[Local anesthetic mixtures in various regional anesthesia procedures]

The use of local anaesthetic mixtures in regional anaesthesia has been discussed controversially. This assumption led us to conduct an inquiry on anaesthesiologist opinion on local anaesthetic mixtures. The study was performed on 131 anaesthesiologists answering a questionnaire. It was asked how often and how many procedures of regional anaesthesia were performed, whether local anaesthetic mixtures were used or not, and what were the most common mixtures. Other questions were in what kind of regional anaesthesia mixtures were applied, and which causes led to the use of local anaesthetic mixtures. Local anaesthetic mixtures were used by 70.2% of the anaesthesiologists who responded. Generally, however, parent components were preferred (88.3%). The types of regional anaesthesia in which mixtures were applied, were blockades of plexus brachialis (50.4%), spinal anaesthesia (29.0%), and epidural anaesthesia (28.4%). Locally applied anaesthetic mixtures - in 40.5% a mixture of bupivacaine and prilocaine and in 38.2% a mixture of bupivacaine and mepivacaine - were used in 58.0% because of their short latency and their long duration. In 27.5% the reply was that the anaesthesiologists used such combinations since in these the maximal doses of the parent components were not exceeded. In 22.9% it was argued that mixtures were less toxic than the parent components. On the other hand, the application of local anaesthetic mixtures was rejected because of their unpredictable effect (33.6%), and also to avoid local anaesthetic interactions (13.7%). The results of the inquiry demonstrate that the use of local anaesthetic mixtures in regional anaesthesia is common practice. However, mixing local anaesthetics may produce unpredictable interactions. We conclude that mixtures of local anaesthetics should be used only in exceptional cases.