A systematic review of ketamine for complex regional pain syndrome.

OBJECTIVE: This systematic review aims to examine the available literature and to synthesize published data concerning the treatment of Complex Regional Pain Syndrome (CRPS) with ketamine. METHODS: The search was conducted utilizing the databases Medline, Embase and the Cochrane Central Registry of Controlled Trials. All relevant articles were systematically reviewed. RESULTS: The search yielded 262 articles, 45 of which met the inclusion/exclusion criteria. Of those included, 6 were reviews, 5 were randomized placebo-controlled trials, 13 were observational studies, and 21 were case reports. CONCLUSION: There is no high quality evidence available evaluating the efficacy of ketamine for CRPS and all manuscripts examined in this review were of moderate to low quality. Therefore, we conclude there is currently only weak evidence supporting the efficacy of ketamine for CRPS, yet there is clearly a rationale for definitive study.

Refractory Chronic Pain Screening Tool (RCPST): a feasibility study to assess practicality and validity of identifying potential neurostimulation candidates.

OBJECTIVE: An international panel of pain specialists (anesthesiology, neurology, neurosurgery, and psychology) and research methodologists developed a screening tool to identify patients who may be suitable for spinal cord stimulation (SCS)--the Refractory Chronic Pain Screening Tool (RCPST) prototype. We describe a feasibility study to explore practicality and validity of this prototype. DESIGN: Consecutive outpatients were screened in two centers (United Kingdom and United States). Sixty chronic pain adults without satisfactory pain relief despite treatment were assessed using RCPST (by pain specialist without expertise in neurostimulation) and then evaluated by two pain specialists experienced in SCS implantation and management to determine whether the patient should be referred for SCS. To maintain blinding, the participating physicians did not inform each other or the patient of assessment outcome. Sensitivity and specificity of the RCPST prototype were calculated using implanters' judgment as "gold standard." RESULTS: The average age of patients was 47.7 years; 53% were female. Fifty-seven patients completed the study (one withdrew consent, two lost to follow-up). The pain specialists agreed the prototype was easy to use and took <10 minutes to complete. Implanter agreement was moderate (Kappa: 0.63, 95% confidence interval: 0.35-0.91). The prototype had low sensitivity (40%, 19-61%) and moderate specificity (78%, 65-92%). Using the same questionnaire with a modified decision algorithm, new prototypes were generated with range of high sensitivity (80-100%) and specificity (89-97%) values. CONCLUSIONS: The RCPST aims to identify patients that should be referred for consideration for neurostimulation. The final implant decision requires appropriate neurological diagnostic workup, psychological assessment, and trial stimulation. RCPST was considered practical for routine clinical practice and contained appropriate questions. Sensitivity needs to be improved. A future study should select and validate the ideal RCPST prototype.

Medical cost impact of intrathecal drug delivery for noncancer pain.

INTRODUCTION: As healthcare budgets continue to contract, there is increased payer scrutiny on the use of implantable intrathecal drug-infusion devices. This study utilizes claims data to evaluate the economic effects of intrathecal drug delivery (IDD) based on health services utilization and costs of care before and after implantation. METHODS: We performed a retrospective database study involving 555 noncancer pain patients that received an IDD system implant within a 3-year service period (1/2006-1/2009). IDD patient costs were temporally aligned to implant month and repriced to a standardized, national pricing schedule over a 6-year episode cycle (3 years preimplant, implant month, and 3 years postimplant). Additionally, we made an actuarial projection of postimplant experience, in the absence of IDD intervention, simulating a conventional pain therapy (CPT) protocol by assuming the same slope in costs prior to implantation at standardized, national price levels. Cost projections were produced over a 30-year time horizon at various reimplantation rates. RESULTS: IDD therapy was less costly than the CPT protocol over our baseline implantation cycle. Costs in the month of IDD implantation, and in the year following, are cumulatively $17,317 more than the CPT protocol; however, IDD financial break-even occurs soon after the second year postimplant. The lifetime analysis indicates that IDD per patient per year savings is $3,111 compared with CPT. CONCLUSION: The authors found that patients receiving an implantable IDD system may experience reduced cumulative future medical costs relative to anticipated costs in the absence of receiving IDD. This finding complements published literature on the cost-effectiveness of IDD.

What does the mechanism of spinal cord stimulation tell us about complex regional pain syndrome?

