Neuromuscular Agents

Neuromuscular agents, also known as neuromuscular blocking agents, are pharmacological agents that act directly on the neuromuscular junction to prevent the transmission of impulses from motor nerves to muscles. These are primarily used as muscle relaxants in surgical procedures. Neuromuscular agents allow a range of procedural interventions that would not otherwise be possible by providing clinical conditions for a wide variety of surgical approaches and manipulations while preventing patient motion. In medical applications, neuromuscular agents are usually administered intravenously and produce paralysis of skeletal muscles by blocking the transmission of nerve impulses between the motor nerve and the muscle. At the neuromuscular junction, motor neurons secrete acetylcholine, which binds with receptors located on the muscle cell’s surface. When combined, the complex opens electrically gated ion channels, allowing sodium ions to flow in and causing a muscle contraction. Neuromuscular agents bind and block these receptors, preventing the binding of acetylcholine and therefore preventing muscle contraction. There are two types of neuromuscular agents: depolarizing and non-depolarizing. Depolarizing agents mimic the action of acetylcholine, which causes the muscle to remain in a contracted state until the agent is metabolized and its effects subside. Non-depolarizing agents prevent the neuromuscular junction from becoming depolarized, thereby preventing muscle contractions from occurring. Neuromuscular agents are indicated when surgical procedures require mechanical immobility or when respiratory depression is anticipated. Possible contraindications include certain neuromuscular diseases, skeletal or muscular disorders, and certain drug interactions. Side effects can include hypotension, myopathy, and neuromuscular damage if improperly used or administered. Neuromuscular agents are essential for a variety of surgical procedures and are key components of the anesthesia provider's armamentarium. By providing a means for skeletal muscle paralysis, these drugs allow the clinician to use the preferred surgical approach and manipulate the patient in ways that would otherwise not be possible. Care must be taken when administering and monitoring these medications as they can cause significant side effects and can have an extended duration of action.