[Severe hypoxia during right lateral position induced by mediastinal shift]

An 87-year-old woman with osteoarthrosis of her left hip joint was scheduled for total hip arthroplasty. After induction of anesthesia the patient was put into the right lateral position for surgery. Oxygen saturation had decreased gradually and the respiratory sound of the right lung was not auscultated. Broncofiberscopic examination showed that the position of the tracheal tube was appropriate and no secretion was found. Immediately after the patient was retuned to supine, oxygenation improved and the respiratory sound of the right lung was ausculated clearly. Chest radiographs were taken in both supine and right lateral positions. The chest X-ray findings taken in the right lateral position revealed that the right lung volume was decreased remarkably due to the extreme downward-shift of the mediastinum. The operation was postponed. The right lateral chest X-ray taken during wakefulness showed that the degree of mediastinal shift was not as remarkable as during anesthesia. After 8 days, the operation was performed using the supine position. We concluded that a downward mediastinal shift induced severe right lung volume reduction in the right lateral position during anesthesia.