Examining the effects of lidocaine and dexmedetomidine on compound action potential in rat sciatic nerve

Aims: Recent interest in Peripheral Regional Blocks (PRB) has increased for surgical and nonsurgical implementations. Lidocaine is frequently preferred in PRBs because of its wide safety margin. The short duration of action limits the use of Lidocaine. Dexmedetomidine is a new-generation adjuvant agent. According to our hypothesis, Dexmedetomidine will prolong the duration of the action of Lidocaine. Methods: A total of 48 rat sciatic nerves were isolated and electrophysiological recordings were taken from 28. They were then randomly divided into 4 groups as Group Control (C), Group L given 1 mM Lidocaine, Group D given 5 microgram/L Dexmedetomidine, and Group LD given 1 mM Lidocaine and 5 microgram/L Dexmedetomidine. Compound Action Potentials (CAP) were recorded after the stimulation of the nerves. Maximum Depolarization Value (MD, mV), time to Maximum Depolarization (MDT), Area Under the CAP curve (Area, mV.ms), and conduction velocities were calculated separately for Fast-Conducting Fibers (CVF, m/s) and Medium-Slow-Conducting Fibers (CVM, m/s). Results: In the comparisons of the Areas Under the Curve, significant differences were detected for Group C and Group LD (P=0.001). In the comparisons of CVF values, significant differences were detected for Group C with Group L and Group LD (p=0.007, p=0.000). In the comparisons of Group L and Group LD (p=0.002). In the comparisons of CVM values, significant differences were detected for Group C with Group L and Group LD (p=0.000, p=0.000, respectively). Significant differences were detected between Group L, and Group LD (p=0.009). Conclusion: Results were found showing that perineural Dexmedetomidine when added to Lidocaine as an adjuvant agent, increased the number of fibers that developed block and decreased conduction velocities. These results might indicate that Dexmedetomidine may increase the duration of the block.