Intravenous Induction Agents & Commonly Used Drugs

Intravenous (IV) induction agents rapidly induce unconsciousness, facilitating airway management and surgical anesthesia. They act quickly (15–60 seconds) and allow precise titration. Here’s a breakdown of commonly used agents, their mechanisms, and clinical indications:

1. Propofol

• Mechanism: Enhances GABA_A receptor activity, causing CNS depression.
• Onset/Duration: Rapid onset (15–30 sec); short duration (5–10 min).
• Advantages: Smooth induction, antiemetic effects, rapid recovery.
• Disadvantages: Dose-dependent hypotension, pain on injection, risk of propofol infusion syndrome (PRIS) with prolonged use.
• Clinical Indications:
  • First-line for elective surgery in hemodynamically stable patients.
  • Sedation in ICU/short procedures.
  • Contraindicated in egg/soy allergy (rare with modern formulations).

2. Etomidate

• Mechanism: GABA_A agonist; minimal cardiovascular effects.
• Onset/Duration: Onset in 30–60 sec; duration 5–15 min.
• Advantages: Hemodynamically neutral (ideal for unstable patients).
• Disadvantages: Adrenal suppression (inhibits 11β-hydroxylase), myoclonus.
• Clinical Indications:
  • Rapid sequence intubation (RSI) in trauma, sepsis, or cardiac compromise.
  • Avoid in critically ill patients requiring repeated doses (risk of adrenal insufficiency).

3. Ketamine

• Mechanism: NMDA receptor antagonist; dissociative anesthesia.
• Onset/Duration: Onset in 30–60 sec; duration 10–20 min.
• Advantages: Bronchodilation, cardiovascular stimulation (sympathomimetic), analgesia.
• Disadvantages: Emergence delirium, increased salivation, ↑ ICP.
• Clinical Indications:
  • Asthma/COPD, hypovolemic shock, pediatric sedation.
  • Contraindicated in psychosis, uncontrolled hypertension.

4. Barbiturates (Thiopental)

• Mechanism: GABA_A agonism.
• Onset/Duration: Ultra-rapid onset (10–20 sec); short duration.
• Advantages: Reliable induction, low cost.
• Disadvantages: Cardiovascular depression, histamine release (hypotension/bronchospasm).
• Clinical Indications:
  • Electroconvulsive therapy (ECT).
  • Largely replaced by propofol due to safety concerns.

Key Takeaway: Propofol dominates for routine cases, while etomidate/ketamine are reserved for high-risk scenarios. Always assess hemodynamics, comorbidities, and allergies!