Case 2: Unexplained Hypercarbia in a Neonate in the Neonatal Intensive Care Unit

A male infant is delivered at term via lower-segment cesarean delivery with a birthweight of 3.5 kg to a 25-year-old gravida 2 woman. The mother did not have any significant events during the antenatal period but was noted to have polyhydramnios (amniotic fluid index, 33) during the third trimester. There is no history of consanguinity or sibling death. The infant cried after birth, with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. The infant is transferred to the postnatal ward and begins breastfeeding. He develops central cyanosis 3 hours after birth and is admitted in the NICU. His vital signs at the time of admission are as follows: temperature, 97.8°F (36.6°C); heart rate, 128 beats/min; respiratory rate, 36 breaths/min; capillary refill time, 2 seconds; peripheral pulses, palpable; and oxygen saturation, 72% in room air, which improved with oxygen supplementation. The infant is limp at the time of admission, but improves after oxygen administration. The infant has intermittent stridor. He has repeated episodes of apnea on day 2 after birth, for which he was given pressure-synchronized intermittent mandatory ventilation with minimal settings. Antibiotics are started and a blood sample is sent for culture. Venous blood gas before intubation is suggestive of respiratory acidosis with normoxemia (pH 6.86, partial pressure of carbon dioxide [Pco2] 144 mm Hg [19.15 kPa], partial pressure of oxygen [Po2] 54 mm Hg [7.18 kPa], lactate 3.5 mg/dL [0.39 mmol/L]), which improves within 1 hour of ventilation (pH 7.34, Pco2 36.4 mm Hg [4.8 kPa], Po2 88 mm Hg [11.7 kPa], lactate 3.5 mg/dL [0.39 mmol/]). Clinical possibilities considered include early-onset sepsis, pneumonia, perinatal asphyxia, meningitis, congenital heart disease; congenital anomalies like esophageal atresia with/without tracheoesophageal fistula; airway anomalies; vocal cord palsy; subglottic stenosis; …