Spinal cord stimulation (SCS) can have dramatic effects on painful, vascular, and motor symptoms of complex regional pain syndrome (CRPS), but its precise mechanism of action is unclear. Better understanding of the physiologic effects of SCS may improve understanding not only of this treatment modality but also of CRPS pathophysiology. Effects of SCS on pain perception are likely to occur through activation of inhibitory GABA-ergic and cholinergic spinal interneurons. Increased release of both neurotransmitters has been demonstrated following SCS in animal models of neuropathic pain, with accompanying reductions in pain behaviors. Effects of SCS on vascular symptoms of CRPS are thought to occur through two main mechanisms: antidromic activation of spinal afferent neurons and inhibition of sympathetic efferents. Cutaneous vasodilation following SCS in animal models has been shown to involve antidromic release of calcitonin gene-related peptide and possibly nitric oxide, from small-diameter sensory neurons expressing the transient receptor potential V1 (TRPV1) receptor. The involvement of sympathetic efferents in the effects of SCS has not been studied in animal models of neuropathic pain, but has been demonstrated in models of angina pectoris. In conclusion, SCS is of clinical benefit in CRPS, and although its mechanism of action merits further elucidation, what little we do know is informative and can partially explain some of the pathophysiology of CRPS.

Practice choices and challenges in the current intrathecal therapy environment: an online survey.

OBJECTIVE: The objective of this study was to evaluate current practice characteristics, treatment choices, clinical experiences, and economic concerns associated with intrathecal therapy. DESIGN: Health care professionals in the United States, who were known to actively use intrathecal therapy in their practices, were recruited to participate in an online survey; contact information was obtained via Internet searches, university Websites, association memberships, industry databases, and personal contacts. Survey responses were summarized descriptively. RESULTS: Of the 329 practitioners who were contacted, 87 participated in the survey. Most participants specialized in anesthesiology (77.0%), worked in a private practice or private hospital (74.7%), and had been practicing pain management for more than 10 years (64.4%). Morphine was the most frequently used opioid for the initiation of intrathecal therapy (80.7% of practitioners), and 81.9% had used ziconotide in their practice. Most practitioners (63.9%) had treated at least one patient who developed a granuloma, and 66.0% of those practitioners had a patient experience permanent or temporary neurological injury due to a granuloma. Fewer than half of practitioners were satisfied with reimbursement from private insurance companies (25.3%) or workers compensation (34.9%), and 90.5% believed reimbursement rates for filling, refilling, and programming patient pumps are not adequate to cover practice costs. The majority of practitioners (56.6%) use fewer pumps in their practices because of reimbursement issues. CONCLUSIONS: Intrathecal pain management practices continue to evolve as the options for treatment increase, and the body of applicable scientific literature grows; however, economic considerations can influence clinical decisions and may interfere with treatment choice and patient access to therapy.

Reassessment of evidence synthesis of occupational medicine practice guidelines for interventional pain management.

BACKGROUND: Appropriately developed practice guidelines present statements of best practice based on a thorough evaluation of the evidence from published studies on the outcomes of treatments, which include the application of multiple methods for collecting and evaluating evidence for a wide range of clinical interventions and disciplines. However, the guidelines are neither infallible, nor a substitute for clinical judgment. While the guideline development process is a complex phenomenon, conflict of interest in guideline development and inappropriate methodologies must be avoided. It has been alleged that the guidelines by the American College of Occupational and Environmental Medicine (ACOEM) prevent injured workers from receiving the majority of medically necessary and appropriate interventional pain management services. An independent critical appraisal of both chapters of the ACOEM guidelines showed startling findings with a conclusion that these guidelines may not be applied in patient care as they scored below 30% in the majority of evaluations utilizing multiple standardized criteria. OBJECTIVE: To reassess the evidence synthesis for the ACOEM guidelines for the low back pain and chronic pain chapters utilizing an expanded methodology, which includes the criteria included in the ACOEM guidelines with the addition of omitted literature and application of appropriate criteria. METHODS: For reassessment, randomized trials were utilized as it was in the preparation of the guidelines. In this process, quality of evidence was assessed and recommendations were made based on grading recommendations of Guyatt et al. The level of evidence was determined utilizing the quality of evidence criteria developed by the U.S. Preventive Services Task Force (USPSTF), as well as the outdated quality of evidence criteria utilized by ACOEM in the guideline preparation. Methodologic quality of each individual article was assessed utilizing the Agency for Healthcare Research and Quality (AHRQ) methodologic assessment criteria for diagnostic interventions and Cochrane methodologic quality assessment criteria for therapeutic interventions. RESULTS: The results of reassessment are vastly different from the conclusions derived by the ACOEM guidelines. The differences in strength of rating for the diagnosis of discogenic pain by provocation discography and facet joint pain by diagnostic facet joint nerve blocks is established with strong evidence. Therapeutic cervical and lumbar medial branch blocks and radiofrequency neurolysis, therapeutic thoracic medial branch blocks, cervical interlaminar epidural steroid injections, caudal epidural steroid injections, lumbar transforaminal epidural injections, percutaneous and endoscopic adhesiolysis, and spinal cord stimulation qualified for moderate to strong evidence. Additional insight is also provided for evidence rating for intradiscal electrothermal therapy (IDET), automated percutaneous disc decompression, and intrathecal implantables. CONCLUSION: The reassessment and reevaluation of the low back and chronic pain chapters of the ACOEM guidelines present results that are vastly different from the published and proposed guidelines. Contrary to ACOEM's conclusions of insufficient evidence for most interventional techniques, the results illustrate moderate to strong evidence for most diagnostic and therapeutic interventional techniques.

