Review Question - QID 103306

A 35-year-old woman presents to the emergency room with severe right lower quadrant abdominal pain. The pain began suddenly 2 hours ago and is unremitting. She also has had 2 episodes of emesis since the pain began. She has a history of tubal ligation 3 years ago and a history of chlamydia cervicitis treated 15 years ago. She usually has regular menstrual cycles, but her last menstrual period began 10 weeks ago. She works as a desk clerk and smokes 2 packs of cigarettes per day. She does not drink alcohol or use illicit drugs. The patient's temperature is 98.6°F (37.0°C), blood pressure is 88/56 mmHg, pulse is 126/min, and respirations are 24/min. On exam, she has a normal S1 and S2 without murmurs or gallops. Her lungs are clear to auscultation bilaterally. Her abdomen is rigid and diffusely tender to palpation. Involuntary guarding is present. There is no abnormal vaginal discharge. A urine beta-hCG is positive. A hemoglobin concentration is found to be 9.9 g/dL. A transabdominal ultrasound shows an unremarkable uterus and fluid with debris in the pelvic cul-de-sac. What is the most appropriate next step in management?