Soru

A 62-year-old man is evaluated in the intensive care unit for rapidly worsening oxygenation. Two days ago, he underwent an emergency exploratory laparotomy for a perforated duodenal ulcer. Blood cultures drawn at admission are currently growing *Escherichia coli* susceptible to ceftriaxone. He is receiving intravenous piperacillin-tazobactam, vancomycin, and a continuous norepinephrine infusion.

Current vital signs:
* Temperature: $38.5^\circ\text{C}$ ($101.3^\circ\text{F}$)
* Blood pressure: $90/55\text{ mmHg}$
* Heart rate: $120/\text{min}$

Physical examination reveals flat jugular veins. Lung auscultation demonstrates diffuse bilateral crackles. Echocardiography shows a hyperdynamic left ventricle with an estimated ejection fraction of $65\%$ and no valvular abnormalities. Chest radiography reveals new, dense bilateral alveolar infiltrates.

Prior to intubation, an arterial blood gas (ABG) on a $100\%$ non-rebreather mask showed:
* $\text{pH}$: $7.28$
* $P_a\text{CO}_2$: $30\text{ mmHg}$
* $P_a\text{O}_2$: $55\text{ mmHg}$
* $\text{HCO}_3^-$: $14\text{ mEq/L}$

The patient is immediately intubated. Initial ventilator settings on Assist-Control Volume Control mode are:
* Tidal volume: $450\text{ mL}$ ($6\text{ mL/kg}$ of ideal body weight)
* Respiratory rate: $16/\text{min}$
* $\text{PEEP}$: $8\text{ cm H}_2\text{O}$
* $\text{FiO}_2$: $1.0$

Thirty minutes later, ventilator mechanics show a peak airway pressure of $32\text{ cm H}_2\text{O}$ and a plateau pressure of $22\text{ cm H}_2\text{O}$. A repeat ABG is obtained:
* $\text{pH}$: $7.14$
* $P_a\text{CO}_2$: $48\text{ mmHg}$
* $P_a\text{O}_2$: $58\text{ mmHg}$
* $\text{HCO}_3^-$: $16\text{ mEq/L}$

Which of the following are the most appropriate immediate steps in management? (Select all that apply)