A 65-year-old man with a history of chronic obstructive pulmonary disease (COPD) and type 2 diabetes mellitus is evaluated in the emergency department for progressive fatigue, shortness of breath, and lower extremity tingling over the past 4 weeks. He has not had fever, increased sputum production, or chest pain. Vital signs show a temperature of 37.0 C (98.6 F), blood pressure of 115/75 mmHg, pulse of 112/min, and respiratory rate of 22/min. Pulse oximetry is 94% on room air.
Physical examination reveals pale conjunctivae and a smooth, beefy red tongue. Neurologic examination shows decreased vibratory sensation in the lower extremities bilaterally. Lung auscultation is clear without wheezes or crackles. Heart exam reveals a 2/6 systolic ejection murmur at the left sternal border.
Laboratory results are as follows:
| Test | Result | Reference Range |
|---|---|---|
| Hemoglobin | 7.2 g/dL | 13.5-17.5 g/dL |
| Mean corpuscular volume (MCV) | 116 fL | 80-100 fL |
| Leukocytes | 3,100 /mm³ | 4,500-11,000 /mm³ |
| Platelets | 105,000 /mm³ | 150,000-400,000 /mm³ |
| Sodium | 138 mEq/L | 136-145 mEq/L |
| Chloride | 112 mEq/L | 95-105 mEq/L |
| Bicarbonate | 16 mEq/L | 22-28 mEq/L |
| Blood urea nitrogen | 18 mg/dL | 7-18 mg/dL |
| Creatinine | 0.9 mg/dL | 0.6-1.2 mg/dL |
| TSH | 2.1 µU/mL | 0.5-5.0 µU/mL |
| Free T4 | 0.8 ng/dL | 0.9-2.4 ng/dL |
Arterial blood gas on room air shows pH 7.31, PaCO2 32 mmHg, and PaO2 75 mmHg. Peripheral blood smear reveals hypersegmented neutrophils and macro-ovalocytes. Blood cultures drawn 2 days ago in the outpatient clinic are negative.
Which of the following is the most appropriate next step in the management of this patient?
- Measure serum vitamin B12 and methylmalonic acid levelsCevap
- BAdminister inhaled albuterol and oral glucocorticoids
- CStart empirical intravenous vancomycin and cefepime
- DInitiate oral levothyroxine therapy
- EAdminister intravenous sodium bicarbonate