[Development of a soft tissue ulcer after long-term peridural infusion].

Local anaesthetic agents (LA) in clinical concentrations have the potential for tissue toxicity, although this is rarely observed in clinical practice. The case of a 74-year-old female patient (BMI 16.8 kg/m(2)) with a metastasising bronchial carcinoma is reported, who suffered from severe back pain due to tumour infiltration. For pain management a tunnelled continuous thoracic peridural catheter (PC) was placed and a mixture of bupivacaine 0.49%, morphine 0.0036% and clonidine 0.0001% was infused at 3 ml/h. After 8 weeks of continuous infusion an ulcer developed in the soft tissue close to the thoracic spine containing whitish crystalline material (CM). A computed tomography examination revealed a subcutaneously displaced PC with extensive fluid collection reaching down to the sacrospinalis muscle. Histologically an unreactive necrosis with enclosed CM of unknown etiology was found. The result of the chemical analysis of the deposits demonstrated bupivacaine, morphine and sodium chloride. It is concluded that the soft tissue ulcer was probably caused by precipitation of the LA mixture.