[A case of ligating both upper and anomalous lower left pulmonary veins in the left upper lobectomy].

A 53-year-old male was anesthetized for left upper lobectomy under one-lung ventilation using a double-lumen endobronchial tube in the lateral position. When the upper left pulmonary vein was ligated, Pao2/FIo2 ratio (PF ratio) was elevated despite the one-lung ventilation. After the operation, the patient was repositioned onto spine position and massive bleeding occurred from the anomalous lower left pulmonary vein, which was ligated during the operation. The lower left pulmonary vein was restored and the bleeding stopped. Because the pulmonary shunt flow from the lower left pulmonary vein had stopped, the PF ratio was unusually elevated. We urge anesthesiologists to pay attention to the arterial blood gas data even when it is better than expected.