Neonatal Respiratory Distress Syndrome

Neonatal respiratory distress syndrome (NRDS) more frequently affects the Caucasian boys, especially born to diabetic mothers by cesarean section, second born twins and children with a positive family history. On the other hand, maternal hypertension, antenatal steroid administration and prolonged membrane rupture seem to act as protective factors. Keeping this in mind, mothers should be counseled upon discharge in case they ever want to have another child.

The more prematurely the baby is born, the higher the chances of suffering from this ailment are. However, late prematurity is also associated with this disease [1]. The problem becomes apparent soon after birth, progressively worsens and its signs consist of tachypnea, increased respiratory effort with intercostal, suprasternal and substernal retractions, flaring of the nasal alae, expiratory grunting and cyanosis. In extreme situations, irregular breathing, apnea, and hypothermia are encountered. The consciousness state may be diminished and severe fatigability may be reported. In advanced cases, the patient requires ventilatory support and intensive care [2] [3].

Clinical examination reveals decreased breath sounds and peripheral pulses. Oliguria and peripheral edema can be encountered.

The surfactant deficiency may be secondary to several pathological processes, such as infectious or meconium aspiration pneumonia or pulmonary hemorrhage, intrapartum asphyxia, pulmonary hypoplasia or oxygen toxicity. Furthermore, the newborn may have other associated diseases, such as congenital diaphragmatic hernia, necrotizing enterocolitis or patent ductus arteriosus.

An amniocentesis is able to predict if NRDS will occur after birth, based on the lecithin-to-sphingomyelin ratio the presence of phosphatidylglycerol in the amniotic fluid. If these tests are not available, birth is in progress at the time the mother comes to the hospital or fetal distress is seen and childbirth is required, the diagnosis is made after the delivery is done.

Once respiratory distress is noticed, the physician should determine its severity and arterial blood gases offer a good measurement tool. Central (umbilical) or peripheral arterial blood should be analyzed [4] and may show hypoxemia, hypercapnia and respiratory (caused by alveolar atelectasis) and metabolic (due to lactic acid accumulation) acidosis. If a congenital right to left shunt heart malformation coexists, hypoxia will be severe and the child is likely to be cyanotic. A patent ductus arteriosus can have the same results. Blood workup should include a blood glucose level, that is often low, a complete cell count, bilirubin level, renal and liver function and electrolytes.

Oxygenation may also be monitored using a less invasive method, pulse oximetry. Probes should be placed on the right wrist or palm in order to establish the preductal saturation and on either foot for postductal saturation. Saturation should be kept at 91-95% [5]. This is a good screening technique for congenital heart disease, but the diagnosis should finally be evaluated by echocardiography in selected cases.

A thoracic radiography is done in order to observe the pulmonary aspect. Pleural effusion, atelectasis or air bronchograms, interstitial emphysema, pneumothorax, bronchogenic cyst or pulmonary sequestration may be described by this exam. Cardiomegaly is often found and further characterization by echocardiography is required. Doppler echocardiography is reliable in determining if pulmonary hypertension is present. Hyperinflation (in a non-ventilated patient) or a normal aspect at 6 hours of age exclude the NRDS.

Pulmonary ultrasonography may be a reliable method [6] [7] that visualizes the existing pleural effusions [8]. However, pneumothorax is harder to find by lung ultrasonography [9].

If infection signs are detected, tracheal aspirate, cerebrospinal fluid and blood cultures should be obtained.

In situations where the outcome is unfavorable, a histology evaluation will describe the presence of hyaline membranes - an amorphous material, lining the alveolar spaces, collapsed alveoli alternating with hyper aerated ones and vascular congestion.

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2. Escobar GJ, Clark RH, Greene JD. Short-term outcomes of infants born at 35 and 36 weeks’ gestation: we need to ask more questions. Semin Perinatol. 2006;30:28-33.
3. Jain L, Eaton DC. Physiology of fetal lung fluid clearance and the effect of labor. Semin Perinatol. 2006;30:34-43
4. Billman GF, Hughes AB, Dudell GG, et al. Clinical performance of an in-line, ex vivo point-of-care monitor: a multicenter study. Clin Chem. 2002;48(11):2030-43.
5. Tarnow-Mordi W, Stenson B, Kirby A, et al. Outcomes of Two Trials of Oxygen-Saturation Targets in Preterm Infants. N Engl J Med. 2016; 374(8):749-60.
6. Liu J, Cao HY, Liu Y. Lung ultrasonography for the diagnosis of neonatal respiratory distress syndrome: a pilot study. Zhonghua Er Ke Za Zhi. 2013; 51(3):205-10.
7. Vergine M, Copetti R, Brusa G, et al. Lung ultrasound accuracy in respiratory distress syndrome and transient tachypnea of the newborn. Neonatology. 2014;106(2):87-93.
8. Ahuja CK, Saxena AK, Sodhi KS, et al. Role of transabdominal ultrasound of lung bases and follow-up in premature neonates with respiratory distress soon after birth. Indian J Radiol Imaging. 2012;22(4):279-83.
9. Sawires HK, Abdel Ghany EA, Hussein NF, et al. Use of lung ultrasound in detection of complications of respiratory distress syndrome. Ultrasound Med Biol. 2015;41 (9):2319-25.