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Acute Pain | Chronic Pain | General

Pre-emptive analgesia

Clinical bottom line:

Patients do not benefit from pre-emptive analgesia with NSAIDs and paracetamol at conventional dosing. There is weak evidence for local anaesthetic, but trials lack the necessary power. There is some evidence for pre-emptive opioid action, especially with intravenous administration, but trials are not of adequate design.

Trials of adequate design and size are required to assess the role of local anaesthetic and opioids in pre-emptive analgesia.


Pre-emptive analgesia in pain relief

Basic science suggests that analgesia given before a nociceptive stimulus begins will be more effective than the same dose given after the stimulus. The findings of two main animal models have been extrapolated to the clinical situation, and it has been suggested that the same dose of an analgesic given by the same route may be more effective if given before surgery compared with after. However, the animal models do not provide clear indications of a timeframe for the analgesic effect, or the underlying mechanism (for example, inflammatory change vs. nerve damage), or to which pain models these findings may apply (for example, somatic versus visceral pain, chronic versus acute).

Systematic review

McQuay HJ. Pre-emptive analgesia: a systematic review of clinical studies. Ann Med 1995; 27:249-56

Inclusion criteria were randomised controlled trials of pre-emptive analgesia with post-treatment comparison.

Findings

NSAID and paracetamol trials (with local anaesthetic)

Four trials were included (three NSAID and one paracetamol), all in oral surgery patients. Although trials demonstrated internal sensitivity, they consistently demonstrated no measurable differences between same doses given preoperatively and postoperatively.

Local anaesthetic trials (epidural, nerve block and infiltration)

Four of four epidural trials and the only nerve block trial demonstrated no evidence of a pre-emptive effect. One of two infiltration trials demonstrated a significant pre-emptive effect on time taken to remedication. However, it is unclear whether the negative trials were sufficiently sensitive to measure an effect if there had been one.

Opioid trials (epidural and intravenous)

The only spinal trial demonstrated a significant reduction in six hour pain intensity scores with pre-emptive analgesia. Two of three intravenous trials demonstrated increased pain relief with pre-emptive analgesia on a range of measures, and one of three trials demonstrated the opposite effect. Because of flaws in trial design, the evidence from these trials is inconclusive.

Adverse effects

No data available / not reported.

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