Is succinylcholine safe to use in patients with hyperkalemia?

Succinylcholine in Raised Potassium

Succinylcholine is absolutely contraindicated in patients with pre-existing hyperkalemia and should never be used in this setting due to the risk of life-threatening cardiac arrest from further potassium elevation. 1

Absolute Contraindications

The FDA explicitly states that succinylcholine should be administered with "GREAT CAUTION" to patients with electrolyte abnormalities, as it may induce serious cardiac arrhythmias or cardiac arrest due to hyperkalemia. 1 More specifically, succinylcholine is contraindicated after the acute phase of injury in patients with major burns, multiple trauma, extensive denervation, or upper motor neuron injury because it can result in severe hyperkalemia leading to cardiac arrest. 1

High-Risk Populations Requiring Absolute Avoidance

Beyond pre-existing hyperkalemia, succinylcholine must be avoided in the following conditions due to acetylcholine receptor upregulation that causes massive potassium efflux:

• Muscular dystrophies (including Duchenne and Becker): Cardiac arrest can occur within minutes of injection, with numerous reports of sudden death from hyperkalemic cardiac arrest 2, 3
• Burns (extensive/deep): Risk period begins 24-48 hours post-injury and peaks at 7-10 days, lasting up to 1 year 3, 1
• Spinal cord injury: Lower motor neuron lesions or lesions above motor units create denervation risk 4
• Prolonged immobilization/critical illness: Even pharmacologic neuromuscular blockade can predispose to severe hyperkalemia 5, 3
• Neuromuscular diseases and skeletal muscle myopathies: Absolute contraindication due to unstable cell membranes 1, 3
• Sepsis with immobilization: Case reports document fatal hyperkalemia (potassium rising from 3.19 to 8.64 mEq/L within 2 minutes) 6
• Chemotherapy-induced mucositis: Fatal hyperkalemia (13.1 mEq/L) reported, likely due to mechanism similar to thermal injury 7

Mechanism of Hyperkalemia

When acetylcholine receptors become upregulated in the conditions above, they migrate across the entire muscle membrane surface and become more ionically active. 3 Succinylcholine then causes massive potassium efflux from cells, with serum potassium potentially rising by >5 mEq/L within 2 minutes. 6 This disrupts unstable cell membranes, causing acute rhabdomyolysis and massive potassium release. 3

Limited Evidence for Modest Pre-existing Hyperkalemia

One retrospective study of 38 patients with preoperative potassium ≥5.6 mEq/L (range 5.6-6.4 mEq/L) who received succinylcholine showed 100% survival with no documented dysrhythmias. 8 However, this evidence cannot override FDA contraindications and should not be used to justify succinylcholine use in hyperkalemic patients, especially given:

• The 95% confidence interval for maximal risk was 7.9% 8
• Multiple case reports document fatal outcomes in specific high-risk populations 6, 7, 4
• The study excluded patients with conditions causing receptor upregulation 8

Recommended Alternative: Rocuronium

Rocuronium at doses ≥0.9 mg/kg is the recommended alternative for rapid sequence intubation in all high-risk patients. 3 While rocuronium has a longer duration of action (30-60 minutes vs. 5-10 minutes for succinylcholine), the safety benefit dramatically outweighs this disadvantage. 3 Sugammadex can provide rapid reversal if needed. 3

Critical Management Points

• Pretreatment with defasciculating doses of non-depolarizing agents does NOT adequately protect against hyperkalemia in high-risk patients 3
• If cardiac arrest occurs immediately after succinylcholine administration, suspect hyperkalemia and treat aggressively with calcium gluconate/chloride, insulin/glucose, sodium bicarbonate, and hyperventilation 3, 1
• Neuromuscular monitoring should be employed when any muscle relaxant is used in high-risk patients 3
• The American Academy of Pediatrics warns that cardiac arrest occurring immediately after succinylcholine may be due to hyperkalemia, particularly in young patients 3

Common Pitfalls to Avoid

• Never assume a "normal" baseline potassium makes succinylcholine safe if the patient has any condition causing receptor upregulation 3, 1
• Do not use succinylcholine in critically ill patients who have received prolonged neuromuscular blockade, even if baseline potassium is normal 5
• The risk period for burns and denervation injuries is prolonged (peaks at 7-10 days but duration is undetermined), so avoid succinylcholine well beyond the acute injury phase 1