Question

Emergency medical services bring a $32$-year-old gravid patient (estimated $32$ weeks gestation) to the trauma bay following a high-speed motor vehicle collision. Paramedics report she was a restrained passenger wearing a lap belt without a shoulder strap. Upon arrival, the patient is immobilized on a backboard with a left lateral tilt. She is pale, diaphoretic, and confused. Vital signs are temperature $36.5^\circ\text{C}$ ($97.7^\circ\text{F}$), pulse $138/\text{min}$, respirations $28/\text{min}$, and blood pressure $78/42\text{ mm Hg}$. Physical examination reveals a protuberant abdomen that is rigid, with diffuse rebound tenderness and a transverse ecchymosis across the lower abdomen. Fetal heart rate monitoring demonstrates a baseline of $105/\text{min}$ with absent variability and recurrent late decelerations. Despite the rapid intravenous infusion of $2\text{ L}$ of warmed crystalloids and $2\text{ units}$ of uncrossmatched type O-negative blood, her blood pressure remains $82/45\text{ mm Hg}$. A bedside focused assessment with sonography for trauma (FAST) shows a large volume of anechoic fluid in the hepatorenal and splenorenal recesses. Which of the following is the most appropriate next step in management?