In which of the following situations is succinylcholine most likely to cause severe hyperkalemia?

In which of the following situations is succinylcholine most likely to cause severe hyperkalemia?

• A. 24 hours after a right hemisphere stroke
• B. 14 days after a severe burn injury
• C. 24 hours after a mid-thoracic spinal cord transection
• D. 2 days with a severe abdominal infection

Answer: (B)

The key concept is that succinylcholine can cause dangerous hyperkalemia when there is upregulation of extrajunctional nicotinic acetylcholine receptors on skeletal muscle. In severe burn injury, these receptors proliferate beyond the neuromuscular junction and spread across the muscle membrane. Depolarization by succinylcholine then opens many more receptors than normal, allowing a large amount of potassium to exit muscle cells and sharply raise serum potassium. This receptor upregulation after burns typically becomes substantial within days and peaks around the first couple of weeks, with risk persisting for a long time thereafter. Thus, 14 days after a severe burn represents the scenario with the greatest likelihood of severe hyperkalemia from succinylcholine, because the extensive extrajunctional receptor upregulation has already developed. The other situations either do not produce this level of receptor upregulation at the given time points or do so to a much lesser extent, making severe hyperkalemia far less likely in those contexts.

The key concept is that succinylcholine can cause dangerous hyperkalemia when there is upregulation of extrajunctional nicotinic acetylcholine receptors on skeletal muscle. In severe burn injury, these receptors proliferate beyond the neuromuscular junction and spread across the muscle membrane. Depolarization by succinylcholine then opens many more receptors than normal, allowing a large amount of potassium to exit muscle cells and sharply raise serum potassium. This receptor upregulation after burns typically becomes substantial within days and peaks around the first couple of weeks, with risk persisting for a long time thereafter.

Thus, 14 days after a severe burn represents the scenario with the greatest likelihood of severe hyperkalemia from succinylcholine, because the extensive extrajunctional receptor upregulation has already developed. The other situations either do not produce this level of receptor upregulation at the given time points or do so to a much lesser extent, making severe hyperkalemia far less likely in those contexts.