She feels terrible and is unable to keep anything down. On examination she is alert and oriented but in significant distress. Her vital signs are as shown in the status monitor. Although she is tachypnoeic her chest is clear on auscultation. Abdominal examination reveals a diffusely tender abdomen with no evidence of guarding or rebound tenderness. Bowel sounds are present but diminished.

Mrs. M's past medical history includes an appendectomy and tonsillectomy, mild hypertension and diet controlled diabetes. Her only regular medication is a calcium channel blocker. She is married, has 3 children and smokes 5-10 cigarettes a day and denies regular alcohol intake.

What do you first?