The results of blood gas analyses in 24 patients who had a rhytidoplasty under local anesthesia indicated that a moderate degree of hypoxemia can be elicited in these patients when they have had standard doses of the usual sedatives. While the acid-base abnormalities were generally corrected spontaneously, the extent of the hypoxemia can be aggravated further by the additional use of diazepam during the operation. Therefore, over-sedation of such a patient during the operation, without a secured airway, must be avoided. Additionally, we recommend deep breathing at frequent intervals, with or without supplemental oxygen through a high flow system.