THE EFFECTIVENESS OF APPLIED SPINAL AND PERIPHERAL INHIBITORY MEDIATORS AND THEIR UNDERLYING PHYSIOLOGICAL MECHANISMS IN PATIENTS SUFFERING FROM NEUROPATHIC PAIN

Abstract

INTRODUCTION: Neuropathic pain is defined by the IASP as "pain initiated or caused by a primary lesion or dysfunction in the nervous system" (Merskey and Bogduk 1994). There has been diversity of opinion about the effectiveness of specific treatments for the control of neuropathic pain. Diagnostic techniques available now are not sufficiently specific to discriminate between several pathophysiological mechanisms. Using the epidural route for the application of therapeutic test substances it is possible to target neuropathic mechanisms that at least partially located in the dorsal horn and at the same time produce much lower systemic levels of test substance than after systemic application. It has been shown that the epidural administration of clonidine, fentanyl, ketamine and midazolam has analgesic effect in different painful conditions. Despite the extensive studies, the clinical role of using these agents epidurally in the management of neuropathic pain remains unresolved. In addition, there is a lack in the published placebo-controlled studies on the effectiveness of the epidural route of these agents 111 neuropathic pain patients.

AIM OF THE WORK: The relative effectiveness and side effects of clonidine, fentanyl, ketamine and midazolam via the epidural route in patients with neuropathic pain.

PATIENTS AND METHODS: The study was carried out 111 the Pain Management Unit, Department of Anaesthetics, Guy's Hospital. The study design was randomised, double-blind, placebo controlled, prospective. It was approved by the local ethics committee. Fifty patients aged between 24 75 years of both sexes with neuropathic pain were recruited for this study. Each patient gave written informed consent. An epidural catheter was inserted between L 2 -L4 interverte bra! spaces using the loss of resistance technique to normal • saline.