Question

A 74-year-old woman is brought to the emergency department due to sudden-onset, severe abdominal pain that began 3 hours ago. She reports nausea and one episode of non-bloody emesis. Her past medical history is significant for heart failure with preserved ejection fraction and paroxysmal atrial fibrillation, for which she recently stopped taking her prescribed direct oral anticoagulant due to financial constraints. Temperature is $37.4^\circ\text{C}$ ($99.3^\circ\text{F}$), blood pressure is $142/85$ mmHg, pulse is $118$/min and irregular, and respirations are $20$/min. Physical examination reveals a soft, non-distended abdomen with diffuse mild tenderness to deep palpation, but no rebound tenderness, guarding, or rigidity. Bowel sounds are hypoactive. Rectal examination shows trace heme-occult positive stool. Laboratory studies show a leukocyte count of $18,500/\text{mm}^3$, serum bicarbonate of $16$ mEq/L, and serum lactate of $4.8$ mmol/L. Based on standard surgical guidelines, arrange the following management steps in the most appropriate chronological order for this patient.