This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
A 75-year-old, obese female is admitted with acute myocardial infarction and congestive hea failure, then has an episode of ventricular tachycardia. She is prescribed multiple medications and soon develops confusion and slurred speech. The most likely cause of this confusion is 
Select and explain. 
A. Captopril, B. Digoxin, C. Furosemide, D. Lidocaine
D: Lidocaine
Answer: D: Lidocaine 
Explanation: (Fuster, 10/e, pp 902-905.) While the clinical picture itself could lead to these neurological symptoms, the only cardiovascular medication on this list likely to do so is lidocaine. Lidocaine is paicularly likely to cause confusion in the elderly patient, for whom a lower dose of the drug should generally be given. Other potential adverse effects of lidocaine include tremor, convulsions, respiratory depression, bradycardia, and hypotension.