Neuromuscular Blockers

Depolarizing and nondepolarizing agents are both apart of the neuromuscular blockade group. Neuromuscular blockers work by impeding motor nerve impulses from passing to the skeletal muscles. The purpose of blocking these passes is to make the muscles weak or paralyzed in surgery. Neuromuscular blockers can be used in many surgical procedures, like inserting an endotracheal tube, by relaxing the jaw muscles. They are also useful for relaxing the diaphragm and intercostal muscles (responsible for respirations) so that the patient can be manually ventilated. Neuromuscular blockers also aid in relaxing any muscles around the surgical site so that retracting for exposure is made easier. Broadly speaking, neuromuscular blockers’ main purpose is to
Depolarizing agents work by breaking down in two separate phases. First, they are used to cause muscle contraction by binding to acetylcholine. The contractions that the agents produce, called fasciculation, are forceful enough to be seen. During the second phase, muscles stop responding to acetylcholine, proving that neuromuscular blockade is in effect. When depolarizing agents are used, they still prompt the action potential to occur; this means that the neurons will still send information. (Source) However, even though the neurons are still working, the depolarizing agent causes the effector site to become desensitized, allowing the block to be successful. In comparison with nondepolarizing agents, depolarizing agents have a much faster onset but a shorter duration. These qualities make depolarizing agents ideal in emergency situations. The quick onset is useful for emergent cases when patient’s need to be intubated immediately. (Source
In order for them to work efficiently, they need to block at least 70-80% of acetylcholine receptors. This makes nondepolarizing agents an antagonist to acetycholine. When nondepolarizing agents are given, they do not trigger the action potential. Without that action, they are preventing the acetylcholine from binding, therefore preventing muscle contraction. (Source 2) Nondepolarizing agents are most commonly used when prolonged paralysis will be necessary for a procedure. (Source