Regional anaesthesia always works—provided you put the right dose of the right drug in the right place

Abstract

Secondly, the rate of failure of the operators performing the ISB using peripheral nerve stimulation (7/20; 35%) was very high. Of those blocks performed ‘successfully’ with nerve stimulation, five of 13 (38%) were not successful. It would have been of great interest to use US in these cases to assess the spread of LA to determine whether the drug was in the right place. We suspect that the operators performing the ISB using peripheral nerve stimulation often failed to deploy LA in the right place. The authors imply that this is inherent to the technique and that US-guided blocks are therefore better. However, the postero-lateral in-plane US-guided approach to the brachial plexus used in their study 1 is very different from the anatomical landmark techniques for ISB which aim to enter the interscalene grove from the ventral surface of the neck. It should not be assumed that operators who are proficient in the performance of US-guided blocks are equally proficient in the performance of blocks using the peripheral nerve stimulator. An alternative explanation for the observations is that the operators performing ISB were more familiar with the use of US. At our institution, we recently introduced US-guided ISB, so the reverse is true. In a recent review of our practice of 200 ISBs performed for shoulder surgery with the peripheral nerve stimulator, the brachial plexus was identified in less than three passes in more than 95% of cases. Of these cases, more than 80% provided adequate postoperative analgesia as defined by postoperative requirement for opiate analgesia (admittedly using 30 ml 0.375% bupivacaine). We introduced in-plane US-guided ISB in 2010. We converted to use of the peripheral nerve stimulator if after three passes we were unsuccessful. In the first 50 blocks, we converted to the use of the peripheral nerve stimulator in 50% of cases. Of those ISB performed successfully with US, 88% provided adequate postoperative analgesia. In the light of our observations, we feel that the observations of McNaught and colleagues 1 should not be used as the benchmark against which to judge the performance of ISB using the peripheral nerve stimulator. Thirdly, we occasionally perform shoulder surgery with ISB as the sole anaesthetic and analgesic technique without any sedation. Unfortunately, the observations of McNaught and colleagues 1 cannot be applied to the performance of ISB as a sole anaesthetic technique. Assessment of the quality of the block before surgery could have given some suggestion as to whether surgery could have been contemplated without general anaesthesia. Finally, it is important to recognize that the MEAV 50 is a theoretical construct and that we want all of our blocks to be successful. It would therefore be more useful to calculate an MEAV 99. As there were no significant differences in motor and sensory block and no difference in respiratory impairment between groups, we would question the value of using ,10 ml LA for ISB.