Persistent Pulmonary Hypertension of the Newborn (PPHN)

Persistent pulmonary hypertension of the newborn (PPHN) occurs when a newborn’s circulation system does not adapt to breathing outside the womb.

While a fetus is in the womb, it gets its oxygen from its mother’s placenta through the umbilical cords, so the lungs need little blood supply. There is high blood pressure in the lungs, so blood in the pulmonary artery is sent away from the lungs to the other organs through a fetal blood vessel, called the ductus arteriosus.

When a baby is born and takes its first breaths, the blood pressure in their lungs falls and there is an increased blood flow to the lungs, where oxygen and carbon dioxide are exchanged. The blood is then returned to the heart and pumped back out to the body. The ductus arteriosus constricts and permanently closes in the first days of life. However, in babies with PPHN, the pressure in the lungs remains high and the ductus arterious remains open, allowing blood to be directed away from the lungs.

Persistent pulmonary hypertension of the newborn is a cardiopulmonary disorder characterized by systemic arterial hypoxemia secondary to elevated pulmonary vascular resistance with resultant shunting of pulmonary blood flow to the systemic circulation. This pathophysiologic syndrome has been variously described as:

Persistent pulmonary vascular obstruction
Persistent fetal circulation
Pulmonary vasospasm
Neonatal pulmonary ischemia
Persistent transitional circulation

This disorder can be classified into three forms dependent on the likely etiology of the pulmonary hypertension:

PPHN associated with pulmonary parenchymal disease, such as hyaline membrane disease, meconium aspiration, or transient tachypnea of the newborn as the cause of alveolar hypoxia, known as secondary PPHN or appropriate PPHN
PPHN with radiographically normal lungs and no evidence of parenchymal disease, frequently called Persistent Fetal Circulation (PFC), or primary or inappropriate PPHN
PPHN associated with hypoplasia of the lungs, most often in the form of diaphragmatic hernia

What Causes PPHN?

In an otherwise healthy newborn, the cause of PPHN is often unknown. However, the following are believed to be possible causes of PPHN.

Stress while the baby is in the uterus (associated with certain pregnancy complications, such as maternal diabetes, high blood pressure or anemia, or delivery after 40 weeks) may increase the risk.
Meconium aspiration syndrome, anemia, severe pneumonia, infection, hypoglycemia (low blood sugar), and birth asphyxia (when the baby is deprived of oxygen during a complicated delivery) have all been associated with PPHN.
SSRIs or selective serotonin reuptake inhibitors antidepressants such as citalopram, fluoxetine, paroxetine and sertraline sold under 19 brand names, including Celexa, Prozac, Paxil and Zoloft. Normally, the lung disorder is rare, with one to two per 1,000 births. But when pregnant women took the drugs in question after the 20th week of pregnancy, the incidence rose to six to 12 per 1,000 births.

These conditions or antidepressants may cause the pressure in the blood vessels leading to the lungs to increase to the point where the baby’s blood continues to bypass the lungs after birth, resulting in PPHN. These conditions are often temporary and reversible, with intensive care and time for the lungs and body to heal.

PPHN is a rare, but life-threatening condition. It occurs most often in full-term or post-term babies who have had a difficult birth, or conditions such as infection or birth asphyxia, in which a baby receives an inadequate amount of oxygen during delivery.

Signs and Symptoms

The following signs and symptoms may indicate that a baby has persistent pulmonary hypertension of the newborn (PPHN):

Rapid breathing, also called tachypnea;
Rapid heart rate;
Respiratory distress, including signs such as flaring nostrils and grunting;
Cyanosis, a condition in which the baby’s skin has a bluish tint, even while they are receiving extra oxygen to breathe;
Heart murmur, where a baby has an extra or abnormal heart sound;
Low oxygen levels — a baby with PPHN may continue to have low oxygen levels in their blood, even while receiving 100 percent oxygen.

Treatment

The main goal of treatment for persistent pulmonary hypertension of the newborn (PPHN) is to increase oxygen levels to the baby’s organs to avoid serious health problems. Treatment may include a wide range of mechanical ventilation and respiratory therapy options, including high frequency oscillatory ventilation and inhaled nitric oxide.

Oxygen — 100 percent supplemental oxygen may be given to your baby through a mask or plastic hood.
Assisted Ventilation — During this procedure, a tube is inserted into your baby’s windpipe and a ventilator takes over your baby’s breathing and oxygen is given.
Nitric Oxide — Research has shown that this gas is effective in treating PPHN because it relaxes contracted lung blood vessels and improves blood flow to the lungs. It is given through the ventilator.
High Frequency Oscillatory Ventilation — This type of ventilation may improve the oxygen level in the blood if other types of ventilation are not effective.
Extracorporeal Membrane Oxygenation — In addition, an extracorporeal membrane oxygenation (ECMO) machine may be used for patients who are experiencing serious heart or lung failure. It delivers oxygen to the brain and body as temporary support while the PPHN resolves. ECMO is similar to a heart-lung bypass machine, which takes over your baby’s heart and lung functions with an external pump and oxygenator. Blood is drained from the patient to an artificial lung, where oxygen is added and carbon dioxide is removed, and then the blood is pumped back into your child.

Complications and Prognosis

PPHN is a serious condition and intensive monitoring and treatment are critical. Even with prompt recognition and treatment, an infant with PPHN may continue to supply an inadequate amount of oxygen to the body’s tissues, resulting in shock, heart failure, brain hemorrhage, seizures, kidney failure, multiple organ damage, and possibly even death.

Some causes of PPHN are treatable and reversible; others are associated with a poor survival rate, even if nitric oxide and Extracorporeal Membrane Oxygenation (ECMO) are used. In some newborns with PPHN, the lungs are too diseased or malformed to heal adequately, even if the baby stays on ECMO for a longer period of time.

Periods of inadequate oxygenation can have long-term effects on infants who survive PPHN, such as bronchopulmonary dysplasia (a chronic lung disease associated with scarred, stiffened lungs) and breathing difficulties. Seizure disorders, developmental delay, and neurological deficits may also be seen.

For several weeks following treatment, infants who’ve had PPHN may not be able to take feedings by mouth. A temporary feeding tube may have to be inserted into the baby’s nose, or for longer-term feeding problems, directly into the stomach through the skin on the abdomen. Feeding tubes will be needed if the baby cannot eat enough to meet his nutritional requirements for growth.

Hearing problems are another common condition associated with PPHN. If your child had PPHN, he will probably need to be evaluated by a hearing specialist during early childhood to check for hearing loss, and the development of his speech will also need to be followed closely.

Medical treatments such as high frequency ventilation, nitric oxide, and ECMO have significantly decreased the percentage of children who die from PPHN. Fifteen years ago, almost half of infants diagnosed with PPHN died; today, less than 20% of infants with PPHN die, and only about one fifth of surviving infants experience long-term physical or developmental complications.

Persistent pulmonary hypertension (PPHN) is also referred to as persistent fetal circulation. In this condition, a newborn baby’s circulation changes back to the circulation of a fetus, where much of the blood flow bypasses the lungs. Generally, one to two newborns per 1,000 suffer from persistent pulmonary hypertension. These infants have pulmonary arterial pressure that is too high at birth. As a result, their lungs can’t provide enough oxygen, which causes their bodies to produce oxygen-poor blood, sometimes resulting in death. In one study, nearly half the survivors were cognitively delayed, had major neurological problems, and could not hear.

Source: Persistent-Pulmonary-Hypertension-Newborn.com and Washington.edu