Why should succinylcholine be avoided in patients with acute traumatic brain injury?

Why Succinylcholine Should Be Avoided in Head Injury Patients

In patients with acute traumatic brain injury requiring intubation, rocuronium (0.9–1.2 mg/kg) is the safer alternative to succinylcholine, particularly in those with severe head injuries, where succinylcholine has been associated with increased mortality. 1

Primary Concerns with Succinylcholine in Head Injury

Increased Intracranial Pressure Risk

• Succinylcholine causes muscle fasciculations that may transiently increase intracranial pressure (ICP), though the clinical significance remains debated. 2, 3
• The mechanism involves sustained depolarization at the neuromuscular junction, which can trigger fasciculations in 22–42% of patients even with pretreatment strategies. 2
• Pretreatment with defasciculating doses of non-depolarizing agents (e.g., pancuronium 0.03 mg/kg or minidose succinylcholine 0.1 mg/kg) does not reliably prevent ICP elevation and does not protect against hyperkalemia in high-risk patients. 4, 2

Mortality Risk in Severe Traumatic Brain Injury

• In patients with severe or critical head injury (abbreviated injury score ≥4), succinylcholine was associated with 44% mortality compared to 23% with rocuronium—a statistically significant increase (OR 4.10,95% CI 1.18–14.12). 5
• This mortality difference was not observed in patients with less severe head injuries (score <4), where succinylcholine mortality was 14% versus rocuronium 22%. 5
• The 2023 Society of Critical Care Medicine guidelines acknowledge this single observational study but note it was limited by retrospective design and potential selection bias. 1

Hyperkalemia Risk in Trauma Patients

• Traumatic brain injury patients, especially those with prolonged immobilization (>3 days), extensive trauma, or tissue wasting, are at risk for life-threatening hyperkalemia from succinylcholine. 1, 4, 6
• Trauma causes upregulation of nicotinic acetylcholine receptors across the entire muscle membrane, leading to massive potassium efflux when depolarized by succinylcholine. 6
• Cardiac arrest can occur within minutes of succinylcholine administration in susceptible patients, presenting as sudden ventricular fibrillation, wide complex tachycardia, or asystole. 6, 7

Absolute Contraindications to Succinylcholine in Head Injury Context

• Personal or family history of malignant hyperthermia. 4, 8
• Skeletal muscle myopathies (e.g., Duchenne or Becker muscular dystrophy). 4, 8
• Prolonged immobilization >3 days, which is common in severe head injury patients. 1, 4
• Extensive trauma or crush injuries beyond 24–48 hours post-injury. 8, 6
• Denervation syndromes or spinal cord injuries, which may coexist with traumatic brain injury. 4, 8

Recommended Alternative: Rocuronium

Dosing and Efficacy

• Administer rocuronium 0.9–1.2 mg/kg IV (preferably 1.0–1.2 mg/kg) for rapid sequence intubation in head injury patients. 1, 4
• Rocuronium at 1.2 mg/kg provides onset within 60 seconds and first-pass intubation success rates of approximately 79%, comparable to succinylcholine's 82–84%. 4, 9
• Duration of action is 30–60 minutes versus succinylcholine's 4–6 minutes, but this disadvantage is outweighed by the superior safety profile. 4, 9

Reversal Capability

• Sugammadex must be immediately available when rocuronium is used, allowing rapid reversal if neurologic examination is urgently needed. 4, 9
• The availability of sugammadex has eliminated the historical concern about rocuronium's prolonged duration precluding timely neurologic assessment. 9

Post-Intubation Management

• Implement protocolized post-intubation analgosedation immediately after rocuronium administration to prevent awareness during the 30–60 minute paralysis period. 1, 4
• Incorporate clinical pharmacists or structured protocols to ensure timely analgosedation, as rocuronium's longer duration may delay recognition of inadequate sedation. 1

Clinical Decision Algorithm for Head Injury Intubation

1. Assess for absolute contraindications to succinylcholine:

   • Malignant hyperthermia history
   • Known myopathy
   • Immobilization >3 days
   • Extensive trauma >24–48 hours old
   • Denervation or spinal cord injury 4, 8

2. Stratify head injury severity:

   • Severe/critical (abbreviated injury score ≥4): Use rocuronium 1.0–1.2 mg/kg 5
   • Less severe (score <4): Either agent acceptable per 2023 guidelines, but rocuronium preferred given overall safety profile 1

3. Ensure availability of:

   • Sugammadex for rocuronium reversal 4, 9
   • Dantrolene if succinylcholine is used (though not recommended) 1, 8
   • Hyperkalemia treatment (calcium, insulin/glucose, bicarbonate) 4, 6

4. Monitor continuously:

   • ECG and heart rate from induction until ≥2 minutes post-intubation 4
   • Neuromuscular monitoring (train-of-four) in high-risk patients 4
   • Serial potassium and creatine kinase if succinylcholine was used 4, 6

Critical Pitfalls to Avoid

• Do not assume pretreatment with defasciculating agents protects against ICP elevation or hyperkalemia—it does not provide adequate protection in high-risk patients. 4, 2
• Do not underdose rocuronium (<0.9 mg/kg)—inadequate dosing results in poor intubating conditions. 4, 8
• Do not delay post-intubation sedation after rocuronium—the prolonged paralysis can mask inadequate analgosedation and lead to awareness. 1, 4
• Do not use succinylcholine in patients immobilized >3 days, even if they had uneventful prior anesthetics with succinylcholine, as receptor upregulation develops over time. 1, 6, 7
• Do not assume negative family history rules out malignant hyperthermia susceptibility—patients can develop MH even after previous uneventful exposures. 4, 8

Emergency Management of Succinylcholine Complications

If Cardiac Arrest Occurs After Succinylcholine

• Suspect hyperkalemia immediately and treat aggressively: 4, 6

  • Calcium gluconate or calcium chloride for membrane stabilization
  • Insulin 0.1 U/kg + glucose 400 mg/kg to shift potassium intracellularly
  • Sodium bicarbonate to alkalinize urine
  • Hyperventilation to reduce PaCO₂
  • CPR for 10–12 minutes as needed

• Initiate definitive potassium elimination early: 6

  • Loop diuretics
  • Potassium-binding agents
  • Hemodialysis for refractory cases

• Monitor serum potassium and creatine kinase for 2–4 hours after stabilization to detect rebound hyperkalemia. 4, 6

If Malignant Hyperthermia Develops

• Administer dantrolene 2–2.5 mg/kg IV every 10 minutes (maximum 300 mg per dose) until symptoms regress. 1, 4
• Discontinue all triggering agents, apply aggressive cooling, and provide supportive care for hyperkalemia and metabolic acidosis. 4, 8

Guideline Consensus

The 2023 Society of Critical Care Medicine guidelines suggest either rocuronium or succinylcholine may be used when no contraindications exist (conditional recommendation, low-quality evidence), but explicitly acknowledge the single study showing increased mortality with succinylcholine in severe head injury. 1 Given this mortality signal, the availability of sugammadex for rocuronium reversal, and the multiple safety concerns with succinylcholine in trauma patients, rocuronium represents the safer choice for head injury intubation in real-world clinical practice. 9, 5