Which single feature best distinguishes etomidate from ketamine as an induction agent?

Question

Accepted Answer

D. Etomidate maintains cardiovascular stability; ketamine causes sympathomimetic effects. ## Discriminating Feature: Cardiovascular Stability

**Key Point:** Etomidate is the ONLY induction agent that maintains cardiovascular stability (minimal change in BP and HR), whereas ketamine causes sympathomimetic stimulation with increased heart rate and blood pressure.

### Comparison Table: Etomidate vs Ketamine

| Feature | Etomidate | Ketamine |
| --- | --- | --- |
| **Cardiovascular effect** | Minimal (stable BP/HR) | Sympathomimetic (↑BP, ↑HR) |
| **Airway reflexes** | Preserved | Preserved |
| **Analgesia** | Absent | Present (potent) |
| **Dissociation** | No | Yes (characteristic) |
| **Muscle tone** | Decreased | Increased (muscle rigidity) |
| **Respiratory depression** | Mild | Mild–moderate |
| **Emergence phenomena** | Rare | Common (hallucinations, dysphoria) |
| **Adrenal suppression** | YES (single dose) | No |

### Why Cardiovascular Stability Matters

**High-Yield:** Etomidate's hemodynamic stability makes it the agent of choice in:
  - Hypovolemic patients
  - Septic shock / hemodynamic instability
  - Critically ill ICU patients
  - Cardiogenic shock
  - Elderly with poor cardiac reserve

**Clinical Pearl:** Ketamine's sympathomimetic effects (catecholamine release) are beneficial in hypovolemia but problematic in hypertensive patients or those with coronary artery disease.

**Warning:** Single-dose etomidate causes transient adrenal suppression (↓ cortisol for 4–8 hours), which is clinically significant in septic shock. Ketamine does NOT suppress adrenal function.

### Mechanism of Cardiovascular Stability

Etomidate's preservation of sympathetic tone and lack of direct myocardial depression result in:
  - No change or minimal decrease in systolic BP
  - Maintained or slightly increased HR
  - Preserved cardiac output

Ketamine's sympathomimetic effect (via catecholamine release and CNS stimulation) causes:
  - Increased systolic and diastolic BP
  - Tachycardia
  - Increased myocardial oxygen demand

[cite:Gupta & Rao Anesthesia 3e Ch 8]

Answer

A. Etomidate preserves airway reflexes; ketamine does not

Answer

B. Etomidate has analgesic properties; ketamine does not

Answer

C. Etomidate causes dissociation; ketamine causes deep hypnosis

Which single feature best distinguishes etomidate from ketamine as an induction agent?

Explanation

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