A 45 year old man with previously known duodenal ulcer disease presents with complaints of persistent vomiting for the past 36 hours.  The vomit is clear-looking and acidic in taste.  He has no abdominal pain.  Prior to the vomiting, he had difficulty with solid foods causing "fullness" in the stomach and he had been taking only liquids for one week.  His heartburn had been aggravated at the time of the "fullness", but antacids did not help and he did not seek medical attention until today.  He complains of being dizzy when he stands up.  His blood pressure changes from 120/70 when lying to 105/55 when standing, his pulse changes from 100 to 130.