During the study, the randomization list was held securely at the hospital pharmacy and released only after study completion. The study drugs (gabapentin and placebo supplied by Pfizer-Pharmacia, Ballerup, Denmark, as identical-appearing capsules) were prepared by the hospital pharmacy in identical containers marked with the name of the project and consecutive patient numbers. Patients were randomly assigned to receive gabapentin or placebo for 30 days after the amputation, using a computer-generated randomization list in block sizes of 8 and 10.
Only a large effect of treatment was considered clinically relevant for the following reasons: (1) The incidence of phantom pain is 70%, but in most cases the pain is not severe (2) elderly patients are more likely to develop side effects from medication and (3) patients who undergo amputation because of peripheral vascular disease are often on multidrug regimens, and further medication should be avoided unless a relevant effect of treatment is documented. Therefore, we decided to investigate whether treatment with gabapentin started immediately after amputation and continued for 30 days could reduce the incidence and intensity of postamputation pain and associated phenomena, such as allodynia, hyperalgesia, and temporal summation. Elderly patients are prone to the anticholinergic side effects of tricyclic antidepressants, and tricyclic antidepressants are also contraindicated in various cardiovascular conditions. There is only limited published evidence to help clinicians decide whether to start postoperative treatment before or as soon as phantom pain occurs or to await further development to avoid additional drugs. Therefore, a true preemptive treatment approach, i.e. , start of oral medication days or weeks before surgery, is almost impossible. In most cases, the decision about amputation is not made until the day before or even on the same day as the amputation. The patients often have multiple medical comorbidities and receive several different drugs for treatment. In Denmark, most amputations are performed in fragile, elderly patients mainly because of peripheral vascular disease. 15These findings could not be replicated in a recent randomized controlled study. In a smaller study using historic controls, it was suggested that a perioperative infusion of ketamine started intraoperatively and continued for 72 h could reduce the incidence of severe phantom pain. 12–14The lack of effect of some of these trials may be due to insufficient duration of the treatment before and after surgery. Also, postoperative infusions of local anesthetics via peripheral nerve sheath catheters are of no benefit in preventing phantom pain. 11showed no effect of an aggressive epidural pain treatment started 18 h before the amputation and continued into the postoperative period.
PHANTOM PAIN MANAGEMENT ALGORITHM TRIAL
The use of epidural blocks was prompted in some early clinical studies, 8–10but a randomized, placebo-controlled trial by Nikolajsen et al. 7).Īlthough experimental studies have shown that acute neuroplastic responses can be prevented by early and effective pain-reducing treatment, this positive effect is not matched by a similar response in the clinic. 2,4–6Chronic postamputation stump and phantom pain is notoriously difficult to treat, and although a wide variety of treatments have been proposed, there is little evidence from randomized, placebo-controlled trials to guide clinicians with treatment (for review, see Halbert et al. In some patients, however, stump pain persists and may even get worse.
Stump pain is common in the early postoperative period, but it usually subsides with healing. The frequency and intensity of phantom pain attacks diminish over time, but it is assumed that approximately 5–10% of patients continue to have severe pain (for review, see Nikolajsen and Jensen 3). The pain is typically intermittent, and few patients are in constant pain. 1,2The onset of phantom pain is usually within the first days after amputation. Phantom pain affects a large proportion of amputees, with an incidence of 60–80%. BOTH phantom pain (pain referred to the missing limb) and stump pain (pain in the residual limb) are frequent problems after amputation.
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