Review of occupational medicine practice guidelines for interventional pain management and potential implications.

In the modern day environment, workers' compensation costs continue to be a challenge, with a need to balance costs, benefits, and quality of medical care. The cost of workers' compensation care affects all stakeholders including workers, employers, providers, regulators, legislators, and insurers. Consequently, a continued commitment to quality, accessibility to care, and cost containment will help ensure that workers are afforded accessible, high quality, and cost-effective care. In 2004, workers' compensation programs in all 50 states, the District of Columbia, and federal programs in the United States combined received an income of $87.4 billion while paying out only $56 billion in medical and cash benefits with $31.4 billion or 37% in administrative expenses and profit. Occupational diseases represented only 8% of the workers' compensation claims and 29% of the cost. The American College of Occupational and Environmental Medicine (ACOEM) has published several guidelines; though widely adopted by WCPs, these guidelines evaluate the practice of medicine of multiple specialties without adequate expertise and expert input from the concerned specialties, including interventional pain management. An assessment of the ACOEM guidelines utilizing Appraisal of Guidelines for Research and Evaluation (AGREE) criteria, the criteria developed by the American Medical Association (AMA), the Institute of Medicine (IOM), and other significantly accepted criteria, consistently showed very low scores (< 30%) in most aspects of the these guidelines. The ACOEM recommendations do not appear to have been based on a careful review of the literature, overall quality of evidence, standard of care, or expert consensus. Based on the evaluation utilizing appropriate and current evidence-based medicine (EBM) principles, the evidence ratings for diagnostic techniques of lumbar discography; cervical, thoracic, and lumbar facet joint nerve blocks and sacroiliac joint nerve blocks; therapeutic cervical and lumbar medial branch blocks and radiofrequency neurolysis; cervical interlaminar epidural steroid injections, caudal epidural steroid injections, and lumbar transforaminal epidural injections; caudal percutaneous adhesiolysis; abd spinal cord stimulation were found to be moderate with strong recommendation applying for most patients in most circumstances. The evidence ratings for intradiscal electrothermal therapy (IDET), an automated percutaneous disc decompression and also deserve further scrutiny and analysis. In conclusion, these ACOEM guidelines for interventional pain management have no applicability in modern patient care due to lack of expertise by the developing organization (ACOEM), lack of utilization of appropriate and current EBM principles, and lack of significant involvement of experts in these techniques resulting in a lack of clinical relevance. Thus, they may result in reduced medical quality of care; may severely hinder access to appropriate, medically needed and essential medical care; and finally, they may increase costs for injured workers, third party payors, and the government by transferring the injured worker into a non-productive disability system.

Spinal cord stimulation has comparable efficacy in common pain etiologies.

