A 30-minute-old boy is evaluated in the neonatal intensive care unit for cyanosis. The patient's 1-minute Apgar score was 8, but he developed cyanosis a few minutes after delivery. He was born by spontaneous vaginal delivery at 32 weeks gestation after his mother had preterm prelabor rupture of membranes and preterm labor. The mother received a dose of glucocorticoids and penicillin prophylaxis for group B Streptococcus prior to delivery. Birth weight was 1.7 kg (3 lb 12 oz). Temperature is 37 C (98.6 F), blood pressure is 66/42 mm Hg, pulse is 160/min, and respirations are 70/min. Pulse oximetry in the right upper extremity and left lower extremity is 65% on room air. Oxygen is administered, and the oxygen saturation improves to 92%. Cardiac examination shows a grade 1/6 systolic murmur at the left sternal border. Pulmonary examination shows grunting, intercostal and subcostal retractions, nasal flaring, and shallow respirations. Chest x-ray is shown in the exhibit. Which of the following is the most likely diagnosis in this patient?

Question

A 30-minute-old boy is evaluated in the neonatal intensive care unit for cyanosis.  The patient's 1-minute Apgar score was 8, but he developed cyanosis a few minutes after delivery.  He was born by spontaneous vaginal delivery at 32 weeks gestation after his mother had preterm prelabor rupture of membranes and preterm labor.  The mother received a dose of glucocorticoids and penicillin prophylaxis for group B Streptococcus prior to delivery.  Birth weight was 1.7 kg (3 lb 12 oz).  Temperature is 37 C (98.6 F), blood pressure is 66/42 mm Hg, pulse is 160/min, and respirations are 70/min.  Pulse oximetry in the right upper extremity and left lower extremity is 65% on room air.  Oxygen is administered, and the oxygen saturation improves to 92%.  Cardiac examination shows a grade 1/6 systolic murmur at the left sternal border.  Pulmonary examination shows grunting, intercostal and subcostal retractions, nasal flaring, and shallow respirations.  Chest x-ray is shown in the exhibit.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d71e_3290_bc81_d1f692835061_MD0003_00 This premature neonate has respiratory distress and hypoxia shortly after birth. Given his preterm status, cyanosis, x-ray findings, and responsiveness to oxygen supplementation, his presentation is most consistent with respiratory distress syndrome (RDS). RDS is due to surfactant deficiency: Immature alveoli are unable to produce sufficient surfactant to reduce alveolar surface tension, leading to diffuse alveolar collapse. This explains why the incidence of RDS is inversely related to gestational age; preterm neonates (particularly if born ≤28 weeks gestation) are at highest risk. Respiratory symptoms begin within minutes to hours after birth and include the following: Tachypnea Grunting (to increase end-expiratory pressure and maintain alveolar volume) Nasal flaring (to decrease airway resistance) Retractions (due to high intrathoracic pressure) Hypoxia and cyanosis (due to atelectasis and ventilation/perfusion mismatch) Hypoxia also leads to vasoconstriction of pulmonary vasculature, causing increased pulmonary vascular resistance and right-to-left shunting across the ductus arteriosus [DA] or foramen ovale, further worsening cyanosis. X-ray findings of RDS include diffuse, reticular, ground-glass opacities and air bronchograms (air-filled bronchi surrounded by atelectasis). X-ray findings of RDS Administration of maternal antenatal glucocorticoids, which stimulate fetal surfactant synthesis, reduces but may not eliminate the risk for RDS. Neonatal treatment includes continuous positive airway pressure ventilation; mechanical ventilation and exogenous surfactant therapy are reserved for severe cases. (Choice A) Severe aortic coarctation can present with shock due to poor distal perfusion on closure of the DA. However, the DA begins to constrict as early as 12 hours (not immediately) after birth. Moreover, a lower postductal (eg, left lower extremity) than preductal (eg, right upper extremity) oxygen saturation would be expected. This patient's soft murmur likely represents a physiologically open DA. closure of the DA (Choice B) D-transposition of the great arteries causes systemic circulation of deoxygenated blood, resulting in tachypnea and cyanosis without retractions or grunting. Because most of the systemic blood flow bypasses the pulmonary vasculature, supplemental oxygen does not significantly improve oxygenation. D-transposition of the great arteries (Choice C) Persistent pulmonary hypertension of the newborn is characterized by high pulmonary vascular resistance, causing right-to-left shunting across the DA. Cyanosis and respiratory distress occur, but chest x-ray is often normal, and preductal oxygen saturation is typically higher than postductal saturation. (Choice E) Transient tachypnea of the newborn causes respiratory distress in the first few hours of life due to delayed resorption of alveolar fluid. Respiratory symptoms and cyanosis are typically mild, unlike in this patient, and chest x-ray reveals perihilar streaking and fluid in the interlobar fissures. chest x-ray Educational objective: Respiratory distress syndrome classically presents in preterm infants with grunting, flaring, retractions, and cyanosis immediately after birth. Chest x-ray shows diffuse, ground-glass opacities and air bronchograms. References: Respiratory development and respiratory distress syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/26802638) Respiratory distress in neonates: underlying causes and current imaging assessment. (http://www.ncbi.nlm.nih.gov/pubmed/28601172)

A 30-Minute-Old Boy Is Evaluated in the Neonatal Intensive Care