Trauma-related embolic events in pulmonary vascular bed are generally due to fat or thrombus embolism. In this report, we present a patient who had severe hypoxia and tachycardia at postoperative period after surgery of an open tibia fracture. Because of the clinical and electrocardiographic findings, we calculated patients Wells score as “pulmonary embolism likely” (N4 points, 28%-52% pulmonary embolism risk), and we performed chest contrast computed tomography. There was no abnormal finding in contrast to chest contrast computed tomography that could suggest fat or thrombus embolism. Because of persistent hypoxemia, we performed transthoracic echocardiographic examination to exclude an intracardiac shunt. In transthoracic echocardiographic examination, we found an atrial septal defect with intermittent right-to-left shunt due to high central venous pressure.