**5. Antioxidant activity of local anesthetics**

We analyzed the antioxidant activity of lidocaine using this analysis system and the results showed that the rate of fluorescence decay was slowed in a concentration‐dependent man‐ ner (**Figure 9**). The effect was evaluated by determining the percent inhibition against B‐PE oxidation, an index used for the reactivity of peroxyl radicals, in which 100% inhibition indi‐ cates the same level of fluorescence decay as that by Trolox and 0% inhibition indicates the same decay as that in the absence of the antioxidant. The dose‐dependent effects of lidocaine are summarized in **Figure 10**, which indicates that lidocaine has potent antioxidant activity, while other local anesthetics such as mepivacaine showed similar but slightly weaker effects.

Combined with the findings of neutrophils, local anesthetics have effects to counter oxidative stress in a manner opposite of inhalation anesthetics, indicating that use of local anesthetics can reverse the deleterious effects of inhalation anesthetics. Thus, from the standpoint of oxidative stress management, anesthesia with a combination of local and general inhalation anesthetics provides better anesthesia management. The advantage of local anesthetics in oxi‐ dative stress management was also revealed in a study by Budic et al., who examined cases of pediatric extremity surgery using pneumatic tourniquets [21]. They measured generation of the oxidative products malondialdehyde and protein carbonyl groups in plasma and found that peripheral nerve block anesthesia did not increase the levels after tourniquet release as compared with general anesthesia with sevoflurane, which significantly increased those levels. These findings indicate that regional anesthesia provides an antioxidant defense that is superior to that of general inhalation anesthesia.

Regional Anesthesia: Advantages of Combined Use with General Anesthesia and Useful Tips for Improving... http://dx.doi.org/10.5772/66573 35

 R = K × [AAPH] (6) where K is the rate constant for radical generation from AAPH and [AAPH] is the concentra‐ tion of AAPH in M. The rate of radical generation is virtually constant during the first few hours of this assay [20], since the half‐life of AAPH is approximately 175 h in neutral pH water at 37°C [19]. The rate of peroxyl radical generation at 38°C under the present assay conditions

B‐PE is a multisubunit protein extracted from the unicellular red alga, *Porphyridium cruentum* [16, 20]. Since it is easily oxidized, which decreases its fluorescence, B‐PE functions as a reporting molecule of oxidative stress induced by peroxyl radicals from AAPH. In addition, because of its very high extinction coefficient and fluorescence quantum yields, B‐PE can be readily detected by fluorescence spectroscopy at concentrations as low as 10‐12 M [20].

For this assay, the fluorescence decay of B‐PE by the AAPH‐generated peroxyl radical was spectrophotometrically monitored at an excitation of 545 nm (3‐nm slit) and emission of 575 nm (5‐nm slit). The reaction mixture (2 ml) contained 1.78 nM B‐PE and 6.25 mM AAPH in 40 mM Tris‐HCl buffer (pH 7.4) at 38°C. Since the system is not closed, oxygen for the reac‐ tions is freely supplied from the atmosphere through the surface of the reaction mixture. As shown in **Figure 9**, B‐PE fluorescence was linearly decreased by exposure to AAPH, which has a linear relationship with B‐PE concentration. This peroxidative destruction of B‐PE can

We analyzed the antioxidant activity of lidocaine using this analysis system and the results showed that the rate of fluorescence decay was slowed in a concentration‐dependent man‐ ner (**Figure 9**). The effect was evaluated by determining the percent inhibition against B‐PE oxidation, an index used for the reactivity of peroxyl radicals, in which 100% inhibition indi‐ cates the same level of fluorescence decay as that by Trolox and 0% inhibition indicates the same decay as that in the absence of the antioxidant. The dose‐dependent effects of lidocaine are summarized in **Figure 10**, which indicates that lidocaine has potent antioxidant activity, while other local anesthetics such as mepivacaine showed similar but slightly weaker effects. Combined with the findings of neutrophils, local anesthetics have effects to counter oxidative stress in a manner opposite of inhalation anesthetics, indicating that use of local anesthetics can reverse the deleterious effects of inhalation anesthetics. Thus, from the standpoint of oxidative stress management, anesthesia with a combination of local and general inhalation anesthetics provides better anesthesia management. The advantage of local anesthetics in oxi‐ dative stress management was also revealed in a study by Budic et al., who examined cases of pediatric extremity surgery using pneumatic tourniquets [21]. They measured generation of the oxidative products malondialdehyde and protein carbonyl groups in plasma and found that peripheral nerve block anesthesia did not increase the levels after tourniquet release as compared with general anesthesia with sevoflurane, which significantly increased those levels. These findings indicate that regional anesthesia provides an antioxidant defense that is

be temporarily stopped by addition of a typical radical scavenger, such as Trolox.

was 1.56 × 10‐6

34 Current Topics in Anesthesiology

 × [AAPH] (M•s‐1

**5. Antioxidant activity of local anesthetics**

superior to that of general inhalation anesthesia.

) [3].

**Figure 10.** Dose‐dependent effects of lidocaine and mepivacaine on B‐PE fluorescence decay in the antioxidant assay system shown in **Figure 9**. These results indicated that both local anesthetics have a potent antioxidant activity.
