Continuous brachial plexus blockade in combination with the NMDA receptor antagonist memantine prevents phantom pain in acute traumatic upper limb amputees.

Author(s): Schley M, Topfner S, Wiech K, Schaller HE, Konrad CJ, Schmelz M, Birbaumer N

Affiliation(s): Department of Anaesthesiology and Intensive Care Medicine, Experimental Pain Research/Pain Centre, University of Heidelberg, Faculty of Clinical Medicine, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tubingen, Germany.

Publication date & source: 2006-05-19, Eur J Pain., [Epub ahead of print]

BACKGROUND: Hyperexcitability of N-methyl-d-aspartate acid (NMDA) receptors may play an important role in the development of phantom limb pain (PLP). AIM OF THE STUDY: To investigate whether early treatment with the NMDA antagonist memantine attenuates phantom pain memory formation in traumatic amputees. METHODS: In a randomized, double-blind, controlled trial 19 patients with acute traumatic amputation of the upper extremity were investigated. All patients received postoperative analgesia by continuous brachial plexus anesthesia (ropivacaine 0.375% 5ml/h) for at least 7 days. In addition, the patients received either memantine (20-30mg daily, n=10) or placebo (n=9) for 4 weeks. RESULTS: Memantine treatment reduced the number of requested ropivacacine bolus injections during the first week and resulted in a significant decrease of PLP prevalence and intensity at 4 weeks and 6 months follow up, but not at 12 months follow up. CONCLUSIONS: We conclude that memantine can reduce intensity of phantom limb pain and might also prevent the development of PLP. However, despite the very early begin of treatment; no long-term effect on established PLP was evident.