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Acute Pain | Chronic Pain | General

Preemptive analgesia update

Clinical bottom line

A large systematic review confirms that pre-emptive analgesia for postoperative pain relief provides no more analgesia than the same intervention given after surgery.


Reference

S Møiniche et al. A Qualitative and Quantitative systematic review of preemptive analgesia for postoperative pain relief. The role of timing of analgesia. Anesthesiology 2002 96: 725-741.

Review

Randomised double-blind studies for acute or chronic postoperative pain involving the same intervention before versus after surgical incision were sought using Cochrane Library and Medline. Reports with preoperative use of analgesic compared with placebo or no treatment, or preoperative versus preoperative plus postoperative treatment were not considered because they provide no evidence of a preemptive effect, where the timing of the start of pain therapy is important.

Weighted mean difference for VAS pain scored averaged over the first 24 postoperative hours was used, and where categorical data only were available, these were converted into VAS scores. Analysis was by type of analgesic (opioid, local anaesthetic, NMDA antagonist, NSAID, nerve blocks or wound infiltration).

Results

There were 80 randomised trials with 3,761 patients (mean size 10 to 128). The median quality score was 4 (range 2-5).

Preemptive use of analgesics in no instance resulted in better postoperative pain relief (Figure 1). In each case the weighted mean difference in VAS scores over the first 24 hours included no difference, except intravenous opioids, where the balance favoured postoperative use.

Figure 1: 95% confidence interval of the difference between intervention before and after incision. Numbers in brackets are the number of trials for each intervention.

Only one study reported on longer-term chronic pain.

Comment

This was a terrific and detailed review. With many more studies, it confirms the findings of an earlier review. It would require significant evidence to demonstrate that preemptive analgesia was better than postoperative for acute pain outcomes.

This leaves open other possible outcomes for investigation. First is whether preincisional use of analgesics could reduce the incidence of chronic pain after surgery . Another might be whether preoperative use of analgesics resulted in less use of opioids (which can result in PONV), or resulted in some other beneficial outcome.