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Patent Ductus Arteriosus (PDA) in the newborn

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Incidence

PDA is a problem in ventilated very low birth weight infants. About 40% of these will have a large PDA at 3 days of age.

Diagnosis

  • Early: Mostly silent, with no murmur. BP may be low (systolic, diastolic and mean) with normal pulse pressure.
  • Late: Murmur. Hyperactive precordium.
  • Increased pulses. Wide pulse pressure. These are not reliable signs in the first few days.
  • Congestive Heart Failure
    -  Cardiomegaly
    -  Hepatomegaly
    -  Pulmonary congestion/oedema/plethora
  • Clinical respiratory deterioration.
  • Rising PaCO2.

Usually diagnosed late. Most babies treated before this stage.

Investigations

Echocardiogram

Chest x-ray

CXR

To look at heart size and lung fields.

Electrocardiogram (ECG)

The ECG is usually normal. It is rarely done in preterm infants.

Management

Indications for treatment


<28 weeks or <1000gms, and on IPPV or CPAP

Significant shunt in a small baby with ongoing lung disease.
Closure of the ductus is aimed mainly at improving lung function.

Echocardiogram at 3 days. If
Significant PDA: Consider indomethacin

 Other babies on IPPV  Investigate if clinical suspicion.
 Indomethacin See drug protocol 
Monitor creatinine, electrolytes, urine output and platelets before and at least daily initially. If these parameters remain normal, then they do not need to be routinely checked after the 3rd dose.
Review baby and results before each dose.
Contraindications:
Thrombocytopenia
NEC
Bleeding diathesis
Poor renal function
Pulmonary haemorrhage (note: may occur because there is a PDA)
Fluid restriction  While on indomethacin, reduce by 20-40ml/kg/day.
There is no evidence that fluid restriction per se results in closure of the duct but there are studies suggesting that early, liberal fluid intakes are associated with a higher incidence of PDA. 
Surgery If PDA is still clinically significant after indomethacin, or if indomethacin is contraindicated.
Surgery will usually be performed on NICU (see Surgical Closure of PDA below).
Note that a increase in respiratory support is often required immediately after surgery. 

Surgical Closure of PDA

Pre-operative process and referral

The decision regarding the need for PDA ligation is to be made by the Neonatology team. The Neonatologist will speak with the family to explain the reason for the PDA and the process involved.

With permission of the Neonatologist, the following documents must be completed/obtained:

The above documents are to be faxed to the Cardiac surgical scheduler on 23636

The Cardiac surgical team will discuss the request for ligation with the surgeon at the earliest convenience and the surgeon will liaise with the neonatologist who is listed on the booking form.

Surgeon will obtain consent for surgery from the family after the neonatologist has spoken with them.

If you have any questions about this process, please speak with one of the following:

Cardiac scheduler, on 23619
Ana Kennedy, Nurse Practitioner, on 021332861
Marion Hamer, Nurse Practitioner, on 021983986

Preparation of Equipment/Consent Forms

  • Ensure parents are kept informed by Cardiac Team/Paediatrician prior to surgery.
  • Check Consent form has been completed for surgery and the administration of blood and blood products. Anaesthetic consent completed just prior to surgery.
  • Check pre op blood results are available and blood is available for transfusion.
  • Anaesthetist may require 4% albumin and/or packed RBC to be available on the unit (Dr/NS-ANP to confirm).

Equipment required for surgery is prepared:

  • Radiant heat table (must be away from the wall).
  • Diathermy pad, machine and cable (brought by theatre staff)
  • Trolley and large sterile trolley covers (brought by theatre staff).
  • Suture material (brought by theatre staff).
  • Theatre hats.
  • Separate suction bottle connected to wall suction (for Surgeon to use) [the Scrub Nurse brings packs and instruments from Starship Hospital].
  • Alcohol Povodine-Iodine solution

Equipment required by the Anaesthetist is prepared:

  • Check resuscitation trolley.
  • Ensure Neopuff and mask are working and easily accessible on heat table (the baby is usually kept on the ventilator during surgery).
  • Check the following drugs are available in the room:
    Neostigmine 0.08mg/kg (reversal for Pancuronium).
    Adrenaline 1:10,000
    Atropine 0.01mg/kg
    Fentanyl
    0.9% NaCl
    Sodium bicarbonate

Preparation of baby

  1. Place baby on heat table (away from the wall).
  2. Continuous monitoring (recorded hourly):
    - cardiorespiratory
    - SpO2
    - blood pressure or Dinamap
    - skin temperature
  3. Ventilation as per orders. Suction ET tube immediately prior to surgery.
  4. IV fluids as prescribed.
  5. Baby is kept nil by mouth for 4 hours prior to surgery.
  6. Ensure preoperative preparation check list has been completed.
  7. Ensure two identification labels are on baby.
  8. Ensure there is no metal touching the baby, e.g. metal splint.
  9. Aspirate gastric tube (immediately pre-op).
  10. Place the baby on right side.
  11. Keep left chest clear (left chest electrode may be placed on left groin).
  12. Close room to visitors/parents while procedure in progress (takes approximately 1 hour). Place notice on door re room closed, also ensure masks are available outside door.

Postoperative care

  1. Ensure continuous monitoring is maintained and recorded hourly.
  2. Maintain ventilation as per orders.
  3. Keep baby nil by mouth until further orders.
  4. IV fluids as prescribed.
  5. Observe wound site for bleeding.
  6. Comfel dressing to be left insitu for one week (or as per surgeon's order).
  7. Pain relief as prescribed.
  8. 6 hourly urine output totals - urinalysis every nappy change.
  9. Keep parents informed of baby's condition.
  10. Pleural drain insitu - remove on surgeon's orders.

