Rescue Emetic Therapy for Children Having Elective Surgery

To compare ondansetron, metoclopramide, diphenhydramine, and placebo in order to determine which anti-emetic is most efficacious as a "rescue therapy" for pediatric patients ages 3-18 who have post-operative vomiting after a standardized prophylactic regimen of ondansetron and dexamethasone. We hypothesize that anti-emetics with a different mechanism of action than the prophylactic regimen will be the most effective "rescue therapy" in children having surgery in an ambulatory surgery center. 1. Problem: Despite commonly-used anti-emetics for prophylaxis, some children still go on to develop post-operative vomiting (POV). Goal: To determine which anti-emetic--ondansetron, metoclopramide, diphenhydramine, or placebo--is most efficacious for pediatric patients in this situation. 2. Hypothesis: Anti-emetic medications that have a different mechanism of action than the prophylactic regimen will be the most efficacious "rescue therapy." 3. Hypothesis: Metoclopramide at the dose of 0.5 mg/kg (max dose 20 mg) will be more effective than ondansetron, diphenhydramine, or placebo as "rescue therapy."