1. PATENT DUCTUS ARTERIOSUS By: Nicole Stevens

2. Patent Ductus Arteriosus is a functional connection between the pulmonary artery and the descending aorta. In the fetus the DA allows blood to be diverted away from the pulmonary artery (the high resistance pulmonary circulation) to the descending aorta (the low resistance systemic circulation) The duct remains open due to the prostaglandin supply coming from the placenta. The DA protects the lungs from circulatory overload.

3. After the birth the baby’s lungs expand as they begin to take breaths. Pulmonary resistance decreases and the oxygen levels in the blood rise causing the DA to constrict. Sometimes the DA doesn’t constrict and the baby is left with a PDA. This can be due to lack of oxygen or an increase in the amounts of prostaglandin. Sometimes the PDA will functionally close but will reopen in response to certain stimuli such as hypercarbia, acidosis, infection, hypoxia and cold

4. It is approximately 10mm in diameter Functional closure occurs between 12 hours and 4 days of age in healthy term babies Structural closure takes between 2 to 6 weeks

5. It is common in premature infants Serious concern as the pulmonary artery is not getting enough blood for the lungs to function effectively It can cause worsening RDS and an escalation in the respiratory support that is required Diagnosed on ECHO Treated with Indomethacin and sometimes may require surgical closure (called a PDA ligation)

6. PDA in the preterm infant:  There is nothing wrong with the heart, the PDA just doesn’t close and usually causes a left to right shunt  The tissue is immature; the fetal haemoglobin has a higher affinity for oxygen (doesn’t release it as easily)  The lower the gestational age the greater the risk of PDA  VLBW infants will have up to 50 – 60% chance of a PDA  The immature ductal tissue is much less reactive to oxygen, therefore less likely to readily close in response to the increase in partial pressure of oxygen that occurs after birth

7. PDA in the term infant:  If there is pulmonary hypertension (numerous causes for this, eg. meconium aspiration, infection) the blood shunts right to left through the PDA  Deoxygenated blood that should be going to the lungs goes back to the body, this causes hypoxia and acidosis, which causes vascular smooth muscle to constrict, and the end result can be persistent fetal circulation (without the presence of placenta for oxygenation)

8.  When trying to determine if shunting of blood is occuring across a PDA you may be asked to measure pre and post ductal oxygen saturations  Pre ductal SaO2 are measured on the right hand/wrist, and post ductal SaO2 can be measured on any of the other limbs, usually a difference of 10% or more is considered significant and may be caused by shunting of blood across a PDA  The arteries that supply part of the brain, and right arm, branch off the aorta prior to where the duct joins it, and the arteries that supply the other limbs branch off after the point where the PDA joins the aorta – hence, the reason we can measure pre and post ductal SaO2 at these points.

9. Pulmonary oedema Poor perfusion Bounding pulses Swinging saturations Desaturations Renal compromise Heart murmur Congestive cardiac failure Mottled or pale

10. If a neonate is symptomatic of an existing PDA they may require treatment  Chemical treatment: Indomethacin (usually given IV but oral route can be used, although thought to be not as effective) (Note: there is currently a world-wide shortage of indomethacin as its production has stopped, in the near future an alternate drug may be used)  If chemical treatment fails surgical treatment may be used: PDA ligation

11. First line treatment Urea & Creatinine are checked before commencing Indomethacin to ensure normal renal function before commencement of the drug. Platelets are also checked to ensure normal range 3 daily doses of 200mcg/kg at 2200hrs Side Effects include impairment of renal function, reduce platelet aggregation, GI tract bleeding, hypoglycaemia, hyponatreamia, hyperkaleamia and can mask infection.

12. Monitor urine output Daily Urinalysis BP monitoring Observe for bleeding and or NEC Contraindicated in infants with recent IVH and NEC

13. Some cardiac abnormalities are considered “duct-dependent”; these can be cyanotic or acyanotic Duct-dependent defects can be related to pulmonary flow (for example pulmonary stenosis or pulmonary atresia); or related to systemic flow (for example hyperplastic left heart or transposition of the greater arteries) If there is a definite or suspected diagnosis of a cardiac abnormality, that is duct dependent, a prostaglandin infusion is the treatment of choice (a synthetic version of the hormone that keeps it open inutero); the use of prostaglandin before further investigations and/or surgery has improved the mortality and morbidity outcomes for these neonates