A 42-year-old man has had a rocky course for the 3 days following a bowel resection for intestinal perforation due to inflammatory bowel disease. His CVP had been 12 to 14 but is now 6, in the face of diminished blood pressure and oliguria. Which of the following is the most likely etiology of his hypotension?
Pulmonary embolism Hypervolemia Positive-pressure ventilation Gram-negative sepsis