Objectives. The probability of success with spinal cord stimulation (SCS) depends largely on appropriate patient selection. Here, we have assessed the predictive value of pain etiology as it relates to pain relief with SCS as part of a prospective multicenter clinical trial. Methods. Sixty-five subjects with chronic and intractable pain tested an epidural SCS system. Subjects reported pain ratings (visual analog scale) with stimulation off and stimulation on at scheduled follow-up visits for up to 18 months after activation of the system. Visual analog scale scores were averaged and stratified by dominant pain etiologies, comprising failed back surgery syndrome, complex regional pain syndrome, and a subgroup of subjects with miscellaneous other pain etiologies. Results. More than 70% of subjects in each subgroup had successful outcomes during the temporary trial period and similar percentages of subjects from each etiology subgroup subsequently went on to permanent implantation. After permanent implantation, all subgroups reported more than 50% pain relief, on average, at each follow-up time point. No predictive value of pain etiology was observed. Conclusions. Spinal cord stimulation is an effective therapy for neuropathic pain arising from a variety of causes. Failed back surgery syndrome, complex regional pain syndrome, and pain of other etiologies responded equally well to SCS.

A new spinal cord stimulation system effectively relieves chronic, intractable pain: a multicenter prospective clinical study.

Objectives. A prospective, open label, multicenter clinical trial confirmed the functionality of a new spinal cord stimulation (SCS) system for the treatment of chronic, intractable pain of the trunk and/or limbs. Materials and Methods. Sixty-five subjects tested a rechargeable 16-channel SCS system with individual current control of each contact on one or two percutaneous eight-contact epidural leads. After baseline measurements, subjects were tracked on pain ratings and complication rates for up to 18 months. Results. After a trial period, 75% of subjects underwent permanent implantation of the entire SCS system. More than one-half the implanted subjects experienced 50% or greater relief of pain after permanent implantation; some subjects reported relief of 90% or more of their pain. The most common complications after permanent implantation were lead migration, uncomfortable stimulation, and component failure; most resolved after reprogramming or device replacement. Conclusions. The new SCS system provided good pain relief to a majority of subjects, and the results confirm a favorable safety and efficacy profile for the SCS system.

Spinal cord stimulation: mechanisms of action.

STUDY DESIGN: A literature review and synthesis were performed. OBJECTIVE: To present the current understanding of the mechanisms of spinal cord stimulation in relation to the physiology of pain. SUMMARY OF BACKGROUND DATA: Spinal cord stimulation has been used for more than 30 years in the armamentarium of the interventional pain specialist to treat a variety of pain syndromes. Traditionally used for persisting leg pain after lumbar spinal surgery, it has been applied successfully in the treatment of angina pectoris, ischemic pain in the extremity, complex regional pain syndrome Types 1 and 2, and a variety of other pain states. This review presents the current status of what is known concerning how electrical stimulation of the spinal cord may achieve pain relief. METHODS: A literature review was conducted. RESULTS: The literature supports the theory that the mechanism of spinal cord stimulation cannot be completely explained by one model. It is likely that multiple mechanisms operate sequentially or simultaneously. CONCLUSION: Some clinical or experimental support can be found in the literature for 10 specific mechanisms or proposed mechanisms of spinal cord stimulation.

Neuraxial medication delivery: the development and maturity of a concept for treating chronic pain of spinal origin.

STUDY DESIGN: A literature review and synthesis were performed. OBJECTIVE: To summarize the history, use, and innovation related to neuraxial drug delivery for the treatment of intractable back pain. SUMMARY OF BACKGROUND DATA: The discovery of opioid receptors in the early 1970s provided a rational basis for the delivery of opioid drugs intraspinally. Epidural or intrathecal infusions deliver drugs directly to opioid receptors, limit systemic exposure, and by decreasing the opioid dosage required for pain relief, generally reduce side effects. The benefits of short-term spinal analgesia led to investigation of longer-term continuous subarachnoid opioid infusions for the management of both cancer pain and noncancer pain, such as that of spinal origin. RESULTS: Unique features of this article include an updated pain continuum, updated indications for intrathecal therapy, a detailed comparison of trial techniques, a detailed comparison of the advantages of different types of pumps, a synopsis of troubleshooting for inadequate efficacy, and an updated statement regarding intrathecal pumps and radiologic procedures, including MRI scanning. Some challenges remain. Large-scale well-controlled studies could answer some perplexing questions regarding efficacy in patients with noncancer or neuropathic pain. Patient selection criteria undoubtedly will be refined and validated as more patients are treated. In addition, further investigation of specifically targeted medications or drug combinations for intraspinal use could increase efficacy, reduce side effects, and expand indications. CONCLUSIONS: Intraspinal medication delivery has become an effective technique for control of intractable pain in appropriately selected patients seen by spine surgeons.