An 11-year-old girl arrived in the emergency department after 15 hours of abdominal pain and vomiting and 3 hours of sweating. A nonproductive cough developed 3 days before presentation. There was no associated fever, and the cough did not limit her activity. In the 3 hours before presentation, her abdominal pain increased in intensity, breathing became labored, and she began to perspire. Her medical history was unremarkable.
Results of the initial physical examination showed moderate respiratory distress and diaphoresis. The child was ambulatory, alert, and cooperative, and pointed to her midabdomen as a source of discomfort. Her respiratory rate was 40 breaths per minute; heart rate, 120 beats per minute; blood pressure, 106/38 mm Hg; and temperature, 36.3°C. Her skin was cool, clammy, and cyanotic. Her oral mucous membranes were dry, and her heart sounds were normal, although distant. No murmurs or gallop were present, pulses were weak at all