Index
It is a syndrome that occurs in premature babies due to insufficient development of the production of pulmonary surfactant and structural immaturity in the lungs.
Causes
It can be caused by a neonatal infection. It can also result from a genetic problem with the production of proteins associated with surfactants.
It is currently known as infant respiratory distress syndrome (SDRI), also called neonatal respiratory distress syndrome (RDSS), respiratory distress syndrome of the newborn, or surfactant deficiency disorder (SDRRN).
Infant respiratory distress syndrome affects approximately 1% of newborns and is the leading cause of death in preterm infants.
With advancing gestational age, the incidence decreases from approximately 50% in babies born at 26-28 weeks to about 25% at 30-31 weeks.
The syndrome is more frequent in men, Caucasians, babies of diabetic mothers, and the second born of premature twins.
Infant respiratory distress syndrome is distinct from pulmonary hypoplasia, another major cause of neonatal death that involves respiratory distress.
Signs and symptoms of hyaline membrane disease
Hyaline membrane disease begins soon after birth and is manifested by rapid breathing, more than 60 per minute, rapid heart rate, retractions of the chest wall (recession), expiratory grunts, nasal flaring, and blue discoloration of the skin during the efforts of breathing.
As the disease progresses, the baby may develop ventilatory failure (increased concentrations of carbon dioxide in the blood) and prolonged cessation of breathing (” apnea “).
Whether it is treated or not, the clinical course of the acute disease lasts 2 to 3 days. During the first day, the patient gets worse and needs more help.
During the second day, the baby can be remarkably stable with adequate support, and the resolution is observed during the third day, announced by an early diuresis.
Despite the significant advances in attention, the syndrome of infantile respiratory difficulty continues to be the most common cause of death in the first month of life in the developed world.
Complications include:
- Metabolic disorders ( acidosis, low blood sugar).
- Persistent ductus arteriosus.
- Low blood pressure.
- Chronic lung changes.
- Brain hemorrhage.
The disease is often complicated by prematurity and its additional defects in the function of other organs.
Histopathology of hyaline membrane disease
The characteristic histopathology observed in babies dying from respiratory distress syndrome was the source of the name “hyaline membrane disease.”
The layers of waxy-looking hyaline membrane line the alveoli of the collapsed lung.
In addition, the lungs show bleeding, excessive distension of the airways, and damage to the lining cells.
Pathophysiology
The lungs of babies with respiratory distress syndrome are deficient in their development in a material called surfactant, which helps prevent the collapse of terminal air spaces (the future site of alveolar development) throughout the normal inhalation and exhalation cycle.
This deficiency of surfactant is related to an inhibition of insulin that occurs in the newborn, especially in diabetic mothers.
The surfactant is packaged by the cell in structures called lamellar bodies and extruded into the air spaces. The lamellar bodies unfold in a complex lining of the airspace.
This layer reduces the surface tension of the fluid that covers the alveolar airspace. In addition, the decreased surface tension allows the reopening of the airspace with a smaller amount of force.
Therefore, the air spaces collapse without adequate amounts of surfactant and are very difficult to expand.
Microscopically, a lung deficient in pulmonary surfactant is characterized by collapsed air spaces alternating with hyperextending areas, vascular congestion, and, over time, hyaline membranes.
The hyaline membranes are fibrin, cell debris, red blood cells, rare neutrophils, and macrophages. They appear as an eosinophilic, amorphous material that covers or fills the air spaces and blocks the exchange of gases.
As a result, blood that passes through the lungs can not capture oxygen and discharge carbon dioxide. The oxygen levels in the blood decrease, and the carbon dioxide increases, which increases the levels of acid in the blood and hypoxia.
Structural immaturity, as manifested by the decrease in the number of gas exchange units and thicker walls, also contributes to the disease process.
Therapeutic oxygen and positive pressure ventilation, although they can save lives, can damage the lung.
Diagnosis
The diagnosis is made through the clinical picture and the chest X-ray, which shows a decrease in lung volumes (bell-shaped chest).
Absence of thymus (after approximately 6 hours), a small, discrete, uniform infiltrate (0.5-1 mm) (sometimes described as a “frosted glass” appearance or recently described as “diffuse airspace and interstitial opacities”) ).
This involves all lung lobes and air bronchograms (i.e., the infiltrate will outline the ducts of the larger airways that remain filled with air).
In severe cases, this is exaggerated until the cardiac borders become inapparent (a “whitening” appearance).
Prevention of hyaline membrane disease
Giving the glucocorticoid mother accelerates the production of surfactant. For very preterm deliveries, a glucocorticoid is administered without evaluating fetal lung maturity.
