Authors: Michael A. Evans, MD – Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern Feinberg School of Medicine


A previously healthy four-year-old child undergoes surgical closure of a large secundum-type atrial septal defect (ASD). After separation from cardiopulmonary bypass and release of caval snares, the oxygen saturation (SpO₂) decreases to 85% from 100% with a fractional inspired oxygen (FiO₂) of 60% and normal peak inspiratory pressures. The FiO2 is increased to 100%, but the SpO2 remains at 85%. Transesophageal echocardiography (TEE) reveals an underfilled right atrium and right ventricle with normal systolic function and no tricuspid regurgitation. The left atrium and left ventricle are of normal size and function. An agitated saline study is performed through the right internal jugular central venous catheter and is negative.


Which of the following is the BEST INITIAL STEP to correct this patient’s hypoxemia?