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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.

Background: Gabapentin is an antiepileptic drug used in a variety of chronic pain conditions. Increasing numbers of randomized trials indicate that gabapentin is effective as a postoperative analgesic. This procedure-specific systematic review aims to analyse the 24-hour postoperative effect of gabapentin on acute pain in adults.

Substantial progress has been made during the last decades in our understanding of acute pain mechanisms, and this knowledge has encouraged the search for novel treatments. Of particular interest has been the observation that tissue injury initiates a number of modulations of both the peripheral and the central pain pathways, which convert the system from a 'physiological' to a 'pathological' mode of processing afferent information. Gabapentin, which binds to the alpha(2)delta subunit of the voltage-dependent calcium channel, is active in animal models of 'pathological' but not in models of 'physiological' pain. Consequently, attention has so far been focused on neuropathic pain as a target for the clinical use of gabapentin and analogues. Recently, several reports have indicated that gabapentin may have a place in the treatment of post-operative pain. This article presents a brief summary of the potential mechanisms of post-operative pain, and a systematic review of the available data of gabapentin and pregabalin for post-operative analgesia. It is concluded that the results with gabapentin and pregabalin in post-operative pain treatment published so far are promising. It is suggested that future studies should explore the effects of 'protective premedication' with combinations of various antihyperanalgesic and analgesic drugs for post-operative analgesia.

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