Intrathecal opioids for intractable pain syndromes

Abstract

For more than 20 years intrathecal opioid application with implantable pumps is an option for selected patients with malignant as well as non-malignant pain. In general, most types of pain should be treatable by opioid medication. However, the associated systemic side-effects such as nausea, vomiting, constipation or the risk of suppression of the central nervous system hinder the application of oral or intravenous opioid therapy as a sole, widely applicable treatment. Causes of non-malignant pain that may represent an indication for intrathecal drug-delivery systems include: failed back syndrome, neuropathic pain, axial spinal pain, complex regional pain syndrome, diffuse pain, brachial plexitis, central pain, failed spinal cord stimulation (SCS) therapy, arachnoiditis, poststroke pain, spinal cord injury pain and peripheral neuropathy. Due to the proximity to the receptor sites, the therapeutic effect of intrathecal drug application lasts longer and the rate of systemic side effects is reduced. Before definitive pump implantation, the therapeutic effect of intrathecal opioid therapy is tested with an external pump. If there is no clear and satisfactory effect in this trial application, pump implantation is not indicated. In our patients, with a follow-up exceeding 3 years, the reduction of non-malignant pain (assessed with the Visual Analogue Scale, VAS) was good or excellent (pain decrease >50%) in 71.3% of the patients, fair (VAS 5-6) in 19.8% and poor (VAS 7-10) in 8.9%. After 3 years of continuous treatment, we observed catheter-related technical problems (catheter dislocation, obstruction, kinking, disconnection or rupture) in 17 of 165 patients. Pump malfunctions were very rare (8 of 165 cases) and limited to older pump types. Reversible, specific drug-related side effects of long-term therapy with intrathecal pumps developed in 32 of the 165 patients. In our series, the mean serum/cerebrospinal fluid (CSF) concentration ratio for morphine was 1/3000, which explains the low rate of systemic side effects. Local diffusion difficulties in CSF cause an uneven distribution of morphine in CSF. Therefore the clinical effect is markedly influenced by the position of the catheter tip, a fact that should be kept in mind during catheter implantation. Intrathecal drug application is cost effective and can significantly improve the quality of life in selected patients. An intensive training in this method and awareness of its specific complications is necessary for everyone to participate in the consulting and implanting team. Pumps for chronic intrathecal opioid application should only be implanted in specialized centers. © 2007 Springer-Verlag.