Why is succinylcholine (a neuromuscular blocking agent) contraindicated in burn patients even after 1 year?

Contraindication of Succinylcholine in Burn Patients Even After 1 Year

Succinylcholine is contraindicated in burn patients even after 1 year due to the risk of life-threatening hyperkalemia caused by up-regulation of nicotinic acetylcholine receptors throughout the muscle membrane. 1, 2

Pathophysiological Mechanism

• Burn injuries cause up-regulation of nicotinic acetylcholine receptors (nAChRs) at the motor end plate and throughout the muscle membrane 1
• When depolarized by succinylcholine, these up-regulated receptors lead to excessive potassium efflux, resulting in potentially fatal hyperkalemia 3
• This pathophysiological change persists for an extended period of time after the initial injury 3, 2

FDA Labeling and Contraindications

• The FDA explicitly contraindicates succinylcholine "after the acute phase of injury following major burns" without specifying a safe time period for reintroduction 2
• The FDA warning states: "The risk of hyperkalemia in these patients increases over time and usually peaks at 7 to 10 days after the injury. The risk is dependent on the extent and location of the injury. The precise time of onset and the duration of the risk period are not known." 2

Evidence for Prolonged Risk

• While the peak risk occurs at 7-10 days post-burn, the duration of the risk period remains undefined in clinical guidelines 2
• The up-regulation of acetylcholine receptors can persist for an extended period, potentially beyond one year in extensive burns 3
• The American Society of Anesthesiologists and other authorities do not specify a safe time for reintroduction of succinylcholine after burns, indicating ongoing caution even after 1 year 1, 4

Alternative Approaches

• Rocuronium at doses ≥0.9 mg/kg is the recommended alternative for rapid sequence intubation in burn patients 1, 4
• While rocuronium has a longer duration of action (30-60 minutes) compared to succinylcholine, this disadvantage is outweighed by the safety benefit in burn patients 1, 4
• If rapid reversal capability is needed, sugammadex can be considered for reversal of rocuronium-induced neuromuscular blockade 1

Clinical Implications and Recommendations

• Quantitative neuromuscular monitoring is essential when administering any neuromuscular blocking drugs to burn patients due to altered pharmacodynamics 5
• The risk of hyperkalemia with succinylcholine in burn patients is dependent on the extent and location of the burn injury 2
• Given the potentially fatal consequences of hyperkalemia and the lack of clear guidelines on when succinylcholine becomes safe again, the prudent approach is to avoid succinylcholine indefinitely in patients with a history of major burns 1, 2

Other Conditions with Similar Contraindications

• Similar contraindications for succinylcholine exist for other conditions involving up-regulation of acetylcholine receptors:
  • Chronic motor deficits and upper motor neuron injuries 3, 2
  • Extensive denervation of skeletal muscle 2
  • Multiple trauma 2
  • Prolonged critical illness (>16 days in ICU) 6
  • Neuromuscular diseases 3

The evidence strongly supports avoiding succinylcholine in burn patients even after 1 year due to the unpredictable duration of receptor up-regulation and the potentially fatal consequences of hyperkalemia, with rocuronium being the preferred alternative for rapid sequence intubation in these patients.