Lumbar Sympathetic Plexus Block as a Treatment for Postamputation Pain: Methodology for a Randomized Controlled Trial.

Objective: We present a technical protocol for rigorous assessment of patient-reported outcomes and psychophysical testing relevant to lumbar sympathetic blocks for the treatment of postamputation pain (PAP). This description is intended to inform future prospective investigation. Design: Series of four participants from a blinded randomized sham-controlled trial. Setting: Tertiary, urban, academic pain medicine center. Subjects: Four participants with a single lower limb amputation and associated chronic PAP. Methods: Participants were randomized to receive a lumbar sympathetic block with 0.25% bupivacaine or sham needle placement. Patient-rated outcome measures included the numerical rating scale (NRS) for pain, the McGill Pain Questionnaire-Short Form, Center for Epidemiological Studies Depression Scale, Pain and Anxiety Symptoms Scale-short version, and Pain Disability Index (PDI). Psychophysical and biometric testing was also performed, which included vibration sensation testing, pinprick sensation testing, brush sensation testing, Von Frey repeated weighted pinprick sensation, and thermal quantitative sensory testing. Results: In the four described cases, treatment of PAP with a single lumbar sympathetic block but not sham intervention resulted in reduction of both residual limb pain and phantom limb pain as well as perceived disability on the PDI at three-month follow-up. Conclusions: An appropriately powered randomized controlled study using this methodology may not only aid in determining the possible clinical efficacy of lumbar sympathetic block in PAP, but could also improve our understanding of underlying pathophysiologic mechanisms of PAP.

"Managing" the Placebo Effect: The Single-Blind Placebo Lead-in Response in Two Pain Models.

OBJECTIVE: "Placebo effects" in analgesic medication trials for chronic pain are pervasive; however, little is known regarding mechanisms or factors that may influence the presence or magnitude of these effects. Our objective is to consider elements of the placebo response in the context of two pain models using a "single-blind placebo lead-in" design (SBPLI). METHODS: As part of two pilot drug trials using knee osteoarthritis (KOA) and non-radicular low back pain (LBP) subjects, SBPLI protocols were conducted. We examined whether gender and/or diagnosis affected placebo responses as observed in changes in patient self-reported pain, depressive and pain anxiety symptoms. We also evaluated the placebo response on performance-based tests (stair climbing, range of motion (ROM), sit to stand repetitions, and 6-minute treadmill distance). RESULTS: VAS Pain Intensity (Now) values decreased significantly during the SBPLI for the sample as a whole, but the effects appeared stronger among LBP subjects. CES-D short form values (depressive symptoms) did not decrease significantly during the SBPLI for the sample as a whole, but some placebo effects appeared to emerge for women in the KOA group. PASS values (pain anxiety symptoms) decreased significantly, albeit mildly, during the SBPLI for the sample as a whole.Stair Climb (time) revealed no significant SBPLI effects. Bend Forward to Floor (ROM) increased significantly at the end of the SBPLI period for the sample as a whole, but the effects appeared stronger among KOA subjects. Sit to Stand Repetitions increased during the SBPLI for the sample as a whole. Treadmill Distance did not change significantly from Visit 1 to Visit 2; however, a significant Sex difference for the KOA group was found such that women showed greater Treadmill Distance at Visit 2. CONCLUSION: Placebo effects emerged across psychometric and performance-based measures, indicating the pervasiveness of this phenomenon. In this design, diagnostic and (to a lesser extent) gender categories differentials were observed during the placebo period. The SBPLI design may prove not only a robust method in studying the placebo phenomena, but also as a design element to mitigate some aspects of the placebo response in clinical trials.

A prospective, multisite, international validation of the Complex Regional Pain Syndrome Severity Score.

Clinical diagnosis of complex regional pain syndrome (CRPS) is a dichotomous (yes/no) categorization, a format necessary for clinical decision making. Such dichotomous diagnostic categories do not convey an individual's subtle gradations in the severity of the condition over time and have poor statistical power when used as an outcome measure in research. This prospective, international, multicenter study slightly modified and further evaluated the validity of the CRPS Severity Score (CSS), a continuous index of CRPS severity. Using a prospective design, medical evaluations were conducted in 156 patients with CRPS to compare changes over time in CSS scores between patients initiating a new treatment program and patients on stable treatment regimens. New vs stable categorizations were supported by greater changes in pain and function in the former. Results indicated that CSS values in the stable CRPS treatment group exhibited much less change over time relative to the new treatment group, with intraclass correlations nearly twice as large in the former. A calculated smallest real difference value revealed that a change in the CSS of ≥4.9 scale points would indicate real differences in CRPS symptomatology (with 95% confidence). Across groups, larger changes in CRPS features on the CSS over time were associated in the expected direction with greater changes in pain intensity, fatigue, social functioning, ability to engage in physical roles, and general well-being. The overall pattern of findings further supports the validity of the CSS as a measure of CRPS severity and suggests it may prove useful in clinical monitoring and outcomes research.