Use of Muscle Relaxants in Emergency Medicine: A Review

Introduction

The modern anesthesia and intensive care, as well as emergency medicine, require the use of many drug groups, and one of the main ones are NMBAs, which were introduced in 1942. The blockage of neuromuscular transmission is not only useful to facilitate intubation for the anesthesiologists, but it also provides better conditions for the surgical team by preventing muscle reactions in response to surgical stimulation [1]. The search for the ideal NMBAs (criteria: a rapid onset, no adverse effects, a simple way to reverse the relaxation, no accumulation, no active metabolites) continues, and from the 1950s until today, we do not know the drug which would meet all the listed conditions. There are 2 main mechanisms by which NMBAs work. The first one is the depolarizing mechanism, which consists of prolonging the depolarization of ion channels of the post-synaptic receptor. The second one is non-depolarizing, which depends on blockage of the acetylcholine access to post-synaptic receptor. Currently, only 1 depolarizing NMBA is in use (succinylcholine), while there is a variety of the non-depolarizing NMBAs and there is ongoing research to introduce another [2]. Considering the wide use of NMBAs, there is insufficient information available on their characteristics and medical indications, especially in the context of possible risks of use and adverse effects. Non-depolarizing NMBAs are characterized by the strong ionization in physiological pH, which results in the weak penetration through the blood–brain barrier and the placenta, as they do not dissolve well in fat. Non-depolarizing NMBAs can be divided into groups according to their chemical structure: atracurium, cisatracurium, and mivacurium are benzylisoquinolinium relaxants (their names end with -urium), while vecuronium, rocuronium or pancuronium are considered steroid-like relaxants (their names end with -uronium). Aminosteroids do not trigger histamine release, they have a strong relaxation effect and weaker vagolytic effect, and are metabolized by the liver (apart from rocuronium). Benzylisoquinolinium relaxants also have strong relaxations effect, but do trigger histamine release (apart from cisatracurium), are metabolized by Hoffman elimination or with serum pseudocholinesterase, and are excreted by the kidneys. Aminosteroids do not have a vagolytic effect. Another way of dividing NMBAs into groups is based on their time of action. Very short-acting NMBAs, such as succinylcholine, act for less than 10 minutes, short-acting ones (eg, mivacurium) act for 10–30 minutes, intermediate-acting ones (eg, atracurium, cisatracurium, vecuronium, rocuronium) act for up to 90 minutes, and long-acting NMBAs (eg, pancuronium, pipecuronium) act for more than 90 minutes [2]. NMBAs are responsible for about 63% of immediate allergic reactions during anesthesia, with a mortality rate of 4.1%. Moreover, there can be cross-sensitivity among drugs from the same group, which occurs in up to 70% of patients sensitive to NMBAs, especially aminosteroids [3].

In emergency medicine, NMBAs are used both in prehospital settings and in hospital EDs. Their primary purpose is to prepare the patient for the definitive securing of airway patency. Due to a number of challenging conditions, intubation in emergency medicine is initially classified as a difficult airway. This is because patients must be considered unprepared, potentially having a full stomach, and due to the environmental conditions in which intubation is often performed.

Both in prehospital settings and in the ED, a wide range of patients can be encountered. These may include patients with multiple comorbidities, sepsis, polytrauma, impaired consciousness, or an unknown medical history from whom no medical interview can be obtained. For this reason, intubation in emergency medicine is performed using the RSI protocol along with the administration of NMBAs. The agents used for this purpose are succinylcholine and rocuronium. Therefore, this paper will discuss their use in emergency medicine.

This article is a narrative review of the literature concerning the use of NMBAs in emergency medicine. Relevant articles were identified through a comprehensive search of several databases, including PubMed, Embase, and Google Scholar. The search included publications up to May 2025, using a variety of keywords, including “neuromuscular blocking agents”, “muscle relaxants”, “emergency medicine”, “rapid-sequence intubation”, “succinylcholine”, and “rocuronium”. Preference was given to studies published in English, including randomized controlled trials, observational studies, systematic reviews, clinical guidelines, and expert consensus statements. Additional references were obtained by manually screening the bibliographies of key articles. The review focuses on the pharmacological profiles of NMBAs, their clinical applications in emergency settings, and relevant controversies regarding agent selection, dosing, monitoring, and adverse effects.

Depolarizing Neuromuscular Blocking Agents – Succinylcholine

Based on their mechanism of action, muscle relaxants can be divided into depolarizing agents, with succinylcholine being the only commonly used representative, including in EDs. Its mechanism of action involves binding to the post-synaptic cholinergic receptor, blocking it and preventing acetylcholine from binding, which leads to muscle depolarization and paralysis.

Succinylcholine is metabolized by pseudocholinesterase (butyrylcholinesterase or plasma cholinesterase). Due to the rapidity of this process, only a small fraction of the drug reaches the motor end-plate. Various factors can influence plasma pseudocholinesterase levels. These include pregnancy, advanced age, severe liver disease, burn injuries, and drug interactions [4].

The elimination of succinylcholine and its metabolites occurs through the kidneys. In patients with renal impairment, succinylcholine appears to be a relatively safe choice (provided there is no neuropathy or previously diagnosed hyperkalemia). However, in patients with renal failure, repeat doses of succinylcholine should not be administered [5]. In the case of liver dysfunction, an extended activity time of succinylcholine may occur, while in patients with liver cirrhosis, prolonged muscle relaxation should be expected [6].

In patients with decreased plasma cholinesterase activity, the drug breaks down more slowly, leading to an extended duration of its paralytic and other effects. The effects of depolarizing skeletal muscle relaxants are influenced by acid-base balance disorders. Acidosis (both metabolic and respiratory) shortens the action of succinylcholine, while alkalosis has the opposite effect, enhancing it [7]. The effects of succinylcholine become apparent within 60 seconds after intravenous administration [6].

Adverse Effects and Contraindications of Succinylcholine

The use of succinylcholine in the ED must be considered in light of its potential adverse effects and contraindications. Succinylcholine has the highest number of adverse effects among all muscle relaxants [8].

Muscle relaxants, like other drugs administered intravenously over a short period of time, can cause allergic reactions. In emergency medicine, where these drugs are usually given to critically ill patients, this may lead to additional complications. Marantuan and colleagues report that in France, during anesthesia, anaphylactic reactions most commonly occur after the administration of NMBAs. Moreover, these reactions can be severe and even fatal. They state that approximately 4% of identified cases were fatal [9]. One of the most significant concerns is the risk of hyperkalemia and the resulting cardiac rhythm disturbances, including arrhythmias that can lead to cardiac arrest [4].

