Pre-emptive analgesia: How important is it in clinical reality?

Surgical trauma induces nociceptive sensitization leading to amplification and prolongation of postoperative pain. In experimental studies, preinjury (e.g. pre-emptive) neural blockade using local anaesthetics or opioids has been shown to prevent or to reduce postinjury sensitization of the central nervous system, while similar techniques applied after the injury had less or no effect. Several clinical studies have evaluated possible preemptive a nalgesic effects by administering prior to surgery a variety of analgesic d rugs both systemically or epidurally. These treatment modalities were compa red to the same treatment following surgery or to control groups not given such treatment. In general, the results from these studies have been disapp ointing, although some clinical studies have confirmed the impressive resul ts from animal studies. The present paper discusses deficiencies in study d esign of clinical trials, since the question regarding the effectiveness of pre-emptive analgesic regimens lies not so much in the timing of analgesic administration (e.g, preinjury vs. postinjury treatment), but in the effec tive prevention of altered central sensitization. Recent evidence suggests that administration of analgesics in order to effectively pre-empt postoper ative pain should start before surgery and furthermore, this treatment shou ld be extended into the early postoperative period.