What are the commonly used airway induction agents and paralytic agents, their clinical uses, side effects, and considerations for use in emergency airway management?

Airway Induction and Paralytic Agents for Emergency Airway Management

Neuromuscular blocking agents (NMBAs) should always be used when a sedative-hypnotic induction agent is administered for emergency intubation to improve first-pass success and reduce complications. 1

Induction Agents

Etomidate

• Dose: 0.3 mg/kg IV
• Mechanism: GABA receptor agonist, blocks vascular K+ channels
• Clinical uses: Hemodynamically unstable patients, trauma, sepsis
• Advantages:
  • Maintains cardiovascular stability
  • Minimal effect on blood pressure
  • Rapid onset (30-60 seconds) and short duration (3-5 minutes)
• Disadvantages:
  • Adrenal suppression (even single dose)
  • Myoclonus (0-21% of patients)
  • Pain on injection
• Considerations: Despite concerns about adrenal suppression, recent guidelines suggest no difference in mortality between etomidate and other induction agents 1

Ketamine

• Dose: 1-2 mg/kg IV
• Mechanism: NMDA receptor antagonist, blocks NF-kappa B transcription
• Clinical uses: Hemodynamically unstable patients, asthma, septic shock
• Advantages:
  • Maintains cardiovascular stability
  • Bronchodilator effect (good for asthma/COPD)
  • Preserves respiratory drive
  • Maintains intact adrenal axis 1
• Disadvantages:
  • May increase ICP (controversial)
  • Emergence reactions/hallucinations
  • May increase secretions
• Considerations: Recommended with atropine premedication for septic shock patients 1

Propofol

• Dose: 1-2 mg/kg IV (reduce in elderly/unstable patients)
• Mechanism: GABA receptor agonist
• Clinical uses: Hemodynamically stable patients, status epilepticus
• Advantages:
  • Rapid onset, short duration
  • Antiemetic properties
  • Anticonvulsant effect
• Disadvantages:
  • Significant hypotension (dose-dependent)
  • Respiratory depression
  • Pain on injection
  • No analgesic properties
• Drug interactions: Dose requirements reduced with opioids and other sedatives; may cause serious bradycardia when combined with fentanyl in pediatric patients 2

Ketofol (Ketamine/Propofol Admixture)

• Dose: Typically 1:1 mixture (e.g., 0.75 mg/kg of each)
• Clinical uses: When hemodynamic stability is desired but full ketamine effects not wanted
• Advantages: Improved hemodynamic stability compared to propofol alone 3
• Considerations: May provide better hemodynamic control during induction 3

Neuromuscular Blocking Agents (Paralytics)

Succinylcholine

• Dose: 1.5 mg/kg IV
• Mechanism: Depolarizing NMBA
• Clinical uses: First-line agent for RSI when no contraindications exist
• Advantages:
  • Rapid onset (30-60 seconds)
  • Short duration (5-10 minutes)
  • Excellent intubating conditions
• Disadvantages:
  • Multiple contraindications (burns, crush injuries, neuromuscular disease, hyperkalemia)
  • Fasciculations
  • Malignant hyperthermia risk
  • Bradycardia with repeat doses
• Warning: Causes respiratory arrest; facilities must be immediately available for artificial respiration

Rocuronium

• Dose: 1.0-1.2 mg/kg IV for RSI (higher dose for faster onset)
• Mechanism: Non-depolarizing NMBA
• Clinical uses: When succinylcholine is contraindicated
• Advantages:
  • Rapid onset at higher doses (60-90 seconds)
  • Fewer contraindications than succinylcholine
  • Can be reversed with sugammadex
• Disadvantages:
  • Longer duration (30-40 minutes)
  • No reversal agent readily available in many EDs
• Warning: Paralyzing agent that causes respiratory arrest 4

Administration Sequence

• Recent evidence suggests administering the paralytic agent first may reduce first-attempt failure during emergency intubation 5

Clinical Decision Algorithm for Induction Agent Selection

1. Assess hemodynamic stability:

   • Unstable (hypotension, shock): Choose ketamine or etomidate
   • Stable: Any agent appropriate; propofol may be preferred

2. Consider specific conditions:

   • Septic shock: Ketamine with atropine premedication 1
   • Status epilepticus: Propofol
   • Asthma/COPD: Ketamine
   • Elevated ICP: Etomidate or propofol
   • Trauma: Etomidate or ketamine

3. For paralytic selection:

   • No contraindications: Succinylcholine
   • Contraindications to succinylcholine: Rocuronium at 1.0-1.2 mg/kg
   • When using rocuronium: Ensure sugammadex is rapidly available 1

Special Considerations

Preoxygenation Techniques

• For difficult airways: Use high-flow nasal oxygen (HFNO)
• For severe hypoxemia (PaO₂/FiO₂ < 150): Use noninvasive positive pressure ventilation (NIPPV) 1

Pediatric Patients

• Ketamine (3-4 mg/kg < 18 months; 2 mg/kg > 18 months) or etomidate (> 2 years old) recommended 1
• Succinylcholine is first-line for RSI in children with respiratory or cardiovascular compromise 1

Common Pitfalls to Avoid

1. Not using a paralytic agent: Leads to worse intubating conditions and higher complication rates 1
2. Underdosing induction agents: Results in awareness or inadequate intubating conditions
3. Overdosing induction agents: Causes hemodynamic collapse in unstable patients
4. Neglecting pre-oxygenation: Critical for preventing desaturation
5. Not having rescue devices ready: Always prepare for difficult airway scenarios

The choice of induction and paralytic agents should be guided by the patient's clinical condition, with careful consideration of hemodynamic status and specific comorbidities. Always have emergency airway equipment and vasopressors immediately available when performing RSI.