The administration of this drug can cause a temporary rise in blood potassium levels – up to approximately 1.0 mEq/L. This increase typically appears within a few minutes after intravenous injection and lasts for about 15 minutes. In many ED scenarios – such as trauma, severe burns, systemic infections, spinal cord injuries, upper motor neuron damage, structural brain injuries, Parkinson disease, or tetanus – the potassium increase following succinylcholine administration can be significantly higher, greatly raising the risk of serious complications [4].

A serious complication of succinylcholine use is malignant hyperthermia, which can occur in genetically predisposed individuals after administration of inhalational anesthetics and depolarizing skeletal muscle relaxants. If trismus is observed along with a significant increase in temperature and metabolic disturbances after the administration of succinylcholine, malignant hyperthermia should be suspected. In such cases, appropriate differential diagnosis should be initiated, and preparations should be made for the proper therapeutic management [4].

In a study published in 2013 by Dexter et al, the impact of succinylcholine and inhalational anesthetics on the occurrence of malignant hyperthermia was evaluated. It was found that while succinylcholine alone has an extremely low incidence of inducing malignant hyperthermia, it markedly increases the risk when administered in combination with volatile anesthetics. In the case of malignant hyperthermia, the administration of inhalational anesthetics and depolarizing NMBAs should be discontinued. Dantrolene is used for treatment. Therefore, it seems that in cases where succinylcholine is used, dantrolene should be readily available [10].

Another adverse effect of succinylcholine is bradycardia, especially in the pediatric population. Studies have shown that pretreatment with an age-appropriate dose of atropine has been beneficial in preventing or minimizing bradycardia that may result from succinylcholine administration.

Succinylcholine is believed to cause an increase in intraocular, intracranial, and intra-abdominal pressure. Therefore, in cases of head and facial injuries, it should be used with particular caution, or an alternative drug should be considered [8].

Succinylcholine should not be used in individuals with known conditions such as reduced plasma cholinesterase activity or muscle disorders. The use of muscle relaxants in patients with muscle diseases carries a higher risk of complications, including hyperkalemia, malignant hyperthermia, and cardiac arrest, as well as prolonged paralysis, muscle rigidity, rhabdomyolysis, or even death. Special caution is required in pediatric patients, as they may have undiagnosed underlying conditions that can lead to severe adverse effects such as rhabdomyolysis, hyperkalemia, or metabolic acidosis following administration. For this reason, the use of succinylcholine in children is reserved for exceptional cases only [4].

Rocuronium – A Representative of Non-Depolarizing Neuromuscular Blocking Agents in the ED

Non-depolarizing skeletal muscle relaxants are classified into 3 subclasses depending on their chemical structure: steroidal, benzylisoquinolinium, and asymmetrical mixed-onium chlorofumarate.

Rocuronium is a steroidal drug primarily used in EDs, characterized by fast onset of action – in approximately 1–3 minutes [11].

Rocuronium is hepatically metabolized to a less active metabolite [11]. Rocuronium is primarily excreted in the bile and partially through the kidneys in urine. In patients with hepatic insufficiency, rocuronium exhibits increased onset and duration of action, and recovery time is significantly prolonged, with high variability in response, particularly in cirrhotic patients. In patients with decreased renal clearance, prolonged time of action may occur [5,6]. Acidosis enhances and alkalosis reduces the effects of rocuronium [7].

For intubation, it is administered at a dose of 0.6 mg/kg to 1.2 mg/kg. In the case of RSI, higher doses, like 1.0 to 1.2 mg/kg, can provide intubating conditions similar to succinylcholine, with a short onset time of approximately 1 minute. However, this comes with a duration of action similar to longer-acting non-depolarizing drugs. For neuromuscular blockade maintenance, doses of 0.1 to 0.2 mg/kg/dose iv are given as needed [11].

In geriatric patients, it is important to remember the reduced elimination of rocuronium, which causes approximately a 2-fold prolongation of the drug’s duration of action [11].

It is believed that rocuronium is very cardiac-stable and has no impact on heart rate or blood pressure [11,12].

Rocuronium has off-label uses, such as preventing fasciculations during depolarizing muscle paralysis to prevent myalgias (administered in a defasciculating dose) and preventing shivering in patients after cardiac resuscitation after the return of spontaneous circulation during therapeutic hypothermia [11].

Rocuronium, like other steroidal non-depolarizing muscle relaxants, contains a component that can induce a vagolytic effect. Common adverse events include transient hypotension and hypertension. However, in the case of rocuronium, such effects are generally mild, if they occur at all. Kosciuczuk et al conducted a study in 2021 to assess the effect of rocuronium on heart rate and arterial blood pressure. As previously mentioned, rocuronium was considered cardiac-safe. Any potential increases in heart rate and blood pressure were typically transient and returned to normal following the end of anesthesia [12].

The absolute contraindication to using rocuronium would be a documented allergic reaction to the drug. Rocuronium should also not be given to any patient who is not sedated or not under the influence of anesthesia, to avoid the risk of awareness [11].

Rapid-Sequence Intubation

RSI (also known as “rapid-sequence induction”, “Crush intubation”, or “Crush induction”) is an airway management technique used for induction of anesthesia to quickly secure the respiratory tract in patients with gastric contents or those at risk of regurgitation or aspiration, in patients with acute respiratory failure due to poor oxygenation or ventilation, and for patients who cannot protect their airway due to altered mental status. RSI may also be used in patients with an acute upper-gastrointestinal bleed at a high risk of aspiration. The most important factor in selecting a best muscle relaxant in emergency medicine is the time required to achieve full relaxation. The classic RSI protocol involves the use of succinylcholine, which has the fastest onset of action). However, due to frequent contraindications and potential adverse effects, rocuronium has become a widely used alternative in this procedure [13] (Figure 1). Succinylcholine is most commonly used for RSI in adults, despite its numerous adverse effects; rocuronium is an alternative but a high dose is needed and sugammadex protection is then required [13].

Dosage in RSI

The selection of the optimal dosage of muscle relaxants in RSI is crucial for safely and quickly performing the procedure. The currently used dose of succinylcholine in RSI (approved by the FDA) is 1.5 mg/kg intravenously, while rocuronium is used at 1.2 mg/kg. In the case of RSI, it seems that using a higher dose than necessary is safer than administering too low a dose due to the potential for difficulties and possible delays in intubation [14,15].

