What are examples of intravenous induction agents for general anesthesia (GA) in adult and pediatric patients?

Intravenous Induction Agents for General Anesthesia

Three Primary IV Induction Agents

The three most commonly used intravenous induction agents for general anesthesia in both adult and pediatric patients are propofol, ketamine, and etomidate. 1

1. Propofol

Propofol is the most widely used induction agent due to its rapid onset (within 40 seconds) and predictable recovery profile. 1, 2

• Standard induction dose: 1-2.5 mg/kg IV in adults; 1-3.6 mg/kg in pediatric patients 2
• Mechanism: Positive modulation of GABA-A receptors producing rapid loss of consciousness 2
• Advantages: Rapid, clear-headed recovery with minimal hangover effect; reduced postoperative nausea and vomiting compared to volatile agents 3, 4
• Key considerations: Causes significant cardiovascular depression with arterial hypotension (sometimes >30% decrease), particularly with bolus dosing or in elderly/debilitated patients 2, 4
• Respiratory effects: Frequently causes apnea (43% of adults experience apnea >30 seconds; 27% of pediatric patients) 2

Common pitfall: Avoid rapid bolus administration in hemodynamically unstable patients, elderly, or ASA-PS III-IV patients, as this significantly increases risk of profound hypotension and cardiovascular collapse 2, 4

2. Ketamine

Ketamine is particularly valuable in hemodynamically compromised patients as it maintains systemic vascular resistance and contractility. 3, 1, 5

• Standard induction dose: 1-2 mg/kg IV 1
• Mechanism: NMDA receptor antagonist with dissociative anesthetic properties 5
• Advantages: Maintains blood pressure and cardiac output; provides analgesia; preserves airway reflexes; safer profile in patients with cardiovascular instability or shock 3, 5
• Specific indications: Preferred in patients with significant myocardial hypertrophy (e.g., Pompe disease), ruptured abdominal aortic aneurysm, polytrauma, or septic shock 3, 5
• Use in pediatrics: Can be used for mask induction or IV induction; particularly useful when spontaneous ventilation must be maintained 3

Common pitfall: Traditional contraindication in brain injury has been challenged; adverse effects on intracranial pressure are attenuated by controlled ventilation and subsequent anesthesia 5

3. Etomidate

Etomidate is an excellent alternative induction agent, particularly in hemodynamically unstable patients, due to minimal cardiovascular depression. 3, 1, 6

• Standard induction dose: 0.2-0.3 mg/kg IV 1, 6
• Mechanism: GABA-A receptor modulator with rapid onset and short duration 6
• Advantages: Minimal cardiovascular and respiratory depression even in patients with poor cardiac reserve; approximately 25 times more potent than thiopental with six times greater therapeutic index 6
• Key considerations: Acceptable for patients with advanced cardiac disease or minimal cardiovascular reserve 3, 6
• Side effects: Myoclonus (can be attenuated with fentanyl or droperidol pretreatment), pain on injection, suppression of adrenocortical function 3, 6

Common pitfall: Single-dose etomidate causes temporary suppression of cortisol synthesis, though clinical significance of single induction dose remains debated; avoid in patients requiring prolonged adrenal function 3, 6

Comparative Selection Algorithm

For hemodynamically stable patients: Propofol is first-line due to superior recovery profile and reduced PONV 3, 1, 4

For hemodynamically unstable/shocked patients: Ketamine or etomidate are preferred; ketamine offers additional analgesic benefit 3, 1, 5

For patients with severe cardiac disease: Etomidate or ketamine; avoid propofol due to significant afterload reduction and risk of myocardial ischemia 3, 4, 6

For pediatric mask induction: Sevoflurane is typically preferred over IV agents, but propofol or ketamine can be used IV 3, 1

For patients requiring maintained spontaneous ventilation: Ketamine is preferred as it preserves airway reflexes and respiratory drive 3, 5