[Prophylaxis of phantom pain: is regional analgesia ineffective?]

A recently published randomized study failed to show a significant reduction of phantom limb pain after perioperative epidural analgesia EDA [9]. Since these findings were not supported by previous studies,we conducted an analysis of factors contributing to the results of phantom limb pain prophylaxis. We calculated the efficacy of perioperative EDA as "Number Needed to Treat" (NNT).

Included studies were retrieved by a medline-search from 1966 to 1999 and published articles on phantom limb pain prophylaxis. First,we analyzed the influence of patient data, type of intervention and study design on the results. Then,we stratified studies in comparable groups and outcome measures. The efficacy of perioperative EDA in phantom limb pain prophylaxis was calculated using NNT's. The outcome criterion in this analysis was "free of phantom limb pain < or = 3 on an analogue scale from 0 ( no pain) to 10 (worst pain) 12 months after amputation".

Variations in preoperative pain, start and duration of regional analgesia and the definition of phantom limb pain were associated with different results. After stratifying the results by the above mentioned definition of phantom pain intensity, only time and duration of regional analgesia showed effects on the study results. Pre-, intra- and postoperative EDA was associated with a significant reduction of phantom limb pain 12 months after amputation, NNT = 5,8 (95%-CI 3,2-28,6). However, a reduction of phantom limb pain by postoperative EDA alone could not be confirmed on the basis of the analysed data.

Perioperative EDA has been shown to be an effective prophylaxis of phantom limb pain. The most important differences between studies were the definition of phantom limb pain by intensity ratings. Thus, perioperative EDA does not completely abolish phantom limb pain, but increases the number of patients with a mild form of phantom pain.