In 2015, a paper was published comparing the classic RSI with a new regimen: ketamine with fentanyl and rocuronium – 274 cases of trauma patients were analyzed and it was observed that intubation was easier with the use of the new protocol and that it had a better effect on safety and hemodynamic parameters [16].

A 2019 study found that using a higher dose of rocuronium instead of succinylcholine may be more beneficial, although more expensive [17]. A 2018 study found that if there were no contraindications, succinylcholine could also be used as a muscle relaxant in RSI [18].

A study addressing the topic of drug dosing in RSI was conducted in the British Helicopter Emergency Medical Services since 2015, where high intubation success was demonstrated using a combination of 0.3 mcg/kg fentanyl, 2 mg/kg ketamine, and 1 mg/kg rocuronium. This regimen has since become a pharmacological standard used in RSI. This study result reflects current trends moving away from rigid drug administration protocols [19].

In the 2024 study by Morton et al, a 3: 2: 1 dosing regimen was compared with another regimen that reduced the fentanyl dose while increasing the doses of ketamine and rocuronium to 1: 2: 2. The new regimen showed no difference in episodes of absolute hypotension, but in trauma patients, it was associated with an increased first-pass success rate and fewer episodes of immediate hypoxia [20].

As the studies presented above show, the selection of muscle relaxants and their dosing remains a topic of ongoing research and discussion. An interesting solution to the issue of drug selection during RSI in the ED is described in a paper highlighting the role of the emergency medicine pharmacist as an important team member. The pharmacist in this role assists in the proper selection of drugs, determining drug interactions, their dosing, preparation, and administration. Of course, their role does not end after a successful intubation; they are also involved in designing and implementing post-intubation pharmacological strategies [21].

Rocuronium vs Succinylcholine in RSI

Succinylcholine and rocuronium are the most commonly used drugs in emergency medicine. They differ in their duration of action and adverse effects. Due to ongoing efforts to select the best drug, many studies comparing these 2 drugs in RSI have been conducted in recent years.

A 2019 study comparing the success of outpatient intubation with rocuronium (1.2 mg/kg) and succinylcholine (1 mg/kg) showed succinylcholine superiority (79.4% vs 74.6% first-intubation success), although in the group with a depolarizing drug, hypotension and hypoxemia were more frequent [22]. In a 2018 study, similar results of intubation efficiency were observed after the use of succinylcholine and rocuronium doses based on actual body weight [23]. Dose reduction has been shown to result in significantly poorer intubation conditions compared to the conventional rocuronium dose used for RSI, although the use of a video laryngoscope greatly facilitates intubation under these conditions. Moreover, with such a procedure, there is less risk of residual block occurrence [24].

In 2022, Tang et al conducted a prospective cohort study that assessed the impact of 1.5 mg/kg succinylcholine or 1.2 mg/kg rocuronium, vs 1.0 mg/kg succinylcholine, on apnea duration in patients undergoing RSI. The results suggested that lower doses of succinylcholine and 1.2 mg/kg rocuronium could be feasible in clinical practice. In conclusion, this study revealed that a relatively low dose of succinylcholine and rocuronium led to a longer non-hypoxic apnea duration. Therefore, 1.0 mg/kg succinylcholine or 1.2 mg/kg rocuronium may be recommended for RSI to satisfy the required intubation conditions. However, it was emphasized that further, broader studies should be conducted in this regard [25].

In 2022, Hayes-Bradley and Tarrant conducted a retrospective review of patient prehospital notes and airway database records from 2017 to 2018 for all cases using rocuronium for RSI. The aim of the study was to assess muscle function in laryngoscopy in patients who received rocuronium. Comparisons were made between rocuronium doses ≤1.5 mg/kg and >1.5 mg/kg by estimated weight. Of the 211 patients receiving rocuronium ≤1.5 mg/kg, 5 cases were inadequately paralyzed, compared with 2 cases from among 384 patients receiving >1.5 mg/kg rocuronium. The amount of insufficient paralysis in both groups was low and similar to the baseline, and did not reach statistical significance, presumably because of the low event rate. Further investigation into rocuronium dosing for RSI is warranted [26].

In a controlled, randomized, double-blinded study published in 2022, single-dose suxamethonium and rocuronium were evaluated after pretreatment with dexmedetomidine in RSI. Initially, a total of 240 participants were enrolled and divided into 2 equal groups (control and experimental). For the final analysis, 113 patients in the control group (who received 1 mg/kg of suxamethonium) were included, while 115 patients in the experimental group (who received dexmedetomidine 1 μg/kg in 10 ml of 0.9% saline over 10 minutes and rocuronium 0.6 mg/kg) were assessed. A combination of dexmedetomidine 1μg/kg and the standard intubating dose of rocuronium 0.6 mg/kg provided comparable endotracheal intubation conditions to suxamethonium 1 mg/kg during RSI and might be used as an alternative to suxamethonium in situations where suxamethonium is contraindicated [27].

In a 2022 study by Wang et al, the “modified timing principle” of rocuronium was assessed alongside a combination of lidocaine, remifentanil, and propofol for RSI. A total of 124 patients were randomly assigned to 2 groups: one receiving rocuronium in which patients like were given 0.6 mg/kg of rocuronium, with anesthesia induced by propofol 2 mg/kg and remifentanil 2 μg/kg, and the other group in which patients were given succinylcholine 1.5 mg/kg after losing consciousness from the same anesthesia regimen. Intubation occurred 60 seconds later. The results indicated that using the “modified timing principle”, a moderate dose of rocuronium led to optimal intubating conditions in 90% of patients, which was comparable to the success rate of succinylcholine 1.5 mg/kg. Furthermore, the apnea time in the rocuronium group was shorter than in the succinylcholine group [28].

In 2024, Wang et al conducted a single-center retrospective study assessing first-attempt intubation success using rocuronium vs succinylcholine in RSI. The study included 448 patients who received rocuronium and 183 patients who received succinylcholine. Patients were divided into subgroups: Rocuronium weight-based doses were categorized into ranges of less than 1 mg/kg, 1.0 to 1.1 mg/kg, 1.2 to 1.3 mg/kg, and greater than or equal to 1.4 mg/kg. Succinylcholine weight-based doses were divided into ranges of less than 1.5 mg/kg, 1.5 to 1.9 mg/kg, and greater than or equal to 2.0 mg/kg. The authors found no difference in first-attempt success between succinylcholine and rocuronium at increasing weight-based doses. The study also observed no significant change in systolic blood pressure or heart rate [29].