Usual follow-up

  • Drain to be removed the day after surgery if no drainage or bubbling.
  • Dressing / Glue will peel off
  • A variety of sutures are used for closure and are usually dissolvable. If there are knots to be trimmed this is done at 14 days. Call the surgical fellow or nurse assist on 021380548 for any queries.
  • Diuretics for one week post-op and then stop (unless otherwise indicated for non-cardiac reasons)
  • Follow up with Paediatrician in 1 month, no need for cardiology follow up unless there is a new issue

Echocardiography images

Echocardiography is the best way to determine:

  • the presence of a duct
  • the size of the duct
  • the haemodynamic significance of a duct

In practice, there are several things to evaluate:

The presence and size of the duct

The presence of a duct can best be determined by the demonstration of flow between aorta and main pulmonary artery (MPA), and by a pattern of disturbed diastolic flow in the MPA.

The duct is most easily seen in the parasternal short axis and the so-called "ductal" views. Absolute quantification of its diameter is the best way to determine its presence or absence. In general, the duct is measured at its narrowest point. The duct is most easily seen with colour Doppler and this is the mode in which the measurement is taken, although it tends to overestimate ductal diameter.

Sometimes, the views are difficult - even with colour. In this case, placing a Doppler probe on the main pulmonary artery helps. If there is a duct with a significant left-to-right shunt, there will be disturbance of diastolic flow in the main pulmonary artery. This is often useful to exclude a significant duct, rather than quantify the size of any shunt.

Ductal size also helps to evaluate haemodynamic significance. As diameter increases, so too does the amount of flow that occurs. In general, ducts more than 2mm in diameter on colour Doppler are haemodynamically significant.

The Size of the Left Atrium

Left atrial (LA) enlargement signifies increased pulmonary venous return because of left-to-right ductal shunting. The reference measure is the ratio of the LA to aorta at the level of the aortic valve (the LA:Ao ratio). The aortic does not enlarge with even extremely large PDAs so it is a useful measurement that allows for different sized babies. In general, a LA:Ao ratio >1.4:1 indicates a moderate shunt but is dependent on the operator and views. NWH experience suggests that the ratio needs to be greater than 2:1 to support the finding of a significant shunt.

PDLAaoratio

Left Ventricular Size

This will enlarge as cardiac output increases with both increased pulmonary venous return and with increased diastolic run-off from the systemic circulation. There are subjective measures of this (the "paired eyeball test", the presence of mitral regurgitation as the mitral valve ring dilates) and objective measurements (the left-ventricular end-diastolic dimension (LVEDD) :Ao ratio).

Descending Aortic Flow in Diastole

The presence of a significant ductal shunt results in diastolic run-off to the pulmonary circulation. This will result in flow that is retrograde in the descending thoracic aorta beyond the duct during diastole. In practice, this can be a difficult view to obtain.

PDA reversed flow

Left Pulmonary Artery Diastolic Flow Velocity

This is higher with large left-to-right shunts. Values less than 15cm/sec are seen when the duct is closed. Values greater than 40cm/sec are seen in babies with (so-called) symptomatic PDAs.

Flow in Other Organ Blood Vessels

Reversed renal flow

Disturbed flow patterns may be seen in brain, kidney, and gut vessels as an effect of a significant duct.

Summary

None of these measures stands alone in determining which ducts require treatment. Other factors that influence the decision include

  • the gestational age and size of the baby
  • the postnatal age of the baby
  • the requirement for respiratory or cardiovascular support
  • symptoms attributable to a duct (e.g. hypotension, pulmonary haemorrhage, congestive heart failure, poor growth, ...)

References

  1. Knight DB. The treatment of patent ductus arteriosus in preterm infants. A review and overview of randomized trials. Seminars in Neonatology. 2001; 6: 63-73.
  2. Cooke L, Steer P, Woodgate P. Indomethacin for asymptomatic patent ductus arteriosus in preterm infants. Cochrane Database of Systematic Reviews 2003, Issue 1.
  3. Herrera C, Holberton J, Davis P. Prolonged versus short course of indomethacin for the treatment of patent ductus arteriosus in preterm infants. Cochrane Database of Systematic Reviews 2001, Issue 4.
  4. Brooks JM, Travadi JN et al. Is surgical ligation of patent ductus Arteriosus necessary? The Western Australian experience of conservative management. Arch Dis Childh. 2005; 90: F235-F239.
  5. Evans N. Current controversies in the diagnosis and treatment of patent ductus arteriosus in preterm infants. Advances in Neonatal Care. 2003; 3: 168-177.
  6. Groves AM, Kuschel CA, Skinner JR. The neonatologist as an echocardiographer. NeoReviews 2006;7:e391-9.
  7. Skinner J. Diagnosis of patent ductus arteriosus. Seminars in Neonatology 2001;6:49-61.
  8. Suzumura H, Nitta A et al. Diastolic velocity of the left pulmonary artery of patent ductus arteriosus in preterm infants. Pediatrics International 2001;43:146-51.
  9. Knight DB. Yu VY. Contrast echocardiographic assessment of the neonatal ductus arteriosus. Arch Dis Child 1986;61:484-8.

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Document Control

  • Date last published: 01 September 2011
  • Document type: Clinical Guideline
  • Services responsible: Neonatology
  • Owner: Newborn Services Clinical Practice Committee
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years