What is a suitable muscle relaxant for a pediatric patient?

Muscle Relaxant Selection for Pediatric Patients

Primary Recommendation

For rapid sequence induction in pediatric patients, succinylcholine remains the first-choice muscle relaxant, with rocuronium (>0.9 mg/kg) as the preferred alternative when succinylcholine is contraindicated. 1

Clinical Context and Agent Selection

Rapid Sequence Induction

• Succinylcholine is the gold standard due to its rapid onset (~1 minute) and short duration of action, which is particularly critical in children who have shorter apnea tolerance times than adults 1
• Age-specific succinylcholine dosing:
  • <1 month: 1.8 mg/kg 1
  • 1 month to 1 year: 2.0 mg/kg 1
  • 1 to 10 years: 1.2 mg/kg 1

  • 10 years: 1.0 mg/kg 1

When Succinylcholine is Contraindicated

• Rocuronium at doses >0.9 mg/kg provides the best alternative for rapid sequence induction 1, 2
• Absolute contraindications to succinylcholine:
  • Primary muscle damage (myopathies) - risk of rhabdomyolysis 1
  • Up-regulation of nicotinic acetylcholine receptors (chronic motor deficit, extensive burns, prolonged critical illness) - risk of life-threatening hyperkalemia 1
  • Known or suspected neuromuscular disease 1

Non-Rapid Sequence Intubation

• For routine intravenous induction: Non-depolarizing muscle relaxants (rocuronium, vecuronium, atracurium) improve intubating conditions and reduce respiratory adverse events compared to intubation without muscle relaxants 1
• Rocuronium 0.6 mg/kg provides excellent to good intubating conditions within 60-75 seconds under sevoflurane or halothane anesthesia 1, 3, 4
• Lower doses (0.45 mg/kg rocuronium) may be used for elective procedures when slower onset is acceptable, though this extends onset time to approximately 3 minutes 3, 5

Practical Dosing Guidelines for Rocuronium

Initial Intubation Doses

• Standard dose: 0.6 mg/kg - provides onset in ~1 minute with clinical duration of 26-41 minutes depending on age 3, 4
• Rapid sequence: >0.9 mg/kg - necessary to match succinylcholine's rapid onset 1, 2
• Reduced dose: 0.45 mg/kg - acceptable for elective cases with slower onset tolerance 3

Maintenance Dosing

• Bolus maintenance: 0.15 mg/kg at reappearance of T3 (third twitch in train-of-four) 3
• Continuous infusion: 7-10 mcg/kg/min initiated at reappearance of T2, with lowest requirements in neonates and highest in children 2-11 years 3

Age-Specific Considerations

• Neonates (birth to <28 days): Longest time to maximum block, lowest infusion requirements 3
• Infants (28 days to 3 months): Shortest time to maximum block 3
• Children (>2 years to 11 years): Shortest duration of clinical relaxation, highest maintenance infusion requirements 3

Critical Safety Requirements

Mandatory Monitoring and Equipment

• Neuromuscular blockade monitoring is essential - residual neuromuscular blockade occurs in 28% of pediatric patients receiving muscle relaxants 1, 6, 2
• Immediate availability required:
  • Age-appropriate equipment for suctioning, oxygenation, intubation, and ventilation 6, 2, 3
  • Personnel skilled in pediatric airway management 6, 2
  • Reversal agents (sugammadex for rocuronium) 1

Reversal Considerations

• Sugammadex for rocuronium reversal:
  • Standard reversal: 2 mg/kg for moderate block 6
  • Deep block reversal: 4 mg/kg 6
  • Emergency rescue: 8-16 mg/kg (use with caution) 6
• Important caveat: Rocuronium provides no sedation, analgesia, or amnesia - concurrent sedative/analgesic agents must be administered 6, 2, 3

Special Populations

Obese Pediatric Patients

• Dose based on actual body weight, not ideal body weight - dosing by ideal body weight results in longer onset time, shorter duration, and inadequate intubating conditions 3

Patients with Neuromuscular Disease

• Avoid succinylcholine entirely in myopathies and conditions with receptor up-regulation 1
• Reduce non-depolarizing muscle relaxant doses by 50-75% in myasthenia gravis due to increased sensitivity 1
• Mandatory neuromuscular monitoring in all patients with neuromuscular disease 1

Hepatic or Renal Impairment

• Onset time unchanged with rocuronium 0.6 mg/kg 3
• Duration extended 1.5 times in hepatic disease 3
• Greater variability in duration with renal failure, though mean duration similar 3

Common Pitfalls to Avoid

• Never use rocuronium for rapid sequence induction in Cesarean section - inadequate intubating conditions documented in obstetric patients 3
• Always flush IV tubing with saline before administering rocuronium after other medications to prevent precipitation and line obstruction 6, 2
• Do not use reduced rocuronium doses (<0.9 mg/kg) for rapid sequence induction - this compromises the rapid onset needed for airway protection 1, 2
• Avoid repeated sugammadex dosing due to concerns about bone toxicity observed in animal studies 6