In the study by Anand et al., published in 2021, the intubating conditions after the administration of succinylcholine, rocuronium, and vecuronium were compared. Sixty patients were randomly divided into 3 groups, with 20 patients in each group. The succinylcholine group received 1.5 mg/kg body weight, Group II received rocuronium 0.6 mg/kg body weight, and Group III received vecuronium 0.1 mg/kg body weight. In this study, laryngoscopy and assessment of intubating conditions were performed 60 seconds after injection of the neuromuscular blocking agent. If the conditions were found to be unsatisfactory, ventilation was provided, and the patients were reassessed at further 30-second intervals until good to excellent intubating conditions were achieved. Based on the study, it was concluded that rocuronium provided comparable intubating conditions to succinylcholine and that it was hemodynamically stable, with only mild tachycardia. Rocuronium may be a good alternative when there are contraindications to succinylcholine. Vecuronium, although hemodynamically stable, had a delayed onset of action, making it unsuitable as an alternative to rocuronium and succinylcholine for RSI [30].

As evidenced by the studies above, it is difficult to determine a clear winner – namely, which agent should be routinely used for RSI and at what universal dose. However, it is worth considering that in emergency situations, using a higher dose to rapidly achieve conditions suitable for intubation is safer than administering a dose that is too low, which may necessitate repeating the attempt after waiting for full drug effect or require an additional dose. It is worth emphasizing, however, that most available studies highlight that rocuronium can be successfully used as a substitute for succinylcholine in RSI.

RSI in Prehospital Trauma

Considerations regarding the superiority of either drug – succinylcholine or rocuronium – also extend to prehospital care. In 2023, Ramsey et al conducted a retrospective, observational study with pre-post analysis involving adult patients who underwent prehospital RSI to assess the relationship between the use of succinylcholine and rocuronium and the time until the first laryngoscopy attempt, first-pass success, and Cormack-Lehane grades. Among 5179 patients in the EMS airway registry, 1475 adults received an NMBA while not in cardiac arrest. The Cormack-Lehane grades for succinylcholine and rocuronium were similar. The median interval from NMBA administration to the start of the first attempt was 57 s for succinylcholine and 83 s for rocuronium. First-attempt success was 84% for succinylcholine and 83% for rocuronium. Hypoxemic events occurred in 25% of succinylcholine cases and 23% of rocuronium cases. The study concluded that prehospital use of either rocuronium or succinylcholine is associated with similar Cormack-Lehane grades, first-pass success rates, and rates of peri-intubation hypoxemia [31]. A retrospective study of all trauma patients who received a prehospital RSI for trauma by a physician-staffed Helicopter Emergency Medical Service, published in 2021, included 322 patients. Of these, 63% received a full-dose induction of 3 μg/kg fentanyl, 2 mg/kg ketamine, and 1 mg/kg rocuronium, while 37% received a reduced-dose induction (1-1-1, 0-1-1, 0-0-1). Blood pressure decreased on average by 12 mmHg in the full-dose group versus 6 mmHg in the reduced-dose group. A hypotensive episode was noted in 29 patients: 17 receiving a full dose and 12 receiving a reduced-dose induction. A hypertensive episode was present in 22 patients. The highest blood pressures were recorded in the first 3 minutes after RSI. The authors found that prehospital induction of anesthesia for trauma with fentanyl, ketamine, and rocuronium is not related to a significant change in hemodynamics in most patients. However, a delayed hypotensive response with a significant drop in SBP should be anticipated in a minority of patients, irrespective of the dose regimen chosen [32]. In a study by Levin et al, which involved a secondary analysis of the National Emergency Airway Registry (NEAR), the relationship between the dose of rocuronium and first-attempt success among ED patients undergoing RSI was evaluated. It was noted that higher doses (≥1.4 mg/kg) were associated with improved first-attempt success using direct laryngoscopy in hypotensive patients [33].

RSI in Traumatic Brain Injury/Increased Cranial Pressure

Intubation in RSI for patients with severe head trauma is an established standard of care [10]. In 2023, Dao et al conducted a literature review and presented results indicating that, in the case of intubating patients with head trauma, the choice of rocuronium appears to be safer than the choice of succinylcholine [34]

Few studies have been conducted so far evaluating the impact of NMBAs on intracranial pressure, and the results of those that have been done are based on small, heterogeneous patient groups and varying research methodologies. In the review article by Grabarczyk et al published in 2025, it was noted that promising drugs with minimal or no effect on intracranial pressure or that can reduce it are cisatracurium and atracurium. However, succinylcholine used in RSI seems to contribute to an increase in intracranial pressure, and thus should generally be avoided in patients with head trauma. Rocuronium, on the other hand, appears not to affect cerebral blood flow, intracranial pressure, or cerebral perfusion pressure, and thus seems to be a better choice for RSI. Further studies should be conducted, particularly in the ED, to assess the use of these drugs in patients with elevated intracranial pressure [35].

RSI in Pediatric Population

RSI is widely used in pediatric anesthesia. According to the UNC Pediatric Emergency Department Guidelines from 2016, in children under 3 months of age and in cases of head trauma/increased intracranial pressure, rocuronium should be used for RSI. This drug is indicated as the first choice for performing RSI in most clinical scenarios, whereas succinylcholine is indicated as an alternative [36].

In children – especially young ones, including newborns and infants – there is a risk of hypoxemia and hypercapnia during the period between anesthesia induction and re-ventilation via the endotracheal tube due to reduced respiratory reserve compared to adults undergoing classical RSI. Minimizing the risk of this phenomenon involves appropriate ventilation (eg, by using pressure-limited mask ventilation with 100% oxygen for several minutes) [13]

When using succinylcholine in the pediatric population, it is important to remember that, due to greater availability of pseudocholinesterase, the duration of action of succinylcholine is shorter than in adults. Therefore, the dose to be used must be increased. This effect diminishes with increasing age of the child. In cases where intravenous access is difficult in children, intraosseous access may be used [13].

Occasionally, after succinylcholine administration in children up to around 6 years of age, an increase in plasma myoglobin and creatine kinase levels may occur [13]. The dosing of rocuronium for the pediatric population is slightly different – for muscular blockade induction, it is 0.6 mg/kg/dose IV for a single dose. For maintenance of blockade and anesthesia, doses are age-dependent and also depend on the anesthetic drug used. For children aged 3 months to 14 years when halothane is used for anesthesia, the doses are given as 0.075–0.125 mg/kg/dose iv as needed. For children younger than 17 years with isoflurane/nitrous oxide used for anesthesia, doses ranged from 0.1 to 0.2 mg/kg/dose iv [37].

