An unusual case of intraoperative hypoxemia in a four year old boy

Various factors may be responsible for intraoperative hypoxemia including either primary pulmonary or cardiac issues. Primary cardiac issues resulting in a right-to-left shunt are generally identified prior to arrival in the operating room. During an intraoperative decrease of oxygen saturation, potential respiratory causes need to be ruled out including a low inspired oxygen concentration, ventilation-perfusion mismatch, hypoventilation or diffusion problems. Of these, ventilation-perfusion mismatch related to bronchospasm, preexisting lung disease, acid aspiration, or inadvertent main stem intubation remain the primary causes of intraoperative hypoxemia. We present a 4year-old boy who presented for surgical repair of an atrial septal defect and a ventricular septal defect during a surgical trip to a developing country. Following endotracheal intubation, despite the absence of respiratory issues, the pulse oximeter value varied from 82-92% with a PaO2 of 60-70 mmHg. Although the patient was initially presumed to have pulmonary hypertension resulting in right-to-left shunting at the ventricular level, surgical exploration revealed the presence of total anomalous systemic venous return. The anatomy of this rare congenital cardiac abnormality is discussed, previous reports from the literature presented, and its inclusion into the differential diagnosis for hypoxemia is discussed.