Persistent Pulmonary Hypertension of the Newborn (PPHN)

The day he was born, my son almost died. He was delivered two weeks late, via an unplanned cesarean section, after a long labour. At some point during his birth he inhaled a massive amount of meconium and immediately developed Meconium Aspiration Syndrome (MAS), which, in turn, caused a far more serious disorder called Persistent Pulmonary Hypertension of the Newborn (PPHN). It took a specialist team almost eight hours to stabilize him enough for transport to our local children's hospital for specialized care in the neonatal intensive care unit (NICU). My newborn son was three days old before the medical professionals treating him began to speak as if he would survive, and he was five days old before I was able to hold him for the first time.

During his hospitalization, one of my greatest frustrations was the absolutely infuriating tendency of other people to dismiss his hospitalization as something almost trivial. No one had ever heard of PPHN but everyone, it seemed, knew of someone who had had a child hospitalized for a day or two with mild meconium aspiration. Everyone seemed to think that my son had suffered an unfortunate, but relatively routine event and that all would be just fine in a day or two. No one seemed to "get" the fact that my baby could die from this; they just did not understand how sick he really was. The biggest problem in trying to explain my son's diagnosis to other people was the lack of information available to help me understand what was happening to him. Even on the Internet there did not seem to be much useful information available, and my inability to fully explain the disorder resulted in a complete lack of understanding on the part of others. This article was written as a result of this frustration, in an effort to help other parents of PPHN babies understand what was happening to their newborns, and to help those people who know someone with a PPHN baby understand the significance and severity of such a diagnosis.

PPHN is a life-threatening cardiopulmonary disorder wherein a newborn infant's system does not adapt to life outside of his mother's body. Normally, in the human circulation system, the heart pumps blood through the lungs, allowing blood cells flowing through the lung tissue to exchange waste carbon dioxide gas for fresh oxygen; with each breath and pump of the heart, this re-oxygenated blood is then circulated back through our bodies to feed our cells and start the cycle again. The prenatal circulation pattern, however, is fundamentally different; for a fetus still in the uterus, oxygen is acquired not through the lungs, but through the placenta. Because all of the fetal body's oxygen requirements are supplied through these means, blood pressure in the fetal lungs is high so that the circulation system actually bypasses the lungs, instead sending oxygenated blood directly from the placenta to other organs through a special blood vessel in the umbilical cord. When a baby is born and takes its first breath an automatic switch is meant to occur to allow the infant to survive outside the womb: blood pressure in the lungs is supposed to fall and that special umbilical blood vessel is supposed to permanently close up so that blood flow can directed through the lungs, allowing oxygen and carbon dioxide to be exchanged in a normal, non-fetal, fashion.

With PPHN, however, pressure within the lungs fails to fall and this switch cannot occur. With the pressure in the lungs remaining so high, the special umbilical blood vessel stays open and the baby's circulation system continues to bypass the lungs, attempting to maintain the prenatal circulation pattern even though the placenta is no longer there to provide desperately needed oxygen. With the circulation system still bypassing his lungs, the baby takes breaths, but the oxygen he brings into his lungs with these breaths cannot get into his bloodstream. Without oxygen and carbon dioxide being exchanged through either the placenta or the lungs, carbon dioxide rapidly builds up in the baby's body and all his organs and tissues quickly become deprived of life-sustaining oxygen. The baby may look like he is breathing but he is, in fact, suffocating with every breath.

Seen most often in term or post-term infants, particularly in those who have had a difficult birth, the most common cause of PPHN is apparently MAS, which itself affects less than one percent of neonates in the United States. According to an eMedicine article, thirteen percent of births are complicated by the presence of meconium in the amniotic fluid, but only five percent of those thirteen percent (approximately 0.65 percent of all births) will actually develop MAS. Some studies also indicate a higher rate of PPHN in infants born to mothers who took certain types of anti-depressant medications during pregnancy.

There are a number of signs that can indicate a newborn is suffering from PPHN. These include: rapid breathing, rapid heart rate, respiratory distress, and a bluish tint to the skin, even with the administration of pure oxygen. A definitive diagnosis usually involves any number of tests, some of which can include: chest x-rays, echocardiograms, blood work, and ultrasounds to determine if there are other complicating factors.

Treatment for PPHN involves the administration of supplemental oxygen and nitric oxide, and assisted ventilation with mechanical ventilators; additional drug therapy may also be used to assist in these treatments. Infants who suffer from MAS in addition to PPHN may also require manual suctioning of the lungs to remove the accumulated meconium, and high-frequency oscillatory ventilation (with a ventilator machine attached to a vibrating platform which helps to shake congealed meconium loose, making it easier to suction the stuff out) if assisted ventilation is ineffective. If the infant also suffers from serious heart or lung failure, treatment with an extracorporeal membrane oxygenation (ECMO) machine, which adds oxygen to the blood outside of the infant's body and then pumps it back in, may be necessary. In addition, infants recovering from PPHN usually have problems feeding for several days or weeks, and often require a nasogastric feeding tube (a thin tube that is inserted through the nose and which runs down the throat and into the stomach) until they are able to begin breast or bottle-feeding on their own. While an infant is being treated, breathing rates, blood-oxygen levels and heart rate are all continuously monitored.

Long-term outcomes for babies with PPHN have improved significantly. When my son was still in the NICU, but on the road to recovery, the nurses explained to me that the new drugs and equipment available to help PPHN babies has made a huge difference in survival rates. They said that before these advances, babies with this disease just died. Even fifteen years ago, the death rate for infants with PPHN was apparently almost fifty percent, with long-term neurological damage resulting from oxygen deprivation reaching up to sixty percent. With the recent advances in treatments, these statistics have decreased to a ten percent mortality rate and a twenty percent rate of long-term damage, still very frightening numbers for a parent with a critically ill baby.

One of the most common long-term complications resulting from PPHN is sensorineural hearing loss. According to the audiologist who performed a hearing test on my son, infants who have suffered from PPHN have a thirty percent chance of developing degenerative hearing loss within the first two years of life, and the longer it takes an infant to recover from the disorder, the more likely it is that such hearing loss will occur. For this reason, several follow-up hearing tests for PPHN babies are normally recommended to ensure that any developing problems are diagnosed early.

Today, my son is seven months old and, so far, has shown no signs of complications from his rough start with PPHN; every day we pray that this will continue to be the case. In his favour is the fact that the on-call pediatrician at his birth realized very early on that he was suffering from PPHN and began treating him almost immediately. According to the nurses at the NICU, this timely start of interventions played a crucial role in how quickly he recovered from the disease. Looking at him now it is hard to reconcile the healthy, outgoing, and highly active little boy he is today with that pale, heartbreakingly sick newborn that he was. I will always be grateful to that first pediatrician and her team, none of whom I ever did meet, and to the nurses at the children's hospital where he spent his first two and a half weeks; their efforts saved my son's life, and their support made it easier to endure the ordeal as my baby suffered, and recovered, from PPHN.

References:

http://www.thechildrenshospital.org/wellness/info/parents/20830.aspx

http://emedicine.medscape.com/article/898437-overview

http://www.ucsfhealth.org/childrens/medical_services/critical/hypertension/index.html

http://depts.washington.edu/nicuweb/NICU-WEB/pphn.stm

http://emedicine.medscape.com/article/904996-overview

http://www.cmaj.ca/cgi/content/full/174/11/1555