**1. Introduction**

Recent advances in ultrasound technology have improved the accuracy and reliability of nerve block procedures [1–3]. As a result, there has been a shift from general anesthesia alone to that in combination with a nerve block. In addition, important related issues are opioid abuse, which has become a matter of public concern [4], as well as possible reduction in the risk of cancer recurrence in patients undergoing surgery with regional anesthesia [5, 6]. Evidence suggesting that general anesthesia in combination with regional anesthesia is superior for intraoperative hemodynamic stability and postoperative recovery has been reported [7, 8] (**Figure 1**). Those findings further advanced the shift to application of nerve block with general anesthesia, thus techniques to modify the effects of local anesthetics including use of an adjuvant compound have also regained attention [9]. Dextran,

#### **Figure 1.**

*Left panel: Comparison of intraoperative hemodynamic stability between patients with general anesthesia alone (n = 35) and general anesthesia with a transversus abdominis plane block (TAPB) (n = 33) [8]. General anesthesia was maintained in the same manner with sevoflurane and remifentanil in both groups. The period during the operation when both systolic blood pressure and heart rate were within 70–110% of their preanesthesia value was defined as the hemodynamic stable time. The ratio of hemodynamic stable time to total operative time was used as an indicator of hemodynamic stability. The stability ratio was significantly higher in the group receiving general anesthesia with TAPB (91%, range 50–100%) as compared to general anesthesia alone (79%, range 40–91%), indicating greater hemodynamic stability with general anesthesia plus TAPB. Values are presented as the median and minimum-maximum range (mean value indicated by "+"). Right panel: Comparison of anesthesia emergence time between the same groups shown in left panel. Anesthesia emergence time was defined as the time from completion of surgery to extubation. That was significantly shorter in the group receiving general anesthesia plus TAPB (14 minutes, range 4–30 minutes) as compared to general anesthesia alone (18 minutes, range 9–52 minutes). Values are presented as the median and minimummaximum range (mean value indicated by "+").*

which is composed of complex branched polysaccharides derived from sucrose with various lengths and weights, is such a local anesthetic adjuvant and investigated many decades ago, though nearly forgotten in recent times.

Accumulated attention and increased need of regional anesthesia have resulted in development of new nerve block procedures, with transversus abdominis plane and quadratus lumborum blocks typically employed [8, 10] (**Figure 2**). However, these new types of nerve blocks require accurate injection of a sufficient quantity of local anesthetic into the targeted interfascial compartment. A compartment nerve block performed in this manner has potential to serve as a substitute for epidural anesthesia, the current gold standard method for surgical pain control. On the other hand, there is a risk of systemic toxicity of local anesthetics associated with this procedure because the drug is given in a large amount [11]. Furthermore, another weak point to be solved is insufficient analgesic duration for controlling postoperative pain when the nerve block is performed with a single injection.

*New Application of Low-Molecular Weight Dextran as Local Anesthetic Adjuvant… DOI: http://dx.doi.org/10.5772/intechopen.98797*

#### **Figure 2.**

*Ultrasound image obtained during transversus abdominis plane block [8]. A local anesthetic solution was injected into the interfascial compartment between the internal oblique and transversus abdominis muscles.*

#### **Figure 3.** *Molecular structure of low-molecular weight dextran.*

We recently performed a reinvestigation of dextran effects under modern clinical environments and found that low-molecular weight dextran, with an average molecular weight of 40,000 (**Figure 3**), used as a local anesthetic adjuvant resolves the disadvantages of a trunk nerve block by improving the potency and safety of the local anesthetic [10, 12–15]. In this chapter, effects and clinical applications of low-molecular weight dextran as a local anesthetic adjuvant are discussed based on recent findings obtained by our research team.
