Effect of Administration of Lidocaine at Body Temperature on Anesthesia Success in Rodent Model: A Behavioral and Electrophysiology Study

Introduction: Success in anesthesia administration relieves the perception of pain during surgery. Lidocaine is the most commonly used local anesthetic agent in clinical medicine. Moreover, anesthetic agents’ temperature changes can influence cell membrane permeability. Here, the effectiveness of different temperatures of Lidocaine (Lid.) on anesthesia success rate has been investigated in rats. Methods: Wistar male rats were pretreated by fast injection of lidocaine or saline into the hind paw or intradermal cheek at Room Temperature (RT) and Body Temperature (BT) (22°C and 37°C, respectively). Then, rat behaviors were evaluated by formalin-induced hind paw pain and orofacial pain tests, respectively. Moreover, using a single-unit recording technique, the spontaneous activity of the marginal nerve was recorded at room temperature in the RT-Lid. and BT-Lid. groups. Results: Data analysis revealed that lidocaine had significant antinociceptive effects in both the BT-Lid. and RT-Lid. groups compared to the control groups (P<0.05). Also, the number of spikes in the BT-Lid. and RT-Lid. groups were significantly lower than their baselines (P<0.05). However, lidocaine at body temperature decreased the total time spent licking the hind paw, the number of lip rubbings, and the number of spikes firing by about 10%-15% compared to room temperature. Conclusion: In both behavioral and neural levels of the study, our results showed that an increase in the temperature of lidocaine toward body temperature could increase anesthesia success rate compared to administration of lidocaine at room temperature. These findings can be considered in the treatment of patients.