What are the dosing, indications, contraindications, side effects, monitoring, and alternatives for succinylcholine (Scoline/Anectine) in rapid sequence intubation?

Succinylcholine (Scoline) for Rapid Sequence Intubation

Core Pharmacology

Succinylcholine remains the gold standard depolarizing neuromuscular blocker for rapid sequence intubation, providing complete glottic relaxation within 60 seconds with a duration of only 4–6 minutes. 1, 2

• Mechanism: depolarizing agent that causes prolonged depolarization at the neuromuscular junction, producing rapid-onset paralysis ideal for emergency airway management 3, 4
• Onset: approximately 1 minute 1, 5
• Duration: 4–6 minutes (shortest of all neuromuscular blockers) 1, 2

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Standard Dosing

Adults

• 1.0 mg/kg IV for intubation 1, 3
• For full-stomach patients (e.g., bowel obstruction): 1.0–1.5 mg/kg IV to ensure complete glottic relaxation and minimize aspiration risk 2
• Never reduce the dose below 1.0 mg/kg in emergency settings, as inadequate glottic relaxation increases failed intubation and aspiration risk 2

Pediatric (age-specific dosing is critical)

• < 1 month: 1.8 mg/kg 1, 3
• 1 month – 1 year: 2.0 mg/kg 1, 3
• 1–10 years: 1.2 mg/kg 1, 3
• > 10 years: 1.0 mg/kg 1, 3

Special Populations

• Myasthenia gravis: reduce dose to approximately 50% of usual (though generally avoided) 1
• Nerve-agent poisoning or pyridostigmine pretreatment: significantly reduce dose 1, 3

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Absolute Contraindications

Do not use succinylcholine in the following scenarios—switch to rocuronium instead:

• Personal or familial history of malignant hyperthermia 1, 3
• Skeletal muscle myopathies (Duchenne or Becker muscular dystrophy) 1, 3
• Acute phase of injury (24 hours to 7–10 days post-injury) after:
  • Major burns 1, 3
  • Extensive trauma or crush injuries 1, 3
  • Denervation syndromes 1, 3
  • Upper motor neuron or spinal cord injury 1, 3
• Prolonged immobilization (> 3 days) 1, 3
• Any neuromuscular disease predisposing to acetylcholine receptor up-regulation 1

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Life-Threatening Adverse Effects

Severe Hyperkalemia

• Mechanism: up-regulated acetylcholine receptors (burns, denervation, myopathies) release massive potassium from muscle cells, causing cardiac arrest 1, 3
• Presentation: sudden cardiac arrest, peaked T waves, widened QRS, ventricular fibrillation 1
• High-risk population: boys < 9 years old with undiagnosed muscular dystrophy 3

Immediate management of succinylcholine-induced hyperkalemic cardiac arrest: 1

1. Calcium gluconate or calcium chloride IV for membrane stabilization
2. Insulin 0.1 U/kg + glucose 400 mg/kg IV to shift potassium intracellularly
3. Sodium bicarbonate IV to alkalinize and promote renal excretion
4. Hyperventilation to reduce PaCO₂
5. CPR for 10–12 minutes as needed
6. Definitive elimination: loop diuretics, potassium-binding agents, hemodialysis for refractory cases
7. Extended monitoring: serial serum potassium and creatine kinase for 2–4 hours post-stabilization to detect rebound hyperkalemia

Malignant Hyperthermia

• Presentation: masseter spasm, generalized rigidity, tachycardia, marked hyperpyrexia 1, 3
• Management: immediate dantrolene administration, discontinue triggering agents, aggressive cooling, treat hyperkalemia and metabolic acidosis 1
• Critical safety point: dantrolene must be immediately available wherever succinylcholine is used 1, 3
• Pitfall: negative family history does NOT exclude susceptibility—patients can develop MH even after previous uneventful anesthetics 3

Bradycardia

• High-risk population: children aged 28 days to 8 years, especially with septic shock or hypovolemia 3
• Prevention: pretreat with atropine before intubation in this age group 3

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Monitoring Requirements

Intra-operative

• Continuous ECG and heart rate from induction until at least 2 minutes post-intubation 1
• Continuous pulse oximetry throughout procedure 1
• Special vigilance for bradycardia in children 28 days to 8 years 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 quiet environment before discharge 1

High-risk patients

• Serial serum potassium and creatine kinase measurements 1
• Neuromuscular monitoring strongly recommended when receptor up-regulation is possible 1

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Rocuronium as Alternative

When succinylcholine is contraindicated, use rocuronium 1.0–1.2 mg/kg IV (minimum 0.9 mg/kg). 6, 1, 3

Comparative Performance

• First-pass intubation success: rocuronium 1.2 mg/kg achieves ~79% vs. succinylcholine 82–84% 1, 3
• Onset: 60 seconds (comparable to succinylcholine) 1, 2
• Duration: 30–60 minutes (vs. 4–6 minutes for succinylcholine) 1, 3, 2

Critical Safety Considerations with Rocuronium

• Sugammadex must be immediately available to reverse rocuronium if needed 1, 3
• Implement protocolized post-intubation analgosedation immediately to prevent awareness during the prolonged 30–60 minute paralysis period 3
• Do not underdose: doses < 0.9 mg/kg may result in inadequate intubating conditions 1, 3

Dosing in Renal/Hepatic Failure

• Do not modify initial rocuronium dose in renal or hepatic failure (onset unchanged despite prolonged duration) 3
• For maintenance dosing: consider atracurium or cisatracurium due to organ-independent elimination 3

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Rapid Sequence Intubation Context

The European Society of Anaesthesiology and Intensive Care strongly recommends succinylcholine 1–2 mg/kg for rapid sequence intubation based on moderate-quality evidence. 6, 2

• Rationale: complete glottic relaxation within 60 seconds minimizes the unprotected airway period when aspiration can occur in full-stomach patients 2
• Cricoid pressure: practice varies internationally; if direct laryngoscopy is difficult, release cricoid pressure 6
• Emergency laparotomy patients: at particularly high risk for aspiration due to bowel obstruction, distension, sepsis, and opioids 6

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Critical Pitfalls to Avoid

• Never repeat doses of succinylcholine after failed intubation—use a non-depolarizing agent for subsequent paralysis to avoid phase II block and prolonged unprotected airway 1, 2
• Pretreatment with defasciculating doses of non-depolarizing agents does NOT protect against hyperkalemia in high-risk patients 1
• Do not extubate children prematurely—ensure fully awake, cleared secretions, and can maintain upper airway reflexes 1
• Do not assume negative family history rules out malignant hyperthermia—patients can develop MH after previous uneventful anesthetics 3
• Never use reduced doses (< 1.0 mg/kg) in full-stomach patients—inadequate glottic relaxation increases aspiration risk 2

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Drug Interactions

• Drugs that enhance neuromuscular blockade (promazine, oxytocin) should be used with caution 3
• Nerve agent poisoning or pyridostigmine pretreatment requires significantly reduced succinylcholine dose 1, 3

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Contemporary Debate

One 2019 opinion piece argues that with the availability of sugammadex to reverse rocuronium, succinylcholine should be limited to treating acute laryngospasm only, given its numerous risks 7. However, current international guidelines (European Society of Anaesthesiology and Intensive Care, 2023) continue to strongly recommend succinylcholine as first-line for rapid sequence intubation when no contraindications exist, based on its unmatched combination of rapid onset and short duration 6, 2. The choice between succinylcholine and rocuronium should be based on desired duration of relaxation, risk of difficult intubation, presence of contraindications, and whether neuromuscular disease is suspected 3.