Brachial Plexus Infraclavicular Block Success Rate and Appropriate Endpoints

In Response: We appreciate the interesting comments made by Drs. Ilfeld and Enneking regarding our recent description of the modified approach of the Raj technique for the infraclavicular block (1). The principal objective of our study was to evaluate a new approach of the infraclavicular block that would minimize the risks of pneumothorax. We noticed after having done the first 50 cases that the success rate of our technique was closely dependent on the muscle response elicited. Indeed, it was obvious that a proximal response was associated with an unacceptable high failure rate. A distal response may be difficult to obtain, but may “almost” always be obtained. If you are not able to obtain a distal response by slightly changing the direction of the needle, you have to withdraw the needle because you probably did not get the correct landmarks and will have to change by 0.5 cm the puncture point either medially (if you received a musculocutaneous or axillary response) or laterally (if you obtained an isolated weak flexor carpi ulnaris response). It is important, according to our experience, not to administer the drug if you did not get a satisfactory distal response. The anatomical descriptions made by Drs. Ilfeld and Enneking are perfectly correct. However, our experience has shown that it is not usual to observe a visible and palpable contraction of either the carpi flexor radialis or the carpi flexor ulnaris without having a clear flexion of the wrist or the fingers; this type of response was considered a proximal response. If you carefully read the Method section of our article, you will find this statement, “…considered proximal if contraction of the triceps, biceps, flexor carpi radialis, or flexor carpi ulnaris was elicited and distal if flexion or extension of the wrist or the fingers was obtained.” “Each time flexion or extension of the fingers or the wrist was part of the response, the response was considered as distal,” which is in accordance with our clinical observations. In our experience, it is mandatory, whatever the response elicited, to have a clear flexion or extension of the fingers or the wrist. In this context, the best responses are those involving the median or radial nerves. We thank Drs. Ilfeld and Enneking for having given us the opportunity to clarify some points related to the methodology of this new approach to the infraclavicular block.