What are two major contraindications or risk factors for succinylcholine use?

• A. Hyperkalemia risk (e.g., burns after 24 hours, massive muscle trauma, muscular dystrophy, denervation injury) and pseudocholinesterase deficiency
• B. Pseudocholinesterase deficiency alone
• C. History of malignant hyperthermia
• D. Renal failure and hypotension

Answer: (A)

The key idea is understanding why succinylcholine is dangerous in certain patients. Succinylcholine rapidly depolarizes the motor endplate, and its duration depends on plasma cholinesterase activity. In people with upregulated extrajunctional acetylcholine receptors—such as after burns (even if more than 24 hours have passed), massive muscle trauma, denervation injuries, or certain muscular dystrophies—the depolarization triggers a large potassium efflux from muscle cells. This can cause dangerous hyperkalemia and potentially life‑threatening arrhythmias.

At the same time, if a person has pseudocholinesterase deficiency, the drug isn’t broken down quickly enough, so the duration of paralysis is markedly prolonged, leading to extended apnea and ventilation needs.

These two factors—high risk of severe hyperkalemia due to receptor upregulation and prolonged paralysis due to deficient metabolism—represent the major contraindications or risk factors for using succinylcholine. Malignant hyperthermia history is also a concern because succinylcholine can trigger MH, but the combination of hyperkalemia risk with receptor upregulation and pseudocholinesterase deficiency are the most direct, well‑established contraindications.