Preterm baby with PDA, which is the least likely findings?

Ans. is 'a' i.e., CO2 washout PDA in preterm neonate o In previous explanations I have explained that chances of spontaneous closure of PDA are higher in premature infants as there is no structural abnormality. However, you should keep in mind that this fact is true when we are comparing the spontaneous closure of PDA between term and pre-term neonate. Overall, the percentage of spontaneous closure of PDA in preterm neonate is very low. To avoid confusion, I am explaining following facts in brief:? 1) Normal neonate :- Ductus aeriosus closes functionally within about 15 hours of bih. 2) PDA in term (mature) neonate :- The persistence of ductus aeriosus beyond 24 hours after bih is considered as PDA in term neonate. Spontaneous closure of PDA does not usually occur because PDA results from structural abnormality. 3) PDA in pre-term (pre-mature) neonate :- The ductus aeriosus in pre-term neonate is not as responsive to increased oxygen content as it is in term neonate. However, there is no structural abnormality. i) Chances of spontaneous closure are very less (compared to normal term neonate). ii)Chances of spontaneous closure are more than the term-neonate with PDA. However, in premature neonate, where hypoxic pulmonary disease is commonplace, the ductus being sensitive to hypoxia, remains open. o So, it is very unlikely that spontaneous closure of PDA will occur in pre-term neonate. But chances are more when compared to term neonate with PDA (not normal term neonate in which ductus aeriosus closes within 15 hours of bih). Manifestations of PDA in pre-term neonate 1) Apnea for unexplained reasons in an infant recovering from RDS; 2) A hyperdynamic precordium, bounding peripheral pulses, wide pulse pressure, and a continuous or systolic murmur with or without extension into diastole or an apical diastolic murmur, multiple clicks resembling the shaking of dice; 3) Carbon dioxide retention; 4) Increasing oxygen dependence; 5) X-ray evidence of cardiomegaly and increased pulmonary vascular markings; and 6) Hepatomegaly o Increased pulmonary blood flow and compromised ventricular function accompanying dropping pulmonary resistance in the setting of a PDA is a significant risk factor for pulmonary hemorrhage. o The greatest risk factor for NEC is prematurity. Any etiology which leads on to hemodynamic or hypoxic insult predisposes to NEC. PDA is common in preterm infants and it definitely causes hemodynamic stress and is a risk factor for development of NEC.