A 2-hour-old boy is admitted to the neonatal intensive care unit with severe respiratory distress. The patient was born via forceps-assisted vaginal delivery at 38 weeks gestation to a 35-year-old woman, gravida 2 para 2, whose pregnancy was complicated by poorly controlled gestational diabetes mellitus. The delivery was complicated by recurrent late decelerations and thick meconium. The patient was intubated in the delivery room due to respiratory distress. Blood pressure is 58/30 mm Hg, pulse is 158/min, and respirations are 70/min. Pulse oximetry readings are 90% in the right hand and 79% in the right foot on 100% oxygen. Physical examination is remarkable for meconium-stained nails and intercostal and subxiphoid retractions. Chest x-ray reveals bilateral, patchy opacities and hyperinflation consistent with meconium aspiration syndrome. Echocardiogram shows decreased right ventricular output. Which of the following is the best next step in management of this patient?
Persistent pulmonary hypertension of the newborn | |
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This infant has a postductal oxygen saturation level (right foot) lower than the preductal oxygen saturation level (right hand) in the setting of meconium aspiration syndrome. These findings are concerning for persistent pulmonary hypertension of the newborn (PPHN).
After birth, the sudden increase in systemic vascular resistance is normally accompanied by a progressive decrease in pulmonary vascular resistance (PVR). PPHN is characterized by persistently elevated PVR with right-to-left shunting across the ductus arteriosus, resulting in a gradient between preductal and postductal oxygen saturations. PPHN is associated with lung injury (eg, obstruction and inflammation due to meconium aspiration syndrome) and likely reflects dysfunctional vascular development or adaptation to insults. PPHN exacerbates respiratory distress (eg, retractions, tachypnea) and hypoxia from meconium aspiration syndrome, and decreased right ventricular output (from high PVR) is consistent with the diagnosis.
Treatment is aimed at reducing PVR through oxygenation and ventilation. Additional management includes administration of pulmonary vasodilators such as inhaled nitric oxide. By increasing cyclic GMP in smooth muscle cells of the pulmonary arteries, nitric oxide causes dilation of pulmonary vasculature, which decreases PVR and reduces right-to-left shunting through the ductus arteriosus. Nitric oxide has a half-life of only a few seconds, thereby limiting vasodilation to the pulmonary vasculature.
(Choice A) Albuterol is a beta-2 receptor agonist that dilates airways, not pulmonary vessels. PPHN due to meconium aspiration syndrome is characterized by overt obstruction by particulate matter (meconium), not bronchospasm; therefore, albuterol does not improve oxygenation in PPHN.
(Choice B) Diuretics (eg, hydrochlorothiazide) can be considered for chronic pulmonary hypertension and right ventricular dysfunction with signs of fluid overload (eg, hepatomegaly, edema); those signs are not seen here. Pulmonary vasodilation to reduce PVR is the priority in PPHN.
(Choice C) Nonsteroidal anti-inflammatory drugs (eg, ibuprofen) close a patent ductus arteriosus. Although this infant has a patent ductus, as evidenced by the difference between preductal and postductal oxygen saturations, closing the ductus in PPHN would further increase right ventricular afterload and worsen right ventricular output.
(Choice E) Paralytics (eg, vecuronium) can optimize ventilation for severely hypoxic intubated infants, but they do not have a direct effect on the pulmonary vasculature. They are therefore reserved for use in patients who do not respond to first-line treatment.
Educational objective:
Persistent pulmonary hypertension of the newborn (PPHN) can be caused by conditions that injure the lungs (eg, meconium aspiration syndrome). Treatment of PPHN includes oxygenation, ventilation, and administration of pulmonary vasodilators (eg, inhaled nitric oxide).