Question

A 68-year-old man with a history of chronic obstructive pulmonary disease (COPD) is hospitalized for induction chemotherapy for newly diagnosed acute myeloid leukemia. On day 8 of his admission, his absolute neutrophil count is $200/\text{mm}^3$ and his hemoglobin is $6.2\text{ g/dL}$. He is afebrile and hemodynamically stable. He is prescribed a transfusion of two units of packed red blood cells.

Two hours into the transfusion, he develops acute-onset severe dyspnea, tachypnea, and a dry cough.

Vital signs are as follows:
- Temperature: $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$)
- Blood pressure: $178/92\text{ mmHg}$
- Heart rate: $112/\text{min}$
- Respiratory rate: $26/\text{min}$
- $\text{SpO}_2$: $86\%$ on room air

Physical examination reveals a frail man in moderate respiratory distress using accessory muscles of respiration. Jugular venous pressure is $12\text{ cm H}_2\text{O}$. Chest auscultation reveals diffuse, prolonged expiratory wheezing with faint bibasilar crackles.

Arterial blood gas analysis on room air shows:
- pH: $7.28$
- $\text{pCO}_2$: $56\text{ mmHg}$
- $\text{pO}_2$: $54\text{ mmHg}$
- $\text{HCO}_3^-$: $25\text{ mEq/L}$

Routine morning laboratory results (drawn prior to the transfusion) show:
- Sodium: $138\text{ mEq/L}$
- Potassium: $4.2\text{ mEq/L}$
- Chloride: $102\text{ mEq/L}$
- Bicarbonate: $24\text{ mEq/L}$
- Blood urea nitrogen: $18\text{ mg/dL}$
- Creatinine: $0.9\text{ mg/dL}$
- TSH: $0.2\text{ }\mu\text{U/mL}$ (Normal: $0.4–4.0$)
- Free T4: $0.7\text{ ng/dL}$ (Normal: $0.9–1.7$)

The transfusion is immediately halted, and the patient is placed on supplemental oxygen via a non-rebreather mask. Which of the following is the most appropriate next step in the management of this patient?