Timing of Cardiac Arrest After Succinylcholine in Pediatric Myopathy
Cardiac arrest occurs within minutes—typically within 5 to 15 minutes—after succinylcholine administration in pediatric patients with undiagnosed myopathy, often presenting as sudden, catastrophic hyperkalemic arrest without warning signs. 1, 2
Immediate Onset and Clinical Presentation
Cardiac arrest develops abruptly within minutes of succinylcholine injection, with most cases occurring in the immediate post-administration period during what appears to be routine anesthesia induction 2, 3
The syndrome typically manifests as sudden cardiac arrest within 5-15 minutes after drug administration, often preceded by peaked T-waves on ECG (an early warning sign that may be the only indicator) 1, 4
In documented cases, cardiac arrest occurred as rapidly as within minutes in apparently healthy children who were later found to have occult neuromuscular diseases such as Duchenne or Becker muscular dystrophy 2, 3, 5
Pathophysiology Explaining Rapid Onset
Succinylcholine disrupts unstable muscle cell membranes in patients with myopathy, causing acute rhabdomyolysis with massive potassium efflux from muscle cells into the bloodstream 1
The upregulation of nicotinic acetylcholine receptors across the entire muscle membrane surface in myopathic patients leads to dramatically increased ionic activity and catastrophic hyperkalemia when exposed to succinylcholine 1
One documented case showed serum potassium levels reaching 10.3 mmol/L within 15 minutes of cardiac arrest, accompanied by creatine kinase elevation to 99,600 IU/L, confirming massive rhabdomyolysis 6
High-Risk Population Characteristics
The majority of affected patients are males, typically 8 years of age or younger, though adolescents have also been reported 4, 3
These children often appear healthy on preoperative evaluation, with no obvious clinical signs of myopathy, making identification of at-risk patients extremely difficult 4, 2
A study of 200 families with Duchenne or Becker muscular dystrophy found that all six cardiac arrests occurred exclusively in the 45 families with undiagnosed disease at the time of anesthesia 7
Critical Warning Signs and Monitoring
Peaked T-waves on continuous ECG monitoring may be the only early warning sign before full cardiac arrest develops 4
Muscle rigor following succinylcholine administration should raise immediate suspicion for impending hyperkalemic crisis 2, 6
Tachycardia may precede the development of rigor and subsequent cardiac arrest 6
Absolute Contraindication
Succinylcholine is absolutely contraindicated in patients with known or suspected muscular dystrophy, including Duchenne muscular dystrophy, Becker dystrophy, and all skeletal muscle myopathies 1, 8, 4
The FDA recommends that succinylcholine use in pediatric patients should be reserved exclusively for emergency intubation or instances where immediate airway securing is necessary (e.g., laryngospasm, difficult airway, full stomach) 4
The American Academy of Pediatrics warns that cardiac arrest occurring immediately after succinylcholine administration in young patients should trigger immediate suspicion for hyperkalemia 1
Emergency Management
Due to the abrupt onset, routine resuscitative measures are likely to be unsuccessful; extraordinary and prolonged resuscitation efforts are required 4, 3
Immediate treatment must include intravenous calcium (under ECG monitoring), insulin/glucose (0.1 unit/kg insulin with 400 mg/kg glucose), sodium bicarbonate, and hyperventilation 1, 4, 2
Standard glucose/insulin therapy may fail due to pharmacokinetic limitations in the acute setting; intravenous calcium under ECG control appears to be the most rational immediate approach 2
Successful resuscitation has been documented even after more than 30-60 minutes of CPR, requiring extraordinary measures including potential extracorporeal circulation 2, 3
If malignant hyperthermia is also suspected (which can coexist), dantrolene should be administered concurrently, though the primary pathology is hyperkalemic cardiac arrest from rhabdomyolysis 4, 6
Safer Alternative
Rocuronium at doses ≥0.9 mg/kg (preferably 1.0-1.2 mg/kg) is the recommended alternative for rapid sequence intubation in all pediatric patients when myopathy cannot be definitively excluded 1, 8
While rocuronium has a longer duration of action (30-60 minutes versus 4-6 minutes for succinylcholine), this disadvantage is vastly outweighed by its superior safety profile in at-risk populations 1, 8