalgesics' on postoperative pain.

In a qualitative systematic review, we have evaluated randomized controlled trials (RCT) of incisional local anaesthesia compared with placebo or no treatment in the control of postoperative pain after open abdominal operations. Twenty-six studies with data from 1211 patients were considered appropriate for analysis. Five RCT considered inguinal herniotomy, four hysterectomy, eight cholecystectomy and nine studies a variety of surgical procedures. Outcome measures were pain scores, supplementary analgesics and time to first analgesic request. Efficacy was estimated by significant difference (P < 0.05), as reported in the original investigation. All studies of herniotomy showed a 2-7-h duration of clinically relevant improved pain relief. Results of hysterectomy studies were inconclusive, with two being negative. Five of the cholecystectomy studies showed significant differences but questionable clinical importance and validity in three. In various other procedures results were inconsistent and in some of minor clinical importance. Except for herniotomy, there was a lack of evidence for effect of incisional local anaesthesia on postoperative pain and further standardized studies are needed before recommendations can be made.