Succinylcholine for Rapid-Sequence Intubation: Dosing, Contraindications, and Management
Succinylcholine remains the first-line neuromuscular blocker for rapid-sequence intubation in adults and children when no contraindications exist, providing unmatched onset (≈60 seconds) and brief duration (4–6 minutes), but rocuronium 0.9–1.2 mg/kg is the mandatory alternative when absolute contraindications are present. 1
Recommended Dosing
Adults
- Standard dose: 1.0 mg/kg IV based on actual body weight 1, 2
- Dose range may extend from 0.3–1.1 mg/kg depending on individual response 2
- In obese patients (BMI ≥40 kg/m²), calculate the dose using actual body weight, not ideal or lean weight 1
Pediatric (Age-Specific)
- < 1 month: 1.8 mg/kg IV 1, 3
- 1 month to 1 year: 2.0 mg/kg IV 1, 3
- 1–10 years: 1.2 mg/kg IV 1, 3
- > 10 years: 1.0 mg/kg IV 1, 3
- For emergency intubation in infants and small children, use 2 mg/kg; for older children and adolescents, use 1 mg/kg 2
The higher pediatric doses reflect the relatively larger volume of distribution in children compared to adults 2. The European Society of Anaesthesiology and Intensive Care (ESAIC) strongly endorses succinylcholine 1–2 mg/kg for rapid-sequence intubation in both adults and children, citing moderate-quality evidence 1.
Special Populations
- Myasthenia gravis: Reduce dose to approximately 50% of standard; however, succinylcholine is generally avoided in this population 1
- Nerve-agent poisoning or pyridostigmine pretreatment: Significantly reduce the dose 1, 4
Absolute Contraindications
Succinylcholine is absolutely contraindicated in the following scenarios due to risk of life-threatening hyperkalemia or malignant hyperthermia:
- Personal or familial history of malignant hyperthermia 1, 4
- Skeletal-muscle myopathies (e.g., Duchenne or Becker muscular dystrophy) 1, 4, 3
- Acute phase of injury (24 hours to 7–10 days) following:
- Prolonged immobilization (> 3 days) 1, 4
- Any neuromuscular disease predisposing to acetylcholine-receptor up-regulation 1, 3
Critical pitfall: A negative family history does not exclude malignant hyperthermia susceptibility; patients may develop MH even after previous uneventful anesthetics 1. Pretreatment with defasciculating doses of non-depolarizing agents does not protect against hyperkalemia in high-risk patients 1.
Life-Threatening Adverse Effects and Management
Hyperkalemia and Cardiac Arrest
- Severe hyperkalemia can occur in patients with up-regulated acetylcholine receptors (e.g., muscular dystrophy, recent burns, prolonged immobilization), leading to cardiac arrest 1, 4
- If cardiac arrest follows succinylcholine administration, immediately suspect hyperkalemia and treat aggressively: 1
- Calcium gluconate or calcium chloride for myocardial membrane stabilization 1
- Insulin 0.1 U/kg + glucose 400 mg/kg to shift potassium intracellularly 1
- Sodium bicarbonate to alkalinize urine and promote potassium excretion 1
- Hyperventilation to reduce PaCO₂ 1
- CPR for 10–12 minutes as needed 1
- Loop diuretics for renal potassium elimination; consider hemodialysis for refractory cases 1
- Extended monitoring of serum potassium and creatine kinase for 2–4 hours after stabilization to detect rebound hyperkalemia 1
Malignant Hyperthermia
- Succinylcholine is a known trigger for malignant hyperthermia, presenting with masseter spasm, generalized rigidity, tachycardia, and marked hyperpyrexia 1, 4
- Dantrolene must be immediately available wherever succinylcholine is used 1, 4
- Immediate treatment: Administer dantrolene 2–2.5 mg/kg IV every 10 minutes (maximum 300 mg per dose) until symptoms resolve; discontinue all triggering agents and apply aggressive cooling 1, 4
Bradycardia (Pediatric)
- Bradycardia is common in children after an initial dose, particularly in those aged 28 days to 8 years 1, 2
- Pretreatment with atropine is recommended before intubation in children aged 28 days to 8 years, especially in those with septic shock, hypovolemia, or when succinylcholine is used 4, 3
