Review Question - QID 214450

A 40-year-old man with Hodgkin lymphoma presents for a right shoulder arthroscopy to repair a rotator cuff tear. His medications include bleomycin, doxorubicin, methotrexate, and vinblastine. During the operation, a right interscalene brachial plexus block is performed using dilute lidocaine with appropriate loss of pain sensation in his right shoulder, elbow, thumb, and index finger. The procedure proceeds uneventfully. After the patient is extubated and emerges from anesthesia in the recovery unit, he is discharged with anticipatory guidance that the nerve block will wear off in several hours. Ten hours later, the patient complains that all of his right-hand fingers feel more numb than usual. Physical exam reveals decreased sensation to touch of his right upper extremity, left upper extremity, and bilateral lower extremities. The patient's strength and proprioception are otherwise unremarkable. Which of the following medications is the most likely cause of this patient's symptoms?