A 58-year-old woman is brought to the emergency department by her husband due to a 3-day history of increasing confusion, sluggishness, and tremors. Her husband reports that she has been sleeping more than usual and has had difficulty holding a glass of water without spilling it. Her medical history is significant for bipolar I disorder, for which she has been stable on lithium carbonate 900 mg daily for the past 5 years. She also has osteoarthritis and began taking naproxen 500 mg twice daily two weeks ago for worsening knee pain.
On physical examination, temperature is 37.1°C (98.8°F), blood pressure is 118/76 mm Hg, pulse is 88/min, and respirations are 14/min. She appears lethargic but is easily arousable. Neurologic examination reveals a prominent coarse, irregular tremor in her upper extremities bilaterally, as well as hyperreflexia in all four extremities. No nuchal rigidity is noted.
Serial laboratory studies are shown below:
| Parameter | 2 Weeks Ago | Today |
|---|---|---|
| Blood urea nitrogen | 14 mg/dL | 32 mg/dL |
| Serum creatinine | 0.9 mg/dL | 1.6 mg/dL |
| Serum lithium | 0.8 mEq/L | 2.1 mEq/L |
| Serum sodium | 140 mEq/L | 138 mEq/L |
| Serum potassium | 4.0 mEq/L | 4.2 mEq/L |
An electrocardiogram shows normal sinus rhythm with no ST-segment or T-wave abnormalities.
Which of the following is the most appropriate next step in the management of this patient?
- Discontinue lithium and naproxen, and administer intravenous isotonic salineCevap
- BDiscontinue lithium and naproxen, and initiate emergency hemodialysis
- CAdminister oral activated charcoal and discontinue naproxen
- DDiscontinue lithium and administer intravenous furosemide
- EDiscontinue naproxen, decrease the lithium dose by 50%, and observe