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The most commonly used neuromuscular blocking agent for RSI is succinylcholine, typically administered at a dose of 1.0–2.0 mg/kg intravenously (70–140 mg in a typical 70‐kg patient). Succinylcholine’s rapid onset and short duration of action are ideal for RSI. The rationale for using a rapid‐acting paralytic is to achieve intubating conditions as quickly as possible. The rationale for using a short‐acting paralytic is to facilitate rapid recovery of the patient’s spontaneous airway reflexes in the event of unsuccessful laryngoscopy and intubation efforts.

Relative contraindications to succinylcholine include conditions with known hyperkalemia, such as acute renal failure or rhabdomyolysis. Succinylcholine‐induced hyperkalemia in these settings may cause cardiopulmonary arrest. While burn injuries can cause hyperkalemia, this complication usually does not occur until 2 or 3 days after the acute injury. Succinylcholine can be safely used for the acute management of burn victims. Other relative contraindications to succinylcholine include muscular‐wasting diseases (which can cause hyperkalemia) and pseudocholinesterase deficiency that prolongs the neuromuscular blockade due to slower drug metabolism.

Nondepolarizing agents such as rocuronium and vecuronium may be used as alternatives to succinylcholine for RSI. Rocuronium, dosed at 1 mg/kg, has a rapid onset (1–3 minutes), although its duration of action (30–45 minutes) is longer than succinylcholine (5–9 minutes). Vecuronium, dosed at 0.1 mg/kg, has a slightly longer onset of action (2–4 minutes), and duration of 25–40 minutes. “High‐dose” vecuronium (0.15–0.28 mg/kg) has an even longer duration of action (60–120 minutes). Clinicians should anticipate prolonged recovery time from vecuronium in obese patients, elderly patients, and those with hepatorenal dysfunction. Both rocuronium and vecuronium can be reversed by sugammadex (2–4 mg/kg).

After successful RSI, it is essential to administer additional medications to maintain sedation and paralysis. Therefore, EMS clinicians performing RSI should carry longer‐acting paralytics (for example, vecuronium) and longer‐acting sedative agents (for example, lorazepam, midazolam, or diazepam).

Pediatric practices for RSI often vary slightly from adult protocols. The pediatric literature raises concern regarding the possibility of unrecognized muscular myopathies, which would result in hyperkalemia with administration of succinylcholine [78]. Therefore, many specialty pediatric transport teams use nondepolarizing agents to facilitate paralysis. The use of etomidate for children remains unresolved. Prehospital RSI protocols vary between the use of etomidate and midazolam for sedation. Because of paradoxical bradycardia with RSI agents in children, clinicians may pretreat patients with intravenous atropine.