EDAIC - European Diploma in Anesthesiology and Intensive Care Pharmacokinetics and Pharmacodynamics Questions and Answers

Question 1

A 68-year-old patient with Child-Pugh Class C liver cirrhosis is anesthetized for a TIPS procedure. Fentanyl, a highly protein-bound opioid with a high hepatic extraction ratio, is administered. Which pharmacokinetic changes are most significant in this patient compared to a healthy individual?

Accepted Answer

Increased free drug fraction and decreased hepatic clearance.

Answer

In severe liver disease, synthesis of plasma proteins like albumin is reduced, leading to less protein binding and a higher fraction of unbound, pharmacologically active drug. Additionally, both liver blood flow and enzymatic function are impaired, which significantly decreases the clearance of drugs with a high hepatic extraction ratio, like fentanyl. This combination leads to a more pronounced and prolonged effect.

Question 2

Which of the following statements accurately describes the effect of a non-competitive antagonist on an agonist's dose-response curve?

Accepted Answer

A depression of the maximal effect (Emax), which cannot be overcome by increasing the agonist concentration.

Answer

A non-competitive antagonist binds to the receptor at an allosteric site or binds irreversibly to the active site, effectively removing functional receptors from the system. This reduces the maximum possible response (Emax) that can be achieved, regardless of how much agonist is administered. In contrast, a competitive antagonist causes a rightward shift in the curve (decreased potency) but the same Emax can be reached with a higher agonist concentration.

Question 3

A 55-year-old patient with combined severe renal and hepatic failure requires a continuous opioid infusion for sedation in the ICU. Which of the following opioids would provide the most predictable and rapid offset of effect upon discontinuation of the infusion?

Accepted Answer

Remifentanil

Answer

Remifentanil is metabolized by non-specific esterases in the blood and peripheral tissues, a process that is independent of hepatic or renal function. This unique pathway results in a very short and consistent context-sensitive half-time (approximately 3-4 minutes) that does not increase significantly with the duration of the infusion. Fentanyl, morphine, and hydromorphone all rely on hepatic metabolism and/or renal clearance, leading to unpredictable accumulation and prolonged effects in patients with organ failure.

Question 4

A 70-year-old patient with anuria due to end-stage renal disease requires neuromuscular blockade for an emergency laparotomy. Which of the following neuromuscular blocking agents would have the most significantly prolonged duration of action?

Accepted Answer

Pancuronium

Answer

Pancuronium is a long-acting neuromuscular blocker that is primarily cleared by the kidneys (approximately 80% renal excretion). In a patient with anuria, its clearance is drastically reduced, leading to a markedly prolonged duration of action and a risk of postoperative residual paralysis. In contrast, atracurium and cisatracurium undergo organ-independent Hofmann elimination, and succinylcholine is metabolized by plasma pseudocholinesterase, making their durations of action largely unaffected by renal failure.

Question 5

The 'context-sensitive half-time' is a critical pharmacokinetic concept for predicting recovery after an intravenous drug infusion. It is defined as the time required for:

Accepted Answer

the plasma drug concentration to decrease by 50% after stopping an infusion of a specific duration.

Answer

The context-sensitive half-time is the time taken for the plasma concentration of a drug to decrease by 50% after stopping an infusion of a certain duration (the 'context'). It is a more clinically useful measure than elimination half-life for infused drugs because it accounts for the redistribution of the drug from peripheral tissues back into the central compartment, which can significantly prolong the drug's effect. For many lipophilic drugs like fentanyl, the context-sensitive half-time increases with the duration of the infusion.

EDAIC - European Diploma in Anesthesiology and Intensive Care Practice Test

EDAIC - European Diploma in Anesthesiology and Intensive Care Practice Test

EDAIC - European Diploma in Anesthesiology and Intensive Care Pharmacokinetics and Pharmacodynamics Questions and Answers