Question

A 10-day-old male infant weighing 950 g was scheduled for ligation of patent ductus arteriosus (PDA). He was born at 29 weeks gestation and was intubated immediately after delivery because of respiratory distress. His condition improved over the following 4 days. However, on the fifth day of his life the respiratory distress worsened and a murmur was heard over his chest. Medical treatment for PDA was attempted unsuccessfully. His blood pressure was 60/40 mm Hg, heart rate 150 beats/minute. The laboratory data were as follows: white blood cells (WBCs), 17,000/?L; hemoglobin, 11 g/dL; hematocrit, 34%; urine specific gravity, 1.005; protein 1+; sugar 1+; serum calcium 6.0 mg/dL; blood glucose, 60 mg/dL; and arterial blood gases: pH, 7.30; PaCO2, 45 mm Hg, PaO2, 60 mm Hg on FIO2 50%; inspiratory pressure, 30/4 cm H2O; and ventilation rate, 25 breaths/minute.

1. How would you classify prematurity? What are the common problems associated with prematurity?Discuss the incidence and pathophysiology of patent ductus arteriosus (PDA) in preterm infants.

2. How would you make a diagnosis of PDA? Describe its treatment.

3. How does indomethacin close the ductus? What are the adverse effects of indomethacin

Answer 1

Prematurity in children
Premature babies are born before 37 completed weeks of gestation. They are also known as immature, preterm and born early.
They are highly vulnerable to different types of physiological handicapped conditions with high mortality rate because of their anatomical and functional immaturity.

Classification of preterm babies:
- Extremely preterm ( <28 weeks of gestation)
- Very preterm (24-30 weeks of gestation)
-Moderate to late preterm (32- <37 weeks of gestation)

So,it is clear that the given child in the question belongs to very preterm.

COMMON PROBLEMS
Various problems are found in premature babies due to their functional immaturity.

1 - Alteration of respiratory functions.
Respiration:rapid,shallow irregular with periods of apnea and cyanosis.
Breathing:diaphragmatic,periodic,and with intercostal recessions due to soft ribs.
Pulmonary agitation
Atelectasis
Hyaline membrane disease
Poor development and expansion of lungs etc.

2 - Immaturity of CNS.
Inactive,lethargic,poor cough reflex,feeding difficulties,oxygen toxicity causes retinopathy of prematurity etc.

3 - Disturbances of circulatory functions.
Delayed closure of patent ductus arteriosus,Inadequate peripheral circulation,thromboembolic complications, intracranial hemorrhage etc.

4 - Impaired thermoregulation.
Hypothermia,large body surface area related to body weight etc.

5 - Inefficient gastrointestinal and hepatic functions.
Poor Sucking and swallowing reflex,less stomach capacity,aspiration,abdominal distension etc.

They are at high risk for developing many more problems.

PATENT DUCTUS ARTERIOSUS

PDA is the persistent vascular connection between the pulmonary artery and the aorta.
Normally, it is closed soon after birth.
It is common in preterm babies who weigh less than 1.5kg.

Incidence:
Common in female baby and occurs approximately 11% of all congenital heart diseases.

Pathophysiology:
There is left to right shunt as blood flows from aorta to pulmonary artery in PDA. It leads to pulmonary overload.
Thus oxygenated blood of systemic circulation flows back to pulmonary circulation resulting in high vascular pressure in pulmonary tree and volume load on left heart.

How to make diagnosis?
-History and physical examination
-Auscultation of heart sound reveals machinery murmur or continuous murmur at second left intercostal space or below the left clavicle.
-Paradoxical splitting of P_2.
-Chest x-ray shows cardiomegaly and pulmonary vascular marking.
- ECG reveals left arterial dilation and left ventricular hypertrophy.

Treatment
Medical management:
-Indomethacin
-Anti prostaglandin agents
-Aspirin
-Ibuprofen
-Mefenamic acid
Supportive care:
-Rest
-Adequate intake of calorie
-promotion of normal growth and development
-Emotional support
Surgical management:
-Transection or ligation of PDA

INDOMETHACIN
Pharmacotherapeutic class: NSAID
Action: Antiinflammatory,Analgesic
It is used for closure of ductus arteriosus of premature infants weighing between 500g and 1750 g when 24 hour medical treatment is ineffective.

Action in children with PDA;
Prostaglandins are the group of lipids that keep the ductus arteriosus open by the help of certain receptors.
Normally after birth ,the levels of prostaglandin and receptors decreases significantly and results in closure of ductus arteriosus and establishes the normal circulation in baby.

Prostaglandin synthesis is inhibited by Indomethacin and cause constriction of ductus arteriosus. It is effective if it is administered in first 10 -14 days after birth.

Dose;
Route : IV
Initially 0.3mg/kg. Subsequent doses are based on age.
Neonates older than 7 days - 0.25 mg/kg of second and third doses.
Neonates 2-7 days - 0.2 mg/kg for second and third doses.
Neonates < 48 hours - 0.1 mg/kg for the same.

Adverse effects:
Metabolic acidosis/alkalosis,Bradycardia
These problems occur rarely.

Side effects:
Bleeding abnormalities,rarely hypertension, confusion, urticaria, pruritis, rash,blurred vision etc.

Note: Only the pediatric details about Indomethacin are given here. It acts differently in adults.