Persistent Pulmonary Hypertension
Persistent pulmonary hypertension is a serious disorder in which the arteries to the lungs remain narrowed (constricted) after delivery, thus limiting the amount of blood flow to the lungs and therefore the amount of oxygen in the bloodstream.
This disorder is caused by severe respiratory distress in term or postterm newborns or by certain drugs taken by the mother before delivery.
Breathing is rapid, and the skin is bluish.
The diagnosis is confirmed by an echocardiogram.
Treatment involves opening (dilating) the arteries to the lungs by giving oxygen, often while supporting the newborn’s breathing with a ventilator.
To help dilate the arteries in the lungs, sometimes nitric oxide is added to the gas that the newborn is breathing.
Extracorporeal membrane oxygenation is sometimes used.
Normally, the blood vessels to the lungs are tightly constricted during fetal life. The lungs do not need much blood flow before birth because the placenta rather than the lungs eliminates carbon dioxide and transports oxygen to the fetus. Immediately after birth, the umbilical cord is cut and the newborn’s lungs must take over the role of oxygenating the blood and removing carbon dioxide. To achieve this process, it is necessary for the fluid filling the air sacs (alveoli) to be replaced by air and for the pulmonary arteries, which bring blood to the lungs, to widen (dilate) so that an adequate amount of blood flows through the lungs.
In response to severe distress during delivery, to respiratory distress, or as a consequence of certain drugs taken by the mother before delivery (such as large doses of aspirin), the blood vessels to the lungs may not dilate as they normally should. As a result, blood pressure in the pulmonary arteries is too high (pulmonary hypertension), and blood flow to the lungs is insufficient. Because of this insufficient blood flow, not enough oxygen reaches the blood.
Persistent pulmonary hypertension is more common among newborns who are term or postterm and among newborns whose mother had taken very large doses of aspirin or indomethacin during pregnancy. In many newborns, the respiratory distress that initiates persistent pulmonary hypertension results from other lung disorders, such as meconium aspiration syndrome (see Meconium Aspiration Syndrome), pneumothorax, or pneumonia, but persistent pulmonary hypertension can also develop in newborns with no other lung disorder.
Sometimes persistent pulmonary hypertension is present from birth. Other times, it develops over the first day or two. Breathing is usually rapid, and there may be severe respiratory distress if the newborn has an underlying lung disorder (see Respiratory Distress Syndrome). The skin may have a bluish discoloration (cyanosis) due to low blood oxygen levels. Sometimes low blood pressure (hypotension) leads to symptoms, such as weak pulses and a pale, grayish hue to the skin.
Doctors may suspect persistent pulmonary hypertension if the mother used high doses of aspirin or indomethacin for a prolonged period during pregnancy or had a stressful delivery, or if the newborn has severe respiratory distress and oxygen levels are unexpectedly low. A chest x-ray may be entirely normal if there is no underlying lung disorder. A definitive diagnosis requires an echocardiogram to evaluate the pressure in the pulmonary arteries.
Treatment involves placing newborns in an environment with 100% oxygen. In severe cases, a ventilator providing 100% oxygen may be needed. A high percentage of oxygen in the blood helps open the arteries going to the lungs.
In very severe cases, a very small concentration of the gas nitric oxide may be added to the oxygen that the newborn is breathing. Inhaled nitric oxide opens the arteries in the newborn’s lungs and reduces pulmonary hypertension. This treatment may be needed for several days. Rarely, if all other treatments do not work, extracorporeal membrane oxygenation (ECMO) can be used. In this procedure, blood from the newborn is circulated through a machine that adds oxygen and removes carbon dioxide and then returns the blood to the newborn. ECMO has been lifesaving, allowing some newborns with pulmonary hypertension that does not respond to other treatments to survive until the pulmonary hypertension resolves.