What are the considerations and side effects of succinylcholine?

Considerations and Side Effects of Succinylcholine

Succinylcholine should be used with extreme caution due to its numerous potentially life-threatening side effects, and is contraindicated in several conditions including patients with muscle disorders, prolonged immobilization, or history of malignant hyperthermia. 1, 2

Mechanism of Action and Clinical Use

• Succinylcholine is a depolarizing neuromuscular blocking agent that causes prolonged depolarization at the neuromuscular junction, resulting in muscle paralysis 3
• It has a rapid onset (30-45 seconds IV) and short duration of action (5-10 minutes), making it useful for rapid sequence intubation 3
• Standard adult dosing for intubation is typically 1.0 mg/kg, with age-appropriate pediatric dosing: <1 month: 1.8 mg/kg, 1 month to 1 year: 2.0 mg/kg, 1-10 years: 1.2 mg/kg, >10 years: 1.0 mg/kg 1

Major Side Effects and Complications

Hyperkalemia

• Succinylcholine can cause potentially fatal hyperkalemia in patients with:
  • Muscle disorders or myopathies 1
  • Burns or crush injuries 3
  • Spinal cord injuries 3
  • Prolonged immobilization (>3 days) 3, 4
  • Neuromuscular diseases 3
• Hyperkalemia can lead to cardiac arrest, particularly in boys <9 years old 3

Malignant Hyperthermia

• Succinylcholine is a known trigger for malignant hyperthermia in susceptible individuals 3, 2
• This potentially fatal condition presents with hyperthermia, muscle rigidity, tachycardia, and metabolic acidosis 5
• Dantrolene should be immediately available wherever succinylcholine is used 3
• Succinylcholine alone (without volatile anesthetics) can trigger malignant hyperthermia 3

Cardiovascular Effects

• Can cause bradycardia, especially in children, often requiring pretreatment with atropine 3
• May cause tachycardia, hypertension, or hypotension 2
• Arrhythmias can occur, particularly with repeated doses 2

Muscle-Related Effects

• Muscle fasciculations occur commonly during induction 3
• Postoperative myalgia is frequent 2
• Risk of rhabdomyolysis with possible myoglobinuric acute renal failure 2
• Increased intracranial and intraocular pressure due to fasciculations 2

Prolonged Paralysis

• Duration of action may be significantly prolonged in patients with:
  • Reduced plasma cholinesterase activity 2
  • Genetic abnormalities of plasma cholinesterase (e.g., atypical cholinesterase) 2
  • Pregnancy, liver or kidney disease, malignant tumors, infections, burns 2
  • Patients taking certain medications (oral contraceptives, glucocorticoids, MAO inhibitors) 2
• Phase II block (resembling non-depolarizing block) may occur with prolonged or repeated administration 2

Allergic Reactions

• Anaphylaxis and severe allergic reactions have been reported 2
• Cross-reactivity with other neuromuscular blocking agents is possible 2

Special Considerations

Drug Interactions

• Drugs that may enhance neuromuscular blocking action: promazine, oxytocin, antibiotics, beta-blockers, lidocaine, magnesium salts, volatile anesthetics 2
• In patients with nerve agent poisoning or pyridostigmine pretreatment, the dose of succinylcholine should be significantly reduced 3, 1
• Drugs that reduce plasma cholinesterase activity can prolong the effect of succinylcholine 2

Alternatives

• Rocuronium at doses ≥0.9 mg/kg is a suitable alternative when succinylcholine is contraindicated 3
• However, succinylcholine generally provides superior intubating conditions compared to rocuronium 6
• Rocuronium's main disadvantage is its longer duration of action compared to succinylcholine 6

Monitoring Requirements

• Quantitative neuromuscular monitoring is essential when administering succinylcholine 1
• Clinical tests alone are inadequate for assessing recovery from neuromuscular blockade 1

Absolute Contraindications

• History of malignant hyperthermia 3, 2
• Patients immobilized for more than 3 days 3
• Duchenne muscular dystrophy and other myopathies 1
• Severe burns or crush injuries 3
• Spinal cord injuries 3
• Known or suspected hyperkalemia 2

Practical Recommendations

• Always have atropine available (0.02 mg/kg, minimum dose 0.1 mg, maximum 1 mg) to prevent bradycardia 3
• Consider reducing the dose from 1.0 mg/kg to 0.6 mg/kg to shorten recovery time by approximately 90 seconds in appropriate situations 7
• Ventilatory support is mandatory; personnel skilled in airway management must be present 3
• Age-appropriate equipment for suctioning, oxygenation, intubation, and ventilation should be immediately available 3
• For patients with increased intracranial pressure, consider a defasciculation dose of a non-depolarizing agent (e.g., 0.01 mg/kg vecuronium) 3