Persistent Pulmonary Hypertension of the Newborn - Causes and Treatment

Introduction

Persistent pulmonary hypertension of the newborn (PPHN) is a dangerous pulmonary disorder that causes oxygen deficiency in newborn babies. It occurs at a rate of 1 in 500 live births. Inside the womb, the fetus receives oxygen and nutrients from the mother through the placenta. Thus until birth, the blood vessels in the baby's lungs (pulmonary vessels) are almost closed. However, after the baby is born, the pulmonary blood vessels are opened when the newborn takes its first breath. This is because the blood must go through the baby's lungs to get enough oxygen for the normal functioning of body cells. In persistent pulmonary hypertension of the newborn (PPHN), the pulmonary blood vessels do not open fully, resulting in restricted blood flow and reduced oxygen levels in the body, causing severe complications.

What Is Persistent Pulmonary Hypertension of the Newborn?

Persistent pulmonary hypertension (PPH) occurs due to persistent fetal circulation in newborns. It occurs due to the newborn's inability to convert to pulmonary and systemic circulation from fetal circulation. Persistent pulmonary hypertension of the newborn is a serious breathing problem that usually occurs in babies born at 34 weeks of gestation or more (full-term babies). Around 10 to 50 percent of babies born with persistent pulmonary hypertension may die due to associated complications. About 7 to 20 percent develop long-term complications such as chronic lung disease, hearing deficit, and intracranial bleeding.

What Are the Causes of Persistent Pulmonary Hypertension in the Newborns?

The exact cause of the incidence of persistent pulmonary hypertension in newborns is not yet known. The failure of lung vessels to open entirely after childbirth causes back pressure and forces the heart to use pre-birth or fetal circulation pathways. Since the fetus relies on the placenta for oxygen inside the womb, there is a high pulmonary vascular resistance (PVR) and low pulmonary blood flow. However, babies need pulmonary circulation for oxygen transfer and normal functioning when babies are born. Low pulmonary vascular resistance and high blood flow are established. The failure of the newborn baby's circulatory system to adapt to these changes by reducing pulmonary vascular resistance leads to persistent fetal circulation. Thus the newborn may have elevated pulmonary vascular resistance leading to pulmonary hypertension and other health effects. Various conditions may cause the inability of the newborn baby to adapt to new changes.

They are:

• Functional obstruction of pulmonary blood flow.

• Normal vascular anatomy with functional vasoconstriction.

• Decreased size of the pulmonary vascular bed.

• Decreased diameter of pulmonary vessels with hypertrophy of vessel walls.

What Are the Symptoms of Persistent Pulmonary Hypertension in the Newborn?

• Fast breathing.

• Low blood pressure.

• Breathing problems.

• Blue color around the mouth and the lips (cyanosis).

• Low oxygen levels in the blood.

• Moaning or grunting during breathing.

• Rapid heart rate.

• Abnormal heart sounds.

• Cold extremities.

What Are the Risk Factors for Persistent Pulmonary Hypertension in the Newborns?

Certain factors can increase the risk of developing persistent pulmonary hypertension in the newborn (PPHN).

They include:

• Severe infections.

• Lack of oxygen during birth.

• Aspiration of meconium (sticky poop) by the baby.

• Respiratory distress syndrome (RDS).

• Oxygen deficiency before childbirth.

• Lung infections.

• Diabetes mellitus in the mother.

• Heart abnormalities.

• Lung diseases.

• Diaphragmatic hernia.

How To Diagnose Persistent Pulmonary Hypertension of the Newborn?

Persistent pulmonary hypertension of the newborn (PPHN) can be diagnosed using various laboratory and imaging tests.

It includes:

• Pulse oximetry to evaluate the blood oxygen levels and monitor whether the newborn baby's tissues are getting enough oxygen.

• Chest X-rays to identify lung diseases or enlarged heart.

• Ultrasound imaging of the head to evaluate brain bleeding.

• Complete blood count (CBC) to measure the white blood cell count, red blood cells that carry oxygen, and platelets.

• Spinal tap or lumbar puncture and blood tests to rule out infections.

• Serum electrolyte test to measure minerals in the blood.

• Echocardiogram (ultrasound of the heart) to identify heart or lung diseases and evaluate blood flow.

• Arterial blood gas (ABG) is used to evaluate oxygen delivery in the baby's tissues.

What Are the Treatment Options for Persistent Pulmonary Hypertension in the Newborns?

The main goal of treatment for persistent pulmonary hypertension in the newborn is to increase the oxygen flow to the newborn baby's organs, maintain normal blood pressure, and open the lung blood vessels, thus preventing severe complications. It can be achieved using specific medications, oxygen supply, and fluids. Treatment options consist of respiratory therapy and mechanical ventilation. It includes:

• Oxygen - Supplemental oxygen (100 percent) can be given to the baby through a plastic hood or a mask to improve the oxygen levels in the body.

• Mechanical Ventilation - This machine will help the baby to breathe until a normal respiratory mechanism is achieved. A tube is inserted into the baby's windpipe, and the mechanical ventilator takes over the breathing process.

• Nitric Oxide Inhalation - It helps to relax the contracted blood vessels in the lungs and thus improves blood flow to the lungs. Nitric oxide inhalation is the most preferred medication used for persistent pulmonary hypertension in newborns due to its ability to cause selective pulmonary vasodilation compared to other vasodilator agents.

• High-Frequency Oscillatory Ventilation - This type of mechanical ventilation is used in individuals where other types of ventilation are ineffective.

• Extracorporeal Membrane Oxygenation (ECMO) - This technique is used in newborns with severe lung or heart failure.

• Other Medications - Drugs such as antibiotics, surfactants, antihypertensives, and glucocorticoids are also used in treating persistent pulmonary hypertension in newborns.

Conclusion

Persistent pulmonary hypertension of the newborn (PPHN) occurs when the newborn fails to adapt to normal breathing outside the womb and thus establishes normal circulation. Inside the mother's womb, the fetus gets oxygen and nutrients from the placenta; hence, the blood vessels in the lungs are almost closed. However, after childbirth, the pulmonary blood vessels are opened to adapt to normal circulation and breathing. But in babies with persistent pulmonary hypertension, the circulatory system fails to adapt to the new changes, leading to persistent fetal circulation and pulmonary hypertension.