Question

An infant boy born at $27$ weeks of gestation is currently $14$ days old and recovering in the neonatal intensive care unit. Over the past $8$ hours, the nursing staff has reported increased episodes of apnea, bradycardia, and a drop in body temperature. The patient had previously been tolerating slowly advancing orogastric feeds, but a large bilious residual was aspirated prior to his last scheduled feed. On evaluation, his temperature is $36.0^\circ\text{C}$ ($96.8^\circ\text{F}$), blood pressure is $45/28\text{ mm Hg}$, pulse is $182/\text{min}$, and respirations are $62/\text{min}$. Physical examination reveals a lethargic and mottled neonate. His abdomen is markedly distended, firm, and diffusely tender, with prominent erythema spreading across the abdominal wall. Laboratory analysis demonstrates a leukocyte count of $3,200/\text{mm}^3$ with $25\%$ band forms, a platelet count of $55,000/\text{mm}^3$, and a serum lactate level of $4.8\text{ mmol/L}$. A supine abdominal radiograph shows diffusely dilated loops of bowel, branching linear lucencies overlying the right upper quadrant, and a prominent radiolucent outline of the falciform ligament. Intravenous fluid resuscitation, broad-spectrum antimicrobial therapy, and bowel rest (NPO) are promptly initiated. Which of the following is the most appropriate next step in the management of this patient?