What is Persistent Pulmonary Hypertension of the Newborn?
The placenta acts as the main organ for exchanging oxygen and carbon dioxide within a fetus. Once the baby is born, the lungs must quickly take on this role. Persistent pulmonary hypertension happens when this transition doesn’t occur as it should. This might be due to the baby’s blood vessels in the lungs not relaxing and widening properly, leading to the reduction of blood flow.
The signs of this condition can vary. Some babies may have mild breathing problems, while others may struggle to get enough oxygen and need help from machines to breathe or even a process called extracorporeal membrane oxygenation (ECMO), which acts as an artificial lung. Persistent pulmonary hypertension in newborns can be a very serious condition in the first few days after birth, so it’s critical for doctors and nurses to identify and treat this issue quickly.
What Causes Persistent Pulmonary Hypertension of the Newborn?
Newborns can experience persistent pulmonary hypertension – a condition affecting their lung blood vessels – due to several factors. Conditions affecting the lung tissue, like meconium aspiration syndrome (a situation where the baby inhales a substance called meconium while in the womb), pneumonia, respiratory distress syndrome (breathing difficulties), and severe body infections (sepsis) can all lead to this issue.
Additional causes can include oligohydramnios (low amniotic fluid), underdeveloped lungs, being the child of a mother with diabetes, premature closure of the ductus arteriosus (a blood vessel in the heart) while still in the womb, and being abnormally small or large for their gestational age.
Mother’s health and habits can also play a role. Risks increase if the mother is obese, has diabetes, experiences pre-eclampsia (a pregnancy complication involving high blood pressure), has an infection of the tissues surrounding the fetus (chorioamnionitis), smokes, or uses certain kinds of medication during pregnancy, like selective serotonin reuptake inhibitors (SSRIs) or NSAIDs.
Some birth defects, like a condition where the heart’s main arteries are in the wrong place (transposition of great arteries) or a hole in the diaphragm (congenital diaphragmatic hernia) can also lead to persistent high pulmonary pressure immediately after birth.
Risk Factors and Frequency for Persistent Pulmonary Hypertension of the Newborn
Persistent pulmonary hypertension is a condition that can occur in newborns. The overall rate of this condition is about 1.8 in 1000 live births. However, it’s important to know that this condition is even more common in late preterm infants – about 5.4 in 1000 live births – compared to full-term infants where the rate is 1.6 in 1000 live births.
- The mortality rate of the condition varies from 7.6% to 10.7%, based on how severe it is.
- Boys are at a slightly higher risk than girls, with a risk ratio of 0.8.
- In regards to race, African American babies have the highest risk, followed by Hispanic and Asian infants.
Signs and Symptoms of Persistent Pulmonary Hypertension of the Newborn
Usually, babies show signs of this condition a few days after being born. While admitting the baby to the NICU, it is important to gather information about the mother’s health and exposure to drugs during pregnancy. Details about factors during childbirth, such as inflammation of the tissues around the fetus, presence of the baby’s first poop in the amniotic fluid, and any lack of oxygen to the baby, are also beneficial to gather because they can contribute to a condition known as persistent pulmonary hypertension.
When a newborn needs support after birth due to conditions like inhaling meconium (the first fecal matter of an infant), the baby’s health is often assessed at the same time. Babies with ongoing fetal circulation may appear bluish due to lower levels of oxygen. They might show signs of breathing difficulty and may demonstrate significant pulling in around the collarbone, lower ribs, and between the ribs when breathing. Also, the babies with a birth defect like the diaphragmatic hernia may have an abdomen that looks caved in. Babies with severe infections can show signs like low blood pressure that doesn’t respond to treatment, failure of multiple organs, and easy bleeding due to a potentially fatal blood clotting disorder called disseminated intravascular coagulopathy (DIC).
Testing for Persistent Pulmonary Hypertension of the Newborn
If your infant is suspected of having PPHN, various tests will be carried out. These include a blood gas test, a chest X-ray, an echocardiogram, and tests to rule out an infection, also known as sepsis. If the doctors suspect that ECMO (a type of life support) might be needed in future, they may also conduct coagulation studies and a head ultrasound.
The blood gas test measures the level of oxygen in the blood. A low level may indicate PPHN. The tests for sepsis include a complete blood count, which may reveal abnormal white blood cell counts, and a C-reactive protein test, which can indicate inflammation and is often high in cases of sepsis.
The chest X-ray can reveal any underlying lung problems. Another crucial measure is the Oxygenation Index (OI), a calculation that shows the level of oxygen in the blood relative to the amount of oxygen the body is receiving. If the OI is higher than 15, along with a significant difference in blood oxygen levels between two points in the body (pre-post ductal saturation), this might suggest a high resistance to blood flow in the lungs, which is common in PPHN.
The primary tool for diagnosing PPHN is the echocardiogram, which uses sound waves to create pictures of the heart. This test helps doctors estimate the pressure in the right side of the heart and the blood vessels in the lungs. Doctors also use this test to monitor treatment progress. It provides detailed information about the functions of the right and left sides of the heart, essential in treating PPHN. However, in some cases, the information obtained from the echocardiogram may not be entirely accurate if the right side of the heart is not functioning correctly.
Another important test measures the level of a hormone called BNP in the blood. This hormone is released when the right side of the heart is under stress. An elevated BNP level in babies suggests PPHN. Specifically, a BNP level higher than 550pg/ml is predictive of persistent pulmonary hypertension.
Treatment Options for Persistent Pulmonary Hypertension of the Newborn
Managing chronic high blood pressure in the lungs, known as persistent pulmonary hypertension, includes keeping the body warm, maintaining blood sugar levels, and providing cardiovascular support and fluids. Treatment often involves lung therapies and blood pressure medications. Inhaled nitric oxide (iNO), the most studied treatment, is the only FDA-approved medication for pulmonary hypertension in the United States.
Previous treatments included hyperventilation, alkali infusion, sedation, and certain drugs, but most are no longer used given their temporary benefits and potential harm. For example, treatments that induce alkalosis – a condition where there’s too much alkaline in the body – can cause increased reactivity and lead to worse health outcomes.
Drugs that increase the force of heart contraction, known as inotropes, are common in treating persistent pulmonary hypertension. Medications like dopamine and milrinone are often used, though caution must be exercised with higher doses of dopamine. Improving overall blood pressure can help lessen heart defects that lead to lung issues.
Enhancing oxygen levels in the body is a crucial part of treatment. This often involves careful use of oxygen and ventilatory support devices, which help improve lung volume and function. However, going above 50% oxygen is not helpful.
Lung volume can be improved, specifically in newborns with lung diseases, by using a ventilator to correct mismatches in organ function. The use of surfactants, substances that reduce friction between lung tissue, may improve oxygen levels in mild cases of lung diseases.
The oxygenation index (OI) is used to measure disease severity. If OI is consistently over 40, this indicates a severe case and signals the need for extracorporeal membrane oxygenation (ECMO). ECMO is a lifesaving technique that pumps and oxygenates a patient’s blood outside the body, allowing the heart and lungs to rest. However, ECMO is an invasive, complex procedure and may lead to severe complications.
iNO is the primary treatment for newborns with severe pulmonary hypertension. It quickly widens the blood vessels in the lungs, improving oxygen levels in the body. iNO has been proven effective by many studies, although early initiation does not seem to influence the need for ECMO or affect mortality or neurodevelopmental outcomes.
Milrinone and sildenafil are two other vasodilators often used. Milrinone improves heart function and oxygen levels, whereas sildenafil has shown promising results in infants who did not respond to iNO. However, caution should be exercised with milrinone as it can cause a drop in blood pressure, which may affect heart function.
Sedatives may be used in some cases to reduce agitation which can potentially increase pulmonary vascular resistance, worsening the hypertension. Again, this should be done cautiously.
Lastly, the success of ECMO depends largely on the underlying cause of the hypertension. It has shown to be effective, particularly in infants with meconium aspiration syndrome (MAS), a condition where there are fetal feces in a newborn’s lungs. However, ECMO use in other conditions such as trisomy 21 or CDH has resulted in post-ECMO illness or low survival rates. ECMO use has significantly reduced due to improving ventilation strategies and the introduction of iNO. Despite this reduction, ECMO remains a useful rescue therapy option.
What else can Persistent Pulmonary Hypertension of the Newborn be?
The process of diagnosing a condition could include considering several other diseases that show similar symptoms. For instance, a blue or purple appearance of the skin or mucous membranes, also known as cyanosis, might be due to a type of congenital heart disease. Also, some conditions, like total anomalous pulmonary venous return, can worsen with the treatment of inhaled nitric oxide, so it’s best to avoid it. Newborn babies with patent ductus arteriosus (PDA), a condition that causes abnormal blood flow between two of the main arteries connected to the heart, transposition of the great vessels, a condition where the position of the two main arteries going out of the heart is switched, or coarctation of the aorta, a narrowing of the large artery that carries blood to the body, can demonstrate different degrees of skin bluishness.
What to expect with Persistent Pulmonary Hypertension of the Newborn
The outcomes for babies with persistent pulmonary hypertension, a condition affecting the lungs, depend on the underlying cause. Those that survive often face long-term developmental issues, cognitive problems, and hearing difficulties.
About one in four babies with this condition experience developmental delays and hearing issues. The risk of these problems is higher for babies with other conditions such as Congenital Diaphragmatic Hernia (a birth defect of the diaphragm) or genetic disorders. Moreover, being born small for their gestational age and being of Hispanic ethnicity are independent factors leading to a higher risk of death and illness in the first year after leaving the hospital.
Babies with mild forms of persistent pulmonary hypertension are more likely to be readmitted to the hospital than those without this condition.
Possible Complications When Diagnosed with Persistent Pulmonary Hypertension of the Newborn
Persistent pulmonary hypertension in newborns can have various complications, and these complications are largely dependent on the core cause of the condition. For example, in a condition known as Meconium Aspiration Syndrome (MAS), the newborn may frequently encounter air leaks known as pneumothorax and pneumomediastinum. These leaks occur because of a blockage in the air passageway or the need for intense ventilator settings.
In dire circumstances, if infants are severely lacking oxygen (a condition referred to as profound hypoxemia), they might develop multiorgan dysfunction. This could result in diminished urine production (oliguria) and a bleeding disorder due to a condition known as Disseminated Intravascular Coagulation (DIC).
Preventing Persistent Pulmonary Hypertension of the Newborn
It’s important for parents to understand how low oxygen levels can harm a newborn’s brain in the long run. Therapies that are continued after initial treatment can considerably improve the baby’s condition. Babies who experience these oxygen-related injuries tend to have a higher chance of needing to be readmitted to the hospital and unfortunately, also have an increased risk of becoming severely sick or even passing away during their first year.
