Sedation/anesthesia is critical to cardiac catheterization in the pediatric/congenital heart patient. We sought to identify current sedation/anesthesia practices, the serious adverse event rate related to airway, sedation, or anesthesia, and the rate of intra-procedural conversion from procedural sedation to the use of assisted ventilation or an artificial airway. Data from 13,611 patients who underwent catheterization at eight institutions were prospectively collected from 2007 to 2010. Ninety-four (0.69 %) serious sedation/airway-related adverse events occurred; events were more likely to occur in smaller patients (<4 kg, OR 4.4, 95 % CI 2.3–8.2, p < 0.001), patients with non-cardiac comorbidities (OR 1.7, 95 % CI 1.1–26, p < 0.01), and patients with low mixed venous oxygen saturation (OR 2.3, 95 % CI 1.4–3.6, p < 0.001). Nine thousand three hundred and seventy-nine (69 %) patients were initially managed with general endotracheal anesthesia, LMA, or tracheostomy, whereas 4232 (31 %) were managed with procedural sedation without an artificial airway, of which 75 (1.77 %) patients were converted to assisted ventilation/general anesthesia. Young age (<12 months, OR 5.2, 95 % CI 2.3–11.4, p < 0.001), higher-risk procedure (category 4, OR 10.1, 95 % CI 6.5–15.6, p < 0.001), and continuous pressor/inotrope requirement (OR 11.0, 95 % CI 8.6–14.0, p < 0.001) were independently associated with conversion. Cardiac catheterization in pediatric/congenital patients was associated with a low rate of serious sedation/airway-related adverse events. Smaller patients with non-cardiac comorbidities or low mixed venous oxygen saturation may be at higher risk. Patients under 1 year of age, undergoing high-risk procedures, or requiring continuous pressor/inotrope support may be at higher risk of requiring conversion from procedural sedation to assisted ventilation/general anesthesia.