Persistent pulmonary hypertension of the newborn

Overview

Persistent pulmonary hypertension of the newborn (PPHN) is defined as the failure of the normal circulatory transition that occurs after birth. The ductus arteriosus remains open, and the baby's blood flow continues to bypass the lungs. Even though the baby is breathing, oxygen in the breathed air will not reach the bloodstream. Because the blood returning from the body is unable to enter the lungs properly - and instead flows through the still-open ductus arteriosus - it returns to the heart in an oxygen-poor state.

Sources: Medscape & Children's Hospital Colorado

Symptoms

The following signs and symptoms may indicate a baby has PPHN:

  • rapid breathing (also called tachypnea)
  • rapid heart rate
  • respiratory distress, including signs such as flaring nostrils and grunting
  • cyanosis (when the skin has a bluish tinge), even while the baby is receiving extra oxygen to breathe

Sometimes when examining a baby with PPHN, the doctor will hear a heart murmur (an extra or abnormal heart sound). With PPHN, a baby may also continue to have low oxygen levels in the blood while receiving 100% oxygen.

Source: Children's Hospital Colorado

Causes

In an otherwise healthy newborn, the cause of PPHN is usually unknown. Some researchers believe that 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 of developing PPHN.

PPHN may occur with certain diseases or congenital conditions of the infant that affect the lungs in some way. 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.

These conditions 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 PFC. These conditions are often temporary and reversible, with intensive care and time for the lungs and body to heal. Certain congenital conditions that result in immature or incomplete lung development (such as diaphragmatic hernia) may also be associated with PPHN.

Source: Children's Hospital Colorado

Prevention

Most cases of PPHN have no clear cause or are caused by uncontrollable events. For these cases there are no clear preventative steps. Some cases of PPHN may be prevented with proper prenatal care and good health of the mother during pregnancy. General tips for a healthy pregnancy include:

  • Get good prenatal care. Start as early as possible in pregnancy.
  • Eat a healthful diet. Take vitamins as suggested by your doctor.
  • Do not smoke. Avoid alcohol or drug use.
  • Only take medicines that your doctor has approved.

Source: NYU Langone Medical Center

Diagnosis

For any newborn having difficulty breathing and showing signs of poor oxygen delivery to the body's tissues, several tests will be performed to determine possible causes. Various imaging and laboratory tests can help determine if a baby has PPHN.

Imaging tests will be done to get a better look at the lungs, heart, and circulation, and to check for other possible causes of the baby's problems:

  • Chest X-rays can show whether the baby has lung disease and whether the heart is enlarged.
  • An ultrasound of the heart (an echocardiogram) can show whether the baby has heart or lung disease and can determine the direction of blood flow in those organs. This test is often very helpful in diagnosing PPHN because it will show the doctor the baby's circulating blood flow, including whether the ductus arteriosus is open or closed, and can determine if PFC exists.
  • An ultrasound of the head may be used to look for bleeding in the brain.

Laboratory tests can also assist doctors in making a diagnosis of PPHN:

  • An arterial blood gas (ABG) determines how much oxygen, carbon dioxide, and acid buildup are in the arterial blood. Arteries normally contain high levels of oxygen, and this test is the most accurate way to determine how well oxygen is being delivered to the body.
  • A complete blood count (CBC) measures the number of oxygen-carrying red blood cells, white blood cells (which help fight infection), and platelets (which are involved in blood clotting). A CBC usually shows if anemia or possible infection is causing the baby to be ill.
  • Serum electrolyte tests evaluate the balance of minerals in the blood.
  • A lumbar puncture (spinal tap) and other blood tests can help determine whether an infection is present.
  • Pulse oximetry, which measures oxygen levels in the blood, can help doctors monitor whether the baby's tissues are receiving an adequate amount of oxygen.

Source: Children's Hospital Colorado

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 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.

Source: Children's Hospital Colorado

Treatment

The first step in PPHN treatment is to maximize the amount of oxygen delivered to the baby's lungs (and, in turn, to the blood), so 100% oxygen will be given through a tube inserted directly into the baby's trachea (windpipe). The oxygen is administered by a mechanical ventilator, which does the work of breathing for the baby. This treatment is given in conjunction with other treatments for the illnesses that may have contributed to the initial development of PPHN (such as low blood sugar, pneumonia, or other infections).

If your child has PPHN caused by a lung problem, his breathing rate may be set at a higher than usual rate and pressure through the mechanical ventilator. This is known as high- frequency oscillatory ventilation (HFOU). This ventilation technique improves oxygen delivery to the lungs, reduces acid buildup in the blood, and often helps open up the blood vessels leading the lungs - thus allowing more blood to flow to the lungs. Because PPHN is worsened by narrowed lung blood vessels and raised acid levels in the body (a condition called acidosis), sodium bicarbonate may also be given with this form of ventilation to lower acid levels and help dilate blood vessels.

Recent research shows that supplying inhaled nitric oxide to babies with PPHN may also be successful. Nitric oxide has been shown to have a relaxing effect on contracted lung blood vessels, thus improving blood flow to the lungs in some babies with PPHN.

If other methods can't reverse the PPHN and raise the baby's oxygen levels to the necessary range, a type of intensive procedure called extracorporeal membrane oxygenation (ECMO) may be needed. ECMO requires major surgery, is complicated to monitor, and has potentially serious side effects associated with it. It is reserved for the sickest babies who are not responding to other forms of treatment.

The ECMO machine acts as an artificial heart and lung for the baby for several days while the baby's lungs heal and recover. Although ECMO is very successful in treating PPHN, fewer than 100 hospitals (mostly children's hospitals) in the United States have facilities that can provide this treatment.

Source: Children's Hospital Colorado