Early one-lung ventilation unmasks asymptomatic PE in hemodialysis patient with right atrial mass altering surgery

A minimally invasive thoracoscopic approach for right atrial masses is contraindicated in the presence of concomitant pulmonary embolism (PE), as pulmonary embolectomy would be required but cannot be performed through a thoracoscopic incision. A 48-year-old woman on hemodialysis was scheduled for thoracoscopic excision of a right atrial mass. Post-induction, left-sided one-lung ventilation (OLV) precipitated hypoxemia and a sharp drop in end-tidal CO 2 , in contrast to normal findings during right-sided OLV. A widened arterial-to-end-tidal CO 2 gradient (36 mmHg during left sided OLV vs. 7.1 mmHg during right sided OLV) confirmed left-sided PE, prompting conversion to sternotomy for successful mass and emboli removal. This case highlights that asymptomatic PE can be missed preoperatively. Early OLV with capnography is a crucial intraoperative diagnostic tool for unilateral PE, guiding surgical management in high risk patients. For bilateral PE, this technique may not show a side to side difference.