Epidural anesthesia:
To ascertain the ion channel blocked by lidocaine it is necessary to asses which ion channels are important in nerve function. Between action potential conductance of potassium ion and chlorine ion high at rest, mediated respectively by potassium and chlorine ion in the nerve membraine. total charge between the inside and outside of the cell is driven toward the potassium and chlorine ion reversal potentials (Hui, Varadharajan, ., Yousefzadeh, 2017). during upstroke of the nerve action potential voltage-gated sodium ion are more important. Sodium channel opens in response to depolarization and these opening increases depolarization towards the reversal potential.in a depolarized cell there is an increased probability that sodium ions channels will open theirfor an increase in probability that will be inactivated.
when the cell depolarizes, sodium activation gates opens. After a delay the inactivation cell repolarizes (with the help of potassium flowing out of the cell through its own channel). repolarization rests both the activation gates of the sodium channels, allowing the cell to generate another action potential (Naruse, , Uchizaki, , Mimura et al.,2016). Local anesthetic and lidocaine blocks voltage-gated channels in nerve mebraine.at high concentration, upstroke is prevented and no action potential that occurs. while at low concentrations sodium channel blockage leads to slow rate rise of the upstroke of the action potential.
Action potential are propagated along sensory nerve axon by the spread of local currents from active depolarized areas. This local depolarizing current is triggered by inward sodium current of the upstroke of the action potential. When voltage- gated sodium channels are blocked by lidocaine the inward sodium current of the upstroke of the action potential does not occur (Einhorn, & Habib, 2016). This result to prevention of the propagation of the action potential wich depends on depolarizing inward current.
Reference
Naruse, S., Uchizaki, S., Mimura, S., Taniguchi, M., Akinaga, C., & Sato, S. (2016). Pressureulcer caused by long-term keeping of the same body position during epidural labour analgesia. Masui. The Japanese journal of anesthesiology, 65(6), 643-645.
Hui, C., Varadharajan, R., Yousefzadeh, A., Davies, S., & Siddiqui, N. T. (2017). Aseptic techniques for labour epidurals: A survey and review of neuraxial anesthesia practice. Canadian Journal of Infection Control, 32(1), 25-30.
Einhorn, L. M., & Habib, A. S. (2016). Evaluation of failed and high blocks associated with spinal anesthesia for cesarean delivery following inadequate labour epidural: a retrospective cohort study. Canadian Journal of Anesthesia/Journal canadien d’anesthésie, 63(10), 1170-1178.