Review Question - QID 216451

A 40-year-old homeless man with a history of alcohol use disorder presents to the emergency department with shortness of breath and bilateral paresthesias of his hands and feet. He states he has noticed it worsening for months and now he can only walk short distances without needing to take a break. He feels weak and tired all the time. The patient's temperature is 98.9°F (37.2°C), blood pressure is 135/68 mmHg, pulse is 105/min, and respirations are 20/min. On physical exam, his skin is a dark tan color. There are bilateral crackles on lung exam. Inspection of the extremities reveals 2+ bilateral ankle edema. His cardiac exam is significant for an S3 gallop, and the point of maximal impulse can be felt below the 5th intercostal space, lateral to the midclavicular line. There is also a mid-systolic ejection murmur, heard best over the right second intercostal space. Neurologic exam is significant for decreased sensation to light touch in the distal extremities, 1+ deep tendon reflexes throughout, nystagmus, and an ataxic gait. Lab tests are performed with the following significant results:

Serum:
AST: 207 U/L
ALT: 101 U/L
Alkaline phosphatase: 85 U/L
Hemoglobin: 18 g/dL

Which of the following is the most appropriate next treatment for this patient's cardiopulmonary symptoms?