Hypoxemia during one-lung ventilation is uncommon in healthy patients. When standard measures fail, intracardiac shunts should be considered. A healthy 15-year-old girl underwent bilateral thoracic sympathectomy. Profound desaturation occurred during one-lung ventilation despite 100% oxygen. The tube position was correct, and oxygenation returned to normal with two-lung ventilation. Switching from sevoflurane to propofol-based total intravenous anesthesia provided partial improvement. Intraoperative transesophageal echocardiography revealed an atrial septal defect, which was later confirmed postoperatively. Refractory hypoxemia during one-lung ventilation may suggest hidden intracardiac shunting. Prompt intraoperative echocardiography is essential for diagnosis and safety.
Keywords: Atrial septal defect, hypoxic pulmonary vasoconstriction, one-lung ventilation, refractory hypoxemia, sevoflurane