Succinylcholine is a depolarizing neuromuscular blocking agent often used for rapid sequence intubation due to its rapid onset and short duration of action. Despite its efficacy, succinylcholine has several contraindications and is associated with significant adverse effects, limiting its use in clinical practice (1).
One of the most serious contraindications to succinylcholine use is its ability to trigger malignant hyperthermia, a life-threatening hypermetabolic state characterized by hyperthermia, muscle rigidity, and rhabdomyolysis. Malignant hyperthermia is associated with mutations in the ryanodine receptor (RYR1) gene and is often fatal if not treated promptly with dantrolene (2). Because of succinylcholine’s well-documented link to malignant hyperthermia, it is strictly contraindicated in patients with a personal or family history of this condition.
Hyperkalemia is another major risk factor when administering succinylcholine, particularly in patients with conditions that upregulate acetylcholine receptors, such as severe burns, neuromuscular disorders, spinal cord injury, and stroke. The depolarizing effect of the drug causes a transient release of potassium from muscle cells, which can lead to serious arrhythmias, including ventricular fibrillation and cardiac arrest. Patients with renal insufficiency, who may already have elevated baseline potassium levels, are also at increased risk for succinylcholine-induced hyperkalemia (3).
Prolonged paralysis is another potential complication of succinylcholine administration in individuals with pseudocholinesterase deficiency. Normally, succinylcholine is rapidly hydrolyzed by plasma cholinesterase, but in patients with congenital or acquired deficiencies, the effects of the drug are prolonged, resulting in extended paralysis and the need for mechanical ventilation until the drug is metabolized. This condition may not be readily apparent until a patient experiences a prolonged response to succinylcholine, but genetic screening and biochemical testing can help identify individuals at risk (4).
Succinylcholine has significant effects on intraocular pressure, which can rise within minutes of administration and persist for up to 10 minutes. This makes the drug contraindicated in patients with open globe injuries, as increased intraocular pressure can lead to vitreous extrusion and permanent vision loss. Similarly, succinylcholine is known to increase intragastric pressure, which increases the risk of aspiration in patients with inadequate esophageal sphincter control, such as those with gastroesophageal reflux disease or recent food intake (4).
A less serious but commonly reported side effect of succinylcholine is postoperative myalgia, which results from muscle fasciculations induced by the drug. These fasciculations are thought to cause microtrauma to muscle fibers, resulting in myalgia that may persist for several days after administration. Various pretreatment strategies, such as administering a small dose of a non-depolarizing neuromuscular blocking agent prior to succinylcholine, have been explored to reduce these fasciculations (4).
Given these risks, alternative neuromuscular blocking agents such as rocuronium are often preferred in patients with contraindications to succinylcholine. Rocuronium has a slightly slower onset of action but lacks the life-threatening risks of malignant hyperthermia and hyperkalemia and can be rapidly reversed with sugammadex. Although sugammadex itself has potential adverse effects, including hypersensitivity reactions, it offers a safer alternative in high-risk patients (1).
While succinylcholine remains a valuable tool for achieving rapid paralysis, clinicians must carefully evaluate its risks and contraindications before administration. Alternative agents should be considered in patients at high risk for life-threatening complications. The development of newer neuromuscular blocking agents with improved safety profiles continues to challenge the routine use of succinylcholine in clinical practice.
References
- Mraovic B, Timko NJ, Simurina T. Remifentanil vs Neuromuscular Blockers During Rapid Sequence Intubation Among Patients at Risk of Aspiration. JAMA. 2023;329(17):1517. doi:10.1001/jama.2023.3494
- Guihard B, Chollet-Xémard C, Lakhnati P, et al. Effect of Rocuronium vs Succinylcholine on Endotracheal Intubation Success Rate Among Patients Undergoing Out-of-Hospital Rapid Sequence Intubation: A Randomized Clinical Trial. JAMA. 2019;322(23):2303-2312. doi:10.1001/jama.2019.18254
- Plane AF, Marsan PE, du Cheyron D, Valette X. Life-threatening hyperkalaemia after succinylcholine – Authors’ reply. Lancet. 2020;395(10219):e10. doi:10.1016/S0140-6736(19)32593-0
- Bohringer C, Moua H, Liu H. Is There Still a Role for Succinylcholine in Contemporary Clinical Practice?. Transl Perioper Pain Med. 2019;6(4):129-135. doi:10.31480/2330-4871/100
