• M Gehling, M Tryba, H Niebergall, A Hufschmidt, M Schild, and K Geiger.
• Klinik für Anästhesiologie, Intensivmedizin und Schmerztherapie, Klinikum Kassel GmbH. gehling@klinikum-kassel.de
• Schmerz. 2003 Oct 1;17(5):309-16.

IntroductionThe results of clinical studies have raised doubts on the effectiveness of regional sympathetic blocks with guanethidine (IVRSB) in patients suffering from complex regional pain syndrome (CRPS). We conducted a retrospective analysis of long-term results in our patients and searched for possible factors predicting long-term outcome after IVRSB:MethodsAfter approval by our ethics commission and written informed consent, 42/44 patients were included. We documented diagnosis, history, therapy and long-term result from charts. Long-term results were also obtained from a questionnaire administered to the patients. These were defined as very good (reduction of pain > or =75%), good (pain reduction <75% and > or =50%), moderate (pain reduction <50% and > or =25%) or poor (pain reduction <25%). The association of a moderate or poor outcome with the factors age, gender, duration of time until therapy, pain intensity before therapy, dose of applied guanethidine and duration of therapy was calculated by odds ratio. Confidence intervals for the odds ratios were determined by Woolfs approximation.ResultsAfter a mean duration of 18 months, the outcome was classified as very good in 14, good in 13, moderate in 5 and poor in 10 patients. An increased rate of moderate or poor outcome was associated with age<60 years (OR=4.00, CI 1.04-15.26), male gender (OR=2.93, CI 0.71-12.11) and duration of therapy>2 weeks (OR=3.27, CI 0.86-12.36). The factors duration of time until therapy, initial pain intensity and total dose of guanethidine were not associated with increased rates of moderate or poor outcome.ConclusionWe only seldom observed a complete functional restoration after CRPS. Male patients <60 years showed an increased risk of developing chronic pain. It remains unclear whether the risk of chronic pain reflects different responses to therapy or differences in the natural course of the disease in our patients. A meta-analysis of randomised trials of IVRSB in CRPS failed to prove the effectiveness of this intervention. If other investigations confirm our impression, future studies of CRPS-treatments should be planned and analysed with regard to the possible influence of the natural course and different risks of chronic pain among patients with CRPS.

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