Congenital heart defects are classified by which of the following? Select all that apply.

A. Chronic hypoxemia – This is more typical in cyanotic congenital heart defects but is not a hallmark of PDA.

B. Cyanosis with crying – PDA is an acyanotic defect, meaning it does not typically cause cyanosis.

C. Weak pulses – PDA results in bounding pulses, not weak pulses, due to increased systolic pressure.

D. Systolic murmur – A large patent ductus arteriosus (PDA) allows blood to flow abnormally from the aorta to the pulmonary artery, creating a continuous "machine-like" systolic murmur due to turbulent blood flow.

A. The knee-chest position increases systemic vascular resistance, which decreases the right-to-left shunting of blood. This improves pulmonary blood flow and oxygenation, helping to relieve the cyanotic episode.

B. Morphine helps by reducing pulmonary vascular resistance and decreasing the workload of the heart. It also has a sedative effect, reducing agitation and oxygen demand.

C. Although hemoglobin levels are important in assessing chronic cyanosis, drawing blood during a tet spell does not provide immediate relief. The priority is to reduce hypoxia rather than perform diagnostic tests.

D. Benadryl (diphenhydramine) is an antihistamine used for allergic reactions but does not help manage a hypercyanotic episode in Tetralogy of Fallot. It does not affect blood flow or oxygenation.

E. Oxygen is beneficial in a tet spell as it helps reduce pulmonary vascular resistance. However, it is not the most effective intervention alone; it must be combined with positioning and medications.