Chapter 47

Only in the past decade or so has research on functional regional anesthesia anatomy, outcome, and equipment slowly begun to transform regional anesthesia into a modern discipline. However, in many ways the equipment used for peripheral nerve block remains in its infancy. The sophistication and functionality of the equipment used for peripheral nerve blocks (PNBs) are, at best, rudimentary and lag far behind those of general anesthesia, as depicted in the following examples.

### Monitoring the Depth of Needle Insertion

Spinal cord injury after interscalene block is perhaps the most serious complication of a PNB. This devastating complication, however, can occur only with an excessively deep needle insertion (ie, >2.5 cm).1 Monitoring the depth of the needle insertion is substantially important to avoid a too-deep insertion (eg, spinal cord or chest cavity with interscalene block). In fact, the recently suggested standardized block documentation procedure requires clinicians to document the depth at which the needle is inserted. Nevertheless, most commercially available needles still do not have depth markings for such objective documentation.2 Despite that fact, there is much work underway to remedy this deficiency, and it is inevitable that all needles used in regional anesthesia will eventually incorporate depth markings on their shafts.

### Current Delivery & Disconnect Monitoring

Nerve stimulator–assisted nerve localization has become a standard technique in PNB. In contrast to paresthesia techniques, nerve stimulation provides a more objective assessment of the needle position in relation to the nerve, does not require patient cooperation, and permits the use of sedatives and analgesics for patient comfort during a nerve block procedure. The basic premise of the nerve stimulator–assisted nerve blocks is that the electrical current (“field") in front of the advancing needle should elicit a motor response before the tip of the needle enters the nerve. In many nerve block techniques, a functioning nerve stimulator is essential to decrease the risk of inadvertent placement of the needle intraneurally or intravascularly. For instance, because of the close proximity of the subclavian artery anterior and inferior to the brachial plexus during cervical paravertebral block, the functionality of the nerve stimulator is of paramount importance to avoid vascular complications.3 With a functioning nerve stimulator, a motor response of the shoulder muscle is seen when the brachial plexus is stimulated, which should occur before the subclavian artery is punctured by the advancing needle. In the case series on continuous paravertebral blocks using a stimulating catheter reported by Boezaart et al.,3 vascular complications consisting of large-vessel puncture with a 17-gauge needle occurred only in patients in whom the nerve stimulators were found to be malfunctional.

Consequently, the ability of the nerve stimulator to deliver accurate current output and integrity of the stimulator-needle-return (skin) electrode circuit is of utmost importance for both the block success and the safety of the procedure. Problems with the reliability and accuracy of nerve stimulators have long been recognized ...

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

## Subscription Options

### AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more