**Abstract**

Advances in ultrasound technology and the increased risk of opioid overdose following surgery have expanded applications of nerve block for surgical cases, resulting in reevaluation of adjuvants used to potentiate local anesthetics. We have found that a mixture of local anesthetic with low-molecular weight dextran, one such local anesthetic adjuvant, greatly enhances analgesic duration and potency in patients receiving an interfascial compartment nerve block under ultrasoundguidance as well as those receiving a single peripheral nerve block. Notably, a compartment nerve block in the abdominal trunk with an extra-large amount of low-molecular weight dextran mixture, which results in a longer duration of the injected drugs at the injection site, provides good analgesia that is comparable to epidural anesthesia. Such a dextran mixture also suppresses systemic absorption of local anesthetics, thus reducing their systemic toxicity, which enhances regional anesthesia safety. Furthermore, it controls unintended spread of injected local anesthetics, thus increasing nerve block accuracy. In this chapter, recent findings regarding use of low-molecular weight dextran as a local anesthetic adjuvant obtained in our laboratory are presented.

**Keywords:** low-molecular weight dextran, ultrasound-guided nerve block, local anesthetics, adjuvant, regional anesthesia, anesthesia safety, toxicity
