How quickly can patients with muscular dystrophy develop symptomatic hyperkalemia after succinylcholine administration?

Hyperkalemia Onset After Succinylcholine in Muscular Dystrophy

Cardiac arrest from hyperkalemia can occur within minutes of succinylcholine administration in patients with muscular dystrophy, often presenting as sudden cardiac arrest immediately after injection. 1, 2, 3

Timing of Symptomatic Hyperkalemia

The hyperkalemic response is immediate and catastrophic:

• Cardiac arrest typically occurs within minutes of succinylcholine injection in patients with Duchenne muscular dystrophy (DMD) or other muscular dystrophies 1, 2
• The syndrome often presents as sudden cardiac arrest immediately after administration, without warning signs 4
• One documented case showed cardiac arrest during a halothane anesthetic following a single dose of succinylcholine, with asystole that was prolonged and refractory to treatment 3
• Another case report described a 5-year-old boy with unsuspected Becker muscular dystrophy who sustained cardiac arrest following a single dose during induction, requiring 10 minutes of CPR 2

Pathophysiology Explaining Rapid Onset

The mechanism involves acute disruption of dystrophic muscle membranes:

• Succinylcholine disrupts unstable cell membranes in dystrophic muscle, causing acute rhabdomyolysis and massive potassium release 1, 5
• The depolarizing muscle relaxant disrupts unstable cell membranes, leading to hyperkalemia and sudden death from cardiac arrest 5
• Clinical presentation includes lack of fasciculations, muscle rigidity, hyperkalemia, myoglobinuria, and massive elevation of serum creatine phosphokinase 3

Clinical Recognition and Warning Signs

Early signs may be subtle or absent before catastrophic collapse:

• Peaked T-waves on ECG may be an early sign, though cardiac arrest often occurs before monitoring can detect changes 4
• Bilateral masseter muscle spasm may occur, followed in rapid sequence by ventricular tachycardia and cardiac arrest 6
• Hyperkalemia levels can reach extreme values (K+ = 12.57 mEq/L documented in one case) 6
• There may be no signs or symptoms to alert the practitioner to which patients are at risk 4

Absolute Contraindication

Succinylcholine is absolutely contraindicated in all patients with known or suspected muscular dystrophy:

• The FDA labels succinylcholine as contraindicated in persons with skeletal muscle myopathies 4
• The American College of Chest Physicians states succinylcholine is widely recognized as contraindicated in patients with DMD, with numerous reports of sudden death due to hyperkalemic cardiac arrest 5
• This contraindication applies to Duchenne muscular dystrophy, Becker dystrophy, and all skeletal muscle myopathies 1, 7

Critical Management Considerations

If cardiac arrest occurs, suspect hyperkalemia immediately:

• The American Academy of Pediatrics warns that cardiac arrest occurring immediately after succinylcholine may be due to hyperkalemia, particularly in young patients 1
• Aggressive treatment includes intravenous calcium, bicarbonate, glucose with insulin, and hyperventilation 4, 2
• Extraordinary and prolonged resuscitative efforts have been effective in some cases, though routine resuscitative measures are often unsuccessful 4
• One case required 10 minutes of CPR with calcium gluconate, epinephrine, sodium bicarbonate, and DC countershock to restore cardiac activity 2

Alternative Neuromuscular Blockade

Rocuronium is the recommended alternative:

• The American Society of Anesthesiologists recommends rocuronium at doses ≥0.9 mg/kg as an alternative to succinylcholine for rapid sequence intubation in high-risk patients 1
• Rocuronium has a longer duration of action (30-60 minutes) than succinylcholine, but its safety benefit outweighs this disadvantage 1
• Rocuronium is preferred due to its mild vagolytic effect and lack of acetylcholinesterase-dependent metabolism 7

Special Pediatric Considerations

Young males are at particularly high risk:

• Patients are usually, but not exclusively, males and most frequently 8 years of age or younger, though adolescents have also been affected 4
• Many pediatric patients were subsequently found to have skeletal muscle myopathy such as Duchenne's muscular dystrophy whose clinical signs were not obvious 4
• A careful history and physical may identify developmental delays suggestive of myopathy, though a preoperative creatine kinase can identify only some patients at risk 4