The nurse is caring for an infant with tetralogy of Fallot. During a blood draw the nurse observes the infant becoming pale and lethargic with circumoral cyanosis and diminished peripheral pulses. Which action should the nurse take next?

Rationale: A. Situate in knee-chest position: Placing the infant in a knee-chest position increases systemic vascular resistance, which helps reduce right-to-left shunting and improves pulmonary blood flow during a hypercyanotic (“Tet”) spell to improve oxygenation and prevent hypoxic injury. B. Perform chest physiotherapy: Chest physiotherapy is used to mobilize secretions in respiratory conditions but does not address the acute pathophysiology of a Tet spell. It would not rapidly improve oxygenation in this emergency. C. Reduce flow rate of intravenous fluid replacement: Reducing IV fluids may decrease venous return but does not relieve the hypoxic crisis caused by right-to-left shunting. This intervention is not indicated during a hypercyanotic episode. D. Administer prescribed morphine subcutaneously: Morphine can be used to calm the infant and reduce pulmonary resistance in some Tet spell protocols, but positioning the infant in a knee-chest posture is the first, immediate action to improve oxygenation before pharmacologic measures.