The most likely reason a patient on ECMO (extracorporeal membrane oxygenation) is not responding to usual and adequate doses of pharmacological agents is:
The answer is C. Generally, ECMO alters pharmacokinetics by increasing the volume of distribution, decreasing (not accelerating) elimination, and sequestering drugs in the circuit given the large surface area of the tubing and membranes. More lipophilic drugs (e.g. fentanyl, propofol, midazolam, and many psychotropics) are more subject to sequestration.