Question

A $2$-hour-old term male neonate is evaluated in the neonatal intensive care unit for profound cyanosis that developed shortly after birth. His mother had an uncomplicated pregnancy and vaginal delivery. On initial evaluation, his oxygen saturation was $60\%$ on room air and failed to improve significantly during a hyperoxia test. An echocardiogram revealed D-transposition of the great arteries with an intact ventricular septum. An intravenous prostaglandin E1 infusion was promptly initiated. One hour later, the neonate becomes apneic, requiring endotracheal intubation and mechanical ventilation. Despite $100\%$ fraction of inspired oxygen ($FiO_2$) on the ventilator, his oxygen saturation remains at $58\%$. An arterial blood gas shows pH $7.15$, $PaCO_2$ $40$ mmHg, $PaO_2$ $25$ mmHg, and $HCO_3^-$ $14$ mEq/L. The patient is tachycardic and hypotensive. A repeat bedside echocardiogram demonstrates a widely patent ductus arteriosus and a severely restrictive patent foramen ovale bowing right-to-left. Which of the following is the next best step in management?