Local anaesthetic sympathetic blockade for complex regional pain syndrome.

BACKGROUND: This is an update of the original Cochrane review published in The Cochrane Library, 2005, Issue 4, on local anaesthetic blockade (LASB) of the sympathetic chain used to treat complex regional pain syndrome (CRPS). OBJECTIVES: To assess the efficacy of LASB for the treatment of pain in CRPS and to evaluate the incidence of adverse effects of the procedure. SEARCH METHODS: We updated searches of the Cochrane Pain, Palliative and Supportive Care Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) on the Cochrane Library (Issue 11 of 12, 2012), MEDLINE (1966 to 22/11/12), EMBASE (1974 to 22/11/12), LILACS (1982 to 22/11/12), conference abstracts of the World Congresses of the International Association for the Study of Pain (1995 to 2010), and various clinical trial registers (inception to 2012). We also searched bibliographies from retrieved articles for additional studies. SELECTION CRITERIA: We considered for inclusion randomised controlled trials (RCTs) that evaluated the effect of sympathetic blockade with local anaesthetics in children or adults with CRPS. DATA COLLECTION AND ANALYSIS: The outcomes of interest were reduction in pain intensity levels, the proportion who achieved moderate or substantial pain relief, the duration of pain relief, and the presence of adverse effects in each treatment arm. MAIN RESULTS: We included an additional 10 studies (combined n = 363) in this update. Overall we include 12 studies (combined n = 386). All included studies were assessed to be at high or unclear risk of bias.Three small studies compared LASB to placebo/sham. We were able to pool the results from two of these trials (intervention n = 23). Pooling did not demonstrate significant short-term benefit for LASB (in terms of the risk of a 50% reduction of pain scores).Of two studies that investigated LASB as an addition to rehabilitation treatment, the only study that reported pain outcomes demonstrated no additional benefit from LASB.Eight small randomised studies compared sympathetic blockade to another active intervention. Most studies found no difference in pain outcomes between sympathetic block and other active treatments.Only five studies reported adverse effects, all with minor effects reported. AUTHORS' CONCLUSIONS: This update has found similar results to the original systematic review. There remains a scarcity of published evidence to support the use of local anaesthetic sympathetic blockade for CRPS. From the existing evidence it is not possible to draw firm conclusions regarding the efficacy or safety of this intervention but the limited data available do not suggest that LASB is effective for reducing pain in CRPS.

Determinants of thermal pain thresholds in normal subjects.

OBJECTIVE: Measurement of thermal pain thresholds is an essential part of quantitative sensory testing (QST). However, databases of QST show limitations due to large inter-individual variations including unreasonably low thresholds for thermal pain, lack of data on intra-individual variations over time and on the subjects' perception at threshold. This study sought to reduce inter-individual variations, investigated the reproducibility of measurements of thermal pain thresholds and included evaluation of thermally induced perceptions. METHODS: Thermal pain thresholds were investigated in 20 healthy subjects over three weeks using two protocols, one of which differed in making the subjects familiar with the likely range of applied temperatures beforehand. Both protocols included subjective ratings of pain and temperature perception at the pain thresholds. RESULTS: Data obtain using both protocols showed large inter-individual variations, but small intra-individual variations of pain thresholds over time as well as good feasibility and reproducibility of subjects' ratings at threshold. CONCLUSIONS: Previous experience of test stimuli has no influence on the variability of thermal pain thresholds. However, measurement of thermal pain thresholds showed good reproducibility over time. Evaluation of perception at thresholds provided further reproducible data. SIGNIFICANCE: Further approaches are needed to reduce variability of thermal pain thresholds; however, good reproducibility of thermal pain thresholds and thermally induced perceptions warrants consideration of their use in larger longitudinal studies.