comparative study between the analgesic effects of epidural diamorphine and levobupivacaine on established post-amputation stump pain

ABSTRACT

Pain is-necessary for survival but chronic pain is disabling and causes significant health and economic problems. Chronic stump pain [pain localized in the stump for >3 months] after amputation is a significant problem among amputees [5-10%]. The mechanism of this phenomenon is not very clean yet. In this study we attempted to better understand the role of peripheral and central mechanisms in this condition. 12 patients with established lower limb post-amputation stump pain were given lumbar epidural diamonhpine 5 mg in 20 ml normal saline [NS] and levobupivacaine 0.5% [20 ml] I week apart. Baseline pain, then onset, duration and side effects of analgesia were measured. Epidural diamorphine was found to relive the pain of all patients. Its onset was relatively rapid, median = 5.5min [5-9 min] and took 30 mm for complete analgesia to be achieved and continued for a median duration of 20.5 h [18-24 h]. Pruritis in 6 patients was the only side effect due to epidural diamorphine. Levobupivacaine usually relieved the discomfort but failed to do so in 3 patients only despite adequate neural blockade. Its onset of action was slower, median=11 min [10-20 min] and duration of effect was shorter, median=12 h [8-18 h] than diamorphine. The effects of levobupivacaine were inferior to diamorphine due to the associated sensory and motor paralyses as well as absence of euphoria. Epidural diamonphine provided profound analgesia with normalization of stump sensations and euphoria, probably due to absorption into the spinal cord causing segmental action. While peripheral mechanisms played a role, central mechanisms involving the spinal cord were more important in the modulation of established stump pain in the evaluated patients