LAUSR

A 2-hour-old female neonate born at term via vaginal delivery to a 21-year-old woman with routine obstetric care and a delivery complicated by a tight nuchal cord was transferred to a tertiary neonatology intensive care unit for hypotension and hypoxic respiratory failure. Initial blood pressure was 48/28 mm Hg, and oxygen saturation ranged around 85% on room air. Upon arrival, the patient was intubated and placed on 100% fraction of inspired oxygen and inotropic support. The initial arterial blood gas (fraction of inspired oxygen 1.0) demonstrated pH of 7.42, partial pressure of carbon dioxide 35 mm Hg, and partial pressure of oxygen 53 mm Hg. On physical examination the respiratory rate was 44 breaths/min, heart rate was 105 beats/min, and heart sounds, pulses, and peripheral perfusion were normal. Bedside transthoracic echocardiography demonstrated what was believed to be normal segmental anatomy, a small secundum atrial septal defect with left-to-right shunting, normal systemic and pulmonary venous connections, and normal biventricular systolic function. With the clinical picture of persistent hypoxemia despite full respiratory support, the patient was started on inhaled nitric oxide and transitioned to an epinephrine infusion for hypotension, without improved clinical status. With persistent hypotension and hypoxemic respiratory failure, partial pressure of oxygen was 40–50 mmHg, and despite full medical management, the decision was made to place the patient on venovenous extracorporeal membrane oxygenation support. The patient had resolution of hypotension within 24 hours but continued to have low arterial oxygen levels of unclear etiology in the 50–60 mm Hg range. Repeat echocardiographic examinations were performed over the course of 8 days. Although the great artery relationship and systemic and pulmonary venous connections were confirmed normal, the etiology of the persistent hypoxemia was unclear.