Question

A patient in the ER is about to get a laceration stitched up. First the ER nurse practitioner (NP) will infiltrate the area with Lidocaine, a drug that will prevent the patient from feeling pain as the stitches go in. The medication's mechanism of action is to change the permeability of nerve cell membranes so that they decrease the number of Na+ ions that are allowed to come into the cell. Using critical thinking and knowledge of RMP issues, what do you think is the next step?

a. The nerve cells in the area become filled with anions and the RMP is reset from -90mV
to -60mV.
b. Because of the increased influx of cations, the local nerve cell membranes become more positively charged.
c. Because of the decreased influx of cations, the local nerve cell RMPs will be reset from
-90mV to -120mV.
d. The sodium/potassium pump of the cell membranes will cease to work properly, and the
cells will become incapable of holding their normal RMP charge.

Answer 1

Lidocaine acts as a local anesthetic by blocking Na+ channels and preventing depolarization of nerve cells, which stops the transmission of pain signals.

Step-by-step explanation:

Drugs such as lidocaine function as effective local anesthetics because they act as Na+ channel blockers. By blocking voltage-gated sodium channels, these drugs prevent sodium ions from entering the nerve cell, which is essential for conducting an action potential. The inability of Na+ to flow into the cell keeps the membrane potential more negative, preventing depolarization, which means the nerve cell cannot initiate or transmit pain signals. The correct answer to the question is 'Because of the decreased influx of cations, the local nerve cell RMPs will be reset from -90mV to -120mV,' which is not accurate; instead, the resting membrane potential (RMP) will remain closer to its original value, such as -70mV, since an action potential is not triggered.