## Airway Reflex Preservation Among IV Induction Agents **Key Point:** Ketamine is unique among IV induction agents in that it preserves airway reflexes and maintains spontaneous ventilation better than all other agents. ### Mechanism Ketamine causes dissociative anesthesia by antagonizing NMDA receptors. Unlike barbiturates and propofol, it does NOT directly depress the brainstem respiratory centers or airway protective reflexes. Patients maintain airway tone and can cough/swallow. ### Comparative Table | Agent | Airway Reflexes | Respiratory Depression | Spontaneous Ventilation | Clinical Use | | --- | --- | --- | --- | --- | | **Ketamine** | Preserved | Minimal | Maintained | Difficult airway, emergency, pediatric | | **Propofol** | Abolished | Marked | Often apneic | Routine induction, ICU sedation | | **Thiopentone** | Abolished | Marked | Often apneic | Rarely used now (historical) | | **Etomidate** | Abolished | Minimal | Maintained | Hemodynamically unstable patients | **High-Yield:** Ketamine is the safest induction agent for airway management because it maintains airway reflexes AND respiratory drive simultaneously — a combination no other agent offers. **Clinical Pearl:** This property makes ketamine the agent of choice in emergency/trauma settings, difficult airway scenarios, and pediatric anesthesia where maintaining spontaneous ventilation is critical. **Warning:** Do NOT confuse "minimal respiratory depression" with "no respiratory depression." Ketamine still causes some dose-dependent respiratory depression; it is simply the LEAST among the four.
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