Use of Muscle Relaxants in Emergency Medicine: A Review

Modern anesthesia, intensive care, and emergency medicine rely heavily on neuromuscular blocking agents (NMBAs), first introduced in 1942. These agents not only facilitate endotracheal intubation but also improve surgical conditions by suppressing muscle responses to stimuli. NMBAs function via depolarizing (eg, succinylcholine) or non-depolarizing mechanisms. Non-depolarizing agents are further classified by chemical structure into aminosteroids (eg, rocuronium, vecuronium), benzylisoquinolinium compounds (eg, atracurium, cisatracurium), and asymmetric mixed-onium chlorofumarates (gantacurium). These differ in metabolism, histamine release potential, and duration of action. The effect of neuromuscular blocking agents is influenced by numerous patient-related factors, including age, body weight, sex, organ function, and others, which significantly complicates the selection of the optimal drug and its dose. In emergency medicine, NMBAs are critical for rapid-sequence intubation (RSI), used in both prehospital and emergency department (ED) settings. RSI is performed under challenging conditions, often involving critically ill patients with unknown medical histories. Succinylcholine and rocuronium are the primary agents used in this context. Ongoing debates persist regarding the choice between succinylcholine and rocuronium for RSI, the potential superiority of one agent over the other, and the selection of the optimal dosage. Modern technologies allow for neuromuscular blockade monitoring through train-of-four (TOF) assessment. However, such monitoring methods are rarely used in ED. This review article explores the pharmacological characteristics, clinical indications, and emergency applications of NMBAs, emphasizing the need for increased awareness of their risks and proper use.