Concerns regarding the potential complications associated with classical RSI have led to investigations into alternative approaches. In 2024, a proof-of-concept study was conducted to assess the feasibility and safety of using bolus remifentanil, in conjunction with a hypnotic agent, for RSI in pediatric patients presenting with at least 1 risk factor for pulmonary aspiration. The study included 267 children, with a mean age of 7.8 years (±4.4). The results demonstrated that remifentanil provided favorable intubation conditions, evidenced by a high rate of first-attempt success, and had a satisfactory safety profile. No major complications were observed, and minor adverse events – primarily hypotension – were infrequent. Additionally, the prophylactic administration of atropine was correlated with a reduction in the incidence of minor complications. These findings suggest that remifentanil is a viable alternative in modified RSI protocols for the pediatric population; however, the authors noted that more extensive studies are warranted to confirm these outcomes [38].

RSI in Elderly Patients

Due to both pathological and physiological factors associated with aging, elderly patients are more sensitive to neuromuscular blocking agents [39–41]. The effect of mivacurium may be prolonged due to age-related decreases in plasma butyrylcholinesterase (BChE) levels [42].

A randomized study published in 2025 compared intubation conditions during RSI using either rocuronium 1.0 mg/kg or succinylcholine 1.0 mg/kg in an elderly population (≥80 years) with American Society of Anesthesiologists physical status Classes I–IV and a body mass index <35 kg/m2. The study included 90 patients (aged 80 years or older) who underwent RSI with the use of videolaryngoscopy. No significant differences in intubation conditions were observed following the administration of either rocuronium or succinylcholine [43]. In a blinded randomized study published in 2021, Vested et al compared intubation conditions following the administration of either rocuronium 0.6 mg/kg or remifentanil 2 μg/kg in elderly patients. No difference in intubation conditions was observed 2 minutes after administration of either agent. However, intubation conditions were suboptimal in a significant proportion of this patient population [44]. An interesting study conducted by Chen et al in 2024 was a parallel-controlled randomized trial that evaluated the use of alfentanil as a pre-induction agent for muscle relaxation and intubation in patients aged 65–80 years. The study included 96 patients who were divided into groups receiving an initial mixture of etomidate (1 mg/mL) and propofol (5 mg/mL) at a dose of 0.2 mL/kg, followed by 10 μg/kg, 15 μg/kg, 20 μg/kg, or 25 μg/kg of alfentanil, and then rocuronium at a dose of 0.6 mg/kg. The study demonstrated that using alfentanil at a dose of 20 μg/kg for this procedure was associated with more stable hemodynamic changes during the perioperative period. A limitation of the study: patients with cardiovascular disease were excluded, and patients with full stomachs in the ED were not considered [45].

A study published in 2022 by Eichlseder et al, which retrospectively analyzed the impact of age on physician decision-making for or against RSI in unconscious patients, showed that advanced age, especially over 85 years, was associated with significantly less frequent use of RSI in prehospital settings. The authors suggested that this might be due to suspected reasons for unconsciousness and expected chances of recovery, rather than age itself [46]. In a retrospective study from 2011, Theodosiou et al assessed the characteristics and outcomes of 1686 elderly patients (≥80 years) undergoing RSI in the ED, of whom 107 were aged ≥80 years. The most common diagnoses among these patients were ischemic stroke or intracranial hemorrhage and head trauma. The most frequent complication related to RSI and associated procedures was hypotension, occurring in 15% of patients. The study highlighted the high mortality in this patient group (only 20% surviving to hospital discharge). Forty-one patients were admitted to the ICU, 55 were admitted to a ward (31 for palliative care), and 11 died in the ED. Among the survivors, 60% had a good recovery with no requirement for increased support. The study emphasized that the final outcome was more strongly influenced by the underlying diagnosis than by age itself [47].

RSI in Obese Patients

In a prospective, observational non-inferiority study by McDowell et al in 2023, 96 adult patients with a total body weight ≥30% above ideal body weight or a body mass index ≥30 kg/m2, who presented to the ED requiring RSI with rocuronium, were enrolled to evaluate the impact of dosing strategy on intubation conditions. Patients were divided into 2 groups: 54 received dosing based on TBW (mean dose: 1 mg/kg), and 42 based on IBW (mean dose: 0.71 mg/kg). The non-inferiority analysis found no difference in intubation conditions between the 2 dosing strategies, but the difference was not statistically significant. Therefore, the study was unable to demonstrate statistical non-inferiority of IBW-based dosing [48].

RSI Pretreatment with Magnesium Sulfate

Given the slightly slower onset of action of rocuronium compared to succinylcholine, various strategies have been investigated to accelerate its onset time. One such approach involves pretreatment with magnesium sulfate. In the study conducted by Czarnetzky et al, the effects of pretreatment with magnesium sulfate followed by a standard intubating dose of rocuronium were compared to standard RSI using succinylcholine, focusing on intubation conditions and adverse effects. The study included 280 randomized patients, with intubation conditions assessed in 259 of them (133 in the magnesium sulfate–rocuronium group and 126 in the saline–succinylcholine group). No differences in arterial blood pressure were observed between the groups; however, the mean heart rate was significantly higher in the magnesium sulfate–rocuronium group. The percentage of patients experiencing at least 1 adverse event was lower in the magnesium sulfate-rocuronium group compared to the saline-succinylcholine group. In the magnesium sulfate-rocuronium group, a few patients experienced injection pain, nausea and vomiting, or skin rash during the magnesium sulfate infusion. Based on these results, the authors concluded that intravenous pretreatment with magnesium sulfate followed by a standard intubating dose of rocuronium did not result in superior intubation conditions compared to succinylcholine, but was associated with fewer adverse effects. Furthermore, they hypothesized that for RSI, a combination of magnesium sulfate pretreatment and rocuronium may be a viable alternative to succinylcholine in cases where succinylcholine use is contraindicated [49]. A prospective comparative study conducted by Rajasekaran et al compared intubation conditions during RSI between rocuronium with magnesium sulfate pretreatment and succinylcholine in patients undergoing elective surgery under general anesthesia. A total of 150 patients were divided into 2 groups of 75 each. In the first group, patients were pretreated with magnesium sulfate 50 mg/kg in 100 ml of 0.9% normal saline before induction, followed by the administration of rocuronium 0.6 mg/kg for intubation. In the second group, patients were given 100 ml of 0.9% normal saline before induction and received succinylcholine 1.5 mg/kg for intubation. Intubation conditions were comparable between the 2 groups. They concluded that magnesium pretreatment before 0.6 mg/kg rocuronium provides clinically acceptable intubation conditions similar to succinylcholine, making it suitable for RSI, with mild adverse effects that resolve spontaneously without any treatment [50]. In a study conducted in 2024 by Shall et al, a randomized, prospective, double-blind clinical study was done involving 50 patients classified as American Society of Anesthesiologists (ASA) physical status I/II, with no predicted difficult intubation. The patients were divided into 2 groups: one received 60 mg/kg of magnesium 15 minutes before intubation, along with 1.2 mg/kg of rocuronium, while the other group received 60 mg/kg of magnesium before 0.6 mg/kg of rocuronium. Intubation conditions were assessed and graded after the loss of the last twitch following drug administration. The study found that intubation conditions with 0.6 mg/kg of rocuronium were comparable to or equally effective as those achieved with 1.2 mg/kg of rocuronium after magnesium pretreatment. Magnesium pretreatment enhanced the neuromuscular blocking effect of rocuronium, reducing its onset time without clinically significant prolongation of the block’s duration. It is important to consider, however, that although this study evaluated the use of these drugs in the RSI procedure, it was conducted on patients undergoing elective surgery, rather than in an ED setting [51].

These results suggest that use of magnesium sulfate as a pretreatment causes rocuronium to act faster and induce neuromuscular blockade more quickly. As a result, the intubation conditions achieved during the RSI procedure with this approach are comparable to those obtained when using succinylcholine alone. A study published by Shall suggests that it may also allow for a reduction in the dose of rocuronium while maintaining intubation conditions comparable to those achieved with a higher dose. It is worth noting, however, that comparable intubation conditions in available studies are also achieved without the use of pretreatment. Further research should be conducted to identify specific clinical situations in which patients might benefit from the use of magnesium sulfate as pretreatment prior to the administration of rocuronium.

Priming, Timing, Precurarization

Priming is a method used to accelerate the effect of a muscle relaxant at a given dose by reducing the sensitivity of acetylcholine receptors through the administration of non-depolarizing blockers in sub-paralytic doses. The “priming principle”, which has become widely used in recent years, is a method used to provide a faster effect when the actual drug dose is applied by reducing the sensitivity of acetylcholine receptors through non-depolarizing blockers in sub-paralytic doses. To achieve this effect, a small dose of up to 10% of the effective dose is given (higher priming doses are considered unsafe), and the remaining portion of the dose is administered after a specified interval [2,52].

In a randomized, controlled study published in 2024, the effect of priming with rocuronium on the time required for muscle relaxation was evaluated. Patients arriving at the ED and requiring RSI were divided into 2 groups: the RSI intubation group and the priming group (10% of the rocuronium dose was administered approximately 3 minutes before the induction agent). Randomization was done based on the order of patient arrival. A total of 52 patients were included in the study, with 26 patients in the standard group and 26 patients in the priming group. It was observed that priming with rocuronium shortened the intubation time and better preserved the hemodynamic profile [53].

Pallavi et al conducted a randomized double-blinded comparative clinical study on intubating conditions with and without rocuronium priming. Sixty patients, aged 18–60 years, with ASA physical status I and II, were randomly divided into 2 groups: the priming group (0.06 mg/kg of rocuronium as priming) and the control group (30 patients who received normal saline as priming). All patients received fentanyl 1 mcg/kg, followed by thiopentone 5 mg/kg for induction. The intubating dose of rocuronium was 0.54 mg/kg for the priming group and 0.6 mg/kg for the control group, administered 3 minutes after priming. The researchers found that priming with rocuronium provided excellent intubating conditions in less than 60 seconds compared to the non-priming group and was a safe alternative to succinylcholine [54].

In 2023, Postaci et al conducted a prospective randomized, double-blind study to evaluate the effect of rocuronium priming and intubation doses calculated according to actual body weight or corrected body weight on neuromuscular block and intubation quality in RSI and intubation. The study assessed 50 female patients, who were divided into 2 groups. Rocuronium priming and intubation doses based on actual body weight or corrected body weight did not cause any differences in intubation quality and TOF values. Based on the study results, it was suggested that priming and intubation doses of rocuronium based on the patient’s corrected body weight in RSI provide similar intubation conditions compared with those based on actual body weight [55].

Timing refers to administering the full dose of a muscle relaxant to a conscious patient, followed only afterward by the anesthetic. This approach was intended to shorten the time needed to achieve full neuromuscular blockade. However, in this case as well, the fully conscious patient experiences discomfort and dyspnea, which is why this method should be abandoned [2].

Precurarization is administration of a small dose of a non-depolarizing agent before giving succinylcholine, with the aim of reducing muscle fasciculations. According to current state of knowledge, this technique is unjustified and should not be used [2].

Pregnant and Postpartum Patients in the ED

The rapid-induction protocol is also used in obstetrics when emergency cesarean section is required. Studies on the use of succinylcholine and rocuronium in emergency cesarean section have shown that rocuronium provides better conditions for the surgeon, but it is associated with a lower number of Apgar points for the child [56].

When choosing succinylcholine, one should take into account the variability of pseudocholinesterase activity, which changes depending on the duration of pregnancy or the postpartum period. Thus, in the first trimester, the level of pseudocholinesterase decreases, and despite a slight increase in this level during the second trimester, it remains at a reduced level throughout the physiological pregnancy, returning to normal values at around 6 weeks after delivery. Rocuronium is also commonly used during cesarean section. At a dose of 1 mg/kg, it provides rapid muscle relaxation and favorable conditions for intubation [8].

In 2019, the Society for Obstetric Anesthesia and Perinatology issued recommendations to avoid the use of sugammadex for neuromuscular blockade reversal in patients in early pregnancy and to avoid or use it with particular caution in patients during labor. It emphasized that the use of sugammadex may be considered in pregnant women when there is an absolute benefit, such as in unforeseen situations requiring reversal of the relaxant (eg, a “can’t intubate, can’t oxygenate” [CICO] scenario) or when cholinesterase inhibitors fail to adequately reverse the block [57,58].

A 2025 article responding to partially outdated data published by the Anesthesia Patient Safety Foundation (APSF) in the article “Safety of Sugammadex in Pregnancy, Pediatrics, and Renal Failure” emphasizes that a blanket recommendation to avoid sugammadex in pregnancy is not best for patients. Current knowledge also supports the use of sugammadex in breastfeeding women, as it passes into breast milk in low amounts, oral absorption of the drug by the infant is minimal, the risk of harm is low, and there are also reports of the drug being used in newborns and infants undergoing neuromuscular blockade [59].

When using a cholinesterase inhibitor and atropine, it should be borne in mind that atropine passes through the placenta and, given in high doses, can cause fetal tachycardia and unresponsiveness in the OCT recording. The use of magnesium sulfate can prolong the effect of muscle relaxants [57].

Mivacurium as a Potential RSI Agent

Previous studies have assessed the use of mivacurium in emergency medicine and its application in the RSI protocol. Mivacurium is a short-acting non-depolarizing muscle relaxant belonging to the Benzylisoquinolines class. This drug is metabolized by the butyrylcholinesterase enzyme (BChE), which is a pseudocholinesterase. Thus, the metabolism of mivacurium depends on the activity of this enzyme, similar to the case of succinylcholine. The biotransformation of this drug occurs very quickly after administration. However, it can be reduced in patients with abnormal or decreased plasma cholinesterase activity, especially in individuals with a homozygous atypical cholinesterase gene abnormality [60,61].

Because spontaneous recovery after mivacurium is rapid, routine reversal may not always result in a clinical benefit [60]. The onset of action is 1–1.5 minutes, and the duration of action is 15–20 minutes. The ED95 is 0.06–0.08 mg/kg, while the intubation doses are 0.16–0.24 mg/kg. It is important to note that due to the metabolism of mivacurium, a 2xED95 dose may be insufficient – metabolism begins before full blockade is developed; however, a 2–3xED95 dosage can enable tracheal intubation within approximately 2.5 minutes [2].

In the study by Li et al, published in 2022, intubation during RSI using mivacurium was compared with that performed using rocuronium. A total of 158 patients undergoing elective surgery were recruited and randomized into 2 groups: the mivacurium group (0.25 mg/kg in divided doses) and the rocuronium group (0.9 mg/kg). Both groups received a combination of propofol, lidocaine, remifentanil, and ephedrine. Compared to rocuronium, mivacurium in RSI demonstrated non-inferiority in terms of the rate of excellent intubation conditions and provided hemodynamic variations comparable to rocuronium [62].

Reversal Agents

For many years, airway management during RSI was primarily performed using succinylcholine. One of its most important features that made it suitable for RSI was its rapid onset and short duration of muscle relaxation, lasting only a few minutes. This was particularly beneficial in situations where intubation was difficult or unsuccessful. In subsequent years, rocuronium began to be increasingly used for emergency RSI. Unfortunately, its duration of action is significantly longer than that of succinylcholine, which posed a serious concern in the event of failed intubation or critical situations like CICO. The introduction of sugammadex, a drug that reverses the effects of rocuronium, changed this dynamic. Sugammadex works by reducing the availability of rocuronium at the nicotinic receptors of the neuromuscular junction, thereby terminating the neuromuscular blockade. It offers rapid reversal of neuromuscular blockade and is an alternative to classical cholinesterase inhibitors [13,63].

An important aspect to consider when using sugammadex in the ED is its effect on the action of anticoagulants such as heparin and warfarin, as it can enhance their effects, thereby increasing the risk of bleeding [63,64]. It should also be noted that sugammadex can cause adverse effects such as allergic reactions (eg, hypotension, tachycardia, rash, urticaria, angioedema), hypertension, or bradycardia [65].

Sugammadex use in emergency medicine for failed intubations sheds new light on the safety profile of rocuronium and further supports its use as a muscle relaxant in RSI. Supporting this approach, a study examined the dosing of NMBAs before and after the introduction of sugammadex. The results clearly showed that higher doses of aminosteroidal NMBAs were used after the reversal agent became available. The authors suggested that this increase in dosing might reflect a form of risk compensation – an increased willingness to engage in riskier practices due to the availability of a new safety measure [66].

A study by Christodoulides et al described the use of sugammadex in acute neurosurgical patients who had received rocuronium, with the goal of enabling timely and accurate neurological assessment. The authors reported that this approach facilitated more precise clinical decision-making and helped prevent unnecessary invasive procedures [67]

The dosing of sugammadex used to reverse rocuronium-induced neuromuscular blockade was also described in a 2022 ED study. The authors found that doses of 3 to 4 mg/kg were both effective and safe in reversing the effects of rocuronium. In this study, sugammadex was administered 1–2 hours after RSI [68]. In another study, the effectiveness of using sugammadex at half the recommended dose was investigated, showing that low-dose sugammadex was effective in reversing rocuronium-induced neuromuscular blockade in the ED setting [69].

Lee published a study in which 55 patients were split into 2 groups based on the NMBA used and measured values such as the time between recovery of spontaneous ventilation and neuromuscular function. It also measured the intubating conditions found in the 2 groups. Patients were preoxygenated and then received 10 mcg/kg alfentanil and 2 mg/kg propofol, after which, the NMBA drug was used. The results showed that the rocuronium (used in dose 1mg/kg) and sugammadex (16 mg/kg) group had significantly faster recovery of spontaneous ventilation and neuromuscular function in comparison to succinylcholine group (1 mg/kg), and no clinically significant difference was found between intubating conditions in the 2 groups. This led to the conclusion that the use of the use of rocuronium with sugammadex in RSI is more beneficial than the use of succinylcholine [70].

Proper Analgosedation in RSI

Once the entire process of preparation and RSI intubation is successfully completed, it is crucial to maintain ongoing analgesia and sedation in paralyzed patients. This is of great importance, as in recent years there has been an increase in the use of neuromuscular blocking agents with prolonged durations of action. In the past, numerous studies have been conducted regarding the phenomenon of awareness with paralysis in the operating room. However, the same agents are also used in EDs, and the scope of research on awareness under paralysis has not been extended to emergency medicine.

Pappal et al conducted a single-center, prospective, observational cohort study involving 383 mechanically ventilated patients in the ED. After extubation, patients were assessed for awareness with paralysis using a modified Brice questionnaire. This adverse event was identified in 10 of the 383 patients, representing an incidence rate of 2.6%. Although awareness with paralysis occurs in a relatively small proportion of mechanically ventilated patients in the ED, the experience of such a distressing event carries serious consequences [71].

In 2022, Ender et al conducted a study comparing differences in sedation practices among patients who received either rocuronium or succinylcholine during transport by critical care transport teams. The study analyzed 264 intubations – 92 involving succinylcholine and 172 involving rocuronium. Ketamine and etomidate were the most commonly used induction agents. It was noted that the use of rocuronium was associated with a longer time to sedation administration. The mean time from neuromuscular blocker (NMB) administration to the first dose of sedation was 9.2 minutes in the succinylcholine group and 14.8 minutes in the rocuronium group. Following neuromuscular blockade, the total hourly weight-adjusted fentanyl dose was significantly lower in patients intubated with rocuronium compared to those intubated with succinylcholine. The authors concluded that there are opportunities to improve sedation and analgesia practices following rocuronium-assisted RSI [72].

Electroconvulsive Therapy

Electroconvulsive therapy is mostly used in specialized units and in certain intensive care departments, and in some threatening conditions in psychiatry or neurology [73,74]. Indications for performing this procedure may include major depressive disorder with psychotic features or acute suicidal ideation, and catatonia. Electroconvulsive therapy is used patient with rapidly deteriorating conditions caused by psychiatric disorders. Catatonia requires a broad differential diagnosis and must be confirmation by an experienced psychiatrist [73,74]. It has been used in refractory status epilepticus, neuroleptic malignant syndrome, delirium, and catatonia caused by autoimmune diseases [74].

Succinylcholine (0.3–1 mg/kg) is the drug of choice for performing electroconvulsive therapy, but in cases of contraindications, rocuronium or mivacurium are used. In the case series presented by Bulteau et al, atracurium was used [73,74,75]. Bryson et al found that some patients required significantly different doses of succinylcholine compared to the typically used 0.9 mg/kg to achieve an optimal level of muscle relaxation; 29 patients (5.8% of those studied) required an adjustment of 2 SD either above or below the mean dose of succinylcholine, resulting in an increased dose of up to 2.10 mg/kg or a decreased dose as low as 0.29 mg/kg [76].

Cardiac Arrest Patients Treated with Targeted Temperature Management

NMBA are often used to control shivering in comatose cardiac arrest patients during targeted temperature management. However, data on the outcomes are inconclusive, and the strategy requires individualization.

In a 2020 clinical trial, it was hypothesized that continuous NMBA administration would lead to a greater reduction in serum lactate levels among comatose patients after cardiac arrest. It was shown, however, that it did not reduce lactate levels during the first 24 hours after enrollment compared with usual care, and there was no difference in overall hospital survival, hospital survival with good neurologic outcome, or adverse events [77].

In another study in which a secondary analysis of the SAVE-J II study (a retrospective multicenter study of out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation) was conducted, the use of NMBAs was not significantly associated with outcomes in out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation and targeted temperature management [78].

In a 2022 review study with meta-analysis, results showed that using a prophylactic NMBA strategy compared to no NMBA use was associated with improved mortality and neurologic outcomes in cardiac arrest patients undergoing targeted temperature management [79].

Drugs Interactions

One should always be aware of possible drug interactions. In the case of patients requiring RSI, obtaining a medical history may be impossible, and current medication records may not be available. Nevertheless, it is important to remember that drugs such as procainamide, magnesium, lidocaine, and aminoglycoside antibiotics will enhance the effects of succinylcholine. Lithium may enhance the effects of both depolarizing and non-depolarizing skeletal muscle relaxants. Chronic use of statins will lead to a faster onset of blockade with rocuronium and prolong its duration. In the case of esmolol, there may be a delay in the onset of action of rocuronium. Glucocorticoids will cause a weakening of the relaxant effect with both long-term and single-dose administration of corticosteroids [4,80].

RSI Recommendations

According to the latest recommendations given by Society of Critical Care Medicine in 2023:

It is worth citing the NMBAs dosing recommendations for neuromuscular blocking agents outlined in the Consensus Statement on Major Trauma Patients, published in January 2025 by Trauma New Brunswick (Ringuette et al), which also distinguishes dosing for patients in shock. The consensus discusses the use of the Shock Index to help identify patients at risk for hypotension during the peri-intubation phase (the Shock Index is calculated by dividing the patient’s heart rate by their systolic blood pressure; the normal range is 0.5–0.7, with values above 0.8 suggesting significant hemodynamic instability). For rocuronium, a dose of 1.5 mg/kg is recommended for both adult patients and those in shock. In the case of succinylcholine, the recommended dose is 1.5 mg/kg for adult patients and 2.0 mg/kg for patients in shock [82].

Summary

In emergency medicine, NMBAs are usually used to paralyze the muscles to provide optimal conditions for intubation. This is typically performed according to the RSI protocol. The optimal muscle relaxant for this procedure is one that has a short onset of action, which is why succinylcholine is used. However, due to numerous contraindications and the lack of a drug that completely reverses its block after administration, rocuronium is used (increased doses are employed compared with those for surgical relaxation to achieve a faster onset). Recent studies have also been conducted on the use of mivacurium, which also features a rapid onset of action.

It is not easy to determine which drug should be first-line. In a meta-analysis published in 2023, succinylcholine had a higher first-pass success rate than rocuronium for emergency airway management but use of succinylcholine was associated with increased incidence of arrhythmias in comparison to rocuronium [83].

The available evidence shows that in patients with traumatic brain injury necessitating intubation, rocuronium appears to be safer than succinylcholine. In the pediatric population, rocuronium is also usually the first-choice agent.

Recently, scientific studies have emerged exploring various techniques aimed at accelerating the onset of neuromuscular blockade and ensuring optimal intubation conditions, such as priming or pretreatment with magnesium sulfate. However, further evidence is needed to determine the appropriateness and clinical scenarios in which their use would be truly beneficial.

Many factors influence the effects of NMBAs, which are often very difficult to track or predict in advance. Therefore, to safely administer neuromuscular blockade, TOF monitoring should be used. Quantitative methods are currently rarely employed in EDs.

Future Directions

In 2020, Kriswidyatomo et al reviewed the technical variations among RSI protocols. They noted that, depending on the institution, practices differ in many aspects, including patient positioning, choice of induction agent, application of cricoid pressure, selection of neuromuscular blocking agent, and use of positive-pressure ventilation. They discussed the ongoing controversies surrounding these differences and emphasized the need for further research and the development of standardized guidelines [84].

It remains essential to continually emphasize the need to sedate patients undergoing neuromuscular blockade to avoid or, at minimum, minimize the risk of awareness in paralyzed patients. The search continues for agents capable of reversing neuromuscular blockade, as well as for neuromuscular blocking drugs that would embody the characteristics of the so-called ideal neuromuscular blocking agent. Further, systematic research is needed on emergency medicine aspects such as drug use in traumatic brain injury, ocular trauma, and on defining situations in which priming or pretreatment might be beneficial. Advances in technology will undoubtedly facilitate the broader implementation of videolaryngoscopy as a useful method for visualizing the vocal cords and performing visually guided intubation, which will significantly aid both in RSI and in cases where conventional methods fail.

Given the large number of factors influencing the duration of action of skeletal muscle relaxants, routine practice should include monitoring with TOF.