Local anaesthetic sympathetic blockade (LASB) is a common treatment for complex regional pain syndrome (CRPS). It involves blocking the activity of sympathetic nerves alongside the spine. The sympathetic nervous system mainly controls unconscious actions such as heart rate, blood flow, and perspiration. The injection of a local anaesthetic drug around the nerves temporarily blocks the function of the nerves. This updated review aimed to summarise the available evidence regarding whether LASB is effective at reducing pain in CRPS, how long any pain relief might last, and whether LASB is safe.
Key results and quality of the evidence
In September 2015, we found a limited number of small trials, all of which had design flaws. We did not find evidence that LASB was better than placebo in reducing pain, or that it provided additional pain relief when added to rehabilitation. While a number of small studies compared LASB to other treatments, most did not find that LASB was better. One small study found that injecting the thoracic (upper back) sympathetic nerves with local anaesthetic and steroid was better than injecting the same drugs just under the skin at one-year follow-up, but the study may have been prone to bias. Only six studies reported on the type and amount of side effects. These studies reported only minor side effects, but since some studies did not report this information we can draw no firm conclusions about the safety of LASB. The evidence was mostly of low or very low quality.
Overall, the evidence is limited, conflicting, and of low quality. While we cannot draw strong conclusions, the existing evidence is not encouraging.
This update's results are similar to the previous versions of this systematic review, and the main conclusions are unchanged. There remains a scarcity of published evidence and a lack of high quality evidence to support or refute 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.
This review is an update of a previously published review in the Cochrane Database of Systematic Reviews, 2005, Issue 4 (and last updated in the Cochrane Database of Systematic Reviews, 2013 issue 8), on local anaesthetic blockade (LASB) of the sympathetic chain to treat people with complex regional pain syndrome (CRPS).
To assess the efficacy of LASB for the treatment of pain in CRPS and to evaluate the incidence of adverse effects of the procedure.
For this update we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2015, Issue 9), MEDLINE (Ovid), EMBASE (Ovid), LILACS (Birme), conference abstracts of the World Congresses of the International Association for the Study of Pain, and various clinical trial registers up to September 2015. We also searched bibliographies from retrieved articles for additional studies.
We considered randomised controlled trials (RCTs) that evaluated the effect of sympathetic blockade with local anaesthetics in children or adults with CRPS compared to placebo, no treatment, or alternative treatments.
We used standard methodological procedures expected by Cochrane. The outcomes of interest were reduction in pain intensity, the proportion who achieved moderate or substantial pain relief, the duration of pain relief, and the presence of adverse effects in each treatment arm. We assessed the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation) and created a 'Summary of findings' table.
We included an additional four studies (N = 154) in this update. For this update, we excluded studies that did not follow up patients for more than 48 hours. As a result, we excluded four studies from the previous review in this update. Overall we included 12 studies (N = 461), all of which we judged to be at high or unclear risk of bias. Overall, the quality of evidence was low to very low, downgraded due to limitations, inconsistency, imprecision, indirectness, or a combination of these.
Two small studies compared LASB to placebo/sham (N = 32). They did not demonstrate significant short-term benefit for LASB for pain intensity (moderate quality evidence).
One small study (N = 36) at high risk of bias compared thoracic sympathetic block with corticosteroid and local anaesthetic versus injection of the same agents into the subcutaneous space, reporting statistically significant and clinically important differences in pain intensity at one-year follow-up but not at short term follow-up (very low quality evidence).
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 (very low quality evidence).
Eight small randomised studies compared sympathetic blockade to various other active interventions. Most studies found no difference in pain outcomes between sympathetic block versus other active treatments (low to very low quality evidence).
One small study compared ultrasound-guided LASB with non-guided LASB and found no clinically important difference in pain outcomes (very low quality evidence).
Six studies reported adverse events, all with minor effects reported.