Question

A 28-year-old woman, gravida 1, para 0, at 28 weeks gestation is brought to the emergency department due to the sudden onset of severe shortness of breath, orthopnea, and a cough productive of pink, frothy sputum. She recently immigrated to the United States and has had limited prenatal care. Over the past month, she noticed progressive fatigue and palpitations, which she attributed to normal pregnancy. Temperature is $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$), blood pressure is $110/70\text{ mm Hg}$, heart rate is $142\text{/min}$ and irregularly irregular, and respiratory rate is $32\text{/min}$. Pulse oximetry is $86\%$ on room air. Jugular venous distension is prominent. Lung auscultation reveals diffuse bilateral crackles and prolonged expiratory wheezes. Cardiac auscultation demonstrates a loud S1, an early diastolic sound, and a low-pitched, mid-diastolic rumble best heard at the cardiac apex. Arterial blood gas analysis on room air reveals:

$\text{pH}$: $7.30$
$\text{pCO}_2$: $55\text{ mm Hg}$
$\text{pO}_2$: $55\text{ mm Hg}$
$\text{HCO}_3^-$: $26\text{ mEq/L}$

In addition to noninvasive positive pressure ventilation, which of the following is the most appropriate next step in pharmacologic management for this patient?