The American College of Obstetricians and Gynecologists (CEO), the Royal College of Medicine, and other major organizations have recommended prenatal glucocorticoid treatment for women at risk of preterm birth before 34 weeks of gestation.
Compared to a single course, multiple courses of glucocorticoid administration do not seem to increase or decrease the child’s risk of death or neurodevelopmental disorders.
In pregnancies of more than 30 weeks, the lung maturity of the fetus can be analyzed by sampling the amount of surfactant in the amniotic fluid through amniocentesis, where a needle is inserted through the abdomen and uterus of the mother.
Several tests are available that correlate with surfactant production. These include the lecithin-sphingomyelin ratio (“L / S ratio”), the presence of phosphatidylglycerol (FG), and, more recently, the surfactant/albumin (S / A) ratio.
For the lecithin-sphingomyelin (L / S) ratio, if the result is less than 2: 1, the fetus’s lungs may be deficient in surfactant.
The presence of phosphatidylglycerol generally indicates fetal lung maturity. For the surfactant/albumin (S / A) ratio, the result is given as mg of surfactant per g of protein.
A surfactant/albumin (S / A) ratio of <35 indicates immature lungs, between 35-55 is indeterminate, and> 55 indicates the production of mature surfactant (correlates with an L / S ratio of 2.2 or greater).
Treatment
Oxygen is given with a small amount of continuous positive airway pressure (“PPCVR”), and intravenous fluids stabilize the blood sugar level, blood salts, and blood pressure.
If the baby’s condition worsens, an endotracheal tube (breathing tube) is inserted into the trachea, and irregular respirations are given by a mechanical device.
An exogenous surfactant preparation, either synthetic or extracted from the lungs of animals, is administered through the breathing tube into the lungs.
Some of the most commonly used surfactants are Survanta or its generic form Beraksurf, derived from cow lungs, which can decrease the risk of death in hospitalized babies of light birth weight by 30%.
These premature babies can remain ventilated for months.
A study shows that an aerosol of a perfluorocarbon such as perfluorometildecalin can reduce inflammation in the porcine model of infant respiratory distress syndrome.
Chronic lung disease, including bronchopulmonary dysplasia, is common in severe respiratory distress syndrome. The etiology of bronchopulmonary dysplasia is problematic and may be due to oxygen, overventilation, or lack of ventilation.
The mortality rate of babies older than 27 weeks of gestation is less than 20%.
Extracorporeal membrane oxygenation (ECMO) is a potential treatment that provides oxygenation through an apparatus that mimics the gas exchange process of the lungs.
However, newborns can not undergo extracorporeal membrane oxygenation if they weigh less than 4.5 pounds (2kg).
Since they have tiny vessels for cannulation, impeding adequate flow due to the limitations of the size of the cannula and the subsequent resistance to blood flow (compared with vascular resistance).
In addition, in infants less than 34 weeks of gestation, several physiological systems are not well developed, especially the cerebral vasculature and the germinal matrix, resulting in a high sensitivity to slight changes in pH, PaO2 and intracranial pressure.
Subsequently, premature infants have an unacceptably high risk of intraventricular hemorrhage (IVH) if extracorporeal membrane oxygenation is administered at fewer than 32 weeks.
The INSURE method (intubation-surfactant-extubation)
Henrik Verder is the inventor and pioneer of the INSURE method (intubation-surfactant-extubation), an efficient approach for managing premature infants with respiratory distress.
The method itself has been demonstrated through meta-analysis; to successfully reduce the use of mechanical ventilation and reduce the incidence of bronchopulmonary dysplasia (BPD).
Since its conception in 1989, more than 500 articles have cited the INSURE method academically.
The first randomized study on the INSURE method was published in 1994, and the second group published a second randomized study on newborns less than 30 weeks gestation in 1999.
In the last 15 years, Henrik has worked with diagnoses of lung maturity in gastric aspirates obtained at birth. By combining this diagnostic method with INSURE, Henrik has worked further to improve the clinical outcome of the respiratory distress syndrome.
The tests of lung maturity used have been the microbubble test, the lamellar body counts (RCL), and the measurements of the lecithin-sphingomyelin (L / S) ratio with chemometrics, which involved a collaboration with Agnar Höskuldsson.
Disorders related to hyaline membrane disease
Acute respiratory distress syndrome (ARDS) is similar to childhood respiratory distress syndrome. The tachypnea transient newborn occurs with respiratory distress syndrome in premature newborns.
