Abstract
A 50-year-old male without systemic complications received fixation of patella under the spinal anesthesia. A few minutes after the tourniquet release, arterial oxygen saturation suddenly decreased to 63%. Arterial blood gas analysis revealed pH ; 7.42, PaO2 ; 32mmHg and PaCO2 ; 39mmHg. This hypoxemia disappeared immediately after supplemental oxygen therapy via a face mask (4l/min). Arterial blood gases were normalized on the next day. The patient recovered without complications. The "Posthyperventilation hypoxia", respiratory depression by sedatives, the decrease in mixed venous oxygen contents following tourniquet deflation, pulmonary micro-atelectasis and microembolism were suggested as the causes of hypoxemia. Pulse-oximetry was useful in detecting hypoxemia in this case.
