A 16-year-old female with a history of cyclic vomiting syndrome presents to the ED during an acute episode. She has been vomiting for 12 hours and appears dehydrated. Her mother reports that the patient's usual triggers include stress and menses, but this episode started without any apparent trigger. Which of the following is the MOST appropriate next step in management?
Initiate oral propranolol therapy
Administer sumatriptan nasal spray
Give intramuscular lorazepam
Start IV ondansetron infusion