Appendix 2: Disposition of Injectate with Common Regional Anesthesia Techniques

INTRODUCTION

The outcome of regional anesthesia technique is ultimately dependent on the distribution of the local anesthetic in the relevant tissue space that contains the nerve(s) of interest. Prior to the introduction of ultrasound in regional anesthesia, our understanding of the disposition of the local anesthetic had been limited due to the lack of technology that could allow such monitoring. This addendum features studies of computed tomographic (CT) images that we painstakingly acquired by the author over a period of nearly 2 decades in attempt to elucidate the disposition of local anesthetic injections with nerve block injections and their relationship to the outcome of regional anesthesia. The maldistribution of local anesthetic associated with block failures and/or complications due to the spillage of local anesthetic to the undesired places, such as, for example, the phrenic nerv and neuraxial space are also demonstrated. A uniquely educational aspect of these images is the relationship of the volume of the injectate and its physical spread in the tissue spaces.

The all original material presented in this appendix is organized in clusters of images of distribution of local anesthetic containing radiopaque solution. In addition to images of the expected, desired distribution, the images of the maldistribution of local anesthetic are also included as well. Wherever available, images of desired distribution and maldistribution are presented in several imaging planes, as well as in three-dimensional (3D) reconstruction. Importantly, the distribution patterns presented in the images cannot be fully or reliably studied by ultrasonography; hence their relevance in the era of ultrasound-guided regional anesthesia.

CERVICAL PLEXUS BLOCK

INTERSCALENE BRACHIAL PLEXUS BLOCK