Question

A $62$-year-old male is urgently assessed on the general surgery floor on postoperative day $5$ following an elective open sigmoid colectomy for recurrent diverticulitis. Over the preceding $12$ hours, the patient has become increasingly lethargic and reports new-onset, agonizing abdominal pain. Temperature is $39.2^\circ\text{C}$ ($102.6^\circ\text{F}$), blood pressure is $78/46 \text{ mmHg}$, pulse is $132/\text{min}$, and respirations are $28/\text{min}$. Pulse oximetry shows $94\%$ on room air. The patient appears diaphoretic and is poorly responsive to questioning. Physical examination reveals a markedly distended and rigid abdomen with diffuse guarding and severe rebound tenderness across all quadrants. The surgical incision is intact without erythema or drainage. Bowel sounds are absent. Laboratory analysis demonstrates a leukocyte count of $22,000/\text{mm}^3$ with $15\%$ bandemia and a serum lactate of $6.4 \text{ mmol/L}$. Peripheral intravenous access is secured, a $2\text{-L}$ bolus of isotonic crystalloid is rapidly infused, and broad-spectrum antimicrobial therapy is initiated. A repeat blood pressure measurement is $82/50 \text{ mmHg}$.

Which of the following is the most appropriate next step in management?