Effect of oxygen and air inhalation during cataract surgery on blood gas parameters

Purpose: To study the effects of oxygen administered to patients having cataract surgery under local anesthesia. Setting: The Pretoria Eye Institute, Arcadia, South Africa. Methods: in this prospective study, 31 patients were randomly divided into two groups; one received oxygen inhalation during surgery and the other, air. The saturation of oxygen in arterial blood, the partial pressure of oxygen in arterial blood (PaO2), the partial pressure of carbon dioxide in arterial blood (PaCO2), and the pH were evaluated in both groups. Results: The preoperative blood gas parameters were maintained in the air inhalation patients. Oxygen inhalation caused significant increases in the saturation of oxygen in arterial blood and in PaO2. There was no difference between the two groups in PaCO2. The pH of arterial blood showed a statistically significant decrease in the oxygen inhalation patients. This shift to more acidotic levels could cause central nervous system depression with reduced respiratory stimulus. Conclusions: We recommend that air rather than oxygen be administered to patients during cataract surgery.