Monitoring Requirements
Intra-Operative
- Continuous ECG and heart-rate monitoring from induction until at least 2 minutes post-intubation 1
- Continuous pulse oximetry throughout the procedure 1
- Neuromuscular monitoring (train-of-four) is strongly recommended when receptor up-regulation is possible 1
Post-Operative (Pediatric)
- Monitor until full return of airway reflexes, spontaneous ventilation, and ability to maintain airway 1
- Child must remain awake ≥ 20 minutes in a quiet environment before discharge 1
High-Risk Patients
- Serial serum potassium and creatine-kinase measurements 1
Rocuronium as the Alternative
When succinylcholine is contraindicated, rocuronium is the recommended alternative:
Dosing
- 0.9–1.2 mg/kg IV (preferably 1.0–1.2 mg/kg for optimal intubating conditions) 1, 4, 3
- At 1.2 mg/kg, onset occurs within ≈60 seconds, comparable to succinylcholine 1, 5
- First-pass intubation success rate: ≈79% with rocuronium 1.2 mg/kg versus 82–84% with succinylcholine 1
Duration and Reversal
- Duration of action: 30–60 minutes (versus 4–6 minutes for succinylcholine) 1, 4
- Sugammadex must be immediately available for rapid reversal if needed 1, 4, 3
- Protocolized post-intubation analgosedation must be implemented immediately after rocuronium to prevent awareness during the prolonged paralysis window 1, 4
Critical pitfall: Underdosing rocuronium (< 0.9 mg/kg) may result in inadequate intubating conditions 1, 4. Do not forget to establish post-intubation sedation protocols when using rocuronium to prevent awareness during the 30–60 minute paralysis period 4.
Special Clinical Scenarios
Severe Traumatic Brain Injury
- In patients with severe or critical traumatic brain injury (abbreviated injury score ≥4), succinylcholine was associated with 44% mortality versus 23% with rocuronium (OR 4.10,95% CI 1.18–14.12) 1
- Rocuronium is preferred in head-injured patients, especially those immobilized > 3 days or with extensive tissue injury, due to hyperkalemia risk from up-regulated acetylcholine receptors 1
Modified Rapid-Sequence Induction in Children
- Many experts now recommend "controlled" or "modified" rapid-sequence induction in children, which includes preoxygenation, deep anesthesia with an opiate and hypnotic, a non-depolarizing muscle relaxant, and gentle bag-mask ventilation before laryngoscopy 6
- This approach decreases hypoxemia and hemodynamic complications compared to "classic" rapid-sequence induction with apnea 6
- Ventilate the child with FiO₂ 0.8 and small peak inspiratory pressure (< 15 cmH₂O) as soon as SpO₂ falls below 95% to prevent hypoxemia 6
Cricoid Pressure
- ESAIC advises that cricoid pressure should be released if direct laryngoscopy proves difficult, to improve glottic exposure 1
- Some guidelines no longer include cricoid pressure in recommendations for children at risk of aspiration 6
Key Clinical Pitfalls to Avoid
- Do not repeat doses of succinylcholine; use a non-depolarizing agent for subsequent paralysis 1
- Do not assume a negative family history rules out malignant hyperthermia susceptibility 1, 4
- Do not underdose rocuronium (< 0.9 mg/kg) when using it as an alternative 1, 4
- Do not extubate children prematurely; ensure they are fully awake, have cleared secretions, and can maintain upper-airway reflexes 1
- Do not use succinylcholine for continuous infusion in ICU settings; it is recommended only as a single-dose bolus for rapid-sequence intubation 1
Guideline Consensus
The 2023 ESAIC guidelines continue to endorse succinylcholine as the first-line agent for rapid-sequence intubation despite the availability of sugammadex for rocuronium reversal, because succinylcholine offers an unmatched combination of rapid onset and very short duration of action 1. The Society of Critical Care Medicine issues a conditional recommendation (low-quality evidence) that either rocuronium or succinylcholine may be used when no contraindications exist, but explicitly highlights the mortality data favoring rocuronium in severe head injury 1.