A 6-day continuous peripheral nerve block reduces phantom limb pain as well as physical and emotional dysfunction for a month or longer, according to the results of a study published in Pain.
Although phantom limb pain is thought to be caused by dysfunctional reorganization in the somatosensory cortex because of reentrant neural pathways, the effect of disrupting these reentrant pathways with peripheral nerve block has not yet been assessed.
To evaluate the effect of a 6-day-long continuous peripheral nerve block on phantom pain, investigators analyzed data from 144 participants aged 18 years or older, with upper or lower limb amputation occurring 12 weeks or more before presentation, who experienced phantom limb pain of 2 or greater on the Numeric Rating Scale 3 or more times per week for the previous 8 weeks. They randomly assigned participants to receive either ropivacaine 0.5% or saline through perineural catheter infusion at fixed rates over the course of 6 days.
Three weeks after treatment ended, the treatment group experienced significantly less pain than the control group (P =.003) and experienced a significantly greater decrease in pain (P =.002). Individuals who had received active treatment reported less pain-induced physical and emotional dysfunction than individuals in the control group (P =.027). Residual limb pain significantly decreased in the active group compared with control (P =.006). Researchers observed no significant difference in depression improvements between groups.
The results of this study showed that relatively brief ambulatory continuous local anesthetic infusions result in substantial and prolonged benefit to individuals with phantom limb pain. This may be an effective, nonopioid treatment for a difficult-to-treat pain disorder.
Limitations to this study include the inclusion of an option to receive crossover treatment after 4 to 6 weeks, making it difficult to determine the duration of the effect of treatment. In addition, there is no universal protocol for anesthetic infusion, and thus results may vary depending on variations in regimen.
Future research to determine the optional perineural infusion parameters as well as to determine the precise duration of analgesic benefits is warranted.
Ilfeld BM, Khatibi B, Maheshwari K, et al. Ambulatory continuous peripheral nerve blocks to treat post-amputation phantom limb pain a multicenter, randomized, quadruple-masked, placebo-controlled clinical trial. Published online October 1, 2020. Pain. doi: 10.1097/j.pain.0000000000002087