Pharmacology and Anesthetic Agents
Core concepts
Know the pharmacokinetics and pharmacodynamics of induction agents (propofol, etomidate, ketamine, thiopental), opioids, muscle relaxants, and local anesthetics. Understand context-sensitive half-time and how it affects recovery from infusions. Know the differences between depolarizing and nondepolarizing relaxants, their reversal agents (neostigmine, sugammadex), and the risks of residual paralysis. Understand the mechanisms and side effects of common agents: propofol (hypotension, pain on injection), etomidate (adrenal suppression), ketamine (sympathomimetic, emergence reactions), and volatile agents. Recognize drug interactions and the principles of total intravenous anesthesia.
Traps in questions
- Forgetting that etomidate can suppress adrenal steroidogenesis, which matters in sepsis.
- Assuming neostigmine reverses all relaxants; it does not reliably reverse deep blockade.
- Overlooking that propofol causes hypotension and apnea, especially in hypovolemic patients.
- Confusing context-sensitive half-time with elimination half-life.
- Missing that ketamine is a bronchodilator and sympathomimetic, useful in asthma but not in severe hypertension.
Worked example / rule of thumb
For a septic patient needing induction, etomidate provides hemodynamic stability but may worsen adrenal suppression; ketamine is an alternative. Rule of thumb: choose the induction agent by hemodynamic profile, not by habit, and reduce doses in hypovolemia and the elderly.
Exam framing
Questions often ask which agent is best in a specific comorbidity. Match the drug's hemodynamic and side-effect profile to the patient's physiology, and remember that dose reduction is often the safest adjustment.