Question

A 68-year-old man is admitted to the hospital with a 2-day history of progressively worsening, crampy abdominal pain, abdominal distension, and multiple episodes of bilious vomiting. He reports not having passed flatus or stool for the past 24 hours. His past medical history is significant for hypertension and an open appendectomy 15 years ago.

Vital signs are:
Temperature: $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$)
Blood pressure: $105/65\text{ mmHg}$
Heart rate: $110/\text{min}$
Respiratory rate: $18/\text{min}$

Physical examination reveals a markedly distended and tympanitic abdomen. Bowel sounds are high-pitched and hyperactive. There is diffuse, mild tenderness to palpation, but no rebound tenderness or abdominal wall rigidity.

Laboratory results show:
Leukocyte count: $9,500/\text{mm}^3$
Serum sodium: $138\text{ mEq/L}$
Serum potassium: $3.2\text{ mEq/L}$
Serum chloride: $96\text{ mEq/L}$
Serum bicarbonate: $29\text{ mEq/L}$
Blood urea nitrogen: $48\text{ mg/dL}$
Serum creatinine: $1.9\text{ mg/dL}$ (Baseline: $1.0\text{ mg/dL}$)
Lactic acid: $1.1\text{ mmol/L}$ (Normal: $0.5 - 2.2\text{ mmol/L}$)

Upright abdominal radiography reveals multiple dilated loops of small intestine with prominent air-fluid levels and an absence of colonic gas.

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