Question

A $55$-year-old woman is evaluated in the emergency department for severe shortness of breath that has worsened over the past $2$ days. She has a history of asthma and hypertension. Her home medications include inhaled budesonide-formoterol and oral amlodipine. Over the last $12$ hours, she has been using her albuterol rescue inhaler every hour with minimal relief.

On initial presentation, she is in acute respiratory distress, using accessory muscles of respiration. Lung auscultation reveals diffuse expiratory wheezing. She has $1+$ bilateral lower extremity pitting edema, which she states is her baseline. Initial treatment is initiated with oxygen, continuous nebulized albuterol and ipratropium, intravenous methylprednisolone, and intravenous magnesium sulfate.

Four hours later, the patient reports that her breathing is significantly easier. Her work of breathing has decreased, and wheezing is now faint and only audible at the lung bases. However, she now reports new-onset palpitations and hand tremors.

Current vital signs:
Temperature: $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$)
Blood pressure: $122/78\text{ mm Hg}$
Heart rate: $118/\text{min}$
Respiratory rate: $16/\text{min}$
SpO2: $96\%$ on room air

Laboratory evaluation reveals:
Serum sodium: $140\text{ mEq/L}$
Serum potassium: $3.6\text{ mEq/L}$
Serum chloride: $104\text{ mEq/L}$
Serum bicarbonate: $15\text{ mEq/L}$
Serum lactate: $4.8\text{ mmol/L}$ (Normal: $0.5$-$1.0\text{ mmol/L}$)

Arterial blood gas (room air):
pH: $7.32$
PaCO2: $30\text{ mm Hg}$
PaO2: $84\text{ mm Hg}$

Which of the following is the most